diff --git a/PLAN.md b/PLAN.md
index f7bd97c..cd490a2 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -672,7 +672,7 @@ func TestMain(m *testing.M) {
 
 ```hcl
 provider "artifactapi" {
-  endpoint = "https://artifactapi.k8s.syd1.au.unkin.net"
+  endpoint = "https://artifactapi.example.com"
 }
 
 resource "artifactapi_remote" "terraform_registry" {
diff --git a/README.md b/README.md
index 46a9081..21e173f 100644
--- a/README.md
+++ b/README.md
@@ -20,99 +20,27 @@ API: `http://localhost:8000` | Frontend: `http://localhost:5173`
 
 ## Package Types
 
-| Type | Mutable (auto-detected) | Immutable (auto-detected) |
-|---|---|---|
-| `generic` | nothing | everything |
-| `docker` | tag manifests, `/tags/list` | blobs, digest manifests |
-| `helm` | `index.yaml` | `.tgz` charts |
-| `pypi` | `simple/*` index pages | `.whl`, `.tar.gz` |
-| `npm` | package metadata | `.tgz` tarballs |
-| `rpm` | `repomd.xml`, `repodata/*` | `.rpm` |
-| `alpine` | `APKINDEX.tar.gz` | `.apk` |
-| `puppet` | `v3/modules/*`, `v3/releases*` | `.tar.gz` |
-| `terraform` | `*/versions` | `*/download/*/*` |
-| `goproxy` | `@v/list`, `@latest` | `.info`, `.mod`, `.zip` |
-| `cargo` | sparse index files (`config.json` synthesized) | `crates/*/*.crate` |
-| `ansible` | Galaxy `api/` JSON (links rewritten, `limit`/`offset` forwarded) | `artifacts/*.tar.gz` |
-| `nuget` | `index.json` (service index), registration and flat container indexes | `.nupkg`, `.nuspec` |
-| `github_rpm` | `repodata/*` (synthesized) | `.rpm` (redirected) |
-
 Providers classify paths automatically. Users only configure what to proxy and TTLs.
 
-### `github_rpm` — GitHub releases as a yum repo (metadata-only, no precache)
+Classification precedence, TTLs and eviction for every remote: [docs/common/caching.md](docs/common/caching.md).
 
-A `github_rpm` remote turns a GitHub repo's **releases** into a real `dnf`/`yum`
-repository without ever caching the packages. It scans releases for `.rpm`
-assets, derives each package's metadata (NEVRA, requires/provides/conflicts/
-obsoletes, files, checksum) and **synthesizes `repodata/` on the fly**. Package
-metadata comes from a **ranged GET of just the RPM header** (the header sits at
-the front of the file, so the whole package is never downloaded); the sha256
-checksum comes from the GitHub asset `digest` when present, else a one-time
-lazy stream. Derived metadata is cached (keyed by asset) so repodata generation
-is served from primed DB rows, never a cold on-demand derive.
+Each type's paths, Terraform examples and local/virtual behaviour are in `docs/<type>/`:
 
-Each package's `<location>` points back at the remote, which **302-redirects**
-the download to the `releases_remote` — an existing generic `github.com` remote
-that streams the actual bytes. `dnf` follows the redirect transparently.
-
-#### Background syncer
-
-A single process-wide **background syncer** keeps every `github_rpm` remote's
-derived metadata current off the client request path:
-
-- **Prime on create.** Creating a `github_rpm` remote enqueues a background prime
-  scan, so its metadata is derived right away without blocking the create call.
-  The first `dnf` request is served from cache. If a request arrives before the
-  prime lands, it returns a retryable `503` (with `Retry-After`) rather than
-  serving an empty repo or blocking on a multi-minute derive.
-- **Periodic re-check, driven by `mutable_ttl`.** Each remote is re-checked for
-  new or changed releases no more often than its `mutable_ttl`. New/changed
-  assets are derived incrementally; assets already cached are never re-fetched,
-  and assets that disappear upstream are pruned.
-- **ETag / 304 conditional requests.** The releases-list `ETag` is stored per
-  remote and sent as `If-None-Match`; a `304 Not Modified` means nothing changed
-  and the syncer derives nothing. GitHub does not count `304` conditional
-  responses against the rate limit, so an unchanged repo is nearly free — this is
-  the main lever keeping GitHub traffic low.
-- **Global rate limit.** Every GitHub call (releases list + each ranged asset
-  header GET) passes through a single token-bucket limiter **shared across all
-  remotes**, so GitHub is never hammered. Configure a token (`password`) on the
-  remote for the higher authenticated rate limit (~5000/hr vs ~60/hr
-  unauthenticated).
-- **Multi-replica coordination.** State is shared through the database. Before a
-  periodic scan a replica must atomically claim a per-remote lease
-  (`github_rpm_sync_state`: `last_synced_at`, `etag`, `sync_lease_owner`,
-  `sync_lease_expires`); only the winner scans. This bounds total GitHub load to
-  ~once per `mutable_ttl` regardless of replica count, and the shared `etag`
-  lets any replica issue the conditional request.
-
-```hcl
-# Backend that serves the actual .rpm bytes from github.com.
-resource "artifactapi_remote_generic" "github" {
-  name     = "github"
-  base_url = "https://github.com"
-  patterns = [
-    "acme/tools/releases/download/.*\\.rpm$", # allowlist the repo's release assets
-  ]
-}
-
-resource "artifactapi_remote_github_rpm" "acme-tools" {
-  name            = "acme-tools"
-  base_url        = "https://api.github.com/repos/acme/tools" # the releases API root
-  releases_remote = "github"                                  # backend for downloads
-  mutable_ttl     = 3600                                      # release re-scan interval
-
-  # Optional: restrict which release assets become packages (regex on filename).
-  patterns = [".*\\.x86_64\\.rpm$", ".*\\.noarch\\.rpm$"]
-
-  # Optional: a token for private repos / higher API rate limits.
-  # password = "ghp_..."
-}
-```
-
-`dnf` config: `baseurl=https://artifactapi.example/api/v1/remote/acme-tools`.
-The repo is multi-arch (no `$basearch` needed) — `dnf` selects matching packages
-from the synthesized metadata.
+- `alpine`: [remote](docs/alpine/remote.md), [remote-github](docs/alpine/remote-github.md)
+- `ansible`: [remote](docs/ansible/remote.md)
+- `cargo`: [remote](docs/cargo/remote.md)
+- `deb`: [remote](docs/deb/remote.md), [remote-github](docs/deb/remote-github.md)
+- `docker`: [remote](docs/docker/remote.md), [local](docs/docker/local.md)
+- `generic`: [remote](docs/generic/remote.md)
+- `gems`: [remote](docs/gems/remote.md), [local](docs/gems/local.md), [virtual](docs/gems/virtual.md)
+- `goproxy`: [remote](docs/goproxy/remote.md)
+- `helm`: [remote](docs/helm/remote.md), [local](docs/helm/local.md), [virtual](docs/helm/virtual.md)
+- `npm`: [remote](docs/npm/remote.md), [local](docs/npm/local.md), [virtual](docs/npm/virtual.md)
+- `nuget`: [remote](docs/nuget/remote.md)
+- `puppet`: [remote](docs/puppet/remote.md), [local](docs/puppet/local.md)
+- `pypi`: [remote](docs/pypi/remote.md)
+- `rpm`: [remote](docs/rpm/remote.md), [remote-github](docs/rpm/remote-github.md)
+- `terraform`: [remote](docs/terraform/remote.md), [local](docs/terraform/local.md)
 
 ### GitHub authentication
 
@@ -181,105 +109,9 @@ GITHUB_APP_PRIVATE_KEY_PATH=/etc/artifactapi/github-app.pem
 
 ## Terraform
 
-Remotes and virtuals are managed by Terraform. Each package type has its own resource:
+Remotes and virtuals are managed by Terraform. Each package type has its own resource; see `docs/<type>/` for examples.
 
-```hcl
-resource "artifactapi_remote_generic" "github" {
-  name     = "github"
-  base_url = "https://github.com"
-
-  immutable_ttl = 0
-  mutable_ttl   = 7200
-
-  patterns = [
-    "ducaale/xh/.*/xh-.*-x86_64-unknown-linux-musl.tar.gz$",
-    "mikefarah/yq/.*/yq_linux_amd64$",
-  ]
-
-  mutable_patterns = [
-    ".*/archive/refs/heads/.*\\.tar\\.gz$",
-  ]
-}
-
-resource "artifactapi_remote_docker" "dockerhub" {
-  name     = "dockerhub"
-  base_url = "https://registry-1.docker.io"
-
-  immutable_ttl    = 0
-  mutable_ttl      = 300
-  ban_tags_enabled = true
-  ban_tags         = ["latest"]
-
-  patterns = [
-    "^library/postgres",
-    "^library/redis",
-  ]
-}
-
-resource "artifactapi_remote_helm" "jetstack" {
-  name     = "jetstack"
-  base_url = "https://charts.jetstack.io"
-
-  immutable_ttl = 0
-  mutable_ttl   = 3600
-}
-
-resource "artifactapi_virtual" "helm" {
-  name         = "helm"
-  package_type = "helm"
-  members      = [artifactapi_remote_helm.jetstack.name]
-}
-```
-
-Provider: [terraform-provider-artifactapi](../terraform-provider-artifactapi)
-
-### Serving providers as a registry
-
-A local `terraform` repo is a real provider registry: upload
-`terraform-provider-{type}_{version}_{os}_{arch}.zip` files under
-`{namespace}/{type}/`, and Terraform installs them from a bare source address —
-no `.terraformrc` mirror config:
-
-```hcl
-terraform {
-  required_providers {
-    artifactapi = {
-      source  = "artifactapi.k8s.syd1.au.unkin.net/<repo>/<type>"
-      version = "0.1.2"
-    }
-  }
-}
-```
-
-The Terraform *namespace* segment is the artifactapi repo name; the provider is
-matched by *type*. The registry serves service discovery
-(`/.well-known/terraform.json`), the `providers.v1` version/download endpoints,
-and a GPG-signed `SHA256SUMS` per the provider registry protocol.
-
-Signing needs a GPG key. By default artifactapi generates one on first start and
-stores it in the database (`signing_keys` table), so every replica shares it and
-there's nothing to provision. To bring your own key instead, point
-`TF_SIGNING_KEY_PATH` at an armored private key (optionally
-`TF_SIGNING_KEY_PASSPHRASE`), which takes precedence over the generated one.
-`TF_PROVIDER_PROTOCOLS` (default `5.0,6.0`) sets the advertised plugin protocols.
-
-### Local docker registry
-
-A local `docker` repo is a real container registry, not a mirror: it serves the
-Docker Registry HTTP API V2 for both push and pull, so any client (`docker`,
-`podman`, `skopeo`, `buildah`) can use it directly.
-
-```sh
-docker tag myapp:latest artifactapi.k8s.syd1.au.unkin.net/docker-internal/myapp:latest
-docker push        artifactapi.k8s.syd1.au.unkin.net/docker-internal/myapp:latest
-docker pull        artifactapi.k8s.syd1.au.unkin.net/docker-internal/myapp:latest
-```
-
-The first path segment after `/v2/` is the artifactapi repo name; the remainder
-is the image name. Blobs and manifests are stored through the shared
-content-addressable store (deduplicated by digest, reaped by GC once
-unreferenced); tags are mutable references and re-pushing a tag moves it. Blob
-uploads support both the monolithic and chunked (`POST`/`PATCH`/`PUT`) flows.
+Provider: [terraform-provider-artifactapi](https://git.unkin.net/unkin/terraform-provider-artifactapi)
 
 ## Access Control
 
@@ -299,6 +131,8 @@ No patterns + no blocklist = open proxy. Provider handles mutability classificat
 ```
 GET /api/v1/remote/{name}/{path}     Proxy/cache artifact
 GET /api/v1/virtual/{name}/{path}    Virtual repo (merged index)
+PUT /api/v1/local/{name}/{package}   npm publish (local npm repos)
+POST/DELETE /api/v1/local/{name}/api/v1/gems[/yank]   gem push / yank (local gems repos)
 GET /v2/{name}/{path}                Docker Registry v2
 ```
 
diff --git a/docs/alpine/remote-github.md b/docs/alpine/remote-github.md
new file mode 100644
index 0000000..e9e473b
--- /dev/null
+++ b/docs/alpine/remote-github.md
@@ -0,0 +1,7 @@
+# `github_alpine` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `github_alpine` | `APKINDEX.tar.gz` (synthesized) | `.apk` (redirected) |
diff --git a/docs/alpine/remote.md b/docs/alpine/remote.md
new file mode 100644
index 0000000..f415b81
--- /dev/null
+++ b/docs/alpine/remote.md
@@ -0,0 +1,7 @@
+# `alpine` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `alpine` | `APKINDEX.tar.gz` | `.apk` |
diff --git a/docs/ansible/remote.md b/docs/ansible/remote.md
new file mode 100644
index 0000000..c6ea0b5
--- /dev/null
+++ b/docs/ansible/remote.md
@@ -0,0 +1,11 @@
+# `ansible` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `ansible` | Galaxy `api/` JSON (links rewritten, `limit`/`offset` forwarded) | `artifacts/*.tar.gz` |
+
+```bash
+ansible-galaxy collection install community.general -s https://artifactapi.example/api/v1/remote/galaxy/api/
+```
diff --git a/docs/cargo/remote.md b/docs/cargo/remote.md
new file mode 100644
index 0000000..d7bec9e
--- /dev/null
+++ b/docs/cargo/remote.md
@@ -0,0 +1,7 @@
+# `cargo` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `cargo` | sparse index files (`config.json` synthesized) | `crates/*/*.crate` |
diff --git a/docs/common/caching.md b/docs/common/caching.md
new file mode 100644
index 0000000..20fd733
--- /dev/null
+++ b/docs/common/caching.md
@@ -0,0 +1,101 @@
+# Caching and classification (all remotes)
+
+Every proxied request on a remote is classified as **denied**, **immutable** or
+**mutable**. The class picks the storage path and the freshness TTL.
+
+## Fields
+
+| Field | Meaning |
+|---|---|
+| `patterns` | Allowlist of regexes. Empty allows every path; otherwise a non-matching path is denied (403). |
+| `blocklist` | Regexes; a match is denied (403). |
+| `immutable_patterns` | Regexes forcing a path immutable. |
+| `mutable_patterns` | Regexes forcing a path mutable. |
+| `immutable_ttl` | Seconds an immutable path stays fresh. `0` = forever. |
+| `mutable_ttl` | Seconds a mutable path stays fresh. `0` also means never expires. Omitted on create, it defaults to `3600`; omitted on update, the stored value is kept. |
+| `check_mutable` | When a mutable path's `mutable_ttl` expires, sends a conditional `HEAD` (`If-None-Match`) with the stored upstream ETag. A `304` re-arms the TTL and serves the stored copy; anything else refetches in full. The ETag is kept for `max(10 × mutable_ttl, 7 days)`, re-armed on each `304`, so idle paths age out. It is only stored when `check_mutable` is set and `mutable_ttl` is non-zero, and never for immutable paths. |
+| `stale_on_error` | On an upstream network error, serve the stored copy instead of failing. |
+| `quarantine_enabled` / `quarantine_days` | Stored on the remote but not enforced by the proxy yet. |
+| `mirrorlist` / `mirror_strategy` | rpm/deb/alpine only. Upstream pool is `[base_url] + mirrorlist`; `round_robin` (default) rotates the starting mirror, `least_conn` starts at the one with the fewest in-flight requests. Network errors and 5xx fail over to the next mirror; other statuses return as-is. |
+
+## Precedence
+
+The first rule that matches wins:
+
+1. `blocklist` matches: **denied**
+2. `patterns` is non-empty and nothing matches: **denied**
+3. `immutable_patterns` matches: **immutable**
+4. `mutable_patterns` matches: **mutable**
+5. the provider's built-in `Classify` says mutable: **mutable**
+6. anything else: **immutable**
+
+So `blocklist` beats the allowlist, and `immutable_patterns` beats
+`mutable_patterns`. Either user list overrides the built-in rules. `GET` and
+`HEAD` both apply this order.
+
+## Matching rules
+
+- Regexes are Go `regexp`, matched **unanchored** (`MatchString`). Add `^` or `$` yourself when you need them.
+- They match the path after `/api/v1/remote/<name>/`, without a leading slash, e.g. `9/BaseOS/x86_64/os/repodata/repomd.xml`.
+- The query string is not part of the path. It is dropped and not forwarded upstream.
+- `create` and `update` reject an invalid regex in `patterns`, `blocklist`, `mutable_patterns`, `immutable_patterns` or `ban_tags` with a 400. Only invalid regexes already stored before that check are skipped at match time.
+
+## Lifecycles
+
+| | Immutable | Mutable |
+|---|---|---|
+| Stored as | content-addressed blob (sha256), streamed | per-path index object, buffered and rewritten by the provider |
+| Fresh for | `immutable_ttl` (`0` = forever) | `mutable_ttl` |
+| After expiry | refetched from upstream | revalidated with `If-None-Match` when `check_mutable` is set and an ETag is stored, else refetched |
+| Upstream down | `stale_on_error` serves the stored copy and re-arms the TTL; an open circuit breaker always serves stale if a copy exists, else 503 | same |
+
+Concurrent misses on one path share a fetch lock. Waiters poll the store for
+up to 5s instead of all going upstream.
+
+## Eviction
+
+```sh
+curl -X DELETE https://artifactapi.example.com/api/v2/remotes/<name>/objects/<path>
+curl -X DELETE https://artifactapi.example.com/api/v2/remotes/<name>/objects/<dir>/*
+```
+
+- Evict drops the artifact row, the index object and the Redis TTL and ETag keys, so the next request goes upstream whatever the class or TTL.
+- Deleting a remote drops its Redis TTL and ETag keys, so a re-created remote of the same name starts cold.
+- A single-path evict takes the fetch lock first, so an in-flight fetch can't re-cache the path. It returns 503 if the lock stays busy.
+- A wildcard must end in `<dir>/*` and takes no lock.
+- Returns 204, or 404 for an unknown remote.
+
+## Examples
+
+Bodies for `POST https://artifactapi.example.com/api/v2/remotes`.
+
+GitHub release assets through a `generic` remote, allowlisted:
+
+```json
+{"name": "github", "package_type": "generic", "base_url": "https://github.com",
+ "immutable_ttl": 0, "mutable_ttl": 7200,
+ "patterns": ["^mikefarah/yq/releases/download/.*/yq_linux_amd64$"]}
+```
+
+rpm remote: `repodata/*` and `repomd.xml` are mutable by default, so only the TTLs are needed:
+
+```json
+{"name": "almalinux", "package_type": "rpm", "base_url": "https://repo.almalinux.org/almalinux",
+ "immutable_ttl": 0, "mutable_ttl": 3600, "check_mutable": true, "stale_on_error": true}
+```
+
+Force a moving path mutable, e.g. branch tarballs on `generic`:
+
+```json
+{"mutable_patterns": ["/archive/refs/heads/.*\\.tar\\.gz$"], "mutable_ttl": 600}
+```
+
+## Built-in classification per type
+
+Each type's page lists its auto-detected mutable and immutable paths:
+[alpine](../alpine/remote.md), [alpine github](../alpine/remote-github.md),
+[cargo](../cargo/remote.md), [deb](../deb/remote.md), [deb github](../deb/remote-github.md),
+[docker](../docker/remote.md), [generic](../generic/remote.md), [gems](../gems/remote.md), [goproxy](../goproxy/remote.md),
+[helm](../helm/remote.md), [npm](../npm/remote.md), [nuget](../nuget/remote.md),
+[puppet](../puppet/remote.md), [pypi](../pypi/remote.md), [rpm](../rpm/remote.md),
+[rpm github](../rpm/remote-github.md), [terraform](../terraform/remote.md).
diff --git a/docs/deb/remote-github.md b/docs/deb/remote-github.md
new file mode 100644
index 0000000..99d9f11
--- /dev/null
+++ b/docs/deb/remote-github.md
@@ -0,0 +1,7 @@
+# `github_deb` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `github_deb` | `Packages*`, `Release*` (synthesized) | `.deb` (redirected) |
diff --git a/docs/deb/remote.md b/docs/deb/remote.md
new file mode 100644
index 0000000..865d949
--- /dev/null
+++ b/docs/deb/remote.md
@@ -0,0 +1,7 @@
+# `deb` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `deb` | `Packages*`, `Sources*`, `Release`, `InRelease`, `Release.gpg`, `Contents-*` | `.deb` |
diff --git a/docs/docker/local.md b/docs/docker/local.md
new file mode 100644
index 0000000..54d7a55
--- /dev/null
+++ b/docs/docker/local.md
@@ -0,0 +1,17 @@
+# Local docker registry
+
+A local `docker` repo is a real container registry, not a mirror: it serves the
+Docker Registry HTTP API V2 for both push and pull, so any client (`docker`,
+`podman`, `skopeo`, `buildah`) can use it directly.
+
+```sh
+docker tag myapp:latest artifactapi.example.com/docker-internal/myapp:latest
+docker push        artifactapi.example.com/docker-internal/myapp:latest
+docker pull        artifactapi.example.com/docker-internal/myapp:latest
+```
+
+The first path segment after `/v2/` is the artifactapi repo name; the remainder
+is the image name. Blobs and manifests are stored through the shared
+content-addressable store (deduplicated by digest, reaped by GC once
+unreferenced); tags are mutable references and re-pushing a tag moves it. Blob
+uploads support both the monolithic and chunked (`POST`/`PATCH`/`PUT`) flows.
diff --git a/docs/docker/remote.md b/docs/docker/remote.md
new file mode 100644
index 0000000..c8a79f1
--- /dev/null
+++ b/docs/docker/remote.md
@@ -0,0 +1,26 @@
+# `docker` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `docker` | tag manifests, `/tags/list` | blobs, digest manifests |
+
+## Terraform
+
+```hcl
+resource "artifactapi_remote_docker" "dockerhub" {
+  name     = "dockerhub"
+  base_url = "https://registry-1.docker.io"
+
+  immutable_ttl    = 0
+  mutable_ttl      = 300
+  ban_tags_enabled = true
+  ban_tags         = ["latest"]
+
+  patterns = [
+    "^library/postgres",
+    "^library/redis",
+  ]
+}
+```
diff --git a/docs/gems/local.md b/docs/gems/local.md
new file mode 100644
index 0000000..caf720c
--- /dev/null
+++ b/docs/gems/local.md
@@ -0,0 +1,24 @@
+# Local gems repository
+
+A local `gems` repo is a RubyGems source: `gem push`, `gem yank`, `gem install`
+and `bundle install` work against `/api/v1/local/<repo>`. `gem push` needs an
+API key; any value works.
+
+```bash
+GEM_HOST_API_KEY=unused gem push --host https://artifactapi.example.com/api/v1/local/<repo> mygem-1.0.0.gem
+gem install mygem --source https://artifactapi.example.com/api/v1/local/<repo>/
+gem yank mygem -v 1.0.0 --host https://artifactapi.example.com/api/v1/local/<repo>
+```
+
+```ruby
+# Gemfile
+source "https://artifactapi.example.com/api/v1/local/<repo>/"
+gem "mygem"
+```
+
+The repo serves the compact index (`versions`, `info/<gem>`, `names`), `gems/*.gem`
+and `quick/Marshal.4.8/*.gemspec.rz`. The legacy `specs.4.8.gz` indexes are not
+served; current gem and bundler clients use the compact index.
+
+Versions are immutable: pushing an existing name-version-platform is rejected
+with 409. A yanked version disappears from the index and its files are removed.
diff --git a/docs/gems/remote.md b/docs/gems/remote.md
new file mode 100644
index 0000000..9f4707b
--- /dev/null
+++ b/docs/gems/remote.md
@@ -0,0 +1,7 @@
+# `gems` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `gems` | compact index (`versions`, `info/*`, `names`), `*specs.4.8.gz` | `gems/*.gem`, `quick/Marshal.4.8/*.gemspec.rz` |
diff --git a/docs/gems/virtual.md b/docs/gems/virtual.md
new file mode 100644
index 0000000..e894113
--- /dev/null
+++ b/docs/gems/virtual.md
@@ -0,0 +1,28 @@
+# `gems` virtual
+
+A gems virtual serves one RubyGems source over local and remote gems members:
+`gem install` and `bundle install` work against `/api/v1/virtual/<name>/`.
+
+- `info/<gem>` is the union of member lines; on a duplicate version-platform
+  the earlier member wins. A gem only one member has is served verbatim.
+- `versions` regenerates the line (and md5) of every gem several members list
+  from its merged `info`; other gems' lines pass through. `names` is the union.
+- `gems/*.gem` and `quick/Marshal.4.8/*.gemspec.rz` 302 to the member whose
+  `info` line won.
+- A member error fails the request with 502; a member without the gem is
+  skipped. Merges are cached for 60s.
+
+```hcl
+resource "artifactapi_virtual" "gems" {
+  name         = "gems"
+  package_type = "gems"
+  members      = [artifactapi_local_gems.internal.name, artifactapi_remote_gems.rubygems.name]
+}
+```
+
+```ruby
+# Gemfile
+source "https://artifactapi.example.com/api/v1/virtual/gems/"
+```
+
+Push to the local member directly; the virtual is read-only.
diff --git a/docs/generic/remote.md b/docs/generic/remote.md
new file mode 100644
index 0000000..7fac792
--- /dev/null
+++ b/docs/generic/remote.md
@@ -0,0 +1,28 @@
+# `generic` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `generic` | nothing | everything |
+
+## Terraform
+
+```hcl
+resource "artifactapi_remote_generic" "github" {
+  name     = "github"
+  base_url = "https://github.com"
+
+  immutable_ttl = 0
+  mutable_ttl   = 7200
+
+  patterns = [
+    "ducaale/xh/.*/xh-.*-x86_64-unknown-linux-musl.tar.gz$",
+    "mikefarah/yq/.*/yq_linux_amd64$",
+  ]
+
+  mutable_patterns = [
+    ".*/archive/refs/heads/.*\\.tar\\.gz$",
+  ]
+}
+```
diff --git a/docs/goproxy/remote.md b/docs/goproxy/remote.md
new file mode 100644
index 0000000..52d1c49
--- /dev/null
+++ b/docs/goproxy/remote.md
@@ -0,0 +1,7 @@
+# `goproxy` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `goproxy` | `@v/list`, `@latest` | `.info`, `.mod`, `.zip` |
diff --git a/docs/helm/local.md b/docs/helm/local.md
new file mode 100644
index 0000000..898ff88
--- /dev/null
+++ b/docs/helm/local.md
@@ -0,0 +1,15 @@
+# Local helm repository
+
+A local `helm` repo is a real chart repository: `PUT` a packaged chart to
+`/api/v2/remotes/<repo>/files/<chart>-<version>.tgz` and `index.yaml` is
+generated from each chart's `Chart.yaml` (with sha256 digests) at
+`/api/v1/local/<repo>/index.yaml`; a file not named after its `Chart.yaml`
+name and version is stored but left out of the index. Add the local as a
+member of a helm virtual to serve it alongside remotes.
+
+```bash
+helm package ./mychart
+curl -fsSL --upload-file mychart-0.1.0.tgz \
+  https://artifactapi.example.com/api/v2/remotes/<repo>/files/mychart-0.1.0.tgz
+helm repo add <repo> https://artifactapi.example.com/api/v1/local/<repo>
+```
diff --git a/docs/helm/remote.md b/docs/helm/remote.md
new file mode 100644
index 0000000..b51e028
--- /dev/null
+++ b/docs/helm/remote.md
@@ -0,0 +1,19 @@
+# `helm` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `helm` | `index.yaml` | `.tgz` charts |
+
+## Terraform
+
+```hcl
+resource "artifactapi_remote_helm" "jetstack" {
+  name     = "jetstack"
+  base_url = "https://charts.jetstack.io"
+
+  immutable_ttl = 0
+  mutable_ttl   = 3600
+}
+```
diff --git a/docs/helm/virtual.md b/docs/helm/virtual.md
new file mode 100644
index 0000000..91a56b0
--- /dev/null
+++ b/docs/helm/virtual.md
@@ -0,0 +1,9 @@
+# `helm` virtual
+
+```hcl
+resource "artifactapi_virtual" "helm" {
+  name         = "helm"
+  package_type = "helm"
+  members      = [artifactapi_remote_helm.jetstack.name]
+}
+```
diff --git a/docs/npm/local.md b/docs/npm/local.md
new file mode 100644
index 0000000..798a48b
--- /dev/null
+++ b/docs/npm/local.md
@@ -0,0 +1,14 @@
+# Local npm registry
+
+A local `npm` repo is a real npm registry: `npm publish` (scoped and unscoped)
+and `npm install` work against `/api/v1/local/<repo>/`. npm requires an
+`_authToken` for the registry before it will publish; any value works.
+
+```ini
+# .npmrc
+registry=https://artifactapi.example.com/api/v1/local/<repo>/
+//artifactapi.example.com/api/v1/local/<repo>/:_authToken=unused
+```
+
+Versions are immutable: republishing an existing version is rejected. The
+dist-tags sent with a publish (`latest`, or `--tag`) move to that version.
diff --git a/docs/npm/remote.md b/docs/npm/remote.md
new file mode 100644
index 0000000..8559315
--- /dev/null
+++ b/docs/npm/remote.md
@@ -0,0 +1,7 @@
+# `npm` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `npm` | package metadata | `.tgz` tarballs |
diff --git a/docs/npm/virtual.md b/docs/npm/virtual.md
new file mode 100644
index 0000000..19deb9a
--- /dev/null
+++ b/docs/npm/virtual.md
@@ -0,0 +1,30 @@
+# `npm` virtual
+
+An npm virtual serves one registry over local and remote npm members:
+`npm install` and `npm view` work against `/api/v1/virtual/<name>/`.
+
+- Versions are the union across members; on a duplicate version the earlier
+  member wins.
+- Each dist-tag comes from the first member defining it, and is dropped if it
+  names a version missing from the merged set.
+- Tarball URLs point at the virtual (`<member>/<path>`), which 302s to the
+  owning member.
+- Full and abbreviated (`application/vnd.npm.install-v1+json`) packuments are
+  both served.
+- A member error fails the request with 502; a member without the package is
+  skipped. Merges are cached for 60s per package.
+
+```hcl
+resource "artifactapi_virtual" "npm" {
+  name         = "npm"
+  package_type = "npm"
+  members      = [artifactapi_local_npm.internal.name, artifactapi_remote_npm.npmjs.name]
+}
+```
+
+```ini
+# .npmrc
+registry=https://artifactapi.example.com/api/v1/virtual/npm/
+```
+
+Publish to the local member directly; the virtual is read-only.
diff --git a/docs/nuget/remote.md b/docs/nuget/remote.md
new file mode 100644
index 0000000..7e6ed99
--- /dev/null
+++ b/docs/nuget/remote.md
@@ -0,0 +1,7 @@
+# `nuget` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `nuget` | `index.json` (service index), registration and flat container indexes | `.nupkg`, `.snupkg`, `.nuspec`, `readme`, `icon` |
diff --git a/docs/puppet/local.md b/docs/puppet/local.md
new file mode 100644
index 0000000..c5258d0
--- /dev/null
+++ b/docs/puppet/local.md
@@ -0,0 +1,14 @@
+# Local puppet forge
+
+A local `puppet` repo is a Forge: `PUT` a module tarball to
+`/api/v2/remotes/<repo>/files/<owner>-<module>-<version>.tar.gz` and the Forge
+v3 API (`/v3/modules`, `/v3/releases`, `/v3/files`) is served from each
+release's `metadata.json` at `/api/v1/local/<repo>`. Versions are immutable.
+
+```bash
+puppet module build ./hello
+curl -fsSL --upload-file pkg/unkin-hello-0.1.0.tar.gz \
+  https://artifactapi.example.com/api/v2/remotes/<repo>/files/unkin-hello-0.1.0.tar.gz
+puppet module install unkin-hello \
+  --module_repository https://artifactapi.example.com/api/v1/local/<repo>
+```
diff --git a/docs/puppet/remote.md b/docs/puppet/remote.md
new file mode 100644
index 0000000..8c7435e
--- /dev/null
+++ b/docs/puppet/remote.md
@@ -0,0 +1,7 @@
+# `puppet` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `puppet` | `v3/modules/*`, `v3/releases*` | `.tar.gz` |
diff --git a/docs/pypi/remote.md b/docs/pypi/remote.md
new file mode 100644
index 0000000..0f5fe32
--- /dev/null
+++ b/docs/pypi/remote.md
@@ -0,0 +1,7 @@
+# `pypi` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `pypi` | `simple/*` index pages | `.whl`, `.tar.gz` |
diff --git a/docs/rpm/remote-github.md b/docs/rpm/remote-github.md
new file mode 100644
index 0000000..f079b02
--- /dev/null
+++ b/docs/rpm/remote-github.md
@@ -0,0 +1,82 @@
+# `github_rpm` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `github_rpm` | `repodata/*` (synthesized) | `.rpm` (redirected) |
+
+## GitHub releases as a yum repo (metadata-only, no precache)
+
+A `github_rpm` remote turns a GitHub repo's **releases** into a real `dnf`/`yum`
+repository without ever caching the packages. It scans releases for `.rpm`
+assets, derives each package's metadata (NEVRA, requires/provides/conflicts/
+obsoletes, files, checksum) and **synthesizes `repodata/` on the fly**. Package
+metadata comes from a **ranged GET of just the RPM header** (the header sits at
+the front of the file, so the whole package is never downloaded); the sha256
+checksum comes from the GitHub asset `digest` when present, else a one-time
+lazy stream. Derived metadata is cached (keyed by asset) so repodata generation
+is served from primed DB rows, never a cold on-demand derive.
+
+Each package's `<location>` points back at the remote, which **302-redirects**
+the download to the `releases_remote` — an existing generic `github.com` remote
+that streams the actual bytes. `dnf` follows the redirect transparently.
+
+### Background syncer
+
+A single process-wide **background syncer** keeps every `github_rpm` remote's
+derived metadata current off the client request path:
+
+- **Prime on create.** Creating a `github_rpm` remote enqueues a background prime
+  scan, so its metadata is derived right away without blocking the create call.
+  The first `dnf` request is served from cache. If a request arrives before the
+  prime lands, it returns a retryable `503` (with `Retry-After`) rather than
+  serving an empty repo or blocking on a multi-minute derive.
+- **Periodic re-check, driven by `mutable_ttl`.** Each remote is re-checked for
+  new or changed releases no more often than its `mutable_ttl`. New/changed
+  assets are derived incrementally; assets already cached are never re-fetched,
+  and assets that disappear upstream are pruned.
+- **ETag / 304 conditional requests.** The releases-list `ETag` is stored per
+  remote and sent as `If-None-Match`; a `304 Not Modified` means nothing changed
+  and the syncer derives nothing. GitHub does not count `304` conditional
+  responses against the rate limit, so an unchanged repo is nearly free — this is
+  the main lever keeping GitHub traffic low.
+- **Global rate limit.** Every GitHub call (releases list + each ranged asset
+  header GET) passes through a single token-bucket limiter **shared across all
+  remotes**, so GitHub is never hammered. Configure a token (`password`) on the
+  remote for the higher authenticated rate limit (~5000/hr vs ~60/hr
+  unauthenticated).
+- **Multi-replica coordination.** State is shared through the database. Before a
+  periodic scan a replica must atomically claim a per-remote lease
+  (`github_rpm_sync_state`: `last_synced_at`, `etag`, `sync_lease_owner`,
+  `sync_lease_expires`); only the winner scans. This bounds total GitHub load to
+  ~once per `mutable_ttl` regardless of replica count, and the shared `etag`
+  lets any replica issue the conditional request.
+
+```hcl
+# Backend that serves the actual .rpm bytes from github.com.
+resource "artifactapi_remote_generic" "github" {
+  name     = "github"
+  base_url = "https://github.com"
+  patterns = [
+    "acme/tools/releases/download/.*\\.rpm$", # allowlist the repo's release assets
+  ]
+}
+
+resource "artifactapi_remote_github_rpm" "acme-tools" {
+  name            = "acme-tools"
+  base_url        = "https://api.github.com/repos/acme/tools" # the releases API root
+  releases_remote = "github"                                  # backend for downloads
+  mutable_ttl     = 3600                                      # release re-scan interval
+
+  # Optional: restrict which release assets become packages (regex on filename).
+  patterns = [".*\\.x86_64\\.rpm$", ".*\\.noarch\\.rpm$"]
+
+  # Optional: a token for private repos / higher API rate limits.
+  # password = "ghp_..."
+}
+```
+
+`dnf` config: `baseurl=https://artifactapi.example/api/v1/remote/acme-tools`.
+The repo is multi-arch (no `$basearch` needed) — `dnf` selects matching packages
+from the synthesized metadata.
diff --git a/docs/rpm/remote.md b/docs/rpm/remote.md
new file mode 100644
index 0000000..f4a93b2
--- /dev/null
+++ b/docs/rpm/remote.md
@@ -0,0 +1,7 @@
+# `rpm` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `rpm` | `repomd.xml`, `repodata/*` | `.rpm` |
diff --git a/docs/terraform/local.md b/docs/terraform/local.md
new file mode 100644
index 0000000..2b3e0d4
--- /dev/null
+++ b/docs/terraform/local.md
@@ -0,0 +1,29 @@
+# Serving providers as a registry
+
+A local `terraform` repo is a real provider registry: upload
+`terraform-provider-{type}_{version}_{os}_{arch}.zip` files under
+`{namespace}/{type}/`, and Terraform installs them from a bare source address —
+no `.terraformrc` mirror config:
+
+```hcl
+terraform {
+  required_providers {
+    artifactapi = {
+      source  = "artifactapi.example.com/<repo>/<type>"
+      version = "0.1.2"
+    }
+  }
+}
+```
+
+The Terraform *namespace* segment is the artifactapi repo name; the provider is
+matched by *type*. The registry serves service discovery
+(`/.well-known/terraform.json`), the `providers.v1` version/download endpoints,
+and a GPG-signed `SHA256SUMS` per the provider registry protocol.
+
+Signing needs a GPG key. By default artifactapi generates one on first start and
+stores it in the database (`signing_keys` table), so every replica shares it and
+there's nothing to provision. To bring your own key instead, point
+`TF_SIGNING_KEY_PATH` at an armored private key (optionally
+`TF_SIGNING_KEY_PASSPHRASE`), which takes precedence over the generated one.
+`TF_PROVIDER_PROTOCOLS` (default `5.0,6.0`) sets the advertised plugin protocols.
diff --git a/docs/terraform/remote.md b/docs/terraform/remote.md
new file mode 100644
index 0000000..d4fe58b
--- /dev/null
+++ b/docs/terraform/remote.md
@@ -0,0 +1,7 @@
+# `terraform` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+| Type | Mutable (auto-detected) | Immutable (auto-detected) |
+|---|---|---|
+| `terraform` | `*/versions` | `*/download/*/*` |
diff --git a/e2e-docker/README.md b/e2e-docker/README.md
index cd7c07e..4cc17ef 100644
--- a/e2e-docker/README.md
+++ b/e2e-docker/README.md
@@ -22,14 +22,21 @@ already-running stack.
 ## Coverage
 
 - **Repository lifecycle** — add / change / delete for remote, local and virtual repos.
-- **Caching** — one immutable artifact per remote package type (generic, docker,
-  helm, pypi, npm, rpm, alpine, puppet, terraform, goproxy, cargo, nuget, ansible) proxied through the
-  mock upstream: first fetch `X-Artifact-Source: remote`, second `cache`, bytes
+- **Caching** — one immutable artifact per remote package type (one
+  `caching_<type>_test.go` case each) proxied through the mock upstream: first fetch `X-Artifact-Source: remote`, second `cache`, bytes
   verified against the origin fixture.
-- **Local uploads** — generic (upload/download), pypi (wheel + generated `simple/`
-  index), rpm (real package + **automatic repodata** generation).
+- **Local uploads** — puppet (Forge v3 API via real `r10k` and `puppet module install`),
+  generic (upload/download), pypi (wheel + generated `simple/`
+  index), rpm (real package + **automatic repodata** generation), npm (stock
+  `node:22` client: `npm publish` unscoped + scoped, `npm install` + `require()`,
+  second version, republish rejected), gems (stock `ruby:3.3`: `gem push`,
+  `gem install`, `bundle install` + `require`, republish rejected, `gem yank`,
+  yanked re-push rejected).
 - **Virtual repositories** — pypi simple-index merge and helm `index.yaml` merge
-  across two members.
+  across two members; npm packument merge over two locals via a stock `node:22`
+  client (merged versions, install through the member redirect); gems compact
+  index merge over two locals via stock `ruby:3.3` bundler (member order wins,
+  downloads 302 to the owning member).
 - **Mirrorlist** — an rpm remote with a `mirrorlist` of extra upstream mirrors
   (pool = `base_url` + `mirrorlist`): round-robin distribution across both mirrors
   (constant-body `mockupstreama` / `mockupstreamb`), failover past a dead primary,
diff --git a/e2e-docker/caching_alpine_test.go b/e2e-docker/caching_alpine_test.go
new file mode 100644
index 0000000..d970f44
--- /dev/null
+++ b/e2e-docker/caching_alpine_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"alpine", "alpine/x86_64/testpkg-1.0-r0.apk", "alpine/x86_64/testpkg-1.0-r0.apk"})
+}
diff --git a/e2e-docker/caching_ansible_test.go b/e2e-docker/caching_ansible_test.go
new file mode 100644
index 0000000..62c9d19
--- /dev/null
+++ b/e2e-docker/caching_ansible_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"ansible", "galaxy/artifacts/ns-col-1.0.0.tar.gz", "galaxy/artifacts/ns-col-1.0.0.tar.gz"})
+}
diff --git a/e2e-docker/caching_cargo_test.go b/e2e-docker/caching_cargo_test.go
new file mode 100644
index 0000000..e5d6e0d
--- /dev/null
+++ b/e2e-docker/caching_cargo_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"cargo", "crates/mycrate/mycrate-1.0.0.crate", "crates/mycrate/mycrate-1.0.0.crate"})
+}
diff --git a/e2e-docker/caching_docker_test.go b/e2e-docker/caching_docker_test.go
new file mode 100644
index 0000000..87f980c
--- /dev/null
+++ b/e2e-docker/caching_docker_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"docker", "library/testimg/blobs/blobdata", "v2/library/testimg/blobs/blobdata"})
+}
diff --git a/e2e-docker/caching_gems_test.go b/e2e-docker/caching_gems_test.go
new file mode 100644
index 0000000..9ef2c8b
--- /dev/null
+++ b/e2e-docker/caching_gems_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"gems", "gems/mygem-1.0.0.gem", "gems/mygem-1.0.0.gem"})
+}
diff --git a/e2e-docker/caching_generic_test.go b/e2e-docker/caching_generic_test.go
new file mode 100644
index 0000000..ff4dc48
--- /dev/null
+++ b/e2e-docker/caching_generic_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"generic", "blobs/hello.bin", "blobs/hello.bin"})
+}
diff --git a/e2e-docker/caching_goproxy_test.go b/e2e-docker/caching_goproxy_test.go
new file mode 100644
index 0000000..3482bae
--- /dev/null
+++ b/e2e-docker/caching_goproxy_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"goproxy", "goproxy/example.com/mod/@v/v1.0.0.zip", "goproxy/example.com/mod/@v/v1.0.0.zip"})
+}
diff --git a/e2e-docker/caching_helm_test.go b/e2e-docker/caching_helm_test.go
new file mode 100644
index 0000000..548f1f2
--- /dev/null
+++ b/e2e-docker/caching_helm_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"helm", "charts/mychart-1.0.0.tgz", "charts/mychart-1.0.0.tgz"})
+}
diff --git a/e2e-docker/caching_npm_test.go b/e2e-docker/caching_npm_test.go
new file mode 100644
index 0000000..912fa85
--- /dev/null
+++ b/e2e-docker/caching_npm_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"npm", "mypkg/-/mypkg-1.0.0.tgz", "mypkg/-/mypkg-1.0.0.tgz"})
+}
diff --git a/e2e-docker/caching_nuget_test.go b/e2e-docker/caching_nuget_test.go
new file mode 100644
index 0000000..be8ee69
--- /dev/null
+++ b/e2e-docker/caching_nuget_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"nuget", "nuget/e2epkg/1.0.0/e2epkg.1.0.0.nupkg", "nuget/e2epkg/1.0.0/e2epkg.1.0.0.nupkg"})
+}
diff --git a/e2e-docker/caching_puppet_test.go b/e2e-docker/caching_puppet_test.go
new file mode 100644
index 0000000..74d2024
--- /dev/null
+++ b/e2e-docker/caching_puppet_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"puppet", "puppet-releases/author-mod-1.0.0.tar.gz", "puppet-releases/author-mod-1.0.0.tar.gz"})
+}
diff --git a/e2e-docker/caching_pypi_test.go b/e2e-docker/caching_pypi_test.go
new file mode 100644
index 0000000..3948f8e
--- /dev/null
+++ b/e2e-docker/caching_pypi_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"pypi", "packages/foo-1.0-py3-none-any.whl", "packages/foo-1.0-py3-none-any.whl"})
+}
diff --git a/e2e-docker/caching_rpm_test.go b/e2e-docker/caching_rpm_test.go
new file mode 100644
index 0000000..d4ff226
--- /dev/null
+++ b/e2e-docker/caching_rpm_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"rpm", "rpmrepo/Packages/e2e-testpkg-1.0-1.noarch.rpm", "rpmrepo/Packages/e2e-testpkg-1.0-1.noarch.rpm"})
+}
diff --git a/e2e-docker/caching_terraform_test.go b/e2e-docker/caching_terraform_test.go
new file mode 100644
index 0000000..f280d76
--- /dev/null
+++ b/e2e-docker/caching_terraform_test.go
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"terraform", "hashicorp/aws/download/pkg.zip", "v1/providers/hashicorp/aws/download/pkg.zip"})
+}
diff --git a/e2e-docker/caching_test.go b/e2e-docker/caching_test.go
index ddf992a..603ecd1 100644
--- a/e2e-docker/caching_test.go
+++ b/e2e-docker/caching_test.go
@@ -9,34 +9,23 @@ import (
 	"testing"
 )
 
+type cachingCase struct {
+	pkgType string
+	// path is the request path under /api/v1/remote/<name>/. The provider
+	// derives the upstream URL from it (docker prepends /v2/, terraform
+	// prepends /v1/providers/), and the fixture lives at that resolved path.
+	path    string
+	fixture string
+}
+
+// cachingCases is filled by one caching_<type>_test.go file per package type.
+var cachingCases []cachingCase
+
 // TestCachingPerProvider proxies one immutable artifact for every remote
 // package type through the mock upstream and asserts: first fetch is served
 // from the remote, the second from cache, and the bytes match the origin.
 func TestCachingPerProvider(t *testing.T) {
-	cases := []struct {
-		pkgType string
-		// path is the request path under /api/v1/remote/<name>/. The provider
-		// derives the upstream URL from it (docker prepends /v2/, terraform
-		// prepends /v1/providers/), and the fixture lives at that resolved path.
-		path    string
-		fixture string
-	}{
-		{"generic", "blobs/hello.bin", "blobs/hello.bin"},
-		{"npm", "mypkg/-/mypkg-1.0.0.tgz", "mypkg/-/mypkg-1.0.0.tgz"},
-		{"helm", "charts/mychart-1.0.0.tgz", "charts/mychart-1.0.0.tgz"},
-		{"pypi", "packages/foo-1.0-py3-none-any.whl", "packages/foo-1.0-py3-none-any.whl"},
-		{"rpm", "rpmrepo/Packages/e2e-testpkg-1.0-1.noarch.rpm", "rpmrepo/Packages/e2e-testpkg-1.0-1.noarch.rpm"},
-		{"alpine", "alpine/x86_64/testpkg-1.0-r0.apk", "alpine/x86_64/testpkg-1.0-r0.apk"},
-		{"puppet", "puppet-releases/author-mod-1.0.0.tar.gz", "puppet-releases/author-mod-1.0.0.tar.gz"},
-		{"goproxy", "goproxy/example.com/mod/@v/v1.0.0.zip", "goproxy/example.com/mod/@v/v1.0.0.zip"},
-		{"cargo", "crates/mycrate/mycrate-1.0.0.crate", "crates/mycrate/mycrate-1.0.0.crate"},
-		{"ansible", "galaxy/artifacts/ns-col-1.0.0.tar.gz", "galaxy/artifacts/ns-col-1.0.0.tar.gz"},
-		{"nuget", "nuget/e2epkg/1.0.0/e2epkg.1.0.0.nupkg", "nuget/e2epkg/1.0.0/e2epkg.1.0.0.nupkg"},
-		{"terraform", "hashicorp/aws/download/pkg.zip", "v1/providers/hashicorp/aws/download/pkg.zip"},
-		{"docker", "library/testimg/blobs/blobdata", "v2/library/testimg/blobs/blobdata"},
-	}
-
-	for _, tc := range cases {
+	for _, tc := range cachingCases {
 		t.Run(tc.pkgType, func(t *testing.T) {
 			name := "cache-" + tc.pkgType
 			createRepo(t, fmt.Sprintf(`{
diff --git a/e2e-docker/fixtures/gems/mygem-1.0.0.gem b/e2e-docker/fixtures/gems/mygem-1.0.0.gem
new file mode 100644
index 0000000..666781d
--- /dev/null
+++ b/e2e-docker/fixtures/gems/mygem-1.0.0.gem
@@ -0,0 +1 @@
+mygem-1.0.0 e2e fixture
diff --git a/e2e-docker/gems_local_test.go b/e2e-docker/gems_local_test.go
new file mode 100644
index 0000000..17d1068
--- /dev/null
+++ b/e2e-docker/gems_local_test.go
@@ -0,0 +1,67 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestLocalGemsPushInstall drives stock gem and bundler clients against a
+// local gems repo: push two versions, reject a republish, gem install and
+// bundle install the latest via the compact index, then yank it and check a
+// re-push of the yanked version with different bytes is rejected.
+func TestLocalGemsPushInstall(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; run via scripts/docker-e2e.sh")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+
+	name := fmt.Sprintf("e2e-gems-local-%d", time.Now().UnixNano())
+	createRepo(t, fmt.Sprintf(`{"name":%q,"package_type":"gems","repo_type":"local"}`, name))
+	defer deleteRepo(t, name)
+
+	src := strings.TrimRight(internal, "/") + "/api/v1/local/" + name
+	script := `set -euo pipefail
+export GEM_HOST_API_KEY=unused
+mk() { d=/w/src-$1${2:+-b}; mkdir -p $d/lib; cd $d
+  echo "module UnkinE2eHello; VERSION = '$1'; end${2:-}" > lib/unkin-e2e-hello.rb
+  printf 'Gem::Specification.new { |s| s.name = "unkin-e2e-hello"; s.version = "%s"; s.summary = "e2e"; s.authors = ["e2e"]; s.files = ["lib/unkin-e2e-hello.rb"] }' "$1" > g.gemspec
+  gem build g.gemspec >/dev/null 2>&1; }
+mk 0.1.0 && gem push --host "$SRC" unkin-e2e-hello-0.1.0.gem
+mk 0.2.0 && gem push --host "$SRC" unkin-e2e-hello-0.2.0.gem
+if gem push --host "$SRC" unkin-e2e-hello-0.2.0.gem; then echo "republish accepted"; exit 1; fi
+mkdir -p /w/app && cd /w/app
+printf -- "---\n:sources:\n- $SRC/\n" > ~/.gemrc
+gem install --no-document unkin-e2e-hello
+ruby -e 'require "unkin-e2e-hello"; puts "GEM #{UnkinE2eHello::VERSION}"'
+gem uninstall -a -x unkin-e2e-hello >/dev/null
+printf 'source "%s/"\ngem "unkin-e2e-hello"\n' "$SRC" > Gemfile
+bundle install
+bundle exec ruby -e 'require "unkin-e2e-hello"; puts "BUNDLE #{UnkinE2eHello::VERSION}"'
+gem yank unkin-e2e-hello -v 0.2.0 --host "$SRC"
+echo "INFO $(curl -s "$SRC/info/unkin-e2e-hello" | cut -d' ' -f1 | tr '\n' ' ')"
+mk 0.2.0 '# changed' && if gem push --host "$SRC" unkin-e2e-hello-0.2.0.gem; then echo "yanked re-push accepted"; exit 1; fi
+cd /w/app && gem uninstall -a -x unkin-e2e-hello >/dev/null
+if gem install --remote --no-document unkin-e2e-hello -v 0.2.0; then echo "yanked version installed"; exit 1; fi
+echo "VERSIONS $(curl -s "$SRC/versions" | grep '^unkin-e2e-hello ' | cut -d' ' -f2)"`
+
+	out, err := exec.Command("docker", "run", "--rm", "--network", network,
+		"-e", "SRC="+src, "ruby:3.3", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("gem client run failed: %v\n%s", err, out)
+	}
+	for _, want := range []string{"GEM 0.2.0", "BUNDLE 0.2.0", "INFO --- 0.1.0 ", "re-pushing a yanked version is not allowed", "VERSIONS 0.1.0\n"} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q in gem output:\n%s", want, out)
+		}
+	}
+}
diff --git a/e2e-docker/gems_virtual_test.go b/e2e-docker/gems_virtual_test.go
new file mode 100644
index 0000000..1eae0be
--- /dev/null
+++ b/e2e-docker/gems_virtual_test.go
@@ -0,0 +1,69 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestVirtualGemsInstall pushes to two local gems repos and drives stock
+// bundler through a virtual over both: merged versions, member order winning a
+// duplicate version, and downloads redirected to the owning member.
+func TestVirtualGemsInstall(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; run via scripts/docker-e2e.sh")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+
+	id := time.Now().UnixNano()
+	a, b, virt := fmt.Sprintf("e2e-gems-a-%d", id), fmt.Sprintf("e2e-gems-b-%d", id), fmt.Sprintf("e2e-gems-v-%d", id)
+	for _, name := range []string{a, b} {
+		createRepo(t, fmt.Sprintf(`{"name":%q,"package_type":"gems","repo_type":"local"}`, name))
+		defer deleteRepo(t, name)
+	}
+	createVirtual(t, fmt.Sprintf(`{"name":%q,"package_type":"gems","members":[%q,%q]}`, virt, a, b))
+	defer deleteVirtual(t, virt)
+
+	base := strings.TrimRight(internal, "/")
+	script := `set -euo pipefail
+export GEM_HOST_API_KEY=unused
+pub() { d=/w/src-$1-$2; mkdir -p $d/lib; cd $d
+  echo "module UnkinE2eHello; VERSION = '$1:$2'; end" > lib/unkin-e2e-hello.rb
+  printf 'Gem::Specification.new { |s| s.name = "unkin-e2e-hello"; s.version = "%s"; s.summary = "e2e"; s.authors = ["e2e"]; s.files = ["lib/unkin-e2e-hello.rb"] }' "$2" > g.gemspec
+  gem build g.gemspec >/dev/null 2>&1; gem push --host "$BASE/api/v1/local/$1" unkin-e2e-hello-$2.gem; }
+pub "$A" 0.1.0
+pub "$B" 0.1.0
+pub "$B" 0.2.0
+V="$BASE/api/v1/virtual/$V"
+echo "VERSIONS $(curl -s "$V/versions" | grep '^unkin-e2e-hello ' | cut -d' ' -f2)"
+mkdir -p /w/app && cd /w/app
+printf 'source "%s/"\ngem "unkin-e2e-hello", "0.1.0"\n' "$V" > Gemfile
+bundle install
+bundle exec ruby -e 'require "unkin-e2e-hello"; puts "REQ #{UnkinE2eHello::VERSION}"'
+echo "REDIRECT $(curl -s -o /dev/null -w '%{redirect_url}' "$V/gems/unkin-e2e-hello-0.2.0.gem")"`
+
+	out, err := exec.Command("docker", "run", "--rm", "--network", network,
+		"-e", "BASE="+base, "-e", "A="+a, "-e", "B="+b, "-e", "V="+virt,
+		"ruby:3.3", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("bundler run failed: %v\n%s", err, out)
+	}
+	for _, want := range []string{
+		"VERSIONS 0.1.0,0.2.0",
+		"REQ " + a + ":0.1.0",
+		"REDIRECT " + base + "/api/v1/local/" + b + "/gems/unkin-e2e-hello-0.2.0.gem",
+	} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q in bundler output:\n%s", want, out)
+		}
+	}
+}
diff --git a/e2e-docker/helm_local_test.go b/e2e-docker/helm_local_test.go
new file mode 100644
index 0000000..a0c9615
--- /dev/null
+++ b/e2e-docker/helm_local_test.go
@@ -0,0 +1,71 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestLocalHelmRealClient packages a chart with the real helm CLI, publishes it
+// to a helm local, then drives helm repo add/search/pull/template against the
+// local and against a helm virtual that has the local as a member.
+func TestLocalHelmRealClient(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := strings.TrimRight(os.Getenv("ARTIFACTAPI_INTERNAL"), "/")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; run via scripts/docker-e2e.sh")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+
+	createRepo(t, `{"name":"local-helm","package_type":"helm","repo_type":"local"}`)
+	defer deleteRepo(t, "local-helm")
+	createVirtual(t, `{"name":"vhelm","package_type":"helm","members":["local-helm"]}`)
+	defer deleteVirtual(t, "vhelm")
+
+	helm := func(script string) string {
+		t.Helper()
+		out, err := exec.Command("docker", "run", "--rm", "--network", network, "--entrypoint", "sh",
+			"alpine/helm:3.16.4", "-c", "set -eu; "+script).Output()
+		if err != nil {
+			stderr := ""
+			if ee, ok := err.(*exec.ExitError); ok {
+				stderr = string(ee.Stderr)
+			}
+			t.Fatalf("helm script failed: %v\n%s%s", err, out, stderr)
+		}
+		return string(out)
+	}
+
+	chart := helm("cd /tmp && helm create e2echart >/dev/null && helm package e2echart >/dev/null && cat e2echart-0.1.0.tgz")
+	uploadFile(t, "local-helm", "e2echart-0.1.0.tgz", []byte(chart), "application/gzip")
+
+	// Chart metadata is recorded asynchronously after upload; poll the index.
+	var body []byte
+	for deadline := time.Now().Add(15 * time.Second); time.Now().Before(deadline); time.Sleep(500 * time.Millisecond) {
+		var resp *http.Response
+		resp, body = doRequest(t, http.MethodGet, api("/api/v1/local/local-helm/index.yaml"), nil, "")
+		if resp.StatusCode == http.StatusOK && strings.Contains(string(body), "e2echart-0.1.0.tgz") {
+			break
+		}
+	}
+	if !strings.Contains(string(body), "e2echart-0.1.0.tgz") || !strings.Contains(string(body), "digest: ") {
+		t.Fatalf("index.yaml never listed the chart:\n%s", body)
+	}
+
+	for _, repoURL := range []string{internal + "/api/v1/local/local-helm", internal + "/api/v1/virtual/vhelm"} {
+		out := helm("helm repo add e2e " + repoURL + " >/dev/null && " +
+			"helm search repo e2e/e2echart && " +
+			"cd /tmp && helm pull e2e/e2echart --version 0.1.0 && " +
+			"helm template rel e2echart-0.1.0.tgz | grep -c 'kind: Deployment'")
+		if !strings.Contains(out, "e2e/e2echart") || !strings.Contains(out, "0.1.0") || !strings.HasSuffix(strings.TrimSpace(out), "1") {
+			t.Fatalf("helm via %s:\n%s", repoURL, out)
+		}
+	}
+}
diff --git a/e2e-docker/npm_local_test.go b/e2e-docker/npm_local_test.go
new file mode 100644
index 0000000..9455611
--- /dev/null
+++ b/e2e-docker/npm_local_test.go
@@ -0,0 +1,62 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestLocalNPMPublishInstall drives a stock npm client against a local npm
+// repo: publish unscoped and scoped packages, install and require() them in a
+// fresh project, publish a second version, and reject a republish.
+func TestLocalNPMPublishInstall(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; run via scripts/docker-e2e.sh")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+
+	name := fmt.Sprintf("e2e-npm-local-%d", time.Now().UnixNano())
+	createRepo(t, fmt.Sprintf(`{"name":%q,"package_type":"npm","repo_type":"local"}`, name))
+	defer deleteRepo(t, name)
+
+	reg := strings.TrimRight(internal, "/") + "/api/v1/local/" + name + "/"
+	script := `set -euo pipefail
+printf 'registry=%s\n%s:_authToken=unused\n' "$REG" "${REG#http:}" > ~/.npmrc
+mk() { d="/w/src/$1-$2"; mkdir -p "$d"; cd "$d"
+  printf '{"name":"%s","version":"%s","main":"index.js"}' "$1" "$2" > package.json
+  echo "module.exports = '$1@$2';" > index.js; }
+mk e2e-npm-plain 1.0.0 && npm publish
+mk @e2e/npm-scoped 1.0.0 && npm publish
+mk e2e-npm-plain 1.0.0
+if npm publish 2>/dev/null; then echo "republish accepted"; exit 1; fi
+mkdir -p /w/app && cd /w/app && npm init -y >/dev/null
+npm install --no-audit --cache /tmp/fresh-cache e2e-npm-plain @e2e/npm-scoped
+node -e "console.log('REQ', require('e2e-npm-plain'), require('@e2e/npm-scoped'))"
+mk e2e-npm-plain 1.1.0 && npm publish
+echo "VERSIONS $(npm view e2e-npm-plain versions --json | tr -d ' \n')"
+echo "LATEST $(npm view e2e-npm-plain dist-tags.latest)"`
+
+	out, err := exec.Command("docker", "run", "--rm", "--network", network,
+		"-e", "REG="+reg, "node:22", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("npm client run failed: %v\n%s", err, out)
+	}
+	for _, want := range []string{
+		"REQ e2e-npm-plain@1.0.0 @e2e/npm-scoped@1.0.0",
+		`VERSIONS ["1.0.0","1.1.0"]`,
+		"LATEST 1.1.0",
+	} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q in npm output:\n%s", want, out)
+		}
+	}
+}
diff --git a/e2e-docker/npm_virtual_test.go b/e2e-docker/npm_virtual_test.go
new file mode 100644
index 0000000..31f92b0
--- /dev/null
+++ b/e2e-docker/npm_virtual_test.go
@@ -0,0 +1,68 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestVirtualNPMInstall publishes to two local npm repos and drives a stock
+// npm client through a virtual over both: merged versions and dist-tags, and
+// an install whose tarballs resolve via the virtual's member redirect.
+func TestVirtualNPMInstall(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; run via scripts/docker-e2e.sh")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+
+	id := time.Now().UnixNano()
+	a, b, virt := fmt.Sprintf("e2e-npm-a-%d", id), fmt.Sprintf("e2e-npm-b-%d", id), fmt.Sprintf("e2e-npm-v-%d", id)
+	for _, name := range []string{a, b} {
+		createRepo(t, fmt.Sprintf(`{"name":%q,"package_type":"npm","repo_type":"local"}`, name))
+		defer deleteRepo(t, name)
+	}
+	createVirtual(t, fmt.Sprintf(`{"name":%q,"package_type":"npm","members":[%q,%q]}`, virt, a, b))
+	defer deleteVirtual(t, virt)
+
+	base := strings.TrimRight(internal, "/")
+	script := `set -euo pipefail
+pub() { d="/w/src/$2-$3-$1"; mkdir -p "$d"; cd "$d"
+  printf '{"name":"%s","version":"%s","main":"index.js"}' "$2" "$3" > package.json
+  echo "module.exports = '$1:$2@$3';" > index.js
+  printf 'registry=%s\n%s:_authToken=unused\n' "$BASE/api/v1/local/$1/" "${BASE#http:}/api/v1/local/$1/" > .npmrc
+  npm publish; }
+pub "$A" @e2e/virt 1.0.0
+pub "$B" @e2e/virt 1.0.0
+pub "$B" @e2e/virt 1.1.0
+mkdir -p /w/app && cd /w/app && npm init -y >/dev/null
+echo "registry=$BASE/api/v1/virtual/$V/" > .npmrc
+echo "VERSIONS $(npm view @e2e/virt versions --json | tr -d ' \n')"
+npm install --no-audit --cache /tmp/fresh-cache @e2e/virt@1.0.0
+node -e "console.log('REQ', require('@e2e/virt'))"
+echo "RESOLVED $(node -p "require('./package-lock.json').packages['node_modules/@e2e/virt'].resolved")"`
+
+	out, err := exec.Command("docker", "run", "--rm", "--network", network,
+		"-e", "BASE="+base, "-e", "A="+a, "-e", "B="+b, "-e", "V="+virt,
+		"node:22", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("npm client run failed: %v\n%s", err, out)
+	}
+	for _, want := range []string{
+		`VERSIONS ["1.0.0","1.1.0"]`,
+		"REQ " + a + ":@e2e/virt@1.0.0",
+		"RESOLVED " + base + "/api/v1/virtual/" + virt + "/" + a + "/@e2e/virt/-/virt-1.0.0.tgz",
+	} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q in npm output:\n%s", want, out)
+		}
+	}
+}
diff --git a/e2e-docker/puppet_local_test.go b/e2e-docker/puppet_local_test.go
new file mode 100644
index 0000000..9c5acaa
--- /dev/null
+++ b/e2e-docker/puppet_local_test.go
@@ -0,0 +1,88 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+const puppetHelloMetadata = `{"name":"unkin-hello","version":"0.1.0","author":"unkin","summary":"e2e","license":"Apache-2.0","source":"https://example.invalid","dependencies":[{"name":"puppetlabs/stdlib","version_requirement":">= 4.0.0 < 10.0.0"}]}`
+
+func puppetModuleTarball(t *testing.T) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	tw := tar.NewWriter(zw)
+	for name, body := range map[string]string{
+		"unkin-hello-0.1.0/metadata.json":     puppetHelloMetadata,
+		"unkin-hello-0.1.0/manifests/init.pp": "class hello {}\n",
+	} {
+		if err := tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(body)), ModTime: time.Now()}); err != nil {
+			t.Fatal(err)
+		}
+		_, _ = tw.Write([]byte(body))
+	}
+	_ = tw.Close()
+	_ = zw.Close()
+	return buf.Bytes()
+}
+
+// TestLocalPuppetRealClient publishes a module to a puppet local and installs
+// it with the real r10k and puppet module tool. The stdlib dependency is not on
+// a local-only forge, so puppet runs with --ignore-dependencies.
+func TestLocalPuppetRealClient(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := strings.TrimRight(os.Getenv("ARTIFACTAPI_INTERNAL"), "/")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; run via scripts/docker-e2e.sh")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+
+	createRepo(t, `{"name":"local-puppet","package_type":"puppet","repo_type":"local"}`)
+	defer deleteRepo(t, "local-puppet")
+
+	upload := api("/api/v2/remotes/local-puppet/files/unkin-hello-0.1.0.tar.gz")
+	defer doRequest(t, http.MethodDelete, api("/api/v2/remotes/local-puppet/files/v3/files/unkin-hello-0.1.0.tar.gz"), nil, "")
+	tarball := puppetModuleTarball(t)
+	if resp, body := doRequest(t, http.MethodPut, upload, tarball, "application/gzip"); resp.StatusCode != http.StatusCreated {
+		t.Fatalf("upload: %d %s", resp.StatusCode, body)
+	}
+	if resp, _ := doRequest(t, http.MethodPut, upload, tarball, "application/gzip"); resp.StatusCode != http.StatusConflict {
+		t.Fatalf("re-upload of an existing version: %d, want 409", resp.StatusCode)
+	}
+	if resp, body := getEventually(t, api("/api/v1/local/local-puppet/v3/releases/unkin-hello-0.1.0"), 15*time.Second); resp.StatusCode != http.StatusOK || !strings.Contains(string(body), `"file_md5"`) {
+		t.Fatalf("release never indexed: %d %s", resp.StatusCode, body)
+	}
+
+	forge := internal + "/api/v1/local/local-puppet"
+	run := func(image, script string) string {
+		t.Helper()
+		out, err := exec.Command("docker", "run", "--rm", "--network", network, "--entrypoint", "sh", image, "-c", "set -eu; "+script).CombinedOutput()
+		if err != nil {
+			t.Fatalf("%s failed: %v\n%s", image, err, out)
+		}
+		return string(out)
+	}
+
+	out := run("ghcr.io/voxpupuli/r10k:latest", "cd /tmp && printf 'forge:\\n  baseurl: "+forge+"\\n' > r10k.yaml && "+
+		"printf \"forge '"+forge+"'\\nmod 'unkin-hello', '0.1.0'\\n\" > Puppetfile && "+
+		"r10k puppetfile install -c r10k.yaml --verbose && cat modules/hello/metadata.json")
+	if !strings.Contains(out, `"unkin-hello"`) {
+		t.Fatalf("r10k did not install unkin-hello:\n%s", out)
+	}
+
+	out = run("ghcr.io/openvoxproject/openvoxagent:latest", "export PATH=/opt/puppetlabs/bin:$PATH; puppet module install unkin-hello --module_repository "+forge+" --ignore-dependencies --target-dir /tmp/mods && puppet module list --color=false --modulepath /tmp/mods")
+	if !strings.Contains(out, "unkin-hello (v0.1.0)") {
+		t.Fatalf("puppet module install did not install unkin-hello:\n%s", out)
+	}
+}
diff --git a/e2e/head_test.go b/e2e/head_test.go
new file mode 100644
index 0000000..e222551
--- /dev/null
+++ b/e2e/head_test.go
@@ -0,0 +1,182 @@
+//go:build e2e
+
+package e2e
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+)
+
+// assertHeadMatchesGet checks HEAD returns GET's status, type and length with no body.
+func assertHeadMatchesGet(t *testing.T, url string) {
+	t.Helper()
+	get, err := http.Get(url)
+	if err != nil {
+		t.Fatalf("GET: %v", err)
+	}
+	body, _ := io.ReadAll(get.Body)
+	get.Body.Close()
+	if get.StatusCode != http.StatusOK {
+		t.Fatalf("GET %s: %d %s", url, get.StatusCode, body)
+	}
+
+	head, err := http.Head(url)
+	if err != nil {
+		t.Fatalf("HEAD: %v", err)
+	}
+	hb, _ := io.ReadAll(head.Body)
+	head.Body.Close()
+	if head.StatusCode != http.StatusOK {
+		t.Fatalf("HEAD %s: got %d, want 200", url, head.StatusCode)
+	}
+	if len(hb) != 0 {
+		t.Errorf("HEAD returned a %d-byte body", len(hb))
+	}
+	for _, h := range []string{"Content-Type", "Cache-Control", "Vary"} {
+		if head.Header.Get(h) != get.Header.Get(h) {
+			t.Errorf("HEAD %s %q, GET %q", h, head.Header.Get(h), get.Header.Get(h))
+		}
+	}
+	if head.ContentLength != int64(len(body)) {
+		t.Errorf("HEAD Content-Length %d, GET body %d bytes", head.ContentLength, len(body))
+	}
+}
+
+func TestProxyHeadNuGetRewritten(t *testing.T) {
+	var upstream *httptest.Server
+	upstream = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]any{"version": "3.0.0", "resources": []map[string]string{
+			{"@id": upstream.URL + "/v3-flatcontainer/", "@type": "PackageBaseAddress/3.0.0"},
+		}})
+	}))
+	defer upstream.Close()
+
+	createRemote(t, mustFormat(`{"name": "head-nuget", "package_type": "nuget", "base_url": %q}`, upstream.URL+"/v3/index.json"))
+	defer deleteRemote(t, "head-nuget")
+
+	url := apiURL("/api/v1/remote/head-nuget/index.json")
+	assertHeadMatchesGet(t, url)
+
+	req, _ := http.NewRequest(http.MethodHead, url, nil)
+	req.Host = "evil.example:"
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusBadRequest {
+		t.Errorf("HEAD with invalid Host: got %d, want 400", resp.StatusCode)
+	}
+}
+
+func TestProxyHeadGitHubRPMRepodata(t *testing.T) {
+	rpm := testsupport.MinimalRPM("demo", "1.2", "3", "x86_64")
+	var gh *httptest.Server
+	mux := http.NewServeMux()
+	mux.HandleFunc("/repos/acme/tools/releases", func(w http.ResponseWriter, r *http.Request) {
+		if p := r.URL.Query().Get("page"); p != "" && p != "1" {
+			w.Write([]byte("[]"))
+			return
+		}
+		json.NewEncoder(w).Encode([]map[string]any{{"tag_name": "v1.2-3", "assets": []map[string]any{{
+			"name":                 "demo-1.2-3.x86_64.rpm",
+			"size":                 len(rpm),
+			"browser_download_url": gh.URL + "/acme/tools/releases/download/v1.2-3/demo-1.2-3.x86_64.rpm",
+		}}}})
+	})
+	mux.HandleFunc("/acme/tools/releases/download/", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Length", strconv.Itoa(len(rpm)))
+		w.Write(rpm)
+	})
+	gh = httptest.NewServer(mux)
+	defer gh.Close()
+
+	createRemote(t, mustFormat(`{"name": "head-ghrpm", "package_type": "github_rpm", "base_url": %q, "releases_remote": "github"}`, gh.URL+"/repos/acme/tools"))
+	defer deleteRemote(t, "head-ghrpm")
+
+	url := apiURL("/api/v1/remote/head-ghrpm/repodata/repomd.xml")
+	deadline := time.Now().Add(30 * time.Second)
+	for {
+		if _, status := getBody(t, url); status == http.StatusOK || time.Now().After(deadline) {
+			break
+		}
+		time.Sleep(500 * time.Millisecond)
+	}
+	assertHeadMatchesGet(t, url)
+}
+
+func TestProxyHeadNpmUncachedPackument(t *testing.T) {
+	const abbreviated = "application/vnd.npm.install-v1+json"
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		doc := map[string]any{"name": "left-pad", "versions": map[string]any{"1.3.0": map[string]any{}}}
+		if r.Header.Get("Accept") != abbreviated {
+			doc["readme"] = strings.Repeat("full packument ", 200)
+		}
+		json.NewEncoder(w).Encode(doc)
+	}))
+	defer upstream.Close()
+
+	createRemote(t, mustFormat(`{"name": "head-npm", "package_type": "npm", "base_url": %q}`, upstream.URL))
+	defer deleteRemote(t, "head-npm")
+
+	url := apiURL("/api/v1/remote/head-npm/left-pad")
+	do := func(method string) (*http.Response, []byte) {
+		req, _ := http.NewRequest(method, url, nil)
+		req.Header.Set("Accept", abbreviated)
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("%s: %v", method, err)
+		}
+		defer resp.Body.Close()
+		b, _ := io.ReadAll(resp.Body)
+		return resp, b
+	}
+	head, _ := do(http.MethodHead)
+	get, body := do(http.MethodGet)
+	if head.StatusCode != http.StatusOK || get.StatusCode != http.StatusOK {
+		t.Fatalf("HEAD %d, GET %d", head.StatusCode, get.StatusCode)
+	}
+	if head.ContentLength != int64(len(body)) {
+		t.Errorf("uncached HEAD Content-Length %d, GET body %d bytes", head.ContentLength, len(body))
+	}
+}
+
+func TestProxyHeadNonRewritingUsesUpstreamHead(t *testing.T) {
+	methods := make(chan string, 4)
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		methods <- r.Method
+		w.Header().Set("Content-Type", "text/xml")
+		w.Write([]byte("<repomd/>"))
+	}))
+	defer upstream.Close()
+
+	createRemote(t, mustFormat(`{"name": "head-rpm", "package_type": "rpm", "base_url": %q}`, upstream.URL))
+	defer deleteRemote(t, "head-rpm")
+
+	resp, err := http.Head(apiURL("/api/v1/remote/head-rpm/repodata/repomd.xml"))
+	if err != nil {
+		t.Fatalf("HEAD: %v", err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusOK || resp.Header.Get("X-Artifact-Source") != "remote" {
+		t.Fatalf("HEAD %d source %q", resp.StatusCode, resp.Header.Get("X-Artifact-Source"))
+	}
+	close(methods)
+	var seen []string
+	for m := range methods {
+		seen = append(seen, m)
+	}
+	if len(seen) != 1 || seen[0] != http.MethodHead {
+		t.Errorf("upstream saw %v, want a single HEAD", seen)
+	}
+}
diff --git a/e2e/scheme_test.go b/e2e/scheme_test.go
new file mode 100644
index 0000000..4ab636f
--- /dev/null
+++ b/e2e/scheme_test.go
@@ -0,0 +1,59 @@
+//go:build e2e
+
+package e2e
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+func getForwardedHTTPS(t *testing.T, url string) *http.Response {
+	t.Helper()
+	req, _ := http.NewRequest(http.MethodGet, url, nil)
+	req.Header.Set("X-Forwarded-Proto", "https")
+	client := &http.Client{CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("GET %s: %v", url, err)
+	}
+	return resp
+}
+
+func TestForwardedProtoCargoConfig(t *testing.T) {
+	createRemote(t, `{"name": "scheme-cargo", "package_type": "cargo", "base_url": "https://index.crates.io"}`)
+	defer deleteRemote(t, "scheme-cargo")
+
+	resp := getForwardedHTTPS(t, apiURL("/api/v1/remote/scheme-cargo/config.json"))
+	defer resp.Body.Close()
+	var cfg map[string]string
+	if err := json.NewDecoder(resp.Body).Decode(&cfg); err != nil {
+		t.Fatal(err)
+	}
+	if want := "https://" + strings.TrimPrefix(baseURL, "http://") + "/api/v1/remote/scheme-cargo/"; !strings.HasPrefix(cfg["dl"], want) {
+		t.Errorf("dl = %q, want prefix %q", cfg["dl"], want)
+	}
+}
+
+func TestForwardedProtoVirtualRedirect(t *testing.T) {
+	createRemote(t, `{"name": "scheme-rpm", "package_type": "rpm", "base_url": "https://rpm.example.com"}`)
+	defer deleteRemote(t, "scheme-rpm")
+	resp, err := http.Post(apiURL("/api/v2/virtuals"), "application/json",
+		strings.NewReader(`{"name": "scheme-virt", "package_type": "rpm", "members": ["scheme-rpm"]}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusCreated {
+		t.Fatalf("create virtual: status %d", resp.StatusCode)
+	}
+	defer deleteRequest(t, apiURL("/api/v2/virtuals/scheme-virt"))
+
+	resp = getForwardedHTTPS(t, apiURL("/api/v1/virtual/scheme-virt/scheme-rpm/Packages/a.rpm"))
+	resp.Body.Close()
+	loc := resp.Header.Get("Location")
+	if want := "https://" + strings.TrimPrefix(baseURL, "http://") + "/api/v1/remote/scheme-rpm/Packages/a.rpm"; resp.StatusCode != http.StatusFound || loc != want {
+		t.Errorf("redirect = %d %q, want 302 %q", resp.StatusCode, loc, want)
+	}
+}
diff --git a/internal/api/terraform/registry.go b/internal/api/terraform/registry.go
index 7aee9de..cd69aca 100644
--- a/internal/api/terraform/registry.go
+++ b/internal/api/terraform/registry.go
@@ -13,6 +13,7 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
+	v1 "git.unkin.net/unkin/artifactapi/internal/api/v1"
 	"git.unkin.net/unkin/artifactapi/internal/database"
 	tfprov "git.unkin.net/unkin/artifactapi/internal/provider/terraform"
 	"git.unkin.net/unkin/artifactapi/internal/tfsign"
@@ -290,12 +291,5 @@ func writeJSON(w http.ResponseWriter, v any) {
 }
 
 func baseURL(r *http.Request) string {
-	scheme := "http"
-	if r.TLS != nil {
-		scheme = "https"
-	}
-	if fwd := r.Header.Get("X-Forwarded-Proto"); fwd != "" {
-		scheme = fwd
-	}
-	return scheme + "://" + r.Host
+	return v1.Scheme(r) + "://" + r.Host
 }
diff --git a/internal/api/v1/gems.go b/internal/api/v1/gems.go
new file mode 100644
index 0000000..912777f
--- /dev/null
+++ b/internal/api/v1/gems.go
@@ -0,0 +1,308 @@
+package v1
+
+import (
+	"cmp"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"maps"
+	"net/http"
+	"net/url"
+	"slices"
+	"strings"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/provider/gems"
+	"git.unkin.net/unkin/artifactapi/internal/virtual"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// Local gems repos speak the RubyGems push/yank API and compact index. Per gem:
+//   gems/<full>.gem                         package (immutable)
+//   quick/Marshal.4.8/<full>.gemspec.rz     marshalled spec (immutable)
+//   _index/<name>/<full>                    compact index /info line; gates visibility
+//   _yanked/<name>/<full>                   yank tombstone; blocks re-push of the version
+
+var (
+	gemsMaxPushBytes int64 = 256 << 20
+	gemsLockWait           = 30 * time.Second
+)
+
+const (
+	gemsIndexPrefix  = "_index/"
+	gemsYankedPrefix = "_yanked/"
+)
+
+func gemsText(w http.ResponseWriter, status int, msg string) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	w.WriteHeader(status)
+	_, _ = io.WriteString(w, msg)
+}
+
+func (h *ProxyHandler) localGemsRemote(w http.ResponseWriter, r *http.Request) (*models.Remote, bool) {
+	remote, err := h.db.GetRemote(r.Context(), chi.URLParam(r, "localName"))
+	if err != nil || remote.RepoType != models.RepoTypeLocal || remote.PackageType != models.PackageGems {
+		gemsText(w, http.StatusMethodNotAllowed, "only supported on local gems repositories")
+		return nil, false
+	}
+	return remote, true
+}
+
+// lockGemVersion serialises push and yank of one gem version across replicas.
+func (h *ProxyHandler) lockGemVersion(w http.ResponseWriter, r *http.Request, repo, full string) (func(), bool) {
+	unlock, err := h.engine.Lock(r.Context(), repo, "_gemlock/"+full, gemsLockWait, 5*time.Minute)
+	if err != nil {
+		gemsText(w, http.StatusServiceUnavailable, full+" is being pushed or yanked, retry")
+		return nil, false
+	}
+	return unlock, true
+}
+
+func (h *ProxyHandler) handleLocalPost(w http.ResponseWriter, r *http.Request) {
+	if chi.URLParam(r, "*") != "api/v1/gems" {
+		gemsText(w, http.StatusNotFound, "not found")
+		return
+	}
+	remote, ok := h.localGemsRemote(w, r)
+	if !ok {
+		return
+	}
+	gem, err := io.ReadAll(http.MaxBytesReader(w, r.Body, gemsMaxPushBytes))
+	if err != nil {
+		gemsText(w, http.StatusRequestEntityTooLarge, fmt.Sprintf("gem exceeds %d bytes", gemsMaxPushBytes))
+		return
+	}
+	spec, err := gems.ParseGem(gem)
+	if err != nil {
+		gemsText(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	quick, err := gems.QuickSpec(spec)
+	if err != nil {
+		gemsText(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	full := spec.FullName()
+	unlock, ok := h.lockGemVersion(w, r, remote.Name, full)
+	if !ok {
+		return
+	}
+	defer unlock()
+	conflict := func() {
+		gemsText(w, http.StatusConflict, fmt.Sprintf("%s already exists; overwrites are not allowed", full))
+	}
+	index := gemsIndexPrefix + spec.Name + "/" + full
+	for _, p := range []string{gemsYankedPrefix + spec.Name + "/" + full, index} {
+		f, err := h.db.GetLocalFile(r.Context(), remote.Name, p)
+		if err != nil {
+			gemsText(w, http.StatusInternalServerError, err.Error())
+			return
+		}
+		if f != nil && p == index {
+			conflict()
+			return
+		}
+		if f != nil {
+			gemsText(w, http.StatusConflict, fmt.Sprintf("%s was yanked; re-pushing a yanked version is not allowed", full))
+			return
+		}
+	}
+	// The version is not live, so on failure every path is an invisible leftover and safe to drop.
+	paths := []string{"gems/" + full + ".gem", "quick/Marshal.4.8/" + full + ".gemspec.rz", index}
+	fail := func(status int, msg string) {
+		for _, p := range paths {
+			if err := h.db.DeleteLocalFile(context.WithoutCancel(r.Context()), remote.Name, p); err != nil {
+				slog.Error("gem push cleanup failed", "repo", remote.Name, "path", p, "error", err)
+			}
+		}
+		gemsText(w, status, msg)
+	}
+	// The index line gates visibility, so it is written last.
+	for _, f := range []struct {
+		path string
+		data []byte
+	}{
+		{paths[0], gem},
+		{paths[1], quick},
+	} {
+		ok, err := h.npmStoreImmutable(r.Context(), remote.Name, f.path, f.data, "application/octet-stream")
+		if err != nil {
+			fail(http.StatusInternalServerError, err.Error())
+			return
+		}
+		if !ok {
+			fail(http.StatusConflict, fmt.Sprintf("%s already exists; overwrites are not allowed", full))
+			return
+		}
+	}
+	line := gems.InfoLine(spec, gem)
+	if _, err := h.npmStore(r.Context(), remote.Name, index, []byte(line), "text/plain", false); err != nil {
+		fail(http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	slog.Info("local gem pushed", "repo", remote.Name, "gem", full)
+	gemsText(w, http.StatusOK, "Successfully registered gem: "+spec.Name+" ("+spec.Version+")")
+}
+
+func (h *ProxyHandler) handleLocalDelete(w http.ResponseWriter, r *http.Request) {
+	if chi.URLParam(r, "*") != "api/v1/gems/yank" {
+		gemsText(w, http.StatusNotFound, "not found")
+		return
+	}
+	remote, ok := h.localGemsRemote(w, r)
+	if !ok {
+		return
+	}
+	body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, 64<<10))
+	if err != nil {
+		gemsText(w, http.StatusRequestEntityTooLarge, "yank body too large")
+		return
+	}
+	form, err := url.ParseQuery(string(body))
+	if err != nil {
+		gemsText(w, http.StatusBadRequest, "invalid form body")
+		return
+	}
+	for k, v := range r.URL.Query() {
+		if form.Get(k) == "" {
+			form[k] = v
+		}
+	}
+	spec := &gems.Spec{Name: form.Get("gem_name"), Version: form.Get("version"), Platform: form.Get("platform")}
+	if spec.Platform == "" {
+		spec.Platform = "ruby"
+	}
+	if !gems.NameRe.MatchString(spec.Name) || !gems.VersionRe.MatchString(spec.Version) || !gems.PlatformRe.MatchString(spec.Platform) {
+		gemsText(w, http.StatusBadRequest, "invalid gem_name, version or platform")
+		return
+	}
+
+	full := spec.FullName()
+	unlock, ok := h.lockGemVersion(w, r, remote.Name, full)
+	if !ok {
+		return
+	}
+	defer unlock()
+	index := gemsIndexPrefix + spec.Name + "/" + full
+	existing, err := h.db.GetLocalFile(r.Context(), remote.Name, index)
+	if err != nil {
+		gemsText(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if existing == nil {
+		gemsText(w, http.StatusNotFound, "The version "+spec.Version+" does not exist")
+		return
+	}
+	// The tombstone keeps the yanked line and is written before any delete.
+	line, err := h.readLocalBlob(r.Context(), existing.ContentHash)
+	if err != nil {
+		gemsText(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if _, err := h.npmStore(r.Context(), remote.Name, gemsYankedPrefix+spec.Name+"/"+full, line, "text/plain", false); err != nil && !errors.Is(err, database.ErrAlreadyExists) {
+		gemsText(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	for _, p := range []string{index, "gems/" + full + ".gem", "quick/Marshal.4.8/" + full + ".gemspec.rz"} {
+		if err := h.db.DeleteLocalFile(context.WithoutCancel(r.Context()), remote.Name, p); err != nil {
+			gemsText(w, http.StatusInternalServerError, err.Error())
+			return
+		}
+	}
+	slog.Info("local gem yanked", "repo", remote.Name, "gem", full)
+	gemsText(w, http.StatusOK, "Successfully deleted gem: "+spec.Name+" ("+spec.Version+")")
+}
+
+// isGemsIndexPath reports whether path is a compact index document.
+func isGemsIndexPath(path string) bool {
+	return path == "versions" || path == "names" || strings.HasPrefix(path, "info/")
+}
+
+func (h *ProxyHandler) serveLocalGemsIndex(w http.ResponseWriter, r *http.Request, remote *models.Remote, path string) {
+	body, err := h.LocalGemsIndex(r.Context(), remote.Name, path)
+	if errors.Is(err, virtual.ErrNotFound) {
+		gemsText(w, http.StatusNotFound, "not found")
+		return
+	}
+	if err != nil {
+		gemsText(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	w.Header().Set("X-Artifact-Source", "local")
+	gemsText(w, http.StatusOK, string(body))
+}
+
+// LocalGemsIndex builds a local gems repo's versions, names or info/<gem>
+// document, or returns virtual.ErrNotFound.
+func (h *ProxyHandler) LocalGemsIndex(ctx context.Context, repo, path string) ([]byte, error) {
+	if name, ok := strings.CutPrefix(path, "info/"); ok {
+		if !gems.NameRe.MatchString(name) {
+			return nil, virtual.ErrNotFound
+		}
+		lines, err := h.localGemsLines(ctx, repo, gemsIndexPrefix+name+"/")
+		if err != nil {
+			return nil, err
+		}
+		if len(lines[name]) == 0 {
+			return nil, virtual.ErrNotFound
+		}
+		return gems.InfoBody(lines[name]), nil
+	}
+	if path != "versions" && path != "names" {
+		return nil, virtual.ErrNotFound
+	}
+	lines, err := h.localGemsLines(ctx, repo, gemsIndexPrefix)
+	if err != nil {
+		return nil, err
+	}
+	names := slices.Sorted(maps.Keys(lines))
+	var b strings.Builder
+	if path == "names" {
+		b.WriteString("---\n")
+		for _, n := range names {
+			b.WriteString(n + "\n")
+		}
+		return []byte(b.String()), nil
+	}
+	b.WriteString(gems.VersionsHeader(time.Now()))
+	for _, n := range names {
+		b.WriteString(gems.VersionsLine(n, gems.InfoBody(lines[n])) + "\n")
+	}
+	return []byte(b.String()), nil
+}
+
+// localGemsLines returns /info lines per gem name in push order.
+func (h *ProxyHandler) localGemsLines(ctx context.Context, repo, prefix string) (map[string][]string, error) {
+	files, err := h.db.ListLocalFilesByPrefix(ctx, repo, prefix)
+	if err != nil {
+		return nil, err
+	}
+	slices.SortFunc(files, func(a, b database.LocalFile) int { return cmp.Compare(a.ID, b.ID) })
+	out := map[string][]string{}
+	for _, f := range files {
+		// LIKE treats '_' as a wildcard, so the prefix match can over-select.
+		rest, ok := strings.CutPrefix(f.FilePath, prefix)
+		if !ok {
+			continue
+		}
+		name := strings.TrimPrefix(prefix, gemsIndexPrefix)
+		if name == "" {
+			name, _, _ = strings.Cut(rest, "/")
+		} else {
+			name = strings.TrimSuffix(name, "/")
+		}
+		line, err := h.readLocalBlob(ctx, f.ContentHash)
+		if err != nil {
+			return nil, err
+		}
+		out[name] = append(out[name], string(line))
+	}
+	return out, nil
+}
diff --git a/internal/api/v1/gems_handler_test.go b/internal/api/v1/gems_handler_test.go
new file mode 100644
index 0000000..c1cc0cc
--- /dev/null
+++ b/internal/api/v1/gems_handler_test.go
@@ -0,0 +1,254 @@
+package v1
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"context"
+	"crypto/md5"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/cache"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func testGemFile(t *testing.T, name, version, platform string) []byte {
+	t.Helper()
+	meta := fmt.Sprintf(`--- !ruby/object:Gem::Specification
+name: %s
+version: !ruby/object:Gem::Version
+  version: %s
+platform: %s
+dependencies:
+- !ruby/object:Gem::Dependency
+  name: rack
+  requirement: !ruby/object:Gem::Requirement
+    requirements:
+    - - "~>"
+      - !ruby/object:Gem::Version
+        version: '3.0'
+  type: :runtime
+  prerelease: false
+rubygems_version: 3.5.22
+specification_version: 4
+summary: test
+`, name, version, platform)
+	var gz bytes.Buffer
+	zw := gzip.NewWriter(&gz)
+	_, _ = zw.Write([]byte(meta))
+	_ = zw.Close()
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	_ = tw.WriteHeader(&tar.Header{Name: "metadata.gz", Mode: 0o444, Size: int64(gz.Len())})
+	_, _ = tw.Write(gz.Bytes())
+	_ = tw.Close()
+	return buf.Bytes()
+}
+
+func sha256Hex(b []byte) string {
+	s := sha256.Sum256(b)
+	return hex.EncodeToString(s[:])
+}
+
+func TestGemsPushIndexYank(t *testing.T) {
+	h, srv := npmTestServer(t)
+	repo := npmRepo(t, h, models.PackageGems)
+	base := srv.URL + "/api/v1/local/" + repo + "/"
+
+	g1 := testGemFile(t, "hello_gem", "0.1.0", "ruby")
+	g2 := testGemFile(t, "hello_gem", "0.2.0", "ruby")
+	gj := testGemFile(t, "hello_gem", "0.2.0", "java")
+	other := testGemFile(t, "hello-gem", "1.0.0", "ruby")
+	for _, g := range [][]byte{g1, g2, gj, other} {
+		if code, body := npmDo(t, http.MethodPost, base+"api/v1/gems", string(g)); code != http.StatusOK {
+			t.Fatalf("push = %d: %s", code, body)
+		}
+	}
+	if code, _ := npmDo(t, http.MethodPost, base+"api/v1/gems", string(g1)+"x"); code != http.StatusConflict {
+		t.Fatalf("repush with different bytes = %d, want 409", code)
+	}
+	if code, _ := npmDo(t, http.MethodPost, base+"api/v1/gems", string(g1)); code != http.StatusConflict {
+		t.Fatalf("identical repush = %d, want 409", code)
+	}
+	if code, _ := npmDo(t, http.MethodPost, base+"api/v1/gems", "not a gem"); code != http.StatusBadRequest {
+		t.Fatalf("garbage push = %d, want 400", code)
+	}
+
+	code, info := npmDo(t, http.MethodGet, base+"info/hello_gem", "")
+	want := "---\n0.1.0 rack:~> 3.0|checksum:" + sha256Hex(g1) + "\n0.2.0 rack:~> 3.0|checksum:" + sha256Hex(g2) +
+		"\n0.2.0-java rack:~> 3.0|checksum:" + sha256Hex(gj) + "\n"
+	if code != http.StatusOK || info != want {
+		t.Fatalf("info = %d\n%q\nwant\n%q", code, info, want)
+	}
+	if code, _ := npmDo(t, http.MethodHead, base+"versions", ""); code != http.StatusOK {
+		t.Fatalf("HEAD versions = %d; gem probes the compact index with HEAD", code)
+	}
+	_, versions := npmDo(t, http.MethodGet, base+"versions", "")
+	head, body, ok := strings.Cut(versions, "\n---\n")
+	if !ok || !strings.HasPrefix(head, "created_at: ") {
+		t.Fatalf("versions header = %q", versions)
+	}
+	_, otherInfo := npmDo(t, http.MethodGet, base+"info/hello-gem", "")
+	wantBody := fmt.Sprintf("hello-gem 1.0.0 %x\nhello_gem 0.1.0,0.2.0,0.2.0-java %x\n", md5.Sum([]byte(otherInfo)), md5.Sum([]byte(info)))
+	if body != wantBody {
+		t.Fatalf("versions body =\n%q\nwant\n%q", body, wantBody)
+	}
+	if _, names := npmDo(t, http.MethodGet, base+"names", ""); names != "---\nhello-gem\nhello_gem\n" {
+		t.Fatalf("names = %q", names)
+	}
+	if code, got := npmDo(t, http.MethodGet, base+"gems/hello_gem-0.2.0-java.gem", ""); code != http.StatusOK || got != string(gj) {
+		t.Fatalf("download = %d", code)
+	}
+	if code, _ := npmDo(t, http.MethodGet, base+"quick/Marshal.4.8/hello_gem-0.1.0.gemspec.rz", ""); code != http.StatusOK {
+		t.Fatalf("quick spec = %d", code)
+	}
+	if code, _ := npmDo(t, http.MethodGet, base+"info/missing", ""); code != http.StatusNotFound {
+		t.Fatalf("missing info = %d", code)
+	}
+
+	yank := func(form string) int {
+		req, _ := http.NewRequest(http.MethodDelete, base+"api/v1/gems/yank", strings.NewReader(form))
+		req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		_ = resp.Body.Close()
+		return resp.StatusCode
+	}
+	if c := yank("gem_name=hello_gem&version=0.2.0&platform=java"); c != http.StatusOK {
+		t.Fatalf("yank = %d", c)
+	}
+	if c := yank("gem_name=hello_gem&version=0.2.0&platform=java"); c != http.StatusNotFound {
+		t.Fatalf("second yank = %d, want 404", c)
+	}
+	if c := yank("gem_name=../x&version=1"); c != http.StatusBadRequest {
+		t.Fatalf("bad yank = %d, want 400", c)
+	}
+	if _, info := npmDo(t, http.MethodGet, base+"info/hello_gem", ""); strings.Contains(info, "java") || !strings.Contains(info, "0.2.0 ") {
+		t.Fatalf("info after yank = %q", info)
+	}
+	if code, _ := npmDo(t, http.MethodGet, base+"gems/hello_gem-0.2.0-java.gem", ""); code != http.StatusNotFound {
+		t.Fatalf("yanked download = %d, want 404", code)
+	}
+	if _, v := npmDo(t, http.MethodGet, base+"versions", ""); strings.Contains(v, "java") || !strings.Contains(v, "hello_gem 0.1.0,0.2.0 ") {
+		t.Fatalf("versions after yank = %q", v)
+	}
+	for _, g := range []string{string(gj), string(gj) + "x"} {
+		if code, body := npmDo(t, http.MethodPost, base+"api/v1/gems", g); code != http.StatusConflict || !strings.Contains(body, "yanked") {
+			t.Fatalf("push after yank = %d %q, want 409", code, body)
+		}
+	}
+	if _, info := npmDo(t, http.MethodGet, base+"info/hello_gem", ""); strings.Contains(info, "java") {
+		t.Fatalf("info after rejected re-push = %q", info)
+	}
+
+	if c := yank("gem_name=hello-gem&version=1.0.0"); c != http.StatusOK {
+		t.Fatalf("yank last version = %d", c)
+	}
+	if code, _ := npmDo(t, http.MethodGet, base+"info/hello-gem", ""); code != http.StatusNotFound {
+		t.Fatalf("info for fully yanked gem = %d, want 404", code)
+	}
+	if _, names := npmDo(t, http.MethodGet, base+"names", ""); names != "---\nhello_gem\n" {
+		t.Fatalf("names after yanking every version = %q", names)
+	}
+}
+
+func TestGemsPushRejects(t *testing.T) {
+	h, srv := npmTestServer(t)
+	npmLocal := npmRepo(t, h, models.PackageNPM)
+	g := string(testGemFile(t, "g", "1.0.0", "ruby"))
+	if code, _ := npmDo(t, http.MethodPost, srv.URL+"/api/v1/local/"+npmLocal+"/api/v1/gems", g); code != http.StatusMethodNotAllowed {
+		t.Fatalf("push to npm local = %d, want 405", code)
+	}
+	repo := npmRepo(t, h, models.PackageGems)
+	if code, _ := npmDo(t, http.MethodPost, srv.URL+"/api/v1/local/"+repo+"/other", g); code != http.StatusNotFound {
+		t.Fatalf("push to other path = %d, want 404", code)
+	}
+	old := gemsMaxPushBytes
+	gemsMaxPushBytes = 64
+	defer func() { gemsMaxPushBytes = old }()
+	if code, _ := npmDo(t, http.MethodPost, srv.URL+"/api/v1/local/"+repo+"/api/v1/gems", g); code != http.StatusRequestEntityTooLarge {
+		t.Fatalf("oversized push = %d, want 413", code)
+	}
+}
+
+func TestGemsPushYankSerialised(t *testing.T) {
+	h, srv := npmTestServer(t)
+	repo := npmRepo(t, h, models.PackageGems)
+	base := srv.URL + "/api/v1/local/" + repo + "/"
+	g := string(testGemFile(t, "race", "1.0.0", "ruby"))
+	var wg sync.WaitGroup
+	for i := 0; i < 16; i++ {
+		wg.Add(2)
+		go func() {
+			defer wg.Done()
+			if code, body := npmDo(t, http.MethodPost, base+"api/v1/gems", g); code != http.StatusOK && code != http.StatusConflict {
+				t.Errorf("push = %d: %s", code, body)
+			}
+		}()
+		go func() {
+			defer wg.Done()
+			if code, body := npmDo(t, http.MethodDelete, base+"api/v1/gems/yank?gem_name=race&version=1.0.0", ""); code != http.StatusOK && code != http.StatusNotFound {
+				t.Errorf("yank = %d: %s", code, body)
+			}
+		}()
+	}
+	wg.Wait()
+
+	present := func(p string) bool {
+		f, err := h.db.GetLocalFile(context.Background(), repo, p)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return f != nil
+	}
+	live := []string{"_index/race/race-1.0.0", "gems/race-1.0.0.gem", "quick/Marshal.4.8/race-1.0.0.gemspec.rz"}
+	tomb := present("_yanked/race/race-1.0.0")
+	for _, p := range live {
+		if present(p) == tomb {
+			t.Errorf("tombstoned=%v but %s present=%v", tomb, p, !tomb)
+		}
+	}
+	_, info := npmDo(t, http.MethodGet, base+"info/race", "")
+	if strings.Contains(info, "1.0.0") == tomb {
+		t.Errorf("tombstoned=%v but info = %q", tomb, info)
+	}
+}
+
+func TestGemsLockTimeoutIs503(t *testing.T) {
+	h, srv := npmTestServer(t)
+	repo := npmRepo(t, h, models.PackageGems)
+	base := srv.URL + "/api/v1/local/" + repo + "/"
+	redis, err := cache.NewRedis(testRedis)
+	if err != nil {
+		t.Fatal(err)
+	}
+	token, err := redis.AcquireLock(context.Background(), repo, "_gemlock/busy-1.0.0", time.Minute)
+	if token == "" || err != nil {
+		t.Fatalf("hold lock = %q %v", token, err)
+	}
+	prev := gemsLockWait
+	gemsLockWait = 100 * time.Millisecond
+	t.Cleanup(func() { gemsLockWait = prev })
+
+	if code, _ := npmDo(t, http.MethodPost, base+"api/v1/gems", string(testGemFile(t, "busy", "1.0.0", "ruby"))); code != http.StatusServiceUnavailable {
+		t.Fatalf("push under held lock = %d, want 503", code)
+	}
+	if code, _ := npmDo(t, http.MethodDelete, base+"api/v1/gems/yank?gem_name=busy&version=1.0.0", ""); code != http.StatusServiceUnavailable {
+		t.Fatalf("yank under held lock = %d, want 503", code)
+	}
+	if err := redis.ReleaseLock(context.Background(), repo, "_gemlock/busy-1.0.0", token); err != nil {
+		t.Fatal(err)
+	}
+	if code, body := npmDo(t, http.MethodPost, base+"api/v1/gems", string(testGemFile(t, "busy", "1.0.0", "ruby"))); code != http.StatusOK {
+		t.Fatalf("push after release = %d: %s", code, body)
+	}
+}
diff --git a/internal/api/v1/gems_virtual.go b/internal/api/v1/gems_virtual.go
new file mode 100644
index 0000000..fbaf751
--- /dev/null
+++ b/internal/api/v1/gems_virtual.go
@@ -0,0 +1,39 @@
+package v1
+
+import (
+	"errors"
+	"log/slog"
+	"net/http"
+
+	"git.unkin.net/unkin/artifactapi/internal/virtual"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// serveVirtualGems serves the merged compact index and 302s downloads to the
+// member owning that version.
+func (h *ProxyHandler) serveVirtualGems(w http.ResponseWriter, r *http.Request, virt models.Virtual, path, proxyBaseURL string) {
+	var body []byte
+	var loc string
+	var err error
+	if isGemsIndexPath(path) {
+		body, _, err = h.virtualEngine.FetchGems(r.Context(), virt, path)
+	} else {
+		loc, err = h.virtualEngine.GemsRedirect(r.Context(), virt, path, r.URL.RawQuery, proxyBaseURL)
+	}
+	switch {
+	case errors.Is(err, virtual.ErrNotFound):
+		gemsText(w, http.StatusNotFound, "not found")
+	case errors.Is(err, virtual.ErrBadPath):
+		gemsText(w, http.StatusBadRequest, err.Error())
+	case err != nil:
+		slog.Error("virtual gems fetch failed", "virtual", virt.Name, "path", path, "error", err)
+		gemsText(w, http.StatusBadGateway, "bad gateway")
+	case loc != "":
+		w.Header().Set("Cache-Control", "no-store")
+		w.Header().Set("Vary", "Host, X-Forwarded-Proto")
+		http.Redirect(w, r, loc, http.StatusFound)
+	default:
+		w.Header().Set("X-Artifact-Source", "virtual")
+		gemsText(w, http.StatusOK, string(body))
+	}
+}
diff --git a/internal/api/v1/npm.go b/internal/api/v1/npm.go
new file mode 100644
index 0000000..5927f7f
--- /dev/null
+++ b/internal/api/v1/npm.go
@@ -0,0 +1,334 @@
+package v1
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha1"
+	"crypto/sha512"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/storage"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// Local npm repos speak the npm registry publish/read protocol. Per package:
+//   <pkg>/-/<base>-<version>.tgz   tarball (immutable)
+//   <pkg>/-/<base>-<version>.json  version manifest (immutable)
+//   <pkg>/-/dist-tags/<tag>        version string (mutable)
+
+var (
+	npmNameRe   = regexp.MustCompile(`^(@[a-z0-9][a-z0-9._~-]*/)?[a-z0-9][a-z0-9._~-]*$`)
+	npmRefRe    = regexp.MustCompile(`^[0-9A-Za-z][0-9A-Za-z.+_-]*$`)
+	npmSemverRe = regexp.MustCompile(`^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$`)
+
+	npmMaxPublishBytes int64 = 256 << 20
+)
+
+func (h *ProxyHandler) localNPMRemote(r *http.Request, name string) (*models.Remote, bool) {
+	remote, err := h.db.GetRemote(r.Context(), name)
+	if err != nil {
+		return nil, false
+	}
+	return remote, remote.RepoType == models.RepoTypeLocal && remote.PackageType == models.PackageNPM
+}
+
+// npmPackageName returns the package a packument/publish path addresses, or ""
+// when the path is something else (e.g. a tarball under <pkg>/-/).
+func npmPackageName(raw string) string {
+	p, err := url.PathUnescape(raw)
+	if err != nil {
+		return ""
+	}
+	p = strings.TrimSuffix(p, "/")
+	if !npmNameRe.MatchString(p) {
+		return ""
+	}
+	return p
+}
+
+type npmRelease struct {
+	version  string
+	manifest []byte
+	tarball  []byte
+	tags     []string
+}
+
+func parseNPMPublish(body io.Reader, pkg string) (*npmRelease, error) {
+	var doc struct {
+		Name        string                     `json:"name"`
+		DistTags    map[string]string          `json:"dist-tags"`
+		Versions    map[string]json.RawMessage `json:"versions"`
+		Attachments map[string]struct {
+			Data string `json:"data"`
+		} `json:"_attachments"`
+	}
+	if err := json.NewDecoder(body).Decode(&doc); err != nil {
+		return nil, fmt.Errorf("invalid publish body: %w", err)
+	}
+	if doc.Name != pkg {
+		return nil, fmt.Errorf("body name %q does not match %q", doc.Name, pkg)
+	}
+	if len(doc.Versions) != 1 || len(doc.Attachments) != 1 {
+		return nil, errors.New("publish must carry exactly one version and one tarball")
+	}
+
+	rel := &npmRelease{}
+	for v, m := range doc.Versions {
+		rel.version, rel.manifest = v, m
+	}
+	if !npmSemverRe.MatchString(rel.version) {
+		return nil, fmt.Errorf("invalid version %q", rel.version)
+	}
+	var meta struct {
+		Name    string `json:"name"`
+		Version string `json:"version"`
+		Dist    struct {
+			Integrity string `json:"integrity"`
+			Shasum    string `json:"shasum"`
+		} `json:"dist"`
+	}
+	if err := json.Unmarshal(rel.manifest, &meta); err != nil {
+		return nil, fmt.Errorf("invalid version manifest: %w", err)
+	}
+	if meta.Name != pkg || meta.Version != rel.version {
+		return nil, errors.New("version manifest name/version mismatch")
+	}
+
+	for _, a := range doc.Attachments {
+		tgz, err := base64.StdEncoding.DecodeString(a.Data)
+		if err != nil {
+			return nil, fmt.Errorf("invalid tarball encoding: %w", err)
+		}
+		rel.tarball = tgz
+	}
+	if err := verifyNPMDist(rel.tarball, meta.Dist.Integrity, meta.Dist.Shasum); err != nil {
+		return nil, err
+	}
+
+	for tag, v := range doc.DistTags {
+		if !npmRefRe.MatchString(tag) || v != rel.version {
+			return nil, fmt.Errorf("dist-tag %q must point at the published version", tag)
+		}
+		rel.tags = append(rel.tags, tag)
+	}
+	return rel, nil
+}
+
+func verifyNPMDist(tgz []byte, integrity, shasum string) error {
+	if b64, ok := strings.CutPrefix(integrity, "sha512-"); ok {
+		sum := sha512.Sum512(tgz)
+		if base64.StdEncoding.EncodeToString(sum[:]) != b64 {
+			return errors.New("tarball does not match dist.integrity")
+		}
+		return nil
+	}
+	if shasum != "" {
+		sum := sha1.Sum(tgz)
+		if hex.EncodeToString(sum[:]) != shasum {
+			return errors.New("tarball does not match dist.shasum")
+		}
+		return nil
+	}
+	return errors.New("version manifest carries no sha512 integrity or shasum")
+}
+
+func npmError(w http.ResponseWriter, status int, msg string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(map[string]string{"error": msg})
+}
+
+func (h *ProxyHandler) handleLocalPut(w http.ResponseWriter, r *http.Request) {
+	remote, ok := h.localNPMRemote(r, chi.URLParam(r, "localName"))
+	if !ok {
+		npmError(w, http.StatusMethodNotAllowed, "publish is only supported on local npm repositories")
+		return
+	}
+	pkg := npmPackageName(chi.URLParam(r, "*"))
+	if pkg == "" {
+		npmError(w, http.StatusBadRequest, "invalid package name")
+		return
+	}
+	rel, err := parseNPMPublish(http.MaxBytesReader(w, r.Body, npmMaxPublishBytes), pkg)
+	if err != nil {
+		var tooLarge *http.MaxBytesError
+		if errors.As(err, &tooLarge) {
+			npmError(w, http.StatusRequestEntityTooLarge, fmt.Sprintf("publish body exceeds %d bytes", npmMaxPublishBytes))
+			return
+		}
+		npmError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+
+	base := pkg[strings.LastIndex(pkg, "/")+1:]
+	stem := pkg + "/-/" + base + "-" + rel.version
+	// The manifest gates visibility and tags may only name visible versions, so
+	// the order is tarball, manifest, tags. A tarball left by a failed publish is
+	// accepted again only with identical bytes; an existing manifest always conflicts.
+	conflict := func() {
+		npmError(w, http.StatusConflict, fmt.Sprintf("%s@%s already exists; overwrites are not allowed", pkg, rel.version))
+	}
+	ok, err = h.npmStoreImmutable(r.Context(), remote.Name, stem+".tgz", rel.tarball, "application/octet-stream")
+	if err != nil {
+		npmError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if !ok {
+		conflict()
+		return
+	}
+	if _, err := h.npmStore(r.Context(), remote.Name, stem+".json", rel.manifest, "application/json", false); err != nil {
+		if errors.Is(err, database.ErrAlreadyExists) {
+			conflict()
+			return
+		}
+		npmError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	for _, tag := range rel.tags {
+		if _, err := h.npmStore(r.Context(), remote.Name, pkg+"/-/dist-tags/"+tag, []byte(rel.version), "text/plain", true); err != nil {
+			npmError(w, http.StatusInternalServerError, err.Error())
+			return
+		}
+	}
+
+	slog.Info("local npm package published", "repo", remote.Name, "package", pkg, "version", rel.version)
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusCreated)
+	_ = json.NewEncoder(w).Encode(map[string]any{"ok": true, "id": pkg})
+}
+
+// npmStoreImmutable reports false when path already holds different bytes.
+func (h *ProxyHandler) npmStoreImmutable(ctx context.Context, repo, path string, data []byte, contentType string) (bool, error) {
+	hash, err := h.npmStore(ctx, repo, path, data, contentType, false)
+	if !errors.Is(err, database.ErrAlreadyExists) {
+		return err == nil, err
+	}
+	existing, err := h.db.GetLocalFile(ctx, repo, path)
+	if err != nil || existing == nil {
+		return false, fmt.Errorf("read existing %s: %v", path, err)
+	}
+	return existing.ContentHash == hash, nil
+}
+
+func (h *ProxyHandler) npmStore(ctx context.Context, repo, path string, data []byte, contentType string, mutable bool) (string, error) {
+	result, err := h.cas.Store(ctx, bytes.NewReader(data), contentType)
+	if err != nil {
+		return "", err
+	}
+	if err := h.db.UpsertBlob(ctx, result.ContentHash, result.S3Key, result.SizeBytes, contentType); err != nil {
+		return "", err
+	}
+	if mutable {
+		return result.ContentHash, h.db.UpsertLocalFile(ctx, repo, path, result.ContentHash)
+	}
+	return result.ContentHash, h.db.CreateLocalFile(ctx, repo, path, result.ContentHash)
+}
+
+func (h *ProxyHandler) readLocalBlob(ctx context.Context, contentHash string) ([]byte, error) {
+	reader, _, err := h.store.Download(ctx, storage.BlobKey(strings.TrimPrefix(contentHash, "sha256:")))
+	if err != nil {
+		return nil, err
+	}
+	defer reader.Close()
+	return io.ReadAll(reader)
+}
+
+func (h *ProxyHandler) serveNPMPackument(w http.ResponseWriter, r *http.Request, remote *models.Remote, pkg string) {
+	files, err := h.db.ListLocalFilesByPrefix(r.Context(), remote.Name, pkg+"/-/")
+	if err != nil {
+		npmError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	base, ok := requestBaseURL(w, r)
+	if !ok {
+		return
+	}
+	read := func(hash string) ([]byte, error) { return h.readLocalBlob(r.Context(), hash) }
+	tarballBase := base + "/api/v1/local/" + remote.Name + "/"
+	doc, err := buildNPMPackument(pkg, files, read, tarballBase)
+	if err != nil {
+		npmError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if doc == nil {
+		npmError(w, http.StatusNotFound, "not found")
+		return
+	}
+	setNPMPerHostHeaders(w)
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("X-Artifact-Source", "local")
+	w.WriteHeader(http.StatusOK)
+	_ = json.NewEncoder(w).Encode(doc)
+}
+
+// setNPMPerHostHeaders keeps shared caches off packuments whose tarball URLs
+// are built from the request host and Accept (abbreviated vs full).
+func setNPMPerHostHeaders(w http.ResponseWriter) {
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("Vary", "Host, X-Forwarded-Proto, Accept")
+}
+
+// buildNPMPackument returns nil when pkg has no published versions.
+func buildNPMPackument(pkg string, files []database.LocalFile, read func(hash string) ([]byte, error), tarballBase string) (map[string]any, error) {
+	prefix := pkg + "/-/"
+	versions := map[string]any{}
+	tags := map[string]string{}
+	for _, f := range files {
+		// LIKE treats '_' as a wildcard, so the prefix match can over-select.
+		rest, ok := strings.CutPrefix(f.FilePath, prefix)
+		if !ok {
+			continue
+		}
+		if tag, isTag := strings.CutPrefix(rest, "dist-tags/"); isTag {
+			v, err := read(f.ContentHash)
+			if err != nil {
+				return nil, err
+			}
+			tags[tag] = string(v)
+			continue
+		}
+		stem, isManifest := strings.CutSuffix(rest, ".json")
+		if !isManifest {
+			continue
+		}
+		raw, err := read(f.ContentHash)
+		if err != nil {
+			return nil, err
+		}
+		var m map[string]any
+		if err := json.Unmarshal(raw, &m); err != nil {
+			return nil, fmt.Errorf("manifest %s: %w", f.FilePath, err)
+		}
+		dist, _ := m["dist"].(map[string]any)
+		if dist == nil {
+			dist = map[string]any{}
+			m["dist"] = dist
+		}
+		dist["tarball"] = tarballBase + prefix + stem + ".tgz"
+		v, _ := m["version"].(string)
+		versions[v] = m
+	}
+	if len(versions) == 0 {
+		return nil, nil
+	}
+	for tag, v := range tags {
+		if _, ok := versions[v]; !ok {
+			delete(tags, tag)
+		}
+	}
+	return map[string]any{"_id": pkg, "name": pkg, "dist-tags": tags, "versions": versions}, nil
+}
diff --git a/internal/api/v1/npm_handler_test.go b/internal/api/v1/npm_handler_test.go
new file mode 100644
index 0000000..695efe9
--- /dev/null
+++ b/internal/api/v1/npm_handler_test.go
@@ -0,0 +1,347 @@
+package v1
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.unkin.net/unkin/artifactapi/internal/cache"
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/proxy"
+	"git.unkin.net/unkin/artifactapi/internal/storage"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+	"git.unkin.net/unkin/artifactapi/internal/virtual"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+var (
+	testDSN   string
+	testMinio testsupport.MinioConn
+	testRedis string
+)
+
+func TestMain(m *testing.M) {
+	ctx := context.Background()
+	dsn, termPG, err := testsupport.StartPostgres(ctx)
+	if err != nil {
+		os.Exit(m.Run())
+	}
+	conn, termMinio, err := testsupport.StartMinio(ctx)
+	if err != nil {
+		termPG()
+		os.Exit(m.Run())
+	}
+	redisURL, termRedis, err := testsupport.StartRedis(ctx)
+	if err != nil {
+		termMinio()
+		termPG()
+		os.Exit(m.Run())
+	}
+	testDSN, testMinio, testRedis = dsn, conn, redisURL
+	code := m.Run()
+	termRedis()
+	termMinio()
+	termPG()
+	os.Exit(code)
+}
+
+func npmTestServer(t *testing.T) (*ProxyHandler, *httptest.Server) {
+	t.Helper()
+	if testDSN == "" {
+		t.Skip("Docker unavailable")
+	}
+	db, err := database.New(testDSN)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(db.Close)
+	var store *storage.S3
+	for i := 0; i < 20; i++ {
+		if store, err = storage.NewS3(testMinio.Endpoint, testMinio.AccessKey, testMinio.SecretKey, "npm", false, ""); err == nil {
+			break
+		}
+		time.Sleep(500 * time.Millisecond)
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	redis, err := cache.NewRedis(testRedis)
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := NewProxyHandler(proxy.NewEngine(db, redis, store), nil, db, store, nil)
+	r := chi.NewRouter()
+	r.Mount("/api/v1", h.Routes())
+	srv := httptest.NewServer(r)
+	t.Cleanup(srv.Close)
+	return h, srv
+}
+
+func npmRepo(t *testing.T, h *ProxyHandler, pt models.PackageType) string {
+	t.Helper()
+	name := fmt.Sprintf("npm-%s-%d", pt, time.Now().UnixNano())
+	if err := h.db.CreateRemote(context.Background(), &models.Remote{Name: name, PackageType: pt, RepoType: models.RepoTypeLocal}); err != nil {
+		t.Fatal(err)
+	}
+	return name
+}
+
+func npmDo(t *testing.T, method, url, body string) (int, string) {
+	t.Helper()
+	req, _ := http.NewRequest(method, url, strings.NewReader(body))
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+	b, _ := io.ReadAll(resp.Body)
+	return resp.StatusCode, string(b)
+}
+
+func packumentVersions(t *testing.T, url string) map[string]any {
+	t.Helper()
+	code, body := npmDo(t, http.MethodGet, url, "")
+	if code != http.StatusOK {
+		t.Fatalf("GET %s = %d: %s", url, code, body)
+	}
+	var doc struct {
+		Versions map[string]any `json:"versions"`
+	}
+	if err := json.Unmarshal([]byte(body), &doc); err != nil {
+		t.Fatal(err)
+	}
+	return doc.Versions
+}
+
+func packumentTags(t *testing.T, url string) map[string]string {
+	t.Helper()
+	_, body := npmDo(t, http.MethodGet, url, "")
+	var doc struct {
+		Tags map[string]string `json:"dist-tags"`
+	}
+	if err := json.Unmarshal([]byte(body), &doc); err != nil {
+		t.Fatal(err)
+	}
+	return doc.Tags
+}
+
+func concurrentPuts(t *testing.T, url string, bodies ...string) []int {
+	t.Helper()
+	var wg sync.WaitGroup
+	codes := make([]int, len(bodies))
+	for i, b := range bodies {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			codes[i], _ = npmDo(t, http.MethodPut, url, b)
+		}()
+	}
+	wg.Wait()
+	return codes
+}
+
+func TestNPMPublishHandler(t *testing.T) {
+	h, srv := npmTestServer(t)
+	repo := npmRepo(t, h, models.PackageNPM)
+	base := srv.URL + "/api/v1/local/" + repo + "/"
+
+	t.Run("scoped name via %2f", func(t *testing.T) {
+		body := publishBody(t, "@acme/widget", []byte("scoped tgz"), publishOpts{})
+		if code, b := npmDo(t, http.MethodPut, base+"@acme%2fwidget", body); code != http.StatusCreated {
+			t.Fatalf("publish = %d: %s", code, b)
+		}
+		v := packumentVersions(t, base+"@acme%2fwidget")
+		dist := v["1.0.0"].(map[string]any)["dist"].(map[string]any)
+		tarball := dist["tarball"].(string)
+		if !strings.HasPrefix(tarball, base+"@acme/widget/-/widget-1.0.0.tgz") {
+			t.Fatalf("tarball = %s", tarball)
+		}
+		if code, b := npmDo(t, http.MethodGet, tarball, ""); code != http.StatusOK || b != "scoped tgz" {
+			t.Fatalf("tarball fetch = %d %q", code, b)
+		}
+	})
+
+	t.Run("republish", func(t *testing.T) {
+		if code, b := npmDo(t, http.MethodPut, base+"repub", publishBody(t, "repub", []byte("v1"), publishOpts{})); code != http.StatusCreated {
+			t.Fatalf("first publish = %d: %s", code, b)
+		}
+		if code, _ := npmDo(t, http.MethodPut, base+"repub", publishBody(t, "repub", []byte("different"), publishOpts{})); code != http.StatusConflict {
+			t.Errorf("different bytes = %d, want 409", code)
+		}
+		if code, b := npmDo(t, http.MethodPut, base+"repub", publishBody(t, "repub", []byte("v2"), publishOpts{version: "1.1.0"})); code != http.StatusCreated {
+			t.Fatalf("publish 1.1.0 = %d: %s", code, b)
+		}
+		if code, _ := npmDo(t, http.MethodPut, base+"repub", publishBody(t, "repub", []byte("v1"), publishOpts{})); code != http.StatusConflict {
+			t.Errorf("identical republish = %d, want 409", code)
+		}
+		if tags := packumentTags(t, base+"repub"); tags["latest"] != "1.1.0" {
+			t.Errorf("latest = %q, want 1.1.0", tags["latest"])
+		}
+	})
+
+	t.Run("rejected republish leaves tags", func(t *testing.T) {
+		for _, v := range []string{"1.0.0", "1.1.0"} {
+			if code, b := npmDo(t, http.MethodPut, base+"rej", publishBody(t, "rej", []byte("tgz "+v), publishOpts{version: v})); code != http.StatusCreated {
+				t.Fatalf("publish %s = %d: %s", v, code, b)
+			}
+		}
+		if code, _ := npmDo(t, http.MethodPut, base+"rej", publishBody(t, "rej", []byte("tgz 1.0.0"), publishOpts{shasum: "x"})); code != http.StatusConflict {
+			t.Fatalf("re-PUT 1.0.0 = %d, want 409", code)
+		}
+		if tags := packumentTags(t, base+"rej"); tags["latest"] != "1.1.0" {
+			t.Errorf("latest = %q, want 1.1.0", tags["latest"])
+		}
+	})
+
+	t.Run("mid-publish window", func(t *testing.T) {
+		if code, b := npmDo(t, http.MethodPut, base+"mid", publishBody(t, "mid", []byte("v1"), publishOpts{})); code != http.StatusCreated {
+			t.Fatalf("publish = %d: %s", code, b)
+		}
+		ctx := context.Background()
+		if _, err := h.npmStore(ctx, repo, "mid/-/mid-1.0.1.tgz", []byte("v2"), "application/octet-stream", false); err != nil {
+			t.Fatal(err)
+		}
+		if tags := packumentTags(t, base+"mid"); tags["latest"] != "1.0.0" {
+			t.Errorf("tarball-only 1.0.1: latest = %q", tags["latest"])
+		}
+		if _, err := h.npmStore(ctx, repo, "mid/-/dist-tags/latest", []byte("1.0.1"), "text/plain", true); err != nil {
+			t.Fatal(err)
+		}
+		if tags := packumentTags(t, base+"mid"); tags["latest"] == "1.0.1" {
+			t.Error("latest points at invisible 1.0.1")
+		}
+	})
+
+	t.Run("concurrent identical", func(t *testing.T) {
+		body := publishBody(t, "same", []byte("same tgz"), publishOpts{})
+		codes := concurrentPuts(t, base+"same", body, body)
+		if codes[0]+codes[1] != http.StatusCreated+http.StatusConflict || codes[0] == codes[1] {
+			t.Fatalf("codes = %v, want one 201 and one 409", codes)
+		}
+		if tags := packumentTags(t, base+"same"); len(tags) != 1 || tags["latest"] != "1.0.0" {
+			t.Errorf("tags = %v", tags)
+		}
+	})
+
+	t.Run("concurrent different manifests", func(t *testing.T) {
+		tgz := []byte("race tgz")
+		codes := concurrentPuts(t, base+"race",
+			publishBody(t, "race", tgz, publishOpts{shasum: "a", tags: map[string]string{"a": "1.0.0"}}),
+			publishBody(t, "race", tgz, publishOpts{shasum: "b", tags: map[string]string{"b": "1.0.0"}}))
+		won := map[int]string{}
+		for i, c := range codes {
+			won[c] = []string{"a", "b"}[i]
+		}
+		if len(won) != 2 || won[http.StatusCreated] == "" || won[http.StatusConflict] == "" {
+			t.Fatalf("codes = %v, want one 201 and one 409", codes)
+		}
+		v := packumentVersions(t, base+"race")["1.0.0"].(map[string]any)
+		if got := v["dist"].(map[string]any)["shasum"]; got != won[http.StatusCreated] {
+			t.Errorf("manifest shasum = %v, winner %s", got, won[http.StatusCreated])
+		}
+		tags := packumentTags(t, base+"race")
+		if len(tags) != 1 || tags[won[http.StatusCreated]] != "1.0.0" {
+			t.Errorf("tags = %v, winner %s", tags, won[http.StatusCreated])
+		}
+	})
+
+	t.Run("retry after tarball-only write", func(t *testing.T) {
+		tgz := []byte("half published")
+		if _, err := h.npmStore(context.Background(), repo, "retry/-/retry-1.0.0.tgz", tgz, "application/octet-stream", false); err != nil {
+			t.Fatal(err)
+		}
+		if code, _ := npmDo(t, http.MethodGet, base+"retry", ""); code != http.StatusNotFound {
+			t.Fatalf("tarball-only version visible: %d", code)
+		}
+		if code, _ := npmDo(t, http.MethodPut, base+"retry", publishBody(t, "retry", []byte("other bytes"), publishOpts{})); code != http.StatusConflict {
+			t.Errorf("retry with different bytes = %d, want 409", code)
+		}
+		if code, b := npmDo(t, http.MethodPut, base+"retry", publishBody(t, "retry", tgz, publishOpts{})); code != http.StatusCreated {
+			t.Fatalf("retry with identical bytes = %d: %s", code, b)
+		}
+		if _, ok := packumentVersions(t, base+"retry")["1.0.0"]; !ok {
+			t.Error("retried version missing from packument")
+		}
+	})
+
+	t.Run("concurrent versions", func(t *testing.T) {
+		codes := concurrentPuts(t, base+"conc",
+			publishBody(t, "conc", []byte("tgz 1.0.0"), publishOpts{version: "1.0.0"}),
+			publishBody(t, "conc", []byte("tgz 2.0.0"), publishOpts{version: "2.0.0"}))
+		if codes[0] != http.StatusCreated || codes[1] != http.StatusCreated {
+			t.Fatalf("codes = %v", codes)
+		}
+		v := packumentVersions(t, base+"conc")
+		if _, ok := v["1.0.0"]; !ok {
+			t.Error("1.0.0 missing")
+		}
+		if _, ok := v["2.0.0"]; !ok {
+			t.Error("2.0.0 missing")
+		}
+	})
+
+	t.Run("body too large", func(t *testing.T) {
+		old := npmMaxPublishBytes
+		npmMaxPublishBytes = 64
+		defer func() { npmMaxPublishBytes = old }()
+		if code, _ := npmDo(t, http.MethodPut, base+"big", publishBody(t, "big", []byte("x"), publishOpts{})); code != http.StatusRequestEntityTooLarge {
+			t.Errorf("oversized body = %d, want 413", code)
+		}
+	})
+
+	t.Run("non-npm local", func(t *testing.T) {
+		generic := npmRepo(t, h, models.PackageGeneric)
+		if code, _ := npmDo(t, http.MethodPut, srv.URL+"/api/v1/local/"+generic+"/pkg", publishBody(t, "pkg", []byte("x"), publishOpts{})); code != http.StatusMethodNotAllowed {
+			t.Errorf("publish to generic local = %d, want 405", code)
+		}
+	})
+}
+
+func TestNPMPackumentPerHost(t *testing.T) {
+	h, srv := npmTestServer(t)
+	h.virtualEngine = virtual.NewEngine(h.db, nil)
+	h.virtualEngine.NPMLocal = h.LocalNPMPackument
+	repo := npmRepo(t, h, models.PackageNPM)
+	virt := "v" + repo
+	if err := h.db.CreateVirtual(context.Background(), &models.Virtual{Name: virt, PackageType: models.PackageNPM, Members: []string{repo}}); err != nil {
+		t.Fatal(err)
+	}
+	if code, b := npmDo(t, http.MethodPut, srv.URL+"/api/v1/local/"+repo+"/hostpkg", publishBody(t, "hostpkg", []byte("tgz"), publishOpts{})); code != http.StatusCreated {
+		t.Fatalf("publish = %d: %s", code, b)
+	}
+	routes := h.Routes()
+	get := func(path, host, proto string) *httptest.ResponseRecorder {
+		r := httptest.NewRequest(http.MethodGet, path, nil)
+		r.Host = host
+		if proto != "" {
+			r.Header.Set("X-Forwarded-Proto", proto)
+		}
+		w := httptest.NewRecorder()
+		routes.ServeHTTP(w, r)
+		return w
+	}
+	for _, path := range []string{"/local/" + repo + "/hostpkg", "/virtual/" + virt + "/hostpkg"} {
+		for _, host := range []string{"x@evil.com", "evil.example:"} {
+			if w := get(path, host, ""); w.Code != http.StatusBadRequest {
+				t.Errorf("%s Host %q = %d, want 400", path, host, w.Code)
+			}
+		}
+		w := get(path, "aa.example", "https")
+		if w.Code != http.StatusOK || !strings.Contains(w.Body.String(), `"tarball":"https://aa.example/api/v1/`) {
+			t.Fatalf("%s = %d: %s", path, w.Code, w.Body)
+		}
+		if cc, vary := w.Header().Get("Cache-Control"), w.Header().Get("Vary"); cc != "no-store" || vary != "Host, X-Forwarded-Proto, Accept" {
+			t.Errorf("%s Cache-Control %q Vary %q", path, cc, vary)
+		}
+	}
+}
diff --git a/internal/api/v1/npm_test.go b/internal/api/v1/npm_test.go
new file mode 100644
index 0000000..82cf676
--- /dev/null
+++ b/internal/api/v1/npm_test.go
@@ -0,0 +1,166 @@
+package v1
+
+import (
+	"crypto/sha1"
+	"crypto/sha512"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"strings"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/database"
+)
+
+func TestNPMPackageName(t *testing.T) {
+	tests := map[string]string{
+		"left-pad":                "left-pad",
+		"left-pad/":               "left-pad",
+		"@acme%2fwidget":          "@acme/widget",
+		"@acme%2Fwidget":          "@acme/widget",
+		"@acme/widget":            "@acme/widget",
+		"left-pad/-/left-pad.tgz": "",
+		"@acme/widget/-/w-1.tgz":  "",
+		"a/b":                     "",
+		"../etc":                  "",
+		"Upper":                   "",
+		"":                        "",
+	}
+	for in, want := range tests {
+		if got := npmPackageName(in); got != want {
+			t.Errorf("npmPackageName(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+type publishOpts struct {
+	bodyName, manifestName, version, integrity, shasum string
+	tags                                               map[string]string
+	extraVersion                                       bool
+}
+
+func publishBody(t *testing.T, pkg string, tgz []byte, o publishOpts) string {
+	t.Helper()
+	sha := sha512.Sum512(tgz)
+	sh1 := sha1.Sum(tgz)
+	if o.bodyName == "" {
+		o.bodyName = pkg
+	}
+	if o.manifestName == "" {
+		o.manifestName = pkg
+	}
+	if o.version == "" {
+		o.version = "1.0.0"
+	}
+	if o.integrity == "" {
+		o.integrity = "sha512-" + base64.StdEncoding.EncodeToString(sha[:])
+	}
+	if o.shasum == "" {
+		o.shasum = hex.EncodeToString(sh1[:])
+	}
+	if o.tags == nil {
+		o.tags = map[string]string{"latest": o.version}
+	}
+	versions := map[string]any{o.version: map[string]any{
+		"name": o.manifestName, "version": o.version, "main": "index.js",
+		"dist": map[string]any{"integrity": o.integrity, "shasum": o.shasum, "tarball": "http://elsewhere/x.tgz"},
+	}}
+	if o.extraVersion {
+		versions["2.0.0"] = map[string]any{"name": pkg, "version": "2.0.0"}
+	}
+	b, _ := json.Marshal(map[string]any{
+		"_id": pkg, "name": o.bodyName, "dist-tags": o.tags, "versions": versions,
+		"_attachments": map[string]any{pkg + "-" + o.version + ".tgz": map[string]any{
+			"content_type": "application/octet-stream", "data": base64.StdEncoding.EncodeToString(tgz), "length": len(tgz),
+		}},
+	})
+	return string(b)
+}
+
+func TestParseNPMPublish(t *testing.T) {
+	tgz := []byte("fake tarball bytes")
+
+	rel, err := parseNPMPublish(strings.NewReader(publishBody(t, "@acme/widget", tgz, publishOpts{tags: map[string]string{"latest": "1.0.0", "beta": "1.0.0"}})), "@acme/widget")
+	if err != nil {
+		t.Fatalf("valid scoped publish rejected: %v", err)
+	}
+	if rel.version != "1.0.0" || string(rel.tarball) != string(tgz) || len(rel.tags) != 2 {
+		t.Fatalf("unexpected release: %+v", rel)
+	}
+
+	if _, err := parseNPMPublish(strings.NewReader(publishBody(t, "left-pad", tgz, publishOpts{integrity: "none", shasum: hex.EncodeToString(make([]byte, 20))})), "left-pad"); err == nil {
+		t.Fatal("shasum fallback should reject a mismatched tarball")
+	}
+	if _, err := parseNPMPublish(strings.NewReader(publishBody(t, "left-pad", tgz, publishOpts{integrity: "none"})), "left-pad"); err != nil {
+		t.Fatalf("matching shasum fallback rejected: %v", err)
+	}
+
+	bad := map[string]publishOpts{
+		"body name mismatch":        {bodyName: "other"},
+		"manifest name mismatch":    {manifestName: "other"},
+		"integrity mismatch":        {integrity: "sha512-AAAA"},
+		"path-like version":         {version: "../1.0.0"},
+		"non-semver version":        {version: "1..2"},
+		"leading-zero version":      {version: "01.0.0"},
+		"tag at another version":    {tags: map[string]string{"latest": "9.9.9"}},
+		"path-like tag":             {tags: map[string]string{"../x": "1.0.0"}},
+		"multiple versions at once": {extraVersion: true},
+	}
+	for name, o := range bad {
+		if _, err := parseNPMPublish(strings.NewReader(publishBody(t, "left-pad", tgz, o)), "left-pad"); err == nil {
+			t.Errorf("%s: expected rejection", name)
+		}
+	}
+	if _, err := parseNPMPublish(strings.NewReader(`{"name":"left-pad","versions":{}}`), "left-pad"); err == nil {
+		t.Error("deprecate-style body without attachments should be rejected")
+	}
+}
+
+func TestBuildNPMPackument(t *testing.T) {
+	blobs := map[string]string{
+		"h1": `{"name":"my_pkg","version":"1.0.0","dist":{"shasum":"aa","tarball":"http://elsewhere/x.tgz"}}`,
+		"h2": `{"name":"my_pkg","version":"1.1.0"}`,
+		"h3": "1.1.0",
+		"h4": "2.0.0",
+		"hx": `{"name":"myXpkg","version":"6.6.6"}`,
+	}
+	read := func(h string) ([]byte, error) {
+		b, ok := blobs[h]
+		if !ok {
+			return nil, errors.New("missing blob")
+		}
+		return []byte(b), nil
+	}
+	files := []database.LocalFile{
+		{FilePath: "my_pkg/-/dist-tags/latest", ContentHash: "h3"},
+		{FilePath: "my_pkg/-/dist-tags/next", ContentHash: "h4"},
+		{FilePath: "my_pkg/-/my_pkg-1.0.0.json", ContentHash: "h1"},
+		{FilePath: "my_pkg/-/my_pkg-1.0.0.tgz", ContentHash: "nope"},
+		{FilePath: "my_pkg/-/my_pkg-1.1.0.json", ContentHash: "h2"},
+		{FilePath: "myXpkg/-/myXpkg-6.6.6.json", ContentHash: "hx"},
+	}
+
+	doc, err := buildNPMPackument("my_pkg", files, read, "http://reg/api/v1/local/npm/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tags := doc["dist-tags"].(map[string]string); tags["latest"] != "1.1.0" || len(tags) != 1 {
+		t.Errorf("dist-tags = %v", tags)
+	}
+	versions := doc["versions"].(map[string]any)
+	if len(versions) != 2 {
+		t.Fatalf("versions = %v (LIKE over-match must be dropped)", versions)
+	}
+	v1 := versions["1.0.0"].(map[string]any)["dist"].(map[string]any)
+	if v1["tarball"] != "http://reg/api/v1/local/npm/my_pkg/-/my_pkg-1.0.0.tgz" || v1["shasum"] != "aa" {
+		t.Errorf("1.0.0 dist = %v", v1)
+	}
+	if versions["1.1.0"].(map[string]any)["dist"].(map[string]any)["tarball"] != "http://reg/api/v1/local/npm/my_pkg/-/my_pkg-1.1.0.tgz" {
+		t.Error("1.1.0 missing rewritten tarball")
+	}
+
+	if doc, err := buildNPMPackument("absent", files, read, "x/"); err != nil || doc != nil {
+		t.Errorf("absent package: doc=%v err=%v", doc, err)
+	}
+}
diff --git a/internal/api/v1/npm_virtual.go b/internal/api/v1/npm_virtual.go
new file mode 100644
index 0000000..7ac006b
--- /dev/null
+++ b/internal/api/v1/npm_virtual.go
@@ -0,0 +1,26 @@
+package v1
+
+import (
+	"context"
+	"encoding/json"
+
+	"git.unkin.net/unkin/artifactapi/internal/virtual"
+)
+
+// LocalNPMPackument serves a local npm repo's packument to npm virtuals, with
+// tarball paths relative to the repo.
+func (h *ProxyHandler) LocalNPMPackument(ctx context.Context, repo, pkg string) ([]byte, error) {
+	files, err := h.db.ListLocalFilesByPrefix(ctx, repo, pkg+"/-/")
+	if err != nil {
+		return nil, err
+	}
+	read := func(hash string) ([]byte, error) { return h.readLocalBlob(ctx, hash) }
+	doc, err := buildNPMPackument(pkg, files, read, "")
+	if err != nil {
+		return nil, err
+	}
+	if doc == nil {
+		return nil, virtual.ErrNotFound
+	}
+	return json.Marshal(doc)
+}
diff --git a/internal/api/v1/proxy.go b/internal/api/v1/proxy.go
index 8100658..486394b 100644
--- a/internal/api/v1/proxy.go
+++ b/internal/api/v1/proxy.go
@@ -6,8 +6,11 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
+	"net"
 	"net/http"
 	"net/url"
+	"strconv"
+	"strings"
 
 	"github.com/go-chi/chi/v5"
 
@@ -17,6 +20,7 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/proxy"
 	"git.unkin.net/unkin/artifactapi/internal/storage"
 	"git.unkin.net/unkin/artifactapi/internal/virtual"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
 type ProxyHandler struct {
@@ -42,8 +46,14 @@ func NewProxyHandler(engine *proxy.Engine, virtualEngine *virtual.Engine, db *da
 func (h *ProxyHandler) Routes() chi.Router {
 	r := chi.NewRouter()
 	r.Get("/remote/{remoteName}/*", h.handleProxy)
+	r.Head("/remote/{remoteName}/*", h.handleProxyHead)
 	r.Get("/local/{localName}/*", h.handleLocal)
+	r.Head("/local/{localName}/*", h.handleLocal)
+	r.Put("/local/{localName}/*", h.handleLocalPut)
+	r.Post("/local/{localName}/*", h.handleLocalPost)
+	r.Delete("/local/{localName}/*", h.handleLocalDelete)
 	r.Get("/virtual/{virtualName}/*", h.handleVirtual)
+	r.Head("/virtual/{virtualName}/*", h.handleVirtual)
 	return r
 }
 
@@ -69,31 +79,43 @@ func (h *ProxyHandler) handleDockerPing(w http.ResponseWriter, r *http.Request)
 	w.WriteHeader(http.StatusOK)
 }
 
-func (h *ProxyHandler) handleProxy(w http.ResponseWriter, r *http.Request) {
+// remoteFor resolves the remote and provider named in the request, writing the
+// error response itself when either is missing.
+func (h *ProxyHandler) remoteFor(w http.ResponseWriter, r *http.Request) (*models.Remote, provider.Provider, bool) {
 	remoteName := chi.URLParam(r, "remoteName")
-	path := chi.URLParam(r, "*")
-
 	remote, err := h.db.GetRemote(r.Context(), remoteName)
 	if err != nil {
 		http.Error(w, fmt.Sprintf("remote %q not found", remoteName), http.StatusNotFound)
-		return
+		return nil, nil, false
 	}
-
 	prov, err := provider.Get(remote.PackageType)
 	if err != nil {
 		http.Error(w, fmt.Sprintf("no provider for %q", remote.PackageType), http.StatusInternalServerError)
+		return nil, nil, false
+	}
+	return remote, prov, true
+}
+
+// serveRemote lets metadata-only remotes (e.g. github_rpm) synthesize their own
+// responses and redirect package downloads instead of proxying bytes.
+func (h *ProxyHandler) serveRemote(w http.ResponseWriter, r *http.Request, remote *models.Remote, prov provider.Provider, path string) bool {
+	rs, ok := prov.(provider.RemoteServer)
+	return ok && rs.ServeRemote(w, r, *remote, path, fmt.Sprintf("%s://%s", Scheme(r), r.Host), h.db)
+}
+
+func (h *ProxyHandler) handleProxy(w http.ResponseWriter, r *http.Request) {
+	remote, prov, ok := h.remoteFor(w, r)
+	if !ok {
 		return
 	}
-
-	// Metadata-only remotes (e.g. github_rpm) synthesize their own responses and
-	// redirect package downloads to a backend remote instead of proxying bytes.
-	if rs, ok := prov.(provider.RemoteServer); ok {
-		proxyBaseURL := fmt.Sprintf("%s://%s", scheme(r), r.Host)
-		if rs.ServeRemote(w, r, *remote, path, proxyBaseURL, h.db) {
-			return
-		}
+	path := chi.URLParam(r, "*")
+	if h.serveRemote(w, r, remote, prov, path) {
+		return
 	}
+	h.serveFetch(w, r, remote, prov, path)
+}
 
+func (h *ProxyHandler) serveFetch(w http.ResponseWriter, r *http.Request, remote *models.Remote, prov provider.Provider, path string) {
 	result, err := h.engine.Fetch(r.Context(), *remote, forwardQuery(prov, path, r.URL.Query()), prov, r.Header)
 	if err != nil {
 		var proxyErr *proxy.ProxyError
@@ -101,7 +123,7 @@ func (h *ProxyHandler) handleProxy(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, proxyErr.Message, proxyErr.Status)
 			return
 		}
-		slog.Error("proxy fetch failed", "remote", remoteName, "path", path, "error", err)
+		slog.Error("proxy fetch failed", "remote", remote.Name, "path", path, "error", err)
 		http.Error(w, "bad gateway", http.StatusBadGateway)
 		return
 	}
@@ -109,37 +131,43 @@ func (h *ProxyHandler) handleProxy(w http.ResponseWriter, r *http.Request) {
 
 	var body io.Reader = result.Reader
 	if sr, ok := prov.(provider.ServeRewriter); ok && prov.Classify(path) == provider.Mutable {
-		raw, err := io.ReadAll(result.Reader)
-		if err != nil {
-			http.Error(w, "bad gateway", http.StatusBadGateway)
+		raw, ok := rewriteServed(w, r, sr, *remote, result.Reader)
+		if !ok {
 			return
 		}
-		raw = sr.RewriteServed(raw, *remote, fmt.Sprintf("%s://%s", scheme(r), r.Host))
 		body, result.Size = bytes.NewReader(raw), int64(len(raw))
 	}
 
 	w.Header().Set("Content-Type", result.ContentType)
 	w.Header().Set("X-Artifact-Source", result.Source)
 	if result.Size > 0 {
+		w.Header().Set("Content-Length", fmt.Sprintf("%d", result.Size))
 		w.Header().Set("X-Artifact-Size", fmt.Sprintf("%d", result.Size))
 	}
 	w.WriteHeader(http.StatusOK)
 	io.Copy(w, body)
 }
 
-func (h *ProxyHandler) handleProxyHead(w http.ResponseWriter, r *http.Request) {
-	remoteName := chi.URLParam(r, "remoteName")
-	path := chi.URLParam(r, "*")
+func rewritesMutable(prov provider.Provider, path string) bool {
+	_, sr := prov.(provider.ServeRewriter)
+	_, rr := prov.(provider.ResponseRewriter)
+	return (sr || rr) && prov.Classify(path) == provider.Mutable
+}
 
-	remote, err := h.db.GetRemote(r.Context(), remoteName)
-	if err != nil {
-		http.Error(w, fmt.Sprintf("remote %q not found", remoteName), http.StatusNotFound)
+// handleProxyHead answers HEAD like GET without a body. Responses a provider
+// synthesizes or rewrites per request go through the GET path so their headers
+// match; everything else is answered from store metadata or an upstream HEAD.
+func (h *ProxyHandler) handleProxyHead(w http.ResponseWriter, r *http.Request) {
+	remote, prov, ok := h.remoteFor(w, r)
+	if !ok {
 		return
 	}
-
-	prov, err := provider.Get(remote.PackageType)
-	if err != nil {
-		http.Error(w, fmt.Sprintf("no provider for %q", remote.PackageType), http.StatusInternalServerError)
+	path := chi.URLParam(r, "*")
+	if h.serveRemote(w, r, remote, prov, path) {
+		return
+	}
+	if rewritesMutable(prov, path) {
+		h.serveFetch(w, r, remote, prov, path)
 		return
 	}
 
@@ -150,7 +178,7 @@ func (h *ProxyHandler) handleProxyHead(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, proxyErr.Message, proxyErr.Status)
 			return
 		}
-		slog.Error("proxy head failed", "remote", remoteName, "path", path, "error", err)
+		slog.Error("proxy head failed", "remote", remote.Name, "path", path, "error", err)
 		http.Error(w, "bad gateway", http.StatusBadGateway)
 		return
 	}
@@ -173,7 +201,15 @@ func (h *ProxyHandler) handleVirtual(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	proxyBaseURL := fmt.Sprintf("%s://%s", scheme(r), r.Host)
+	proxyBaseURL, ok := requestBaseURL(w, r)
+	if !ok {
+		return
+	}
+
+	if virt.PackageType == models.PackageGems {
+		h.serveVirtualGems(w, r, *virt, path, proxyBaseURL)
+		return
+	}
 
 	loc, ok, err := h.virtualEngine.MemberRedirect(r.Context(), *virt, path, r.URL.RawQuery, proxyBaseURL)
 	if err != nil {
@@ -185,7 +221,14 @@ func (h *ProxyHandler) handleVirtual(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	body, contentType, err := h.virtualEngine.Fetch(r.Context(), *virt, path, proxyBaseURL)
+	var body []byte
+	var contentType string
+	if virt.PackageType == models.PackageNPM {
+		abbreviated := strings.Contains(r.Header.Get("Accept"), virtual.NPMAbbreviatedType)
+		body, contentType, err = h.virtualEngine.FetchNPM(r.Context(), *virt, path, proxyBaseURL, abbreviated)
+	} else {
+		body, contentType, err = h.virtualEngine.Fetch(r.Context(), *virt, path, proxyBaseURL)
+	}
 	if errors.Is(err, virtual.ErrNotFound) {
 		http.Error(w, "not found", http.StatusNotFound)
 		return
@@ -196,6 +239,9 @@ func (h *ProxyHandler) handleVirtual(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if virt.PackageType == models.PackageNPM {
+		setNPMPerHostHeaders(w)
+	}
 	w.Header().Set("Content-Type", contentType)
 	w.Header().Set("X-Artifact-Source", "virtual")
 	w.WriteHeader(http.StatusOK)
@@ -212,6 +258,23 @@ func (h *ProxyHandler) handleLocal(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if remote.PackageType == models.PackageNPM {
+		if pkg := npmPackageName(path); pkg != "" {
+			h.serveNPMPackument(w, r, remote, pkg)
+			return
+		}
+	}
+	if remote.PackageType == models.PackageGems {
+		if isGemsIndexPath(path) {
+			h.serveLocalGemsIndex(w, r, remote, path)
+			return
+		}
+		if strings.HasPrefix(path, gemsIndexPrefix) || strings.HasPrefix(path, gemsYankedPrefix) {
+			http.Error(w, "not found", http.StatusNotFound)
+			return
+		}
+	}
+
 	prov, _ := provider.Get(remote.PackageType)
 	if indexer, ok := prov.(provider.LocalIndexer); ok {
 		if indexer.ServeLocalIndex(w, r, h.db, remote.Name, path) {
@@ -250,11 +313,14 @@ func (h *ProxyHandler) serveLocalFile(w http.ResponseWriter, r *http.Request, re
 	io.Copy(w, reader)
 }
 
-func scheme(r *http.Request) string {
+// Scheme returns the client-facing scheme: TLS, else the first
+// X-Forwarded-Proto value when it is http or https, else http.
+func Scheme(r *http.Request) string {
 	if r.TLS != nil {
 		return "https"
 	}
-	if fwd := r.Header.Get("X-Forwarded-Proto"); fwd != "" {
+	fwd, _, _ := strings.Cut(r.Header.Get("X-Forwarded-Proto"), ",")
+	if fwd = strings.ToLower(strings.TrimSpace(fwd)); fwd == "https" {
 		return fwd
 	}
 	return "http"
@@ -278,3 +344,66 @@ func forwardQuery(prov provider.Provider, path string, query url.Values) string
 	}
 	return path + "?" + kept.Encode()
 }
+
+// rewriteServed rewrites a cached body for the requesting host and marks the
+// response uncacheable by shared caches, since it varies per Host.
+func rewriteServed(w http.ResponseWriter, r *http.Request, sr provider.ServeRewriter, remote models.Remote, src io.Reader) ([]byte, bool) {
+	base, ok := requestBaseURL(w, r)
+	if !ok {
+		return nil, false
+	}
+	raw, err := io.ReadAll(src)
+	if err != nil {
+		http.Error(w, "bad gateway", http.StatusBadGateway)
+		return nil, false
+	}
+	raw = sr.RewriteServed(raw, remote, base)
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("Vary", "Host, X-Forwarded-Proto")
+	w.Header().Set("Content-Length", strconv.Itoa(len(raw)))
+	return raw, true
+}
+
+// requestBaseURL returns the client-facing scheme://host, answering 400 on an
+// invalid Host.
+func requestBaseURL(w http.ResponseWriter, r *http.Request) (string, bool) {
+	if !validHost(r.Host) {
+		http.Error(w, "invalid host header", http.StatusBadRequest)
+		return "", false
+	}
+	return Scheme(r) + "://" + r.Host, true
+}
+
+// validHost accepts host[:port] where host is a DNS name or IP literal.
+func validHost(hostport string) bool {
+	host, port := hostport, ""
+	if h, p, err := net.SplitHostPort(hostport); err == nil {
+		if p == "" {
+			return false
+		}
+		host, port = h, p
+	} else if strings.HasPrefix(hostport, "[") {
+		return strings.HasSuffix(hostport, "]") && net.ParseIP(hostport[1:len(hostport)-1]) != nil
+	}
+	if port != "" {
+		if n, err := strconv.Atoi(port); err != nil || n < 1 || n > 65535 {
+			return false
+		}
+	}
+	if net.ParseIP(host) != nil {
+		return true
+	}
+	if strings.HasPrefix(hostport, "[") {
+		return false
+	}
+	if host == "" || len(host) > 253 {
+		return false
+	}
+	for _, label := range strings.Split(strings.TrimSuffix(host, "."), ".") {
+		if label == "" || len(label) > 63 || label[0] == '-' || label[len(label)-1] == '-' ||
+			strings.Trim(strings.ToLower(label), "abcdefghijklmnopqrstuvwxyz0123456789-_") != "" {
+			return false
+		}
+	}
+	return true
+}
diff --git a/internal/api/v1/rewrite_test.go b/internal/api/v1/rewrite_test.go
new file mode 100644
index 0000000..24fd732
--- /dev/null
+++ b/internal/api/v1/rewrite_test.go
@@ -0,0 +1,74 @@
+package v1
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider/nuget"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func TestValidHost(t *testing.T) {
+	for _, h := range []string{"aa.example", "aa.example:8443", "artifactapi.k8s.syd1.au.unkin.net", "10.0.0.1:80", "[::1]:8080", "[::1]", "::1", "localhost", "my_host.local"} {
+		if !validHost(h) {
+			t.Errorf("validHost(%q) = false, want true", h)
+		}
+	}
+	for _, h := range []string{"", "evil\".example", "a b", "aa.example:0", "aa.example:99999", "aa.example:x", "aa.example:", ":8080", "-bad.example", "a..b", "[::1", "[nope]:80", "a/b", "a<script>", strings.Repeat("a", 64) + ".example"} {
+		if validHost(h) {
+			t.Errorf("validHost(%q) = true, want false", h)
+		}
+	}
+}
+
+var nugetOrg = models.Remote{Name: "nuget-org", BaseURL: "https://api.nuget.org/v3/index.json"}
+
+const serviceIndex = `{"resources":[{"@id":"https://api.nuget.org/v3-flatcontainer/"}]}`
+
+func rewrite(t *testing.T, host, proto string) (*httptest.ResponseRecorder, string, bool) {
+	t.Helper()
+	r := httptest.NewRequest(http.MethodGet, "/api/v1/remote/nuget-org/index.json", nil)
+	r.Host = host
+	if proto != "" {
+		r.Header.Set("X-Forwarded-Proto", proto)
+	}
+	w := httptest.NewRecorder()
+	raw, ok := rewriteServed(w, r, &nuget.Provider{}, nugetOrg, strings.NewReader(serviceIndex))
+	return w, string(raw), ok
+}
+
+func TestRewriteServedHeaders(t *testing.T) {
+	w, body, ok := rewrite(t, "aa.example:8443", "https")
+	if !ok {
+		t.Fatal("valid request rejected")
+	}
+	if want := `{"resources":[{"@id":"https://aa.example:8443/api/v1/remote/nuget-org/v3-flatcontainer/"}]}`; body != want {
+		t.Errorf("body = %s, want %s", body, want)
+	}
+	if got := w.Header().Get("Cache-Control"); got != "no-store" {
+		t.Errorf("Cache-Control = %q, want no-store", got)
+	}
+	if got := w.Header().Get("Vary"); got != "Host, X-Forwarded-Proto" {
+		t.Errorf("Vary = %q", got)
+	}
+	if got := w.Header().Get("Content-Length"); got != "91" || len(body) != 91 {
+		t.Errorf("Content-Length = %q, body len %d", got, len(body))
+	}
+}
+
+func TestRewriteServedIgnoresBogusProto(t *testing.T) {
+	_, plain, _ := rewrite(t, "aa.example", "")
+	_, bogus, _ := rewrite(t, "aa.example", "javascript")
+	if bogus != plain || !strings.Contains(bogus, `"http://aa.example/`) {
+		t.Errorf("bogus X-Forwarded-Proto changed the body: %s", bogus)
+	}
+}
+
+func TestRewriteServedRejectsInvalidHost(t *testing.T) {
+	w, _, ok := rewrite(t, `evil"},{"x":"`, "")
+	if ok || w.Code != http.StatusBadRequest {
+		t.Errorf("invalid host: ok=%v code=%d, want rejected with 400", ok, w.Code)
+	}
+}
diff --git a/internal/api/v1/routes_test.go b/internal/api/v1/routes_test.go
new file mode 100644
index 0000000..e29d8cf
--- /dev/null
+++ b/internal/api/v1/routes_test.go
@@ -0,0 +1,41 @@
+package v1
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/provider/npm"
+	"git.unkin.net/unkin/artifactapi/internal/provider/nuget"
+	"git.unkin.net/unkin/artifactapi/internal/provider/rpm"
+)
+
+func TestRoutesRemoteHead(t *testing.T) {
+	r := (&ProxyHandler{}).Routes()
+	for _, m := range []string{http.MethodGet, http.MethodHead} {
+		if !r.Match(chi.NewRouteContext(), m, "/remote/myremote/some/path") {
+			t.Errorf("%s /remote/myremote/some/path not routed", m)
+		}
+	}
+}
+
+func TestRewritesMutable(t *testing.T) {
+	tests := []struct {
+		name string
+		prov provider.Provider
+		path string
+		want bool
+	}{
+		{"npm packument", &npm.Provider{}, "left-pad", true},
+		{"npm tarball", &npm.Provider{}, "left-pad/-/left-pad-1.3.0.tgz", false},
+		{"nuget index", &nuget.Provider{}, "index.json", true},
+		{"rpm repodata", &rpm.Provider{}, "repodata/repomd.xml", false},
+	}
+	for _, tc := range tests {
+		if got := rewritesMutable(tc.prov, tc.path); got != tc.want {
+			t.Errorf("%s: rewritesMutable = %v, want %v", tc.name, got, tc.want)
+		}
+	}
+}
diff --git a/internal/api/v1/scheme_test.go b/internal/api/v1/scheme_test.go
index e74ce67..6b451c8 100644
--- a/internal/api/v1/scheme_test.go
+++ b/internal/api/v1/scheme_test.go
@@ -7,14 +7,28 @@ import (
 )
 
 func TestScheme(t *testing.T) {
-	if got := scheme(&http.Request{TLS: &tls.ConnectionState{}}); got != "https" {
+	if got := Scheme(&http.Request{TLS: &tls.ConnectionState{}}); got != "https" {
 		t.Errorf("TLS request scheme = %q, want https", got)
 	}
 	r := &http.Request{Header: http.Header{"X-Forwarded-Proto": {"https"}}}
-	if got := scheme(r); got != "https" {
+	if got := Scheme(r); got != "https" {
 		t.Errorf("X-Forwarded-Proto scheme = %q, want https", got)
 	}
-	if got := scheme(&http.Request{Header: http.Header{}}); got != "http" {
+	for fwd, want := range map[string]string{
+		"https, http": "https",
+		"http, https": "http",
+		"HTTPS":       "https",
+		" https ":     "https",
+		"javascript":  "http",
+		"ftp":         "http",
+		"https;evil":  "http",
+	} {
+		r := &http.Request{Header: http.Header{"X-Forwarded-Proto": {fwd}}}
+		if got := Scheme(r); got != want {
+			t.Errorf("X-Forwarded-Proto %q scheme = %q, want %s", fwd, got, want)
+		}
+	}
+	if got := Scheme(&http.Request{Header: http.Header{}}); got != "http" {
 		t.Errorf("default scheme = %q, want http", got)
 	}
 }
diff --git a/internal/api/v2/remotes.go b/internal/api/v2/remotes.go
index a8f679e..b5c3a82 100644
--- a/internal/api/v2/remotes.go
+++ b/internal/api/v2/remotes.go
@@ -67,8 +67,12 @@ func (h *RemotesHandler) get(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, remote)
 }
 
+// defaultMutableTTL matches the remotes.mutable_ttl column default; a create
+// that omits mutable_ttl gets it, an explicit 0 still means never expire.
+const defaultMutableTTL = 3600
+
 func (h *RemotesHandler) create(w http.ResponseWriter, r *http.Request) {
-	var remote models.Remote
+	remote := models.Remote{MutableTTL: defaultMutableTTL}
 	if err := json.NewDecoder(r.Body).Decode(&remote); err != nil {
 		http.Error(w, "invalid json", http.StatusBadRequest)
 		return
@@ -114,7 +118,15 @@ func (h *RemotesHandler) create(w http.ResponseWriter, r *http.Request) {
 
 func (h *RemotesHandler) update(w http.ResponseWriter, r *http.Request) {
 	name := chi.URLParam(r, "name")
+	// Capture the current backend before the update so we can tell whether the
+	// remote's base_url (its upstream) changed. A read failure just means we
+	// skip the freshness flush; it must not block the update.
+	existing, err := h.db.GetRemote(r.Context(), name)
+	oldKnown := err == nil
 	var remote models.Remote
+	if oldKnown {
+		remote.MutableTTL = existing.MutableTTL
+	}
 	if err := json.NewDecoder(r.Body).Decode(&remote); err != nil {
 		http.Error(w, "invalid json", http.StatusBadRequest)
 		return
@@ -132,13 +144,6 @@ func (h *RemotesHandler) update(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
-	// Capture the current backend before the update so we can tell whether the
-	// remote's base_url (its upstream) changed. A read failure just means we
-	// skip the freshness flush; it must not block the update.
-	oldBaseURL, oldKnown := "", false
-	if existing, err := h.db.GetRemote(r.Context(), name); err == nil {
-		oldBaseURL, oldKnown = existing.BaseURL, true
-	}
 	if err := h.db.UpdateRemote(r.Context(), &remote); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
@@ -147,13 +152,13 @@ func (h *RemotesHandler) update(w http.ResponseWriter, r *http.Request) {
 	// Release / APKINDEX): purge it so the next request re-fetches from the new
 	// upstream instead of serving stale data until TTL expiry. A flush failure
 	// is logged but does not fail the request — the DB update already landed.
-	if oldKnown && oldBaseURL != remote.BaseURL && h.cache != nil {
+	if oldKnown && existing.BaseURL != remote.BaseURL && h.cache != nil {
 		if err := h.cache.FlushRemote(r.Context(), name); err != nil {
 			slog.Warn("flush cached metadata after base_url change failed",
 				"remote", name, "error", err)
 		} else {
 			slog.Info("flushed cached metadata after base_url change",
-				"remote", name, "old_base_url", oldBaseURL, "new_base_url", remote.BaseURL)
+				"remote", name, "old_base_url", existing.BaseURL, "new_base_url", remote.BaseURL)
 		}
 	}
 	writeJSON(w, http.StatusOK, remote)
@@ -165,6 +170,11 @@ func (h *RemotesHandler) del(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
+	if h.cache != nil {
+		if err := h.cache.FlushRemote(r.Context(), name); err != nil {
+			slog.Warn("flush cached metadata after delete failed", "remote", name, "error", err)
+		}
+	}
 	w.WriteHeader(http.StatusNoContent)
 }
 
diff --git a/internal/api/v2/remotes_flush_test.go b/internal/api/v2/remotes_flush_test.go
index 09a25b5..4f8036a 100644
--- a/internal/api/v2/remotes_flush_test.go
+++ b/internal/api/v2/remotes_flush_test.go
@@ -94,3 +94,28 @@ func TestUpdateFlushFailureStillSucceeds(t *testing.T) {
 		t.Fatalf("flush calls = %v, want exactly one attempted flush", ff.calls)
 	}
 }
+
+// Deleting a remote flushes its cached state so a re-created remote of the
+// same name starts cold; a flush error does not fail the delete.
+func TestDeleteFlushesCache(t *testing.T) {
+	if testDSN == "" {
+		t.Skip("Docker unavailable")
+	}
+	db, err := database.New(testDSN)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	for _, ff := range []*fakeFlusher{{}, {err: errors.New("redis down")}} {
+		const name = "rpm-flush-delete"
+		seedRemote(t, db, name, "https://example.com/repo")
+		h := NewRemotesHandler(db, ff, nil).Routes()
+		if c := do(t, h, "DELETE", "/"+name, ""); c != 204 {
+			t.Fatalf("delete = %d, want 204", c)
+		}
+		if len(ff.calls) != 1 || ff.calls[0] != name {
+			t.Fatalf("flush calls = %v, want exactly one flush of %q", ff.calls, name)
+		}
+	}
+}
diff --git a/internal/api/v2/remotes_ttl_test.go b/internal/api/v2/remotes_ttl_test.go
new file mode 100644
index 0000000..7beb859
--- /dev/null
+++ b/internal/api/v2/remotes_ttl_test.go
@@ -0,0 +1,57 @@
+package v2
+
+import (
+	"context"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/database"
+)
+
+// An omitted mutable_ttl defaults to 3600 on create and keeps the stored value
+// on update; an explicit 0 is stored as 0 in both.
+func TestMutableTTLOmittedVsZero(t *testing.T) {
+	if testDSN == "" {
+		t.Skip("Docker unavailable")
+	}
+	db, err := database.New(testDSN)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	h := NewRemotesHandler(db, nil, nil).Routes()
+	ttl := func(name string) int {
+		t.Helper()
+		r, err := db.GetRemote(context.Background(), name)
+		if err != nil {
+			t.Fatalf("get %s: %v", name, err)
+		}
+		return r.MutableTTL
+	}
+	const body = `"package_type":"rpm","base_url":"https://example.com/repo"`
+
+	steps := []struct {
+		method, path, json string
+		want               int
+	}{
+		{"POST", "/", `{"name":"ttl-omit",` + body + `}`, 3600},
+		{"PUT", "/ttl-omit", `{` + body + `,"mutable_ttl":120}`, 120},
+		{"PUT", "/ttl-omit", `{` + body + `}`, 120},
+		{"PUT", "/ttl-omit", `{` + body + `,"mutable_ttl":0}`, 0},
+		{"PUT", "/ttl-omit", `{` + body + `}`, 0},
+	}
+	for i, s := range steps {
+		if c := do(t, h, s.method, s.path, s.json); c/100 != 2 {
+			t.Fatalf("step %d %s %s = %d", i, s.method, s.path, c)
+		}
+		if got := ttl("ttl-omit"); got != s.want {
+			t.Errorf("step %d: mutable_ttl = %d, want %d", i, got, s.want)
+		}
+	}
+
+	if c := do(t, h, "POST", "/", `{"name":"ttl-zero",`+body+`,"mutable_ttl":0}`); c != 201 {
+		t.Fatalf("create explicit 0 = %d", c)
+	}
+	if got := ttl("ttl-zero"); got != 0 {
+		t.Errorf("explicit 0 stored as %d", got)
+	}
+}
diff --git a/internal/cache/cache_test.go b/internal/cache/cache_test.go
index 4093a60..a1e1dd3 100644
--- a/internal/cache/cache_test.go
+++ b/internal/cache/cache_test.go
@@ -61,18 +61,54 @@ func TestTTL(t *testing.T) {
 func TestLock(t *testing.T) {
 	requireRedis(t)
 	ctx := context.Background()
-	ok, err := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute)
-	if err != nil || !ok {
-		t.Fatalf("first acquire should succeed: %v %v", ok, err)
+	token, err := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute)
+	if err != nil || token == "" {
+		t.Fatalf("first acquire should succeed: %q %v", token, err)
 	}
-	if ok, _ := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute); ok {
+	if again, _ := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute); again != "" {
 		t.Error("second acquire should fail while held")
 	}
-	if err := testRedis.ReleaseLock(ctx, "r", "lockpath"); err != nil {
+	if err := testRedis.ReleaseLock(ctx, "r", "lockpath", "not-the-owner"); err != nil {
 		t.Fatal(err)
 	}
-	if ok, _ := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute); !ok {
-		t.Error("acquire should succeed after release")
+	if again, _ := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute); again != "" {
+		t.Error("release with a foreign token must not drop the lock")
+	}
+	if err := testRedis.ReleaseLock(ctx, "r", "lockpath", token); err != nil {
+		t.Fatal(err)
+	}
+	next, _ := testRedis.AcquireLock(ctx, "r", "lockpath", time.Minute)
+	if next == "" {
+		t.Fatal("acquire should succeed after release")
+	}
+	if next == token {
+		t.Error("tokens must differ between holders")
+	}
+}
+
+func TestStaleReleaseKeepsNextHolder(t *testing.T) {
+	requireRedis(t)
+	ctx := context.Background()
+	stale, err := testRedis.AcquireLock(ctx, "r", "stale", 50*time.Millisecond)
+	if err != nil || stale == "" {
+		t.Fatalf("acquire: %q %v", stale, err)
+	}
+	time.Sleep(100 * time.Millisecond)
+	fresh, err := testRedis.AcquireLock(ctx, "r", "stale", time.Minute)
+	if err != nil || fresh == "" {
+		t.Fatalf("acquire after expiry: %q %v", fresh, err)
+	}
+	if err := testRedis.ReleaseLock(ctx, "r", "stale", stale); err != nil {
+		t.Fatal(err)
+	}
+	if again, _ := testRedis.AcquireLock(ctx, "r", "stale", time.Minute); again != "" {
+		t.Fatal("stale holder's release dropped the second holder's lock")
+	}
+	if err := testRedis.ReleaseLock(ctx, "r", "stale", fresh); err != nil {
+		t.Fatal(err)
+	}
+	if again, _ := testRedis.AcquireLock(ctx, "r", "stale", time.Minute); again == "" {
+		t.Error("owner release should free the lock")
 	}
 }
 
@@ -86,6 +122,12 @@ func TestETagAndToken(t *testing.T) {
 	if v, _ := testRedis.GetETag(ctx, "r", "p"); v != `"abc"` {
 		t.Errorf("etag = %q", v)
 	}
+	if err := testRedis.SetETag(ctx, "r", "p", "", 0); err != nil {
+		t.Fatal(err)
+	}
+	if v, _ := testRedis.GetETag(ctx, "r", "p"); v != "" {
+		t.Errorf("empty etag should drop the stored one, got %q", v)
+	}
 
 	if v, _ := testRedis.GetToken(ctx, "missing"); v != "" {
 		t.Error("missing token should be empty")
diff --git a/internal/cache/redis.go b/internal/cache/redis.go
index b33e0cc..c120745 100644
--- a/internal/cache/redis.go
+++ b/internal/cache/redis.go
@@ -2,6 +2,7 @@ package cache
 
 import (
 	"context"
+	"crypto/rand"
 	"fmt"
 	"strings"
 	"time"
@@ -46,19 +47,31 @@ func (r *Redis) CheckTTL(ctx context.Context, remote, path string) (bool, error)
 	return exists > 0, nil
 }
 
-func (r *Redis) AcquireLock(ctx context.Context, remote, path string, ttl time.Duration) (bool, error) {
+// AcquireLock returns the owner token on success and "" when the lock is held.
+func (r *Redis) AcquireLock(ctx context.Context, remote, path string, ttl time.Duration) (string, error) {
 	key := fmt.Sprintf("lock:%s:%s", remote, path)
-	ok, err := r.client.SetNX(ctx, key, "1", ttl).Result()
-	return ok, err
+	token := rand.Text()
+	ok, err := r.client.SetNX(ctx, key, token, ttl).Result()
+	if err != nil || !ok {
+		return "", err
+	}
+	return token, nil
 }
 
-func (r *Redis) ReleaseLock(ctx context.Context, remote, path string) error {
+var releaseScript = redis.NewScript(`if redis.call('get',KEYS[1])==ARGV[1] then return redis.call('del',KEYS[1]) else return 0 end`)
+
+// ReleaseLock deletes the lock only while token still owns it.
+func (r *Redis) ReleaseLock(ctx context.Context, remote, path, token string) error {
 	key := fmt.Sprintf("lock:%s:%s", remote, path)
-	return r.client.Del(ctx, key).Err()
+	return releaseScript.Run(ctx, r.client, []string{key}, token).Err()
 }
 
+// SetETag stores etag for path, or drops the stored one when etag is empty.
 func (r *Redis) SetETag(ctx context.Context, remote, path, etag string, ttl time.Duration) error {
 	key := fmt.Sprintf("etag:%s:%s", remote, path)
+	if etag == "" {
+		return r.client.Del(ctx, key).Err()
+	}
 	return r.client.Set(ctx, key, etag, ttl).Err()
 }
 
diff --git a/internal/database/github_sync_test.go b/internal/database/github_sync_test.go
index c97449b..d66dc07 100644
--- a/internal/database/github_sync_test.go
+++ b/internal/database/github_sync_test.go
@@ -207,3 +207,72 @@ func TestGitHubSyncLeaseFailureBackoff(t *testing.T) {
 		t.Fatal("claimed inside freshness window after a successful sync")
 	}
 }
+
+// Deleting a remote drops its sync state, so a recreated remote of the same name
+// starts clean instead of inheriting the old ETag, sync time and retry state.
+func TestGitHubSyncStateDeletedWithRemote(t *testing.T) {
+	requireDB(t)
+	for _, tc := range []struct {
+		table   string
+		pt      models.PackageType
+		claim   func(name string) (bool, string, error)
+		release func(name string, res provider.SyncResult) error
+	}{
+		{"github_rpm_sync_state", models.PackageGitHubRPM,
+			func(n string) (bool, string, error) {
+				return testDB.ClaimGitHubSyncLease(ctx(), n, "r1", time.Hour, time.Minute)
+			},
+			func(n string, res provider.SyncResult) error {
+				return testDB.ReleaseGitHubSyncLease(ctx(), n, "r1", res)
+			}},
+		{"github_deb_sync_state", models.PackageGitHubDeb,
+			func(n string) (bool, string, error) {
+				return testDB.ClaimGitHubDebSyncLease(ctx(), n, "r1", time.Hour, time.Minute)
+			},
+			func(n string, res provider.SyncResult) error {
+				return testDB.ReleaseGitHubDebSyncLease(ctx(), n, "r1", res)
+			}},
+		{"github_alpine_sync_state", models.PackageGitHubAlpine,
+			func(n string) (bool, string, error) {
+				return testDB.ClaimGitHubAlpineSyncLease(ctx(), n, "r1", time.Hour, time.Minute)
+			},
+			func(n string, res provider.SyncResult) error {
+				return testDB.ReleaseGitHubAlpineSyncLease(ctx(), n, "r1", res)
+			}},
+	} {
+		t.Run(tc.table, func(t *testing.T) {
+			name := "gh-recreate-" + time.Now().Format("150405.000000")
+			create := func() {
+				t.Helper()
+				if err := testDB.CreateRemote(ctx(), &models.Remote{
+					Name: name, PackageType: tc.pt, RepoType: models.RepoTypeRemote,
+					BaseURL: "https://api.github.com/repos/acme/tools", ReleasesRemote: "github", MutableTTL: 3600,
+				}); err != nil {
+					t.Fatalf("create remote: %v", err)
+				}
+			}
+
+			create()
+			if ok, _, err := tc.claim(name); err != nil || !ok {
+				t.Fatalf("claim: ok=%v err=%v", ok, err)
+			}
+			if err := tc.release(name, provider.SyncResult{Etag: `"old"`}); err != nil {
+				t.Fatalf("release: %v", err)
+			}
+
+			if err := testDB.DeleteRemote(ctx(), name); err != nil {
+				t.Fatalf("delete remote: %v", err)
+			}
+			var rows int
+			if err := testDB.Pool.QueryRow(ctx(), `SELECT count(*) FROM `+tc.table+` WHERE remote_name = $1`, name).Scan(&rows); err != nil || rows != 0 {
+				t.Fatalf("sync state left after delete: rows=%d err=%v", rows, err)
+			}
+
+			create()
+			ok, etag, err := tc.claim(name)
+			if err != nil || !ok || etag != "" {
+				t.Fatalf("recreated remote claim ok=%v etag=%q err=%v, want a fresh claim with no etag", ok, etag, err)
+			}
+		})
+	}
+}
diff --git a/internal/database/helm_metadata.go b/internal/database/helm_metadata.go
new file mode 100644
index 0000000..6110f03
--- /dev/null
+++ b/internal/database/helm_metadata.go
@@ -0,0 +1,44 @@
+package database
+
+import (
+	"context"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func (db *DB) InsertHelmMetadata(ctx context.Context, meta *provider.HelmMetadata) error {
+	_, err := db.Pool.Exec(ctx, `
+		INSERT INTO helm_metadata (repo_name, file_path, content_hash, name, version, chart_yaml)
+		VALUES ($1,$2,$3,$4,$5,$6)
+		ON CONFLICT (repo_name, file_path) DO NOTHING
+	`, meta.RepoName, meta.FilePath, meta.ContentHash, meta.Name, meta.Version, meta.ChartYAML)
+	return err
+}
+
+func (db *DB) DeleteHelmMetadata(ctx context.Context, repoName, filePath string) error {
+	_, err := db.Pool.Exec(ctx, `DELETE FROM helm_metadata WHERE repo_name = $1 AND file_path = $2`, repoName, filePath)
+	return err
+}
+
+func (db *DB) ListHelmMetadataEntries(ctx context.Context, repoName string) ([]provider.HelmMetadata, error) {
+	rows, err := db.Pool.Query(ctx, `
+		SELECT repo_name, file_path, content_hash, name, version, chart_yaml, created_at
+		FROM helm_metadata
+		WHERE repo_name = $1
+		ORDER BY name, version, file_path
+	`, repoName)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []provider.HelmMetadata
+	for rows.Next() {
+		var m provider.HelmMetadata
+		if err := rows.Scan(&m.RepoName, &m.FilePath, &m.ContentHash, &m.Name, &m.Version, &m.ChartYAML, &m.CreatedAt); err != nil {
+			return nil, err
+		}
+		result = append(result, m)
+	}
+	return result, rows.Err()
+}
diff --git a/internal/database/puppet_metadata.go b/internal/database/puppet_metadata.go
new file mode 100644
index 0000000..036c35d
--- /dev/null
+++ b/internal/database/puppet_metadata.go
@@ -0,0 +1,46 @@
+package database
+
+import (
+	"context"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func (db *DB) InsertPuppetMetadata(ctx context.Context, meta *provider.PuppetMetadata) error {
+	_, err := db.Pool.Exec(ctx, `
+		INSERT INTO puppet_metadata (repo_name, file_path, content_hash, slug, version, metadata_json, file_size, file_md5)
+		VALUES ($1,$2,$3,$4,$5,$6,$7,$8)
+		ON CONFLICT (repo_name, file_path) DO NOTHING
+	`, meta.RepoName, meta.FilePath, meta.ContentHash, meta.Slug, meta.Version, meta.MetadataJSON, meta.Size, meta.MD5)
+	return err
+}
+
+func (db *DB) DeletePuppetMetadata(ctx context.Context, repoName, filePath string) error {
+	_, err := db.Pool.Exec(ctx, `DELETE FROM puppet_metadata WHERE repo_name = $1 AND file_path = $2`, repoName, filePath)
+	return err
+}
+
+// ListPuppetMetadataEntries returns a repo's releases, optionally narrowed to
+// one module slug (empty slug lists every module).
+func (db *DB) ListPuppetMetadataEntries(ctx context.Context, repoName, slug string) ([]provider.PuppetMetadata, error) {
+	rows, err := db.Pool.Query(ctx, `
+		SELECT repo_name, file_path, content_hash, slug, version, metadata_json, file_size, file_md5, created_at
+		FROM puppet_metadata
+		WHERE repo_name = $1 AND ($2 = '' OR slug = $2)
+		ORDER BY slug, file_path
+	`, repoName, slug)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []provider.PuppetMetadata
+	for rows.Next() {
+		var m provider.PuppetMetadata
+		if err := rows.Scan(&m.RepoName, &m.FilePath, &m.ContentHash, &m.Slug, &m.Version, &m.MetadataJSON, &m.Size, &m.MD5, &m.CreatedAt); err != nil {
+			return nil, err
+		}
+		result = append(result, m)
+	}
+	return result, rows.Err()
+}
diff --git a/internal/provider/all/alpine.go b/internal/provider/all/alpine.go
new file mode 100644
index 0000000..dd4d0fd
--- /dev/null
+++ b/internal/provider/all/alpine.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/alpine"
diff --git a/internal/provider/all/ansible.go b/internal/provider/all/ansible.go
new file mode 100644
index 0000000..22c78b1
--- /dev/null
+++ b/internal/provider/all/ansible.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/ansible"
diff --git a/internal/provider/all/cargo.go b/internal/provider/all/cargo.go
new file mode 100644
index 0000000..328b155
--- /dev/null
+++ b/internal/provider/all/cargo.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/cargo"
diff --git a/internal/provider/all/deb.go b/internal/provider/all/deb.go
new file mode 100644
index 0000000..86b87c2
--- /dev/null
+++ b/internal/provider/all/deb.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/deb"
diff --git a/internal/provider/all/docker.go b/internal/provider/all/docker.go
new file mode 100644
index 0000000..00ea7d9
--- /dev/null
+++ b/internal/provider/all/docker.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/docker"
diff --git a/internal/provider/all/gems.go b/internal/provider/all/gems.go
new file mode 100644
index 0000000..ebd6ccf
--- /dev/null
+++ b/internal/provider/all/gems.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/gems"
diff --git a/internal/provider/all/generic.go b/internal/provider/all/generic.go
new file mode 100644
index 0000000..a7c1a1c
--- /dev/null
+++ b/internal/provider/all/generic.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/generic"
diff --git a/internal/provider/all/goproxy.go b/internal/provider/all/goproxy.go
new file mode 100644
index 0000000..c8fb8d8
--- /dev/null
+++ b/internal/provider/all/goproxy.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/goproxy"
diff --git a/internal/provider/all/helm.go b/internal/provider/all/helm.go
new file mode 100644
index 0000000..b42b787
--- /dev/null
+++ b/internal/provider/all/helm.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/helm"
diff --git a/internal/provider/all/npm.go b/internal/provider/all/npm.go
new file mode 100644
index 0000000..f71d089
--- /dev/null
+++ b/internal/provider/all/npm.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/npm"
diff --git a/internal/provider/all/nuget.go b/internal/provider/all/nuget.go
new file mode 100644
index 0000000..bdc0922
--- /dev/null
+++ b/internal/provider/all/nuget.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/nuget"
diff --git a/internal/provider/all/puppet.go b/internal/provider/all/puppet.go
new file mode 100644
index 0000000..266e990
--- /dev/null
+++ b/internal/provider/all/puppet.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/puppet"
diff --git a/internal/provider/all/pypi.go b/internal/provider/all/pypi.go
new file mode 100644
index 0000000..27a48a9
--- /dev/null
+++ b/internal/provider/all/pypi.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/pypi"
diff --git a/internal/provider/all/rpm.go b/internal/provider/all/rpm.go
new file mode 100644
index 0000000..8ec6c17
--- /dev/null
+++ b/internal/provider/all/rpm.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/rpm"
diff --git a/internal/provider/all/terraform.go b/internal/provider/all/terraform.go
new file mode 100644
index 0000000..39e7f75
--- /dev/null
+++ b/internal/provider/all/terraform.go
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/terraform"
diff --git a/internal/provider/alpine/github.go b/internal/provider/alpine/github.go
index b60600e..46aad38 100644
--- a/internal/provider/alpine/github.go
+++ b/internal/provider/alpine/github.go
@@ -372,6 +372,9 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 		return newEtag, false, err
 	}
 
+	// A transiently failed asset fails the scan so the ETag is not advanced and
+	// the retry re-derives it; an invalid package is skipped as no retry fixes it.
+	var failed []error
 	seen := map[string]bool{}
 	for _, rel := range releases {
 		if rel.Draft {
@@ -400,10 +403,14 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			meta, err := p.deriveAsset(ctx, remote, asset, fp)
 			if err != nil {
 				slog.Warn("github_alpine: derive asset failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				if !errors.Is(err, provider.ErrInvalidPackage) {
+					failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
+				}
 				continue
 			}
 			if err := inserter.InsertAlpineMetadata(ctx, meta); err != nil {
 				slog.Error("github_alpine: insert metadata failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
 				continue
 			}
 			slog.Info("github_alpine: derived asset", "remote", remote.Name, "name", meta.Name, "version", meta.Version, "arch", meta.Arch)
@@ -415,7 +422,7 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			_ = deleter.DeleteAlpineMetadata(ctx, remote.Name, fp)
 		}
 	}
-	return newEtag, true, nil
+	return newEtag, true, errors.Join(failed...)
 }
 
 type ghRelease struct {
@@ -496,7 +503,7 @@ func (p *GitHubProvider) deriveAsset(ctx context.Context, remote models.Remote,
 		return nil, err
 	}
 	if meta.Name == "" || meta.Arch == "" {
-		return nil, errors.New(".PKGINFO missing pkgname/arch")
+		return nil, fmt.Errorf("%w: .PKGINFO missing pkgname/arch", provider.ErrInvalidPackage)
 	}
 
 	meta.RepoName = remote.Name
@@ -526,13 +533,13 @@ func (p *GitHubProvider) fetchPkginfo(ctx context.Context, remote models.Remote,
 		}
 		meta, complete, perr := pkginfoFromPrefix(body)
 		if perr != nil {
-			return nil, fmt.Errorf("parse apk .PKGINFO: %w", perr)
+			return nil, fmt.Errorf("%w: parse apk .PKGINFO: %w", provider.ErrInvalidPackage, perr)
 		}
 		if complete {
 			return meta, nil
 		}
 		if full || n >= p.headerMax {
-			return nil, fmt.Errorf(".PKGINFO not found within %d bytes of %s", n, downloadURL)
+			return nil, fmt.Errorf("%w: .PKGINFO not found within %d bytes of %s", provider.ErrInvalidPackage, n, downloadURL)
 		}
 		n *= 2
 		if n > p.headerMax {
@@ -594,7 +601,7 @@ func pkginfoFromPrefix(prefix []byte) (meta *provider.AlpineMetadata, complete b
 }
 
 // rangeGet returns the first n bytes of downloadURL. full is true when the
-// response body was shorter than n (i.e. we already have the whole object).
+// response holds the whole object.
 func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, downloadURL string, n int64) ([]byte, bool, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
 	if err != nil {
@@ -616,15 +623,9 @@ func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, dow
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
-		return nil, false, fmt.Errorf("range GET %s: status %d", downloadURL, resp.StatusCode)
+		return nil, false, fmt.Errorf("range GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
-
-	body, err := io.ReadAll(io.LimitReader(resp.Body, n))
-	if err != nil {
-		return nil, false, err
-	}
-	full := int64(len(body)) < n
-	return body, full, nil
+	return provider.ReadPrefix(resp, n)
 }
 
 // assetPath is the package's location relative to github.com — the path the
diff --git a/internal/provider/alpine/github_test.go b/internal/provider/alpine/github_test.go
index 9f33fb0..69f27f7 100644
--- a/internal/provider/alpine/github_test.go
+++ b/internal/provider/alpine/github_test.go
@@ -8,6 +8,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -88,15 +89,17 @@ type githubFixture struct {
 	notModHit   int
 	releaseAuth string
 	assetAuth   string
+	assetFail   map[string]int // asset filename -> downloads left to answer 500
 	mu          sync.Mutex
 }
 
 func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 	t.Helper()
 	f := &githubFixture{
-		apkBytes: map[string][]byte{},
-		rangeHit: map[string]int{},
-		fullHit:  map[string]int{},
+		apkBytes:  map[string][]byte{},
+		rangeHit:  map[string]int{},
+		fullHit:   map[string]int{},
+		assetFail: map[string]int{},
 	}
 	f.apkBytes["demo-1.2.3-r0.apk"] = testsupport.MinimalApk("demo", "1.2.3-r0", "x86_64")
 
@@ -146,6 +149,12 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 		}
 		rng := r.Header.Get("Range")
 		f.mu.Lock()
+		if f.assetFail[name] > 0 {
+			f.assetFail[name]--
+			f.mu.Unlock()
+			http.Error(w, "boom", http.StatusInternalServerError)
+			return
+		}
 		f.assetAuth = r.Header.Get("Authorization")
 		if rng != "" {
 			f.rangeHit[name]++
@@ -495,3 +504,13 @@ func readAPKIndex(t *testing.T, gzBytes []byte) string {
 		}
 	}
 }
+
+func TestGitHubDeriveAssetMissingPkgnameIsInvalid(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.apkBytes["nameless-1-r0.apk"] = testsupport.MinimalApk("", "1-r0", "x86_64")
+	asset := ghAsset{BrowserDownloadURL: fx.srv.URL + "/acme/tools/releases/download/v1.2.3/nameless-1-r0.apk"}
+	_, err := newTestProvider().deriveAsset(context.Background(), fx.remote(), asset, "fp")
+	if !errors.Is(err, provider.ErrInvalidPackage) {
+		t.Fatalf("want ErrInvalidPackage, got %v", err)
+	}
+}
diff --git a/internal/provider/alpine/syncer_test.go b/internal/provider/alpine/syncer_test.go
index 0401c52..1a6ce96 100644
--- a/internal/provider/alpine/syncer_test.go
+++ b/internal/provider/alpine/syncer_test.go
@@ -308,3 +308,58 @@ func TestSyncerPrimeBypassesRecencyPeriodicDoesNot(t *testing.T) {
 		t.Fatalf("periodic scan ran inside recency window: %d -> %d releases calls", releasesAfterPrime, fx.releasesHit)
 	}
 }
+
+// A transiently failed asset fails the scan: the ETag is not advanced, a retry
+// is scheduled, and the retry against the unchanged release list derives it. An
+// invalid package is skipped instead, since no retry can fix it.
+func TestSyncerFailedAssetRetry(t *testing.T) {
+	for _, tc := range []struct {
+		name      string
+		corrupt   bool
+		wantRetry bool
+	}{
+		{name: "transient", wantRetry: true},
+		{name: "invalid package", corrupt: true},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			fx := newGitHubFixture(t, true)
+			fx.etag = `"v1"`
+			if tc.corrupt {
+				fx.apkBytes["other-9-r0.apk"] = []byte("not a package")
+			} else {
+				fx.apkBytes["other-9-r0.apk"] = testsupport.MinimalApk("other", "9-r0", "aarch64")
+				fx.assetFail["other-9-r0.apk"] = 1
+			}
+			store := newFakeSyncStore()
+			s := newSyncer(store, newTestProvider(), testSyncConfig())
+			remote := fx.remote()
+			bg := context.Background()
+
+			s.process(bg, syncJob{remote: remote, prime: true})
+			_, pending := store.retryAt[remote.Name]
+			if pending != tc.wantRetry {
+				t.Fatalf("retry pending=%v, want %v", pending, tc.wantRetry)
+			}
+			if _, saved := store.etags[remote.Name]; saved == tc.wantRetry {
+				t.Fatalf("etag saved=%v after first scan", saved)
+			}
+			if rows, _ := store.ListAlpineMetadataEntries(bg, remote.Name); len(rows) != 1 {
+				t.Fatalf("healthy asset not served: %d rows", len(rows))
+			}
+			if !tc.wantRetry {
+				return
+			}
+
+			store.mu.Lock()
+			store.retryAt[remote.Name] = time.Now().Add(-time.Second)
+			store.mu.Unlock()
+			s.process(bg, syncJob{remote: remote})
+			if _, pending := store.retryAt[remote.Name]; pending || store.etags[remote.Name] != `"v1"` {
+				t.Fatalf("retry not recorded: pending=%v etag=%q", pending, store.etags[remote.Name])
+			}
+			if rows, _ := store.ListAlpineMetadataEntries(bg, remote.Name); len(rows) != 2 {
+				t.Fatalf("retry did not derive the failed asset: %d rows", len(rows))
+			}
+		})
+	}
+}
diff --git a/internal/provider/cap_file_store.go b/internal/provider/cap_file_store.go
new file mode 100644
index 0000000..a41540f
--- /dev/null
+++ b/internal/provider/cap_file_store.go
@@ -0,0 +1,15 @@
+package provider
+
+import (
+	"context"
+	"io"
+)
+
+type FileStore interface {
+	ListFilesByPrefix(ctx context.Context, repoName, prefix string) ([]FileEntry, error)
+	ListPackages(ctx context.Context, repoName string) ([]string, error)
+}
+
+type BlobReader interface {
+	Download(ctx context.Context, key string) (io.ReadCloser, int64, error)
+}
diff --git a/internal/provider/cap_index_merger.go b/internal/provider/cap_index_merger.go
new file mode 100644
index 0000000..17eb6fc
--- /dev/null
+++ b/internal/provider/cap_index_merger.go
@@ -0,0 +1,10 @@
+package provider
+
+type IndexMerger interface {
+	MergeIndexes(members []MemberIndex, proxyBaseURL string) ([]byte, error)
+}
+
+type MemberIndex struct {
+	RemoteName string
+	Body       []byte
+}
diff --git a/internal/provider/cap_local_indexer.go b/internal/provider/cap_local_indexer.go
new file mode 100644
index 0000000..371681c
--- /dev/null
+++ b/internal/provider/cap_local_indexer.go
@@ -0,0 +1,11 @@
+package provider
+
+import (
+	"context"
+	"net/http"
+)
+
+type LocalIndexer interface {
+	ServeLocalIndex(w http.ResponseWriter, r *http.Request, files FileStore, repoName, path string) bool
+	GenerateLocalIndex(ctx context.Context, files FileStore, repoName, path string) ([]byte, error)
+}
diff --git a/internal/provider/cap_local_uploader.go b/internal/provider/cap_local_uploader.go
new file mode 100644
index 0000000..be5d624
--- /dev/null
+++ b/internal/provider/cap_local_uploader.go
@@ -0,0 +1,6 @@
+package provider
+
+type LocalUploader interface {
+	ValidateUpload(filePath string) (storagePath, contentType string, err error)
+	UploadResponse(storagePath, contentHash string, sizeBytes int64) map[string]any
+}
diff --git a/internal/provider/cap_post_delete_hook.go b/internal/provider/cap_post_delete_hook.go
new file mode 100644
index 0000000..ac6cf56
--- /dev/null
+++ b/internal/provider/cap_post_delete_hook.go
@@ -0,0 +1,11 @@
+package provider
+
+import (
+	"context"
+)
+
+// PostDeleteHook lets a provider clean up derived state (e.g. RPM metadata that
+// feeds generated repodata) after a local file is removed.
+type PostDeleteHook interface {
+	AfterDelete(ctx context.Context, repoName, storagePath string, db MetadataDeleter) error
+}
diff --git a/internal/provider/cap_post_upload_hook.go b/internal/provider/cap_post_upload_hook.go
new file mode 100644
index 0000000..a8f69a0
--- /dev/null
+++ b/internal/provider/cap_post_upload_hook.go
@@ -0,0 +1,9 @@
+package provider
+
+import (
+	"context"
+)
+
+type PostUploadHook interface {
+	AfterUpload(ctx context.Context, repoName, storagePath, contentHash string, blobs BlobReader, db MetadataStore)
+}
diff --git a/internal/provider/cap_query_forwarder.go b/internal/provider/cap_query_forwarder.go
new file mode 100644
index 0000000..096336c
--- /dev/null
+++ b/internal/provider/cap_query_forwarder.go
@@ -0,0 +1,12 @@
+package provider
+
+// QueryForwarder is a remote provider whose upstream answers depend on the
+// query string (e.g. paginated JSON APIs). Only the named params for path are
+// forwarded upstream and kept in the cache key, each as the canonical value
+// its validator returns; a value the validator rejects is dropped.
+type QueryForwarder interface {
+	ForwardedQuery(path string) map[string]QueryValidator
+}
+
+// QueryValidator canonicalises a raw query value, reporting false to drop it.
+type QueryValidator func(v string) (string, bool)
diff --git a/internal/provider/cap_remote_server.go b/internal/provider/cap_remote_server.go
new file mode 100644
index 0000000..f4f3fd2
--- /dev/null
+++ b/internal/provider/cap_remote_server.go
@@ -0,0 +1,25 @@
+package provider
+
+import (
+	"net/http"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// RemoteServer lets a remote provider fully answer a request itself instead of
+// going through the byte-proxy engine. It is the remote-side analog of
+// LocalIndexer: a metadata-only remote (e.g. github_rpm) uses it to synthesize
+// repodata from derived per-asset metadata and to redirect package downloads to
+// a backend remote, without ever precaching the packages. Returning false lets
+// the normal proxy path take over.
+type RemoteServer interface {
+	ServeRemote(w http.ResponseWriter, r *http.Request, remote models.Remote, path, proxyBaseURL string, store RemoteMetadataStore) bool
+}
+
+// RemoteMetadataStore is the persistence surface a RemoteServer needs to cache
+// and read the metadata it derives per upstream asset. *database.DB satisfies it.
+type RemoteMetadataStore interface {
+	RPMMetadataReader
+	MetadataStore
+	MetadataDeleter
+}
diff --git a/internal/provider/cap_response_rewriter.go b/internal/provider/cap_response_rewriter.go
new file mode 100644
index 0000000..2c45d41
--- /dev/null
+++ b/internal/provider/cap_response_rewriter.go
@@ -0,0 +1,7 @@
+package provider
+
+// ResponseRewriter marks providers whose RewriteResponse changes mutable
+// bodies, so the served length is only known after a fetch.
+type ResponseRewriter interface {
+	RewritesResponse()
+}
diff --git a/internal/provider/cap_serve_rewriter.go b/internal/provider/cap_serve_rewriter.go
new file mode 100644
index 0000000..07fc262
--- /dev/null
+++ b/internal/provider/cap_serve_rewriter.go
@@ -0,0 +1,12 @@
+package provider
+
+import (
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// ServeRewriter rewrites a cached mutable remote response per request, for
+// indexes whose URLs must name the requesting host and so cannot be rewritten
+// before caching.
+type ServeRewriter interface {
+	RewriteServed(body []byte, remote models.Remote, proxyBaseURL string) []byte
+}
diff --git a/internal/provider/deb/github.go b/internal/provider/deb/github.go
index 8731db3..83c85de 100644
--- a/internal/provider/deb/github.go
+++ b/internal/provider/deb/github.go
@@ -333,6 +333,9 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 		return newEtag, false, err
 	}
 
+	// A transiently failed asset fails the scan so the ETag is not advanced and
+	// the retry re-derives it; an invalid package is skipped as no retry fixes it.
+	var failed []error
 	seen := map[string]bool{}
 	for _, rel := range releases {
 		if rel.Draft {
@@ -361,10 +364,14 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			meta, err := p.deriveAsset(ctx, remote, asset, fp)
 			if err != nil {
 				slog.Warn("github_deb: derive asset failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				if !errors.Is(err, provider.ErrInvalidPackage) {
+					failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
+				}
 				continue
 			}
 			if err := store.InsertDebMetadata(ctx, meta); err != nil {
 				slog.Error("github_deb: insert metadata failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
 				continue
 			}
 			slog.Info("github_deb: derived asset", "remote", remote.Name, "name", meta.Name, "version", meta.Version, "arch", meta.Architecture)
@@ -376,7 +383,7 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			_ = store.DeleteDebMetadata(ctx, remote.Name, fp)
 		}
 	}
-	return newEtag, true, nil
+	return newEtag, true, errors.Join(failed...)
 }
 
 type ghRelease struct {
@@ -468,7 +475,7 @@ func (p *GitHubProvider) deriveAsset(ctx context.Context, remote models.Remote,
 		Size:         asset.Size,
 	}
 	if meta.Name == "" {
-		return nil, errors.New("control missing Package field")
+		return nil, fmt.Errorf("%w: control missing Package field", provider.ErrInvalidPackage)
 	}
 
 	// The Packages SHA256 must be the sha256 of the whole .deb. Prefer GitHub's
@@ -503,13 +510,13 @@ func (p *GitHubProvider) fetchControl(ctx context.Context, remote models.Remote,
 		}
 		control, complete, perr := controlFromPrefix(body)
 		if perr != nil {
-			return "", fmt.Errorf("parse deb control: %w", perr)
+			return "", fmt.Errorf("%w: parse deb control: %w", provider.ErrInvalidPackage, perr)
 		}
 		if complete {
 			return control, nil
 		}
 		if full || n >= p.headerMax {
-			return "", fmt.Errorf("control.tar not found within %d bytes of %s", n, downloadURL)
+			return "", fmt.Errorf("%w: control.tar not found within %d bytes of %s", provider.ErrInvalidPackage, n, downloadURL)
 		}
 		n *= 2
 		if n > p.headerMax {
@@ -567,7 +574,7 @@ func controlFromPrefix(prefix []byte) (control string, complete bool, err error)
 }
 
 // rangeGet returns the first n bytes of downloadURL. full is true when the
-// response body was shorter than n (i.e. we already have the whole object).
+// response holds the whole object.
 func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, downloadURL string, n int64) ([]byte, bool, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
 	if err != nil {
@@ -589,15 +596,9 @@ func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, dow
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
-		return nil, false, fmt.Errorf("range GET %s: status %d", downloadURL, resp.StatusCode)
+		return nil, false, fmt.Errorf("range GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
-
-	body, err := io.ReadAll(io.LimitReader(resp.Body, n))
-	if err != nil {
-		return nil, false, err
-	}
-	full := int64(len(body)) < n
-	return body, full, nil
+	return provider.ReadPrefix(resp, n)
 }
 
 func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
@@ -620,7 +621,7 @@ func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK {
-		return "", fmt.Errorf("GET %s: status %d", downloadURL, resp.StatusCode)
+		return "", fmt.Errorf("GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
 
 	h := sha256.New()
diff --git a/internal/provider/deb/github_test.go b/internal/provider/deb/github_test.go
index f27fbc7..b03956d 100644
--- a/internal/provider/deb/github_test.go
+++ b/internal/provider/deb/github_test.go
@@ -7,6 +7,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -81,15 +82,17 @@ type githubFixture struct {
 	notModHit   int
 	releaseAuth string
 	assetAuth   string
+	assetFail   map[string]int // asset filename -> downloads left to answer 500
 	mu          sync.Mutex
 }
 
 func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 	t.Helper()
 	f := &githubFixture{
-		debBytes: map[string][]byte{},
-		rangeHit: map[string]int{},
-		fullHit:  map[string]int{},
+		debBytes:  map[string][]byte{},
+		rangeHit:  map[string]int{},
+		fullHit:   map[string]int{},
+		assetFail: map[string]int{},
 	}
 	f.debBytes["demo_1.2-3_amd64.deb"] = testsupport.MinimalDeb("demo", "1.2-3", "amd64")
 
@@ -139,6 +142,12 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 		}
 		rng := r.Header.Get("Range")
 		f.mu.Lock()
+		if f.assetFail[name] > 0 {
+			f.assetFail[name]--
+			f.mu.Unlock()
+			http.Error(w, "boom", http.StatusInternalServerError)
+			return
+		}
 		f.assetAuth = r.Header.Get("Authorization")
 		if rng != "" {
 			f.rangeHit[name]++
@@ -460,3 +469,13 @@ func TestGitHubAssetPatternFilter(t *testing.T) {
 		t.Fatalf("pattern filter failed, rows=%+v", rows)
 	}
 }
+
+func TestGitHubDeriveAssetMissingPackageIsInvalid(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.debBytes["nameless_1_amd64.deb"] = testsupport.MinimalDeb("", "1", "amd64")
+	asset := ghAsset{BrowserDownloadURL: fx.srv.URL + "/acme/tools/releases/download/v1.2-3/nameless_1_amd64.deb", Digest: "sha256:00"}
+	_, err := newTestProvider().deriveAsset(context.Background(), fx.remote(), asset, "fp")
+	if !errors.Is(err, provider.ErrInvalidPackage) {
+		t.Fatalf("want ErrInvalidPackage, got %v", err)
+	}
+}
diff --git a/internal/provider/deb/syncer_test.go b/internal/provider/deb/syncer_test.go
index e3fe662..b3919a5 100644
--- a/internal/provider/deb/syncer_test.go
+++ b/internal/provider/deb/syncer_test.go
@@ -308,3 +308,58 @@ func TestSyncerPrimeBypassesRecencyPeriodicDoesNot(t *testing.T) {
 		t.Fatalf("periodic scan ran inside recency window: %d -> %d releases calls", releasesAfterPrime, fx.releasesHit)
 	}
 }
+
+// A transiently failed asset fails the scan: the ETag is not advanced, a retry
+// is scheduled, and the retry against the unchanged release list derives it. An
+// invalid package is skipped instead, since no retry can fix it.
+func TestSyncerFailedAssetRetry(t *testing.T) {
+	for _, tc := range []struct {
+		name      string
+		corrupt   bool
+		wantRetry bool
+	}{
+		{name: "transient", wantRetry: true},
+		{name: "invalid package", corrupt: true},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			fx := newGitHubFixture(t, true)
+			fx.etag = `"v1"`
+			if tc.corrupt {
+				fx.debBytes["other_9-9_arm64.deb"] = []byte("not a package")
+			} else {
+				fx.debBytes["other_9-9_arm64.deb"] = testsupport.MinimalDeb("other", "9-9", "arm64")
+				fx.assetFail["other_9-9_arm64.deb"] = 1
+			}
+			store := newFakeSyncStore()
+			s := newSyncer(store, newTestProvider(), testSyncConfig())
+			remote := fx.remote()
+			bg := context.Background()
+
+			s.process(bg, syncJob{remote: remote, prime: true})
+			_, pending := store.retryAt[remote.Name]
+			if pending != tc.wantRetry {
+				t.Fatalf("retry pending=%v, want %v", pending, tc.wantRetry)
+			}
+			if _, saved := store.etags[remote.Name]; saved == tc.wantRetry {
+				t.Fatalf("etag saved=%v after first scan", saved)
+			}
+			if rows, _ := store.ListDebMetadataEntries(bg, remote.Name); len(rows) != 1 {
+				t.Fatalf("healthy asset not served: %d rows", len(rows))
+			}
+			if !tc.wantRetry {
+				return
+			}
+
+			store.mu.Lock()
+			store.retryAt[remote.Name] = time.Now().Add(-time.Second)
+			store.mu.Unlock()
+			s.process(bg, syncJob{remote: remote})
+			if _, pending := store.retryAt[remote.Name]; pending || store.etags[remote.Name] != `"v1"` {
+				t.Fatalf("retry not recorded: pending=%v etag=%q", pending, store.etags[remote.Name])
+			}
+			if rows, _ := store.ListDebMetadataEntries(bg, remote.Name); len(rows) != 2 {
+				t.Fatalf("retry did not derive the failed asset: %d rows", len(rows))
+			}
+		})
+	}
+}
diff --git a/internal/provider/gems/gems.go b/internal/provider/gems/gems.go
new file mode 100644
index 0000000..39d324e
--- /dev/null
+++ b/internal/provider/gems/gems.go
@@ -0,0 +1,62 @@
+// Package gems proxies a RubyGems source: mutable compact index (versions,
+// info/*, names) and legacy specs indexes, plus immutable .gem and
+// quick/Marshal.4.8 gemspec downloads.
+package gems
+
+import (
+	"context"
+	"net/http"
+	"strings"
+
+	"git.unkin.net/unkin/artifactapi/internal/auth"
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func init() {
+	provider.Register(&Provider{})
+}
+
+type Provider struct{}
+
+func (p *Provider) Type() models.PackageType { return models.PackageGems }
+
+func (p *Provider) Classify(path string) provider.Mutability {
+	if isGem(path) || isQuickSpec(path) {
+		return provider.Immutable
+	}
+	return provider.Mutable
+}
+
+func (p *Provider) ContentType(path string) string {
+	path = strings.TrimLeft(path, "/")
+	if path == "versions" || path == "names" || strings.HasPrefix(path, "info/") {
+		return "text/plain; charset=utf-8"
+	}
+	if strings.HasPrefix(path, "api/v1/") && strings.HasSuffix(path, ".json") {
+		return "application/json"
+	}
+	return "application/octet-stream"
+}
+
+func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
+	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
+}
+
+func (p *Provider) RewriteResponse(_ []byte, _ models.Remote, _ string) ([]byte, error) {
+	return nil, nil
+}
+
+func (p *Provider) AuthHeaders(_ context.Context, remote models.Remote) (http.Header, error) {
+	return auth.BasicHeaders(remote), nil
+}
+
+func isGem(path string) bool {
+	path = strings.TrimLeft(path, "/")
+	return strings.HasPrefix(path, "gems/") && strings.HasSuffix(path, ".gem")
+}
+
+func isQuickSpec(path string) bool {
+	path = strings.TrimLeft(path, "/")
+	return strings.HasPrefix(path, "quick/Marshal.4.8/") && strings.HasSuffix(path, ".gemspec.rz")
+}
diff --git a/internal/provider/gems/gems_test.go b/internal/provider/gems/gems_test.go
new file mode 100644
index 0000000..9707bb3
--- /dev/null
+++ b/internal/provider/gems/gems_test.go
@@ -0,0 +1,61 @@
+package gems
+
+import (
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func TestClassify(t *testing.T) {
+	p := &Provider{}
+	tests := []struct {
+		path string
+		want provider.Mutability
+	}{
+		{"gems/rack-3.1.8.gem", provider.Immutable},
+		{"/gems/nokogiri-1.16.7-x86_64-linux.gem", provider.Immutable},
+		{"quick/Marshal.4.8/rack-3.1.8.gemspec.rz", provider.Immutable},
+		{"versions", provider.Mutable},
+		{"names", provider.Mutable},
+		{"info/rack", provider.Mutable},
+		{"info/gems", provider.Mutable},
+		{"specs.4.8.gz", provider.Mutable},
+		{"latest_specs.4.8.gz", provider.Mutable},
+		{"prerelease_specs.4.8.gz", provider.Mutable},
+		{"api/v1/dependencies", provider.Mutable},
+		{"quick/Marshal.4.8/", provider.Mutable},
+	}
+	for _, tt := range tests {
+		if got := p.Classify(tt.path); got != tt.want {
+			t.Errorf("Classify(%q) = %v, want %v", tt.path, got, tt.want)
+		}
+	}
+}
+
+func TestContentType(t *testing.T) {
+	p := &Provider{}
+	tests := map[string]string{
+		"versions":                 "text/plain; charset=utf-8",
+		"info/rack":                "text/plain; charset=utf-8",
+		"names":                    "text/plain; charset=utf-8",
+		"gems/rack-3.1.8.gem":      "application/octet-stream",
+		"specs.4.8.gz":             "application/octet-stream",
+		"api/v1/gems/rack.json":    "application/json",
+		"api/v1/dependencies.json": "application/json",
+		"api/v1/dependencies":      "application/octet-stream",
+	}
+	for path, want := range tests {
+		if got := p.ContentType(path); got != want {
+			t.Errorf("ContentType(%q) = %q, want %q", path, got, want)
+		}
+	}
+}
+
+func TestUpstreamURL(t *testing.T) {
+	p := &Provider{}
+	r := models.Remote{BaseURL: "https://rubygems.org/"}
+	if got := p.UpstreamURL(r, "/info/rack"); got != "https://rubygems.org/info/rack" {
+		t.Errorf("UpstreamURL = %q", got)
+	}
+}
diff --git a/internal/provider/gems/local.go b/internal/provider/gems/local.go
new file mode 100644
index 0000000..0cbb54f
--- /dev/null
+++ b/internal/provider/gems/local.go
@@ -0,0 +1,468 @@
+package gems
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"compress/zlib"
+	"crypto/md5"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"maps"
+	"regexp"
+	"slices"
+	"strings"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+var (
+	NameRe     = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]*$`)
+	VersionRe  = regexp.MustCompile(`^[0-9]+(\.[0-9A-Za-z]+)*(-[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$`)
+	PlatformRe = regexp.MustCompile(`^[A-Za-z0-9_.-]+$`)
+	opRe       = regexp.MustCompile(`^(=|!=|>|<|>=|<=|~>)$`)
+)
+
+const maxMetadataBytes = 8 << 20
+
+type Requirement [][2]string
+
+type Dependency struct {
+	Name        string
+	Requirement Requirement
+	Type        string
+	Prerelease  bool
+}
+
+// Spec is the subset of a gemspec the compact index and quick spec need.
+type Spec struct {
+	Name, Version, Platform string
+	Summary, RubyGemsVer    string
+	SpecVersion             int
+	Date                    time.Time
+	Authors, Licenses       []string
+	Email, Description      string
+	Homepage                string
+	Metadata                map[string]string
+	Dependencies            []Dependency
+	RequiredRuby            Requirement
+	RequiredRubyGems        Requirement
+}
+
+// FullName is the gem's file stem: name-version, plus -platform when not ruby.
+func (s *Spec) FullName() string {
+	if s.Platform == "" || s.Platform == "ruby" {
+		return s.Name + "-" + s.Version
+	}
+	return s.Name + "-" + s.Version + "-" + s.Platform
+}
+
+type yamlReq struct {
+	Requirements [][]yaml.Node `yaml:"requirements"`
+}
+
+func (r *yamlReq) decode() (Requirement, error) {
+	if r == nil {
+		return nil, nil
+	}
+	var out Requirement
+	for _, pair := range r.Requirements {
+		var op string
+		var ver struct {
+			Version string `yaml:"version"`
+		}
+		if len(pair) != 2 || pair[0].Decode(&op) != nil || pair[1].Decode(&ver) != nil {
+			return nil, errors.New("malformed requirement")
+		}
+		if !opRe.MatchString(op) || !VersionRe.MatchString(ver.Version) {
+			return nil, fmt.Errorf("invalid requirement %q %q", op, ver.Version)
+		}
+		out = append(out, [2]string{op, ver.Version})
+	}
+	return out, nil
+}
+
+// String renders the requirement as the compact index does: "op ver&op ver".
+func (r Requirement) String() string {
+	parts := make([]string, len(r))
+	for i, p := range r {
+		parts[i] = p[0] + " " + p[1]
+	}
+	return strings.Join(parts, "&")
+}
+
+func (r Requirement) trivial() bool {
+	return len(r) == 0 || len(r) == 1 && r[0] == [2]string{">=", "0"}
+}
+
+// ParseGem reads the gemspec from a .gem archive (a tar holding metadata.gz).
+func ParseGem(gem []byte) (*Spec, error) {
+	tr := tar.NewReader(bytes.NewReader(gem))
+	for {
+		hdr, err := tr.Next()
+		if err == io.EOF {
+			return nil, errors.New("gem has no metadata.gz")
+		}
+		if err != nil {
+			return nil, fmt.Errorf("read gem: %w", err)
+		}
+		if hdr.Name != "metadata.gz" {
+			continue
+		}
+		zr, err := gzip.NewReader(tr)
+		if err != nil {
+			return nil, fmt.Errorf("metadata.gz: %w", err)
+		}
+		raw, err := io.ReadAll(io.LimitReader(zr, maxMetadataBytes+1))
+		if err != nil {
+			return nil, fmt.Errorf("metadata.gz: %w", err)
+		}
+		if len(raw) > maxMetadataBytes {
+			return nil, fmt.Errorf("metadata exceeds %d bytes", maxMetadataBytes)
+		}
+		return parseMetadata(raw)
+	}
+}
+
+func parseMetadata(raw []byte) (*Spec, error) {
+	var doc struct {
+		Name    string `yaml:"name"`
+		Version struct {
+			Version string `yaml:"version"`
+		} `yaml:"version"`
+		Platform     string            `yaml:"platform"`
+		Summary      string            `yaml:"summary"`
+		Authors      []string          `yaml:"authors"`
+		Email        yaml.Node         `yaml:"email"`
+		Description  string            `yaml:"description"`
+		Homepage     string            `yaml:"homepage"`
+		Licenses     []string          `yaml:"licenses"`
+		Metadata     map[string]string `yaml:"metadata"`
+		Date         string            `yaml:"date"`
+		RubyGemsVer  string            `yaml:"rubygems_version"`
+		SpecVersion  int               `yaml:"specification_version"`
+		Dependencies []struct {
+			Name        string   `yaml:"name"`
+			Requirement *yamlReq `yaml:"requirement"`
+			VersionReqs *yamlReq `yaml:"version_requirements"`
+			Type        string   `yaml:"type"`
+			Prerelease  bool     `yaml:"prerelease"`
+		} `yaml:"dependencies"`
+		RequiredRuby     *yamlReq `yaml:"required_ruby_version"`
+		RequiredRubyGems *yamlReq `yaml:"required_rubygems_version"`
+	}
+	if err := yaml.Unmarshal(raw, &doc); err != nil {
+		return nil, fmt.Errorf("gemspec yaml: %w", err)
+	}
+	s := &Spec{
+		Name: doc.Name, Version: doc.Version.Version, Platform: doc.Platform,
+		Summary: doc.Summary, Authors: doc.Authors, Description: doc.Description,
+		Homepage: doc.Homepage, Licenses: doc.Licenses, Metadata: doc.Metadata,
+		RubyGemsVer: doc.RubyGemsVer, SpecVersion: doc.SpecVersion,
+	}
+	if s.Platform == "" {
+		s.Platform = "ruby"
+	}
+	if !NameRe.MatchString(s.Name) || !VersionRe.MatchString(s.Version) || !PlatformRe.MatchString(s.Platform) {
+		return nil, fmt.Errorf("invalid gem name/version/platform %q %q %q", s.Name, s.Version, s.Platform)
+	}
+	if doc.Email.Kind == yaml.ScalarNode {
+		s.Email = doc.Email.Value
+	}
+	if t, err := time.Parse("2006-01-02", strings.SplitN(doc.Date, " ", 2)[0]); err == nil {
+		s.Date = t
+	}
+	var err error
+	if s.RequiredRuby, err = doc.RequiredRuby.decode(); err != nil {
+		return nil, err
+	}
+	if s.RequiredRubyGems, err = doc.RequiredRubyGems.decode(); err != nil {
+		return nil, err
+	}
+	for _, d := range doc.Dependencies {
+		if !NameRe.MatchString(d.Name) {
+			return nil, fmt.Errorf("invalid dependency name %q", d.Name)
+		}
+		req := d.Requirement
+		if req == nil {
+			req = d.VersionReqs
+		}
+		r, err := req.decode()
+		if err != nil {
+			return nil, fmt.Errorf("dependency %s: %w", d.Name, err)
+		}
+		typ := strings.TrimPrefix(d.Type, ":")
+		if typ == "" {
+			typ = "runtime"
+		}
+		s.Dependencies = append(s.Dependencies, Dependency{Name: d.Name, Requirement: r, Type: typ, Prerelease: d.Prerelease})
+	}
+	return s, nil
+}
+
+// InfoLine renders the spec's compact index /info line; checksum is the
+// .gem's sha256 hex.
+func InfoLine(s *Spec, gem []byte) string {
+	sum := sha256.Sum256(gem)
+	var deps []string
+	for _, d := range s.Dependencies {
+		if d.Type == "runtime" {
+			r := d.Requirement
+			if len(r) == 0 {
+				r = Requirement{{">=", "0"}}
+			}
+			deps = append(deps, d.Name+":"+r.String())
+		}
+	}
+	key := s.Version
+	if s.Platform != "ruby" {
+		key += "-" + s.Platform
+	}
+	line := key + " " + strings.Join(deps, ",") + "|checksum:" + hex.EncodeToString(sum[:])
+	if !s.RequiredRuby.trivial() {
+		line += ",ruby:" + s.RequiredRuby.String()
+	}
+	if !s.RequiredRubyGems.trivial() {
+		line += ",rubygems:" + s.RequiredRubyGems.String()
+	}
+	return line
+}
+
+// InfoBody renders an /info document from its lines.
+func InfoBody(lines []string) []byte {
+	var b strings.Builder
+	b.WriteString("---\n")
+	for _, l := range lines {
+		b.WriteString(l)
+		b.WriteByte('\n')
+	}
+	return []byte(b.String())
+}
+
+// InfoKey returns an /info line's version[-platform] token.
+func InfoKey(line string) string {
+	k, _, _ := strings.Cut(line, " ")
+	return k
+}
+
+// InfoLines returns an /info body's version lines.
+func InfoLines(body []byte) []string {
+	var out []string
+	for _, l := range strings.Split(string(body), "\n") {
+		if l != "" && l != "---" {
+			out = append(out, l)
+		}
+	}
+	return out
+}
+
+func MD5Hex(b []byte) string {
+	sum := md5.Sum(b)
+	return hex.EncodeToString(sum[:])
+}
+
+// VersionsLine renders one /versions entry from a gem's /info body.
+func VersionsLine(name string, info []byte) string {
+	var keys []string
+	for _, l := range InfoLines(info) {
+		keys = append(keys, InfoKey(l))
+	}
+	return name + " " + strings.Join(keys, ",") + " " + MD5Hex(info)
+}
+
+// VersionsHeader starts a /versions document.
+func VersionsHeader(at time.Time) string {
+	return "created_at: " + at.UTC().Format(time.RFC3339) + "\n---\n"
+}
+
+// QuickSpec returns the deflated Marshal.4.8 dump of the spec, as served at
+// quick/Marshal.4.8/<full>.gemspec.rz.
+func QuickSpec(s *Spec) ([]byte, error) {
+	var buf bytes.Buffer
+	zw := zlib.NewWriter(&buf)
+	if _, err := zw.Write(MarshalSpec(s)); err != nil {
+		return nil, err
+	}
+	if err := zw.Close(); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// MarshalSpec mirrors Gem::Specification#_dump wrapped by Marshal.dump.
+func MarshalSpec(s *Spec) []byte {
+	var in rbMarshal
+	in.WriteString("\x04\x08")
+	in.array(19)
+	in.str(s.RubyGemsVer)
+	in.WriteByte('i')
+	in.fixnum(s.SpecVersion)
+	in.str(s.Name)
+	in.version(s.Version)
+	in.time(s.Date)
+	in.str(s.Summary)
+	in.requirement(s.RequiredRuby)
+	in.requirement(s.RequiredRubyGems)
+	in.str(s.Platform)
+	in.array(len(s.Dependencies))
+	for _, d := range s.Dependencies {
+		in.WriteByte('o')
+		in.sym("Gem::Dependency")
+		in.fixnum(4)
+		in.sym("@name")
+		in.str(d.Name)
+		in.sym("@requirement")
+		in.requirement(d.Requirement)
+		in.sym("@type")
+		in.sym(d.Type)
+		in.sym("@prerelease")
+		in.boolean(d.Prerelease)
+	}
+	in.str("")
+	in.optStr(s.Email)
+	in.strs(s.Authors)
+	in.optStr(s.Description)
+	in.optStr(s.Homepage)
+	in.boolean(true)
+	in.str(s.Platform)
+	in.strs(s.Licenses)
+	in.WriteByte('{')
+	in.fixnum(len(s.Metadata))
+	for _, k := range slices.Sorted(maps.Keys(s.Metadata)) {
+		in.str(k)
+		in.str(s.Metadata[k])
+	}
+
+	var out rbMarshal
+	out.WriteString("\x04\x08u")
+	out.sym("Gem::Specification")
+	out.fixnum(in.Len())
+	out.Write(in.Bytes())
+	return out.Bytes()
+}
+
+// rbMarshal writes the Ruby Marshal 4.8 subset gemspecs use. It never emits
+// object or symbol links, so every symbol is written in full.
+type rbMarshal struct{ bytes.Buffer }
+
+func (m *rbMarshal) fixnum(n int) {
+	switch {
+	case n == 0:
+		m.WriteByte(0)
+	case n > 0 && n < 123:
+		m.WriteByte(byte(n + 5))
+	case n < 0 && n > -124:
+		m.WriteByte(byte(n - 5))
+	default:
+		var b []byte
+		for x := n; len(b) < 4; x >>= 8 {
+			b = append(b, byte(x))
+			if (n >= 0 && x>>8 == 0) || (n < 0 && x>>8 == -1) {
+				break
+			}
+		}
+		if n >= 0 {
+			m.WriteByte(byte(len(b)))
+		} else {
+			m.WriteByte(byte(-len(b)))
+		}
+		m.Write(b)
+	}
+}
+
+func (m *rbMarshal) raw(s string) {
+	m.fixnum(len(s))
+	m.WriteString(s)
+}
+
+func (m *rbMarshal) sym(s string) {
+	m.WriteByte(':')
+	m.raw(s)
+}
+
+// str writes a UTF-8 String (an ivar-wrapped string with E=true).
+func (m *rbMarshal) str(s string) {
+	m.WriteString("I\"")
+	m.raw(s)
+	m.fixnum(1)
+	m.sym("E")
+	m.WriteByte('T')
+}
+
+func (m *rbMarshal) optStr(s string) {
+	if s == "" {
+		m.WriteByte('0')
+		return
+	}
+	m.str(s)
+}
+
+func (m *rbMarshal) strs(ss []string) {
+	m.array(len(ss))
+	for _, s := range ss {
+		m.str(s)
+	}
+}
+
+func (m *rbMarshal) array(n int) {
+	m.WriteByte('[')
+	m.fixnum(n)
+}
+
+func (m *rbMarshal) boolean(b bool) {
+	if b {
+		m.WriteByte('T')
+	} else {
+		m.WriteByte('F')
+	}
+}
+
+func (m *rbMarshal) version(v string) {
+	m.WriteByte('U')
+	m.sym("Gem::Version")
+	m.array(1)
+	m.str(v)
+}
+
+func (m *rbMarshal) requirement(r Requirement) {
+	if len(r) == 0 {
+		r = Requirement{{">=", "0"}}
+	}
+	m.WriteByte('U')
+	m.sym("Gem::Requirement")
+	m.array(1)
+	m.array(len(r))
+	for _, p := range r {
+		m.array(2)
+		m.str(p[0])
+		m.version(p[1])
+	}
+}
+
+// time writes a UTC Time with day resolution, as Time#_dump lays it out.
+func (m *rbMarshal) time(t time.Time) {
+	t = t.UTC()
+	// Time#_dump holds year-1900 in 16 bits.
+	if t.IsZero() || t.Year() < 1900 || t.Year() > 1900+0xffff {
+		t = time.Unix(0, 0).UTC()
+	}
+	p := uint32(1)<<31 | uint32(1)<<30 | uint32(t.Year()-1900)<<14 | uint32(t.Month()-1)<<10 | uint32(t.Day())<<5 | uint32(t.Hour())
+	s := uint32(t.Minute())<<26 | uint32(t.Second())<<20
+	m.WriteString("Iu")
+	m.sym("Time")
+	m.fixnum(8)
+	for _, w := range []uint32{p, s} {
+		m.Write([]byte{byte(w), byte(w >> 8), byte(w >> 16), byte(w >> 24)})
+	}
+	m.fixnum(1)
+	m.sym("zone")
+	m.WriteString("I\"")
+	m.raw("UTC")
+	m.fixnum(1)
+	m.sym("E")
+	m.WriteByte('F')
+}
diff --git a/internal/provider/gems/local_test.go b/internal/provider/gems/local_test.go
new file mode 100644
index 0000000..4df4f54
--- /dev/null
+++ b/internal/provider/gems/local_test.go
@@ -0,0 +1,223 @@
+package gems
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"compress/zlib"
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"strings"
+	"testing"
+	"time"
+)
+
+const testMetadata = `--- !ruby/object:Gem::Specification
+name: unkin-e2e-hello
+version: !ruby/object:Gem::Version
+  version: 0.1.0
+platform: %PLATFORM%
+authors:
+- e2e
+date: 2026-10-17 00:00:00.000000000 Z
+dependencies:
+- !ruby/object:Gem::Dependency
+  name: rack
+  requirement: &1 !ruby/object:Gem::Requirement
+    requirements:
+    - - ">="
+      - !ruby/object:Gem::Version
+        version: '2.0'
+    - - "<"
+      - !ruby/object:Gem::Version
+        version: '4'
+  type: :runtime
+  prerelease: false
+  version_requirements: *1
+- !ruby/object:Gem::Dependency
+  name: json
+  version_requirements: !ruby/object:Gem::Requirement
+    requirements:
+    - - "~>"
+      - !ruby/object:Gem::Version
+        version: '2.1'
+  type: :runtime
+  prerelease: false
+- !ruby/object:Gem::Dependency
+  name: rake
+  requirement: !ruby/object:Gem::Requirement
+    requirements:
+    - - ">="
+      - !ruby/object:Gem::Version
+        version: '0'
+  type: :development
+  prerelease: false
+email:
+licenses:
+- MIT
+metadata:
+  source_code_uri: https://example.com
+required_ruby_version: !ruby/object:Gem::Requirement
+  requirements:
+  - - ">="
+    - !ruby/object:Gem::Version
+      version: '2.7'
+required_rubygems_version: !ruby/object:Gem::Requirement
+  requirements:
+  - - ">="
+    - !ruby/object:Gem::Version
+      version: '0'
+rubygems_version: 3.5.22
+specification_version: 4
+summary: hi
+`
+
+func buildGem(t *testing.T, metadata []byte) []byte {
+	t.Helper()
+	var gz bytes.Buffer
+	zw := gzip.NewWriter(&gz)
+	_, _ = zw.Write(metadata)
+	_ = zw.Close()
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	for name, body := range map[string][]byte{"data.tar.gz": []byte("x"), "metadata.gz": gz.Bytes()} {
+		if err := tw.WriteHeader(&tar.Header{Name: name, Mode: 0o444, Size: int64(len(body))}); err != nil {
+			t.Fatal(err)
+		}
+		_, _ = tw.Write(body)
+	}
+	_ = tw.Close()
+	return buf.Bytes()
+}
+
+func testGem(t *testing.T, platform string) []byte {
+	return buildGem(t, []byte(strings.Replace(testMetadata, "%PLATFORM%", platform, 1)))
+}
+
+func TestParseGemAndInfoLine(t *testing.T) {
+	gem := testGem(t, "ruby")
+	s, err := ParseGem(gem)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.FullName() != "unkin-e2e-hello-0.1.0" || !s.Date.Equal(time.Date(2026, 10, 17, 0, 0, 0, 0, time.UTC)) {
+		t.Fatalf("spec = %+v", s)
+	}
+	if len(s.Dependencies) != 3 || s.Dependencies[1].Requirement.String() != "~> 2.1" {
+		t.Fatalf("deps = %+v", s.Dependencies)
+	}
+	sum := sha256.Sum256(gem)
+	want := "0.1.0 rack:>= 2.0&< 4,json:~> 2.1|checksum:" + hex.EncodeToString(sum[:]) + ",ruby:>= 2.7"
+	if got := InfoLine(s, gem); got != want {
+		t.Fatalf("InfoLine =\n %s\nwant\n %s", got, want)
+	}
+
+	plat, err := ParseGem(testGem(t, "x86_64-linux"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if plat.FullName() != "unkin-e2e-hello-0.1.0-x86_64-linux" || InfoKey(InfoLine(plat, nil)) != "0.1.0-x86_64-linux" {
+		t.Fatalf("platform gem: %s / %s", plat.FullName(), InfoLine(plat, nil))
+	}
+}
+
+func TestParseGemRejects(t *testing.T) {
+	big := []byte(testMetadata + "description: " + strings.Repeat("a", maxMetadataBytes) + "\n")
+	cases := map[string][]byte{
+		"not a tar":      []byte("garbage"),
+		"no metadata":    func() []byte { var b bytes.Buffer; tw := tar.NewWriter(&b); _ = tw.Close(); return b.Bytes() }(),
+		"bad name":       buildGem(t, []byte(strings.Replace(testMetadata, "name: unkin-e2e-hello", "name: ../x", 1))),
+		"bad version":    buildGem(t, []byte(strings.Replace(testMetadata, "version: 0.1.0", "version: 'a b'", 1))),
+		"bad dep op":     buildGem(t, []byte(strings.Replace(testMetadata, `- - "~>"`, `- - "=~"`, 1))),
+		"metadata bomb":  buildGem(t, big),
+		"bad platform":   buildGem(t, []byte(strings.Replace(testMetadata, "%PLATFORM%", "x/y", 1))),
+		"bad dependency": buildGem(t, []byte(strings.Replace(testMetadata, "name: json", "name: 'a|b'", 1))),
+	}
+	for name, gem := range cases {
+		if _, err := ParseGem(gem); err == nil {
+			t.Errorf("%s: accepted", name)
+		}
+	}
+}
+
+func TestVersionsLineMD5(t *testing.T) {
+	info := InfoBody([]string{"0.1.0 |checksum:aa", "0.2.0-java |checksum:bb"})
+	if string(info) != "---\n0.1.0 |checksum:aa\n0.2.0-java |checksum:bb\n" {
+		t.Fatalf("InfoBody = %q", info)
+	}
+	if got := VersionsLine("g", info); got != "g 0.1.0,0.2.0-java "+MD5Hex(info) {
+		t.Fatalf("VersionsLine = %q", got)
+	}
+}
+
+// Byte layouts below are taken from Ruby 3.3's Marshal.dump.
+func TestRubyMarshalEncoding(t *testing.T) {
+	for n, want := range map[int]string{0: "\x00", 4: "\x09", 122: "\x7f", 123: "\x01\x7b", 255: "\x01\xff", 256: "\x02\x00\x01", 65536: "\x03\x00\x00\x01", -1: "\xfa", -123: "\x80"} {
+		var m rbMarshal
+		m.fixnum(n)
+		if m.String() != want {
+			t.Errorf("fixnum(%d) = %x, want %x", n, m.String(), want)
+		}
+	}
+	var m rbMarshal
+	m.str("3.5.22")
+	if m.String() != "I\"\x0b3.5.22\x06:\x06ET" {
+		t.Errorf("str = %q", m.String())
+	}
+	m.Reset()
+	m.version("0.1.0")
+	if m.String() != "U:\x11Gem::Version[\x06I\"\x0a0.1.0\x06:\x06ET" {
+		t.Errorf("version = %q", m.String())
+	}
+	m.Reset()
+	m.time(time.Date(2026, 10, 17, 0, 0, 0, 0, time.UTC))
+	if want := "Iu:\x09Time\x0d\x20\xa6\x1f\xc0\x00\x00\x00\x00\x06:\x09zoneI\"\x08UTC\x06:\x06EF"; m.String() != want {
+		t.Errorf("time = %q, want %q", m.String(), want)
+	}
+	var epoch rbMarshal
+	epoch.time(time.Time{})
+	for _, y := range []int{1, 1899, 1900 + 0x10000} {
+		m.Reset()
+		m.time(time.Date(y, 1, 1, 0, 0, 0, 0, time.UTC))
+		if m.String() != epoch.String() {
+			t.Errorf("time(year %d) = %q, want the epoch encoding %q", y, m.String(), epoch.String())
+		}
+	}
+}
+
+func TestQuickSpec(t *testing.T) {
+	s, err := ParseGem(testGem(t, "ruby"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	q, err := QuickSpec(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	q2, _ := QuickSpec(s)
+	if !bytes.Equal(q, q2) {
+		t.Fatal("QuickSpec is not deterministic")
+	}
+	zr, err := zlib.NewReader(bytes.NewReader(q))
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, _ := io.ReadAll(zr)
+	head := "\x04\x08u:\x17Gem::Specification"
+	if !strings.HasPrefix(string(raw), head) {
+		t.Fatalf("quick spec prefix = %q", raw[:30])
+	}
+	inner := string(raw[len(head):])
+	at := strings.Index(inner, "\x04\x08[\x18")
+	var length rbMarshal
+	length.fixnum(len(inner) - at)
+	if at < 1 || inner[:at] != length.String() {
+		t.Fatalf("inner dump header = %q", inner[:8])
+	}
+	for _, want := range []string{"o:\x14Gem::Dependency", ":\x0cruntime", ":\x10development", "source_code_uri"} {
+		if !strings.Contains(string(raw), want) {
+			t.Errorf("quick spec missing %q", want)
+		}
+	}
+}
diff --git a/internal/provider/helm/helm.go b/internal/provider/helm/helm.go
index d37765e..d421753 100644
--- a/internal/provider/helm/helm.go
+++ b/internal/provider/helm/helm.go
@@ -1,12 +1,24 @@
 package helm
 
 import (
+	"archive/tar"
+	"compress/gzip"
 	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
 	"net/http"
+	"net/url"
+	"path"
 	"strings"
+	"time"
+
+	"gopkg.in/yaml.v3"
 
 	"git.unkin.net/unkin/artifactapi/internal/auth"
 	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/storage"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
@@ -39,6 +51,8 @@ func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
 	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
 }
 
+func (p *Provider) RewritesResponse() {}
+
 func (p *Provider) RewriteResponse(body []byte, remote models.Remote, proxyBaseURL string) ([]byte, error) {
 	if proxyBaseURL == "" {
 		return nil, nil
@@ -56,3 +70,203 @@ func (p *Provider) RewriteResponse(body []byte, remote models.Remote, proxyBaseU
 func (p *Provider) AuthHeaders(_ context.Context, remote models.Remote) (http.Header, error) {
 	return auth.BasicHeaders(remote), nil
 }
+
+// ValidateUpload stores charts flat by filename so index.yaml can reference
+// them with relative urls, as `helm repo index` does.
+func (p *Provider) ValidateUpload(filePath string) (storagePath, contentType string, err error) {
+	filename := path.Base(path.Clean("/" + filePath))
+	if !strings.HasSuffix(filename, ".tgz") || filename == ".tgz" {
+		return "", "", fmt.Errorf("file must be a .tgz chart package")
+	}
+	return filename, "application/gzip", nil
+}
+
+func (p *Provider) UploadResponse(storagePath, contentHash string, sizeBytes int64) map[string]any {
+	return map[string]any{
+		"filename":     storagePath,
+		"content_hash": contentHash,
+		"size_bytes":   sizeBytes,
+	}
+}
+
+func (p *Provider) AfterUpload(ctx context.Context, repoName, storagePath, contentHash string, blobs provider.BlobReader, db provider.MetadataStore) {
+	reader, _, err := blobs.Download(ctx, storage.BlobKey(strings.TrimPrefix(contentHash, "sha256:")))
+	if err != nil {
+		slog.Error("helm metadata: download failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	defer func() { _ = reader.Close() }()
+
+	meta, err := parseChart(reader)
+	if err != nil {
+		slog.Error("helm metadata: parse failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	if want := meta.Name + "-" + meta.Version + ".tgz"; storagePath != want {
+		slog.Error("helm metadata: filename does not match chart", "repo", repoName, "path", storagePath, "expected", want)
+		return
+	}
+	meta.RepoName = repoName
+	meta.FilePath = storagePath
+	meta.ContentHash = contentHash
+
+	store, ok := db.(provider.HelmMetadataStore)
+	if !ok {
+		slog.Error("helm metadata: store does not support helm metadata", "repo", repoName)
+		return
+	}
+	if err := store.InsertHelmMetadata(ctx, meta); err != nil {
+		slog.Error("helm metadata: insert failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	slog.Info("helm metadata: parsed", "repo", repoName, "name", meta.Name, "version", meta.Version)
+}
+
+func (p *Provider) AfterDelete(ctx context.Context, repoName, storagePath string, db provider.MetadataDeleter) error {
+	deleter, ok := db.(provider.HelmMetadataDeleter)
+	if !ok {
+		return nil
+	}
+	return deleter.DeleteHelmMetadata(ctx, repoName, storagePath)
+}
+
+func isIndexPath(p string) bool {
+	return strings.TrimPrefix(path.Clean("/"+p), "/") == "index.yaml"
+}
+
+func (p *Provider) ServeLocalIndex(w http.ResponseWriter, r *http.Request, files provider.FileStore, repoName, reqPath string) bool {
+	if !isIndexPath(reqPath) {
+		return false
+	}
+	body, err := p.GenerateLocalIndex(r.Context(), files, repoName, reqPath)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return true
+	}
+	w.Header().Set("Content-Type", "text/yaml")
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write(body)
+	return true
+}
+
+func (p *Provider) GenerateLocalIndex(ctx context.Context, files provider.FileStore, repoName, reqPath string) ([]byte, error) {
+	if !isIndexPath(reqPath) {
+		return nil, fmt.Errorf("unsupported index path: %q", reqPath)
+	}
+	reader, ok := files.(provider.HelmMetadataReader)
+	if !ok {
+		return nil, errors.New("helm metadata not available")
+	}
+	metas, err := reader.ListHelmMetadataEntries(ctx, repoName)
+	if err != nil {
+		return nil, err
+	}
+	return generateIndex(metas)
+}
+
+// generateIndex builds index.yaml from stored Chart.yaml documents; it is
+// stamped from the newest upload so every replica serves identical bytes.
+func generateIndex(metas []provider.HelmMetadata) ([]byte, error) {
+	entries := map[string][]map[string]yaml.Node{}
+	var newest time.Time
+	budget := provider.MaxAliasExpandedNodes
+	for _, m := range metas {
+		var raw map[string]yaml.Node
+		if err := yaml.Unmarshal([]byte(m.ChartYAML), &raw); err != nil {
+			return nil, fmt.Errorf("chart %s: %w", m.FilePath, err)
+		}
+		chart, err := provider.ExpandYAMLAliases(raw, &budget)
+		if err != nil {
+			slog.Warn("helm index: dropping chart", "chart", m.Name, "path", m.FilePath, "error", err)
+			continue
+		}
+		chart["name"] = node(m.Name)
+		chart["version"] = node(m.Version)
+		chart["urls"] = node([]string{url.PathEscape(m.FilePath)})
+		chart["digest"] = node(strings.TrimPrefix(m.ContentHash, "sha256:"))
+		chart["created"] = node(m.CreatedAt.UTC().Format(time.RFC3339Nano))
+		entries[m.Name] = append(entries[m.Name], chart)
+		if m.CreatedAt.After(newest) {
+			newest = m.CreatedAt
+		}
+	}
+	return yaml.Marshal(map[string]any{
+		"apiVersion": "v1",
+		"entries":    entries,
+		"generated":  newest.UTC().Format(time.RFC3339Nano),
+	})
+}
+
+func node(v any) yaml.Node {
+	var n yaml.Node
+	_ = n.Encode(v)
+	return n
+}
+
+const (
+	maxChartYAML    = 1 << 20
+	maxChartBytes   = 50 << 20
+	maxChartEntries = 10000
+)
+
+var errChartTooLarge = fmt.Errorf("chart archive exceeds %d decompressed bytes", maxChartBytes)
+
+type capReader struct {
+	r io.Reader
+	n int64
+}
+
+func (c *capReader) Read(p []byte) (int, error) {
+	if c.n <= 0 {
+		return 0, errChartTooLarge
+	}
+	if int64(len(p)) > c.n {
+		p = p[:c.n]
+	}
+	n, err := c.r.Read(p)
+	c.n -= int64(n)
+	return n, err
+}
+
+// parseChart reads the top-level <chart>/Chart.yaml from a packaged chart.
+func parseChart(r io.Reader) (*provider.HelmMetadata, error) {
+	zr, err := gzip.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	tr := tar.NewReader(&capReader{r: zr, n: maxChartBytes})
+	for entries := 0; ; entries++ {
+		if entries >= maxChartEntries {
+			return nil, fmt.Errorf("chart archive exceeds %d entries", maxChartEntries)
+		}
+		hdr, err := tr.Next()
+		if err == io.EOF {
+			return nil, errors.New("no Chart.yaml in chart archive")
+		}
+		if err != nil {
+			return nil, err
+		}
+		dir, file := path.Split(path.Clean(hdr.Name))
+		if file != "Chart.yaml" || strings.Count(dir, "/") != 1 {
+			continue
+		}
+		raw, err := io.ReadAll(io.LimitReader(tr, maxChartYAML+1))
+		if err != nil {
+			return nil, err
+		}
+		if len(raw) > maxChartYAML {
+			return nil, fmt.Errorf("parse Chart.yaml: exceeds %d bytes", maxChartYAML)
+		}
+		var chart struct {
+			Name    string `yaml:"name"`
+			Version string `yaml:"version"`
+		}
+		if err := yaml.Unmarshal(raw, &chart); err != nil {
+			return nil, fmt.Errorf("parse Chart.yaml: %w", err)
+		}
+		if chart.Name == "" || chart.Version == "" {
+			return nil, errors.New("chart metadata missing name or version")
+		}
+		return &provider.HelmMetadata{Name: chart.Name, Version: chart.Version, ChartYAML: string(raw)}, nil
+	}
+}
diff --git a/internal/provider/helm/helm_local_test.go b/internal/provider/helm/helm_local_test.go
new file mode 100644
index 0000000..abe2538
--- /dev/null
+++ b/internal/provider/helm/helm_local_test.go
@@ -0,0 +1,236 @@
+package helm
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"context"
+	"io"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"gopkg.in/yaml.v3"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func chartTgz(t *testing.T, files map[string]string) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	tw := tar.NewWriter(zw)
+	for name, body := range files {
+		if err := tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(body))}); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := tw.Write([]byte(body)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := tw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := zw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	return buf.Bytes()
+}
+
+type fakeBlobs struct{ data []byte }
+
+func (f fakeBlobs) Download(context.Context, string) (io.ReadCloser, int64, error) {
+	return io.NopCloser(bytes.NewReader(f.data)), int64(len(f.data)), nil
+}
+
+type fakeStore struct {
+	inserted *provider.HelmMetadata
+	metas    []provider.HelmMetadata
+}
+
+func (f *fakeStore) InsertRPMMetadata(context.Context, *provider.RPMMetadata) error { return nil }
+func (f *fakeStore) InsertDebMetadata(context.Context, *provider.DebMetadata) error { return nil }
+func (f *fakeStore) InsertHelmMetadata(_ context.Context, m *provider.HelmMetadata) error {
+	f.inserted = m
+	return nil
+}
+func (f *fakeStore) ListHelmMetadataEntries(context.Context, string) ([]provider.HelmMetadata, error) {
+	return f.metas, nil
+}
+func (f *fakeStore) ListFilesByPrefix(context.Context, string, string) ([]provider.FileEntry, error) {
+	return nil, nil
+}
+func (f *fakeStore) ListPackages(context.Context, string) ([]string, error) { return nil, nil }
+
+func TestValidateUpload(t *testing.T) {
+	p := &Provider{}
+	for in, want := range map[string]string{
+		"mychart-0.1.0.tgz":        "mychart-0.1.0.tgz",
+		"charts/mychart-0.1.0.tgz": "mychart-0.1.0.tgz",
+		"../../mychart-0.1.0.tgz":  "mychart-0.1.0.tgz",
+	} {
+		sp, ct, err := p.ValidateUpload(in)
+		if err != nil || sp != want || ct != "application/gzip" {
+			t.Errorf("ValidateUpload(%q) = %q %q %v", in, sp, ct, err)
+		}
+	}
+	for _, bad := range []string{"index.yaml", "chart.tar.gz", ".tgz", ""} {
+		if _, _, err := p.ValidateUpload(bad); err == nil {
+			t.Errorf("ValidateUpload(%q) accepted", bad)
+		}
+	}
+}
+
+func TestAfterUploadParsesTopLevelChart(t *testing.T) {
+	data := chartTgz(t, map[string]string{
+		"mychart/charts/sub/Chart.yaml": "apiVersion: v2\nname: sub\nversion: 9.9.9\n",
+		"mychart/Chart.yaml":            "apiVersion: v2\nname: mychart\nversion: 1.0\ndescription: hi\n",
+		"mychart/values.yaml":           "a: 1\n",
+	})
+	store := &fakeStore{}
+	(&Provider{}).AfterUpload(context.Background(), "r", "mychart-1.0.tgz", "sha256:ab", fakeBlobs{data}, store)
+	m := store.inserted
+	if m == nil || m.Name != "mychart" || m.Version != "1.0" || m.FilePath != "mychart-1.0.tgz" || m.ContentHash != "sha256:ab" {
+		t.Fatalf("inserted %+v", m)
+	}
+}
+
+func TestAfterUploadRejectsChartWithoutMetadata(t *testing.T) {
+	store := &fakeStore{}
+	data := chartTgz(t, map[string]string{"mychart/Chart.yaml": "apiVersion: v2\nname: mychart\n"})
+	(&Provider{}).AfterUpload(context.Background(), "r", "x.tgz", "sha256:ab", fakeBlobs{data}, store)
+	if store.inserted != nil {
+		t.Fatal("chart without version was recorded")
+	}
+	(&Provider{}).AfterUpload(context.Background(), "r", "x.tgz", "sha256:ab", fakeBlobs{[]byte("not gzip")}, store)
+	if store.inserted != nil {
+		t.Fatal("non-gzip upload was recorded")
+	}
+}
+
+func TestServeLocalIndex(t *testing.T) {
+	t1 := time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC)
+	t2 := t1.Add(time.Hour)
+	store := &fakeStore{metas: []provider.HelmMetadata{
+		{FilePath: "mychart-1.0.tgz", ContentHash: "sha256:aa", Name: "mychart", Version: "1.0", CreatedAt: t1,
+			ChartYAML: "apiVersion: v2\nname: mychart\nversion: 1.0\nappVersion: \"2\"\ndescription: hi\n"},
+		{FilePath: "other-0.2.0.tgz", ContentHash: "sha256:bb", Name: "other", Version: "0.2.0", CreatedAt: t2,
+			ChartYAML: "apiVersion: v2\nname: other\nversion: 0.2.0\n"},
+	}}
+	p := &Provider{}
+
+	if p.ServeLocalIndex(httptest.NewRecorder(), httptest.NewRequest("GET", "/", nil), store, "r", "mychart-1.0.tgz") {
+		t.Fatal("chart path handled as index")
+	}
+	rec := httptest.NewRecorder()
+	if !p.ServeLocalIndex(rec, httptest.NewRequest("GET", "/", nil), store, "r", "./index.yaml") {
+		t.Fatal("index.yaml not handled")
+	}
+	if rec.Code != 200 || rec.Header().Get("Content-Type") != "text/yaml" {
+		t.Fatalf("code=%d ct=%q", rec.Code, rec.Header().Get("Content-Type"))
+	}
+
+	var idx struct {
+		APIVersion string `yaml:"apiVersion"`
+		Generated  string `yaml:"generated"`
+		Entries    map[string][]map[string]any
+	}
+	if err := yaml.Unmarshal(rec.Body.Bytes(), &idx); err != nil {
+		t.Fatal(err)
+	}
+	if idx.APIVersion != "v1" || idx.Generated != t2.Format(time.RFC3339Nano) {
+		t.Errorf("header %+v", idx)
+	}
+	e := idx.Entries["mychart"][0]
+	if e["digest"] != "aa" || e["description"] != "hi" || e["appVersion"] != "2" || e["apiVersion"] != "v2" {
+		t.Errorf("entry %v", e)
+	}
+	if urls, _ := e["urls"].([]any); len(urls) != 1 || urls[0] != "mychart-1.0.tgz" {
+		t.Errorf("urls %v", e["urls"])
+	}
+	if e["version"] != "1.0" || e["name"] != "mychart" {
+		t.Errorf("version must stay a string: %#v", e["version"])
+	}
+	if len(idx.Entries["other"]) != 1 {
+		t.Errorf("other entries %v", idx.Entries["other"])
+	}
+
+	again, err := p.GenerateLocalIndex(context.Background(), store, "r", "index.yaml")
+	if err != nil || !bytes.Equal(again, rec.Body.Bytes()) {
+		t.Errorf("index not deterministic: %v", err)
+	}
+}
+
+func TestAfterUploadRejectsFilenameMismatch(t *testing.T) {
+	store := &fakeStore{}
+	data := chartTgz(t, map[string]string{"mychart/Chart.yaml": "apiVersion: v2\nname: mychart\nversion: 1.0.0\n"})
+	(&Provider{}).AfterUpload(context.Background(), "r", "other-1.0.0.tgz", "sha256:ab", fakeBlobs{data}, store)
+	if store.inserted != nil {
+		t.Fatal("chart indexed under a filename that does not match name-version")
+	}
+}
+
+func TestParseChartLimits(t *testing.T) {
+	chart := "apiVersion: v2\nname: c\nversion: 1.0.0\n"
+	for name, tc := range map[string]struct {
+		files map[string]string
+		want  string
+	}{
+		"decompressed": {map[string]string{"c/a.bin": strings.Repeat("\x00", maxChartBytes+1)}, "decompressed bytes"},
+		"chart yaml":   {map[string]string{"c/Chart.yaml": chart + "#" + strings.Repeat("x", maxChartYAML)}, "Chart.yaml: exceeds"},
+	} {
+		_, err := parseChart(bytes.NewReader(chartTgz(t, tc.files)))
+		if err == nil || !strings.Contains(err.Error(), tc.want) {
+			t.Errorf("%s: err = %v, want %q", name, err, tc.want)
+		}
+	}
+
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	tw := tar.NewWriter(zw)
+	for i := 0; i <= maxChartEntries; i++ {
+		_ = tw.WriteHeader(&tar.Header{Name: "c/templates/" + strconv.Itoa(i), Mode: 0o644})
+	}
+	_ = tw.WriteHeader(&tar.Header{Name: "c/Chart.yaml", Mode: 0o644, Size: int64(len(chart))})
+	_, _ = tw.Write([]byte(chart))
+	_ = tw.Close()
+	_ = zw.Close()
+	if _, err := parseChart(&buf); err == nil || !strings.Contains(err.Error(), "entries") {
+		t.Errorf("entries: err = %v", err)
+	}
+
+	if m, err := parseChart(bytes.NewReader(chartTgz(t, map[string]string{"c/Chart.yaml": chart}))); err != nil || m.Name != "c" {
+		t.Errorf("valid chart: %v %v", m, err)
+	}
+}
+
+func TestIndexEscapesURLs(t *testing.T) {
+	out, err := generateIndex([]provider.HelmMetadata{{FilePath: "my chart-1.0.0.tgz", Name: "my chart", Version: "1.0.0", ChartYAML: "name: x\n"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(out), "my%20chart-1.0.0.tgz") {
+		t.Errorf("url not escaped:\n%s", out)
+	}
+}
+
+func TestIndexExpandsAliasesBeforeOverride(t *testing.T) {
+	body, err := generateIndex([]provider.HelmMetadata{{
+		FilePath: "app-1.0.0.tgz", ContentHash: "sha256:aa", Name: "app", Version: "1.0.0",
+		ChartYAML: "apiVersion: v2\nname: app\nversion: &v 1.0.0\nappVersion: *v\n",
+	}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var idx struct {
+		Entries map[string][]map[string]any
+	}
+	if err := yaml.Unmarshal(body, &idx); err != nil {
+		t.Fatalf("index does not parse: %v\n%s", err, body)
+	}
+	if e := idx.Entries["app"]; len(e) != 1 || e[0]["appVersion"] != "1.0.0" {
+		t.Errorf("entries %v", idx.Entries)
+	}
+}
diff --git a/internal/provider/metadata_alpine.go b/internal/provider/metadata_alpine.go
new file mode 100644
index 0000000..19aaf65
--- /dev/null
+++ b/internal/provider/metadata_alpine.go
@@ -0,0 +1,49 @@
+package provider
+
+import (
+	"context"
+)
+
+// AlpineMetadataStore / AlpineMetadataDeleter / AlpineMetadataReader are the
+// Alpine-specific persistence surfaces. They are kept separate from the shared
+// RPM/Deb metadata interfaces so the apk provider can type-assert the generic
+// MetadataStore/MetadataDeleter/FileStore it is handed without widening (and
+// thus perturbing the test doubles of) the rpm and deb providers. *database.DB
+// satisfies all three.
+type AlpineMetadataStore interface {
+	InsertAlpineMetadata(ctx context.Context, meta *AlpineMetadata) error
+}
+
+type AlpineMetadataDeleter interface {
+	DeleteAlpineMetadata(ctx context.Context, repoName, filePath string) error
+}
+
+type AlpineMetadataReader interface {
+	ListAlpineMetadataEntries(ctx context.Context, repoName string) ([]AlpineMetadata, error)
+}
+
+// AlpineMetadata is the derived per-package metadata for an Alpine .apk, holding
+// the fields an APKINDEX record carries plus the apk pull checksum (Q1…, the
+// sha1 of the control gzip stream) and the download/installed sizes.
+type AlpineMetadata struct {
+	RepoName         string
+	FilePath         string
+	ContentHash      string
+	Checksum         string   // C: "Q1" + base64(sha1(control gzip stream))
+	Name             string   // P:
+	Version          string   // V:
+	Arch             string   // A:
+	DownloadSize     int64    // S: on-disk .apk size
+	InstalledSize    int64    // I: unpacked size from .PKGINFO
+	Description      string   // T:
+	URL              string   // U:
+	License          string   // L:
+	Origin           string   // o:
+	Maintainer       string   // m:
+	BuildTime        int64    // t:
+	Commit           string   // c:
+	ProviderPriority string   // k:
+	Depends          []string // D:
+	Provides         []string // p:
+	InstallIf        []string // i:
+}
diff --git a/internal/provider/metadata_deb.go b/internal/provider/metadata_deb.go
new file mode 100644
index 0000000..4fcd2a3
--- /dev/null
+++ b/internal/provider/metadata_deb.go
@@ -0,0 +1,34 @@
+package provider
+
+import (
+	"context"
+	"time"
+)
+
+// DebMetadataReader is the read surface the deb LocalIndexer needs to
+// regenerate a flat apt repository (Packages/Release) from stored rows.
+// *database.DB satisfies it; ServeLocalIndex type-asserts the FileStore to it,
+// mirroring how the rpm provider reaches its RPMMetadataReader.
+type DebMetadataReader interface {
+	ListDebMetadataEntries(ctx context.Context, repoName string) ([]DebMetadata, error)
+}
+
+// DebMetadata is the derived per-package metadata for a Debian .deb, carrying
+// the full raw control stanza so the Packages index can be regenerated
+// faithfully alongside the computed size/md5/sha256 apt requires.
+type DebMetadata struct {
+	RepoName     string
+	FilePath     string
+	ContentHash  string
+	Name         string
+	Version      string
+	Architecture string
+	Control      string
+	Size         int64
+	MD5          string
+	SHA256       string
+	// CreatedAt is the persisted insert time; the Release Date: is derived from
+	// the newest value so the index is byte-identical across replicas and
+	// regenerations (issue #117) rather than stamped from wall clock.
+	CreatedAt time.Time
+}
diff --git a/internal/provider/metadata_helm.go b/internal/provider/metadata_helm.go
new file mode 100644
index 0000000..a69ed1f
--- /dev/null
+++ b/internal/provider/metadata_helm.go
@@ -0,0 +1,30 @@
+package provider
+
+import (
+	"context"
+	"time"
+)
+
+type HelmMetadataStore interface {
+	InsertHelmMetadata(ctx context.Context, meta *HelmMetadata) error
+}
+
+type HelmMetadataDeleter interface {
+	DeleteHelmMetadata(ctx context.Context, repoName, filePath string) error
+}
+
+type HelmMetadataReader interface {
+	ListHelmMetadataEntries(ctx context.Context, repoName string) ([]HelmMetadata, error)
+}
+
+// HelmMetadata is a local chart's Chart.yaml, kept verbatim so index.yaml
+// entries carry every field helm reads.
+type HelmMetadata struct {
+	RepoName    string
+	FilePath    string
+	ContentHash string
+	Name        string
+	Version     string
+	ChartYAML   string
+	CreatedAt   time.Time
+}
diff --git a/internal/provider/metadata_puppet.go b/internal/provider/metadata_puppet.go
new file mode 100644
index 0000000..a99bd0c
--- /dev/null
+++ b/internal/provider/metadata_puppet.go
@@ -0,0 +1,32 @@
+package provider
+
+import (
+	"context"
+	"time"
+)
+
+type PuppetMetadataStore interface {
+	InsertPuppetMetadata(ctx context.Context, meta *PuppetMetadata) error
+}
+
+type PuppetMetadataDeleter interface {
+	DeletePuppetMetadata(ctx context.Context, repoName, filePath string) error
+}
+
+type PuppetMetadataReader interface {
+	ListPuppetMetadataEntries(ctx context.Context, repoName, slug string) ([]PuppetMetadata, error)
+}
+
+// PuppetMetadata is a local module release; MetadataJSON is the tarball's
+// metadata.json verbatim so Forge release objects carry every field.
+type PuppetMetadata struct {
+	RepoName     string
+	FilePath     string
+	ContentHash  string
+	Slug         string
+	Version      string
+	MetadataJSON string
+	Size         int64
+	MD5          string
+	CreatedAt    time.Time
+}
diff --git a/internal/provider/metadata_rpm.go b/internal/provider/metadata_rpm.go
new file mode 100644
index 0000000..4633cf2
--- /dev/null
+++ b/internal/provider/metadata_rpm.go
@@ -0,0 +1,60 @@
+package provider
+
+import (
+	"context"
+	"time"
+)
+
+type RPMMetadataReader interface {
+	ListRPMMetadataEntries(ctx context.Context, repoName string) ([]RPMMetadata, error)
+}
+
+type RPMMetadata struct {
+	RepoName      string
+	FilePath      string
+	ContentHash   string
+	Name          string
+	Epoch         int
+	Version       string
+	Release       string
+	Arch          string
+	Summary       string
+	Description   string
+	RPMSize       int64
+	InstalledSize int64
+	License       string
+	Vendor        string
+	Group         string
+	BuildHost     string
+	SourceRPM     string
+	URL           string
+	Packager      string
+	Requires      []RPMDep
+	Provides      []RPMDep
+	Conflicts     []RPMDep
+	Obsoletes     []RPMDep
+	Files         []RPMFile
+	Changelogs    []RPMChangelog
+	// CreatedAt is the persisted upload timestamp; used as a stable, replica-independent
+	// value for the repodata <time>/<revision> fields so generated indexes are deterministic.
+	CreatedAt time.Time
+}
+
+type RPMDep struct {
+	Name    string `json:"name"`
+	Flags   string `json:"flags,omitempty"`
+	Epoch   string `json:"epoch,omitempty"`
+	Version string `json:"version,omitempty"`
+	Release string `json:"release,omitempty"`
+}
+
+type RPMFile struct {
+	Path string `json:"path"`
+	Type string `json:"type,omitempty"`
+}
+
+type RPMChangelog struct {
+	Author string `json:"author"`
+	Date   int64  `json:"date"`
+	Text   string `json:"text"`
+}
diff --git a/internal/provider/metadata_store.go b/internal/provider/metadata_store.go
new file mode 100644
index 0000000..dc9a201
--- /dev/null
+++ b/internal/provider/metadata_store.go
@@ -0,0 +1,15 @@
+package provider
+
+import (
+	"context"
+)
+
+type MetadataStore interface {
+	InsertRPMMetadata(ctx context.Context, meta *RPMMetadata) error
+	InsertDebMetadata(ctx context.Context, meta *DebMetadata) error
+}
+
+type MetadataDeleter interface {
+	DeleteRPMMetadata(ctx context.Context, repoName, filePath string) error
+	DeleteDebMetadata(ctx context.Context, repoName, filePath string) error
+}
diff --git a/internal/provider/npm/npm.go b/internal/provider/npm/npm.go
index 38cf32d..8bc098d 100644
--- a/internal/provider/npm/npm.go
+++ b/internal/provider/npm/npm.go
@@ -37,6 +37,8 @@ func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
 	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
 }
 
+func (p *Provider) RewritesResponse() {}
+
 func (p *Provider) RewriteResponse(body []byte, remote models.Remote, proxyBaseURL string) ([]byte, error) {
 	if proxyBaseURL == "" || !json.Valid(body) {
 		return nil, nil
diff --git a/internal/provider/nuget/nuget.go b/internal/provider/nuget/nuget.go
index 4857173..7685d4f 100644
--- a/internal/provider/nuget/nuget.go
+++ b/internal/provider/nuget/nuget.go
@@ -1,5 +1,6 @@
 // Package nuget proxies a NuGet v3 feed: the service index, registration pages
-// and flat container indexes are mutable, .nupkg/.nuspec downloads immutable.
+// and flat container indexes are mutable; package, symbol, nuspec, readme and
+// icon blobs are immutable.
 package nuget
 
 import (
@@ -7,6 +8,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/url"
+	pathpkg "path"
 	"strings"
 
 	"git.unkin.net/unkin/artifactapi/internal/auth"
@@ -34,10 +36,12 @@ func (p *Provider) Classify(path string) provider.Mutability {
 
 func (p *Provider) ContentType(path string) string {
 	switch {
-	case strings.HasSuffix(path, ".nupkg"):
+	case strings.HasSuffix(path, ".nupkg"), strings.HasSuffix(path, ".snupkg"), pathpkg.Base(path) == "icon":
 		return "application/octet-stream"
 	case strings.HasSuffix(path, ".nuspec"):
 		return "application/xml"
+	case pathpkg.Base(path) == "readme":
+		return "text/markdown"
 	}
 	return "application/json"
 }
@@ -64,8 +68,8 @@ func (p *Provider) RewriteServed(body []byte, remote models.Remote, proxyBaseURL
 	if from == "" || !json.Valid(body) {
 		return body
 	}
-	to := strings.TrimRight(proxyBaseURL, "/") + "/api/v1/remote/" + remote.Name
-	return []byte(strings.ReplaceAll(string(body), from, to))
+	to, _ := json.Marshal(strings.TrimRight(proxyBaseURL, "/") + "/api/v1/remote/" + remote.Name)
+	return []byte(strings.ReplaceAll(string(body), from, string(to[1:len(to)-1])))
 }
 
 func (p *Provider) AuthHeaders(_ context.Context, remote models.Remote) (http.Header, error) {
@@ -80,6 +84,14 @@ func origin(baseURL string) string {
 	return u.Scheme + "://" + u.Host
 }
 
+// isPackage matches flat container blobs: {id}.{ver}.(s)nupkg, {id}.nuspec and
+// the {id}/{ver}/readme and {id}/{ver}/icon files.
 func isPackage(path string) bool {
-	return strings.HasSuffix(path, ".nupkg") || strings.HasSuffix(path, ".nuspec")
+	for _, ext := range []string{".nupkg", ".snupkg", ".nuspec"} {
+		if strings.HasSuffix(path, ext) {
+			return true
+		}
+	}
+	base := pathpkg.Base(path)
+	return (base == "readme" || base == "icon") && strings.Count(strings.Trim(path, "/"), "/") >= 2
 }
diff --git a/internal/provider/nuget/nuget_test.go b/internal/provider/nuget/nuget_test.go
index 688ca06..5aab56b 100644
--- a/internal/provider/nuget/nuget_test.go
+++ b/internal/provider/nuget/nuget_test.go
@@ -19,7 +19,11 @@ func TestClassify(t *testing.T) {
 	}{
 		{"v3-flatcontainer/newtonsoft.json/13.0.3/newtonsoft.json.13.0.3.nupkg", provider.Immutable},
 		{"v3-flatcontainer/newtonsoft.json/13.0.3/newtonsoft.json.nuspec", provider.Immutable},
+		{"v3-flatcontainer/newtonsoft.json/13.0.3/newtonsoft.json.13.0.3.snupkg", provider.Immutable},
+		{"v3-flatcontainer/newtonsoft.json/13.0.3/readme", provider.Immutable},
+		{"v3-flatcontainer/newtonsoft.json/13.0.3/icon", provider.Immutable},
 		{"v3-flatcontainer/newtonsoft.json/index.json", provider.Mutable},
+		{"readme", provider.Mutable},
 		{"v3/registration5-gz-semver2/newtonsoft.json/index.json", provider.Mutable},
 		{"index.json", provider.Mutable},
 	}
@@ -30,6 +34,28 @@ func TestClassify(t *testing.T) {
 	}
 }
 
+func TestContentType(t *testing.T) {
+	p := &Provider{}
+	for path, want := range map[string]string{
+		"v3-flatcontainer/a/1.0.0/a.1.0.0.snupkg": "application/octet-stream",
+		"v3-flatcontainer/a/1.0.0/icon":           "application/octet-stream",
+		"v3-flatcontainer/a/1.0.0/readme":         "text/markdown",
+		"v3-flatcontainer/a/index.json":           "application/json",
+	} {
+		if got := p.ContentType(path); got != want {
+			t.Errorf("ContentType(%q) = %q, want %q", path, got, want)
+		}
+	}
+}
+
+func TestRewriteServedEscapesJSON(t *testing.T) {
+	body := `{"@id":"https://api.nuget.org/v3-flatcontainer/"}`
+	got := (&Provider{}).RewriteServed([]byte(body), nugetOrg, `http://evil"<x>`)
+	if want := `{"@id":"http://evil\"\u003cx\u003e/api/v1/remote/nuget-org/v3-flatcontainer/"}`; string(got) != want {
+		t.Errorf("RewriteServed = %s, want %s", got, want)
+	}
+}
+
 func TestUpstreamURL(t *testing.T) {
 	p := &Provider{}
 	tests := []struct {
diff --git a/internal/provider/provider.go b/internal/provider/provider.go
index f18d22c..951a897 100644
--- a/internal/provider/provider.go
+++ b/internal/provider/provider.go
@@ -3,9 +3,7 @@ package provider
 import (
 	"context"
 	"fmt"
-	"io"
 	"net/http"
-	"time"
 
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
@@ -34,216 +32,6 @@ type FileEntry struct {
 	ContentHash string
 }
 
-type FileStore interface {
-	ListFilesByPrefix(ctx context.Context, repoName, prefix string) ([]FileEntry, error)
-	ListPackages(ctx context.Context, repoName string) ([]string, error)
-}
-
-type LocalUploader interface {
-	ValidateUpload(filePath string) (storagePath, contentType string, err error)
-	UploadResponse(storagePath, contentHash string, sizeBytes int64) map[string]any
-}
-
-type LocalIndexer interface {
-	ServeLocalIndex(w http.ResponseWriter, r *http.Request, files FileStore, repoName, path string) bool
-	GenerateLocalIndex(ctx context.Context, files FileStore, repoName, path string) ([]byte, error)
-}
-
-type BlobReader interface {
-	Download(ctx context.Context, key string) (io.ReadCloser, int64, error)
-}
-
-type PostUploadHook interface {
-	AfterUpload(ctx context.Context, repoName, storagePath, contentHash string, blobs BlobReader, db MetadataStore)
-}
-
-// PostDeleteHook lets a provider clean up derived state (e.g. RPM metadata that
-// feeds generated repodata) after a local file is removed.
-type PostDeleteHook interface {
-	AfterDelete(ctx context.Context, repoName, storagePath string, db MetadataDeleter) error
-}
-
-type MetadataStore interface {
-	InsertRPMMetadata(ctx context.Context, meta *RPMMetadata) error
-	InsertDebMetadata(ctx context.Context, meta *DebMetadata) error
-}
-
-// QueryForwarder is a remote provider whose upstream answers depend on the
-// query string (e.g. paginated JSON APIs). Only the named params for path are
-// forwarded upstream and kept in the cache key, each as the canonical value
-// its validator returns; a value the validator rejects is dropped.
-type QueryForwarder interface {
-	ForwardedQuery(path string) map[string]QueryValidator
-}
-
-// QueryValidator canonicalises a raw query value, reporting false to drop it.
-type QueryValidator func(v string) (string, bool)
-
-// RemoteServer lets a remote provider fully answer a request itself instead of
-// going through the byte-proxy engine. It is the remote-side analog of
-// LocalIndexer: a metadata-only remote (e.g. github_rpm) uses it to synthesize
-// repodata from derived per-asset metadata and to redirect package downloads to
-// a backend remote, without ever precaching the packages. Returning false lets
-// the normal proxy path take over.
-type RemoteServer interface {
-	ServeRemote(w http.ResponseWriter, r *http.Request, remote models.Remote, path, proxyBaseURL string, store RemoteMetadataStore) bool
-}
-
-// ServeRewriter rewrites a cached mutable remote response per request, for
-// indexes whose URLs must name the requesting host and so cannot be rewritten
-// before caching.
-type ServeRewriter interface {
-	RewriteServed(body []byte, remote models.Remote, proxyBaseURL string) []byte
-}
-
-// RemoteMetadataStore is the persistence surface a RemoteServer needs to cache
-// and read the metadata it derives per upstream asset. *database.DB satisfies it.
-type RemoteMetadataStore interface {
-	RPMMetadataReader
-	MetadataStore
-	MetadataDeleter
-}
-
-type MetadataDeleter interface {
-	DeleteRPMMetadata(ctx context.Context, repoName, filePath string) error
-	DeleteDebMetadata(ctx context.Context, repoName, filePath string) error
-}
-
-type RPMMetadataReader interface {
-	ListRPMMetadataEntries(ctx context.Context, repoName string) ([]RPMMetadata, error)
-}
-
-// DebMetadataReader is the read surface the deb LocalIndexer needs to
-// regenerate a flat apt repository (Packages/Release) from stored rows.
-// *database.DB satisfies it; ServeLocalIndex type-asserts the FileStore to it,
-// mirroring how the rpm provider reaches its RPMMetadataReader.
-type DebMetadataReader interface {
-	ListDebMetadataEntries(ctx context.Context, repoName string) ([]DebMetadata, error)
-}
-
-// DebMetadata is the derived per-package metadata for a Debian .deb, carrying
-// the full raw control stanza so the Packages index can be regenerated
-// faithfully alongside the computed size/md5/sha256 apt requires.
-type DebMetadata struct {
-	RepoName     string
-	FilePath     string
-	ContentHash  string
-	Name         string
-	Version      string
-	Architecture string
-	Control      string
-	Size         int64
-	MD5          string
-	SHA256       string
-	// CreatedAt is the persisted insert time; the Release Date: is derived from
-	// the newest value so the index is byte-identical across replicas and
-	// regenerations (issue #117) rather than stamped from wall clock.
-	CreatedAt time.Time
-}
-
-// AlpineMetadataStore / AlpineMetadataDeleter / AlpineMetadataReader are the
-// Alpine-specific persistence surfaces. They are kept separate from the shared
-// RPM/Deb metadata interfaces so the apk provider can type-assert the generic
-// MetadataStore/MetadataDeleter/FileStore it is handed without widening (and
-// thus perturbing the test doubles of) the rpm and deb providers. *database.DB
-// satisfies all three.
-type AlpineMetadataStore interface {
-	InsertAlpineMetadata(ctx context.Context, meta *AlpineMetadata) error
-}
-
-type AlpineMetadataDeleter interface {
-	DeleteAlpineMetadata(ctx context.Context, repoName, filePath string) error
-}
-
-type AlpineMetadataReader interface {
-	ListAlpineMetadataEntries(ctx context.Context, repoName string) ([]AlpineMetadata, error)
-}
-
-// AlpineMetadata is the derived per-package metadata for an Alpine .apk, holding
-// the fields an APKINDEX record carries plus the apk pull checksum (Q1…, the
-// sha1 of the control gzip stream) and the download/installed sizes.
-type AlpineMetadata struct {
-	RepoName         string
-	FilePath         string
-	ContentHash      string
-	Checksum         string   // C: "Q1" + base64(sha1(control gzip stream))
-	Name             string   // P:
-	Version          string   // V:
-	Arch             string   // A:
-	DownloadSize     int64    // S: on-disk .apk size
-	InstalledSize    int64    // I: unpacked size from .PKGINFO
-	Description      string   // T:
-	URL              string   // U:
-	License          string   // L:
-	Origin           string   // o:
-	Maintainer       string   // m:
-	BuildTime        int64    // t:
-	Commit           string   // c:
-	ProviderPriority string   // k:
-	Depends          []string // D:
-	Provides         []string // p:
-	InstallIf        []string // i:
-}
-
-type RPMMetadata struct {
-	RepoName      string
-	FilePath      string
-	ContentHash   string
-	Name          string
-	Epoch         int
-	Version       string
-	Release       string
-	Arch          string
-	Summary       string
-	Description   string
-	RPMSize       int64
-	InstalledSize int64
-	License       string
-	Vendor        string
-	Group         string
-	BuildHost     string
-	SourceRPM     string
-	URL           string
-	Packager      string
-	Requires      []RPMDep
-	Provides      []RPMDep
-	Conflicts     []RPMDep
-	Obsoletes     []RPMDep
-	Files         []RPMFile
-	Changelogs    []RPMChangelog
-	// CreatedAt is the persisted upload timestamp; used as a stable, replica-independent
-	// value for the repodata <time>/<revision> fields so generated indexes are deterministic.
-	CreatedAt time.Time
-}
-
-type RPMDep struct {
-	Name    string `json:"name"`
-	Flags   string `json:"flags,omitempty"`
-	Epoch   string `json:"epoch,omitempty"`
-	Version string `json:"version,omitempty"`
-	Release string `json:"release,omitempty"`
-}
-
-type RPMFile struct {
-	Path string `json:"path"`
-	Type string `json:"type,omitempty"`
-}
-
-type RPMChangelog struct {
-	Author string `json:"author"`
-	Date   int64  `json:"date"`
-	Text   string `json:"text"`
-}
-
-type IndexMerger interface {
-	MergeIndexes(members []MemberIndex, proxyBaseURL string) ([]byte, error)
-}
-
-type MemberIndex struct {
-	RemoteName string
-	Body       []byte
-}
-
 var registry = map[models.PackageType]Provider{}
 
 func Register(p Provider) {
diff --git a/internal/provider/puppet/local.go b/internal/provider/puppet/local.go
new file mode 100644
index 0000000..b9a3a4c
--- /dev/null
+++ b/internal/provider/puppet/local.go
@@ -0,0 +1,393 @@
+package puppet
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"context"
+	"crypto/md5"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"path"
+	"regexp"
+	"slices"
+	"strconv"
+	"strings"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/storage"
+)
+
+const filesPrefix = "v3/files/"
+
+// releaseRe matches <owner>-<name>-<semver>, the Forge release slug and the
+// tarball basename that `puppet module build` produces.
+var releaseRe = regexp.MustCompile(`^([a-z0-9]+)-([a-z][a-z0-9_]*)-(\d+\.\d+\.\d+(?:-[0-9a-z.-]+)?(?:\+[0-9a-z.-]+)?)$`)
+
+func parseRelease(s string) (slug, version string, ok bool) {
+	m := releaseRe.FindStringSubmatch(strings.ToLower(s))
+	if m == nil {
+		return "", "", false
+	}
+	return m[1] + "-" + m[2], m[3], true
+}
+
+func normalizeSlug(s string) string {
+	return strings.ToLower(strings.ReplaceAll(s, "/", "-"))
+}
+
+// ValidateUpload stores tarballs under v3/files/ so Forge file_uri downloads
+// resolve straight to the stored file.
+func (p *Provider) ValidateUpload(filePath string) (storagePath, contentType string, err error) {
+	filename := strings.ToLower(path.Base(path.Clean("/" + filePath)))
+	if _, _, ok := parseRelease(strings.TrimSuffix(filename, ".tar.gz")); !ok || !strings.HasSuffix(filename, ".tar.gz") {
+		return "", "", fmt.Errorf("file must be named <owner>-<module>-<version>.tar.gz")
+	}
+	return filesPrefix + filename, "application/gzip", nil
+}
+
+func (p *Provider) UploadResponse(storagePath, contentHash string, sizeBytes int64) map[string]any {
+	return map[string]any{
+		"filename":     path.Base(storagePath),
+		"content_hash": contentHash,
+		"size_bytes":   sizeBytes,
+	}
+}
+
+func (p *Provider) AfterUpload(ctx context.Context, repoName, storagePath, contentHash string, blobs provider.BlobReader, db provider.MetadataStore) {
+	reader, size, err := blobs.Download(ctx, storage.BlobKey(strings.TrimPrefix(contentHash, "sha256:")))
+	if err != nil {
+		slog.Error("puppet metadata: download failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	defer func() { _ = reader.Close() }()
+	if size > maxModuleTarball {
+		slog.Error("puppet metadata: tarball too large", "repo", repoName, "path", storagePath, "size", size)
+		return
+	}
+
+	hash := md5.New()
+	src := io.TeeReader(io.LimitReader(reader, maxModuleTarball), hash)
+	meta, err := parseModule(src)
+	if err != nil {
+		slog.Error("puppet metadata: parse failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	if _, err := io.Copy(io.Discard, src); err != nil {
+		slog.Error("puppet metadata: read failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	slug, version, _ := parseRelease(strings.TrimSuffix(path.Base(storagePath), ".tar.gz"))
+	if meta.Slug != slug || meta.Version != version {
+		slog.Error("puppet metadata: metadata.json does not match filename", "repo", repoName, "path", storagePath, "name", meta.Slug, "version", meta.Version)
+		return
+	}
+	meta.RepoName = repoName
+	meta.FilePath = storagePath
+	meta.ContentHash = contentHash
+	meta.Size = size
+	meta.MD5 = hex.EncodeToString(hash.Sum(nil))
+
+	store, ok := db.(provider.PuppetMetadataStore)
+	if !ok {
+		slog.Error("puppet metadata: store does not support puppet metadata", "repo", repoName)
+		return
+	}
+	if err := store.InsertPuppetMetadata(ctx, meta); err != nil {
+		slog.Error("puppet metadata: insert failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	slog.Info("puppet metadata: parsed", "repo", repoName, "module", meta.Slug, "version", meta.Version)
+}
+
+func (p *Provider) AfterDelete(ctx context.Context, repoName, storagePath string, db provider.MetadataDeleter) error {
+	deleter, ok := db.(provider.PuppetMetadataDeleter)
+	if !ok {
+		return nil
+	}
+	return deleter.DeletePuppetMetadata(ctx, repoName, storagePath)
+}
+
+const maxMetadataJSON = 1 << 20
+
+var (
+	maxModuleTarball int64 = 100 << 20
+	maxModuleScan    int64 = 200 << 20
+)
+
+// parseModule reads the top-level <dir>/metadata.json from a module tarball,
+// scanning at most maxModuleScan decompressed bytes.
+func parseModule(r io.Reader) (*provider.PuppetMetadata, error) {
+	zr, err := gzip.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	scan := &io.LimitedReader{R: zr, N: maxModuleScan}
+	tr := tar.NewReader(scan)
+	for {
+		hdr, err := tr.Next()
+		if scan.N <= 0 {
+			return nil, errors.New("module tarball exceeds decompressed scan limit before metadata.json")
+		}
+		if err == io.EOF {
+			return nil, errors.New("no metadata.json in module tarball")
+		}
+		if err != nil {
+			return nil, err
+		}
+		dir, file := path.Split(strings.TrimPrefix(path.Clean(hdr.Name), "./"))
+		if hdr.Typeflag != tar.TypeReg || file != "metadata.json" || strings.Count(dir, "/") != 1 {
+			continue
+		}
+		body, err := io.ReadAll(io.LimitReader(tr, maxMetadataJSON))
+		if err != nil {
+			return nil, err
+		}
+		var md struct {
+			Name    string `json:"name"`
+			Version string `json:"version"`
+		}
+		if err := json.Unmarshal(body, &md); err != nil {
+			return nil, fmt.Errorf("parse metadata.json: %w", err)
+		}
+		if md.Name == "" || md.Version == "" {
+			return nil, errors.New("metadata.json missing name or version")
+		}
+		return &provider.PuppetMetadata{Slug: normalizeSlug(md.Name), Version: md.Version, MetadataJSON: string(body)}, nil
+	}
+}
+
+func (p *Provider) ServeLocalIndex(w http.ResponseWriter, r *http.Request, files provider.FileStore, repoName, reqPath string) bool {
+	clean := strings.TrimPrefix(path.Clean("/"+reqPath), "/")
+	var list func(slug string) ([]provider.PuppetMetadata, error)
+	if reader, ok := files.(provider.PuppetMetadataReader); ok {
+		list = func(slug string) ([]provider.PuppetMetadata, error) {
+			metas, err := reader.ListPuppetMetadataEntries(r.Context(), repoName, slug)
+			sortReleases(metas)
+			return metas, err
+		}
+	} else {
+		list = func(string) ([]provider.PuppetMetadata, error) {
+			return nil, errors.New("puppet metadata not available")
+		}
+	}
+
+	switch {
+	case clean == "v3/releases":
+		serveReleaseList(w, r, list)
+	case strings.HasPrefix(clean, "v3/releases/"):
+		slug, version, ok := parseRelease(strings.TrimPrefix(clean, "v3/releases/"))
+		if !ok {
+			notFound(w)
+			return true
+		}
+		metas, err := list(slug)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return true
+		}
+		for _, m := range metas {
+			if m.Version == version {
+				writeJSON(w, releaseObject(m))
+				return true
+			}
+		}
+		notFound(w)
+	case strings.HasPrefix(clean, "v3/modules/"):
+		slug := normalizeSlug(strings.TrimPrefix(clean, "v3/modules/"))
+		metas, err := list(slug)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return true
+		}
+		if len(metas) == 0 {
+			notFound(w)
+			return true
+		}
+		writeJSON(w, moduleObject(metas))
+	default:
+		return false
+	}
+	return true
+}
+
+func (p *Provider) GenerateLocalIndex(ctx context.Context, files provider.FileStore, repoName, path string) ([]byte, error) {
+	return nil, fmt.Errorf("puppet local index generation for virtual repos not supported")
+}
+
+func serveReleaseList(w http.ResponseWriter, r *http.Request, list func(string) ([]provider.PuppetMetadata, error)) {
+	q := r.URL.Query()
+	slug := normalizeSlug(q.Get("module"))
+	limit, err := strconv.Atoi(q.Get("limit"))
+	if err != nil || limit <= 0 {
+		limit = 20
+	}
+	limit = min(limit, 100)
+	offset, err := strconv.Atoi(q.Get("offset"))
+	if err != nil || offset < 0 {
+		offset = 0
+	}
+
+	metas, err := list(slug)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	offset = min(offset, len(metas))
+	results := []map[string]any{}
+	for _, m := range metas[offset : offset+min(limit, len(metas)-offset)] {
+		results = append(results, releaseObject(m))
+	}
+
+	page := func(off int) any {
+		if off < 0 || off >= len(metas) && off != 0 {
+			return nil
+		}
+		v := url.Values{"limit": {strconv.Itoa(limit)}, "offset": {strconv.Itoa(off)}}
+		if slug != "" {
+			v.Set("module", slug)
+		}
+		return "/v3/releases?" + v.Encode()
+	}
+	var previous any
+	if offset > 0 {
+		previous = page(max(offset-limit, 0))
+	}
+	writeJSON(w, map[string]any{
+		"pagination": map[string]any{
+			"limit":    limit,
+			"offset":   offset,
+			"first":    page(0),
+			"previous": previous,
+			"current":  page(offset),
+			"next":     page(offset + limit),
+			"total":    len(metas),
+		},
+		"results": results,
+	})
+}
+
+func owner(slug string) map[string]any {
+	name, _, _ := strings.Cut(slug, "-")
+	return map[string]any{"uri": "/v3/users/" + name, "slug": name, "username": name}
+}
+
+func moduleRef(slug string) map[string]any {
+	_, name, _ := strings.Cut(slug, "-")
+	return map[string]any{"uri": "/v3/modules/" + slug, "slug": slug, "name": name, "deprecated_at": nil, "owner": owner(slug)}
+}
+
+const forgeTime = "2006-01-02 15:04:05 -0700"
+
+func releaseObject(m provider.PuppetMetadata) map[string]any {
+	slug := m.Slug + "-" + m.Version
+	return map[string]any{
+		"uri":         "/v3/releases/" + slug,
+		"slug":        slug,
+		"module":      moduleRef(m.Slug),
+		"version":     m.Version,
+		"metadata":    json.RawMessage(m.MetadataJSON),
+		"tags":        []string{},
+		"supported":   false,
+		"pdk":         false,
+		"file_uri":    "/" + m.FilePath,
+		"file_size":   m.Size,
+		"file_md5":    m.MD5,
+		"file_sha256": strings.TrimPrefix(m.ContentHash, "sha256:"),
+		"downloads":   0,
+		"readme":      nil,
+		"changelog":   nil,
+		"license":     nil,
+		"created_at":  m.CreatedAt.Format(forgeTime),
+		"updated_at":  m.CreatedAt.Format(forgeTime),
+		"deleted_at":  nil,
+	}
+}
+
+// moduleObject expects metas sorted newest version first.
+func moduleObject(metas []provider.PuppetMetadata) map[string]any {
+	obj := moduleRef(metas[0].Slug)
+	releases := make([]map[string]any, 0, len(metas))
+	for _, m := range metas {
+		slug := m.Slug + "-" + m.Version
+		releases = append(releases, map[string]any{
+			"uri": "/v3/releases/" + slug, "slug": slug, "version": m.Version,
+			"file_uri": "/" + m.FilePath, "file_size": m.Size, "supported": false,
+			"created_at": m.CreatedAt.Format(forgeTime), "deleted_at": nil,
+		})
+	}
+	obj["current_release"] = releaseObject(metas[0])
+	obj["releases"] = releases
+	obj["downloads"] = 0
+	obj["created_at"] = metas[len(metas)-1].CreatedAt.Format(forgeTime)
+	obj["updated_at"] = metas[0].CreatedAt.Format(forgeTime)
+	return obj
+}
+
+func writeJSON(w http.ResponseWriter, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	enc := json.NewEncoder(w)
+	enc.SetEscapeHTML(false)
+	_ = enc.Encode(v)
+}
+
+func notFound(w http.ResponseWriter) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusNotFound)
+	_, _ = io.WriteString(w, `{"message":"404 Not Found","errors":["The requested resource could not be found"]}`)
+}
+
+// sortReleases orders by module slug, then newest semver first.
+func sortReleases(metas []provider.PuppetMetadata) {
+	slices.SortStableFunc(metas, func(a, b provider.PuppetMetadata) int {
+		if c := strings.Compare(a.Slug, b.Slug); c != 0 {
+			return c
+		}
+		return compareSemver(b.Version, a.Version)
+	})
+}
+
+func compareSemver(a, b string) int {
+	a, _, _ = strings.Cut(a, "+")
+	b, _, _ = strings.Cut(b, "+")
+	aCore, aPre, aHasPre := strings.Cut(a, "-")
+	bCore, bPre, bHasPre := strings.Cut(b, "-")
+	if c := compareIdents(strings.Split(aCore, "."), strings.Split(bCore, ".")); c != 0 {
+		return c
+	}
+	switch {
+	case aHasPre && !bHasPre:
+		return -1
+	case !aHasPre && bHasPre:
+		return 1
+	}
+	return compareIdents(strings.Split(aPre, "."), strings.Split(bPre, "."))
+}
+
+func compareIdents(a, b []string) int {
+	for i := 0; i < len(a) && i < len(b); i++ {
+		an, aErr := strconv.Atoi(a[i])
+		bn, bErr := strconv.Atoi(b[i])
+		var c int
+		switch {
+		case aErr == nil && bErr == nil:
+			c = an - bn
+		case aErr == nil:
+			c = -1
+		case bErr == nil:
+			c = 1
+		default:
+			c = strings.Compare(a[i], b[i])
+		}
+		if c != 0 {
+			return c
+		}
+	}
+	return len(a) - len(b)
+}
diff --git a/internal/provider/puppet/local_test.go b/internal/provider/puppet/local_test.go
new file mode 100644
index 0000000..57927d3
--- /dev/null
+++ b/internal/provider/puppet/local_test.go
@@ -0,0 +1,301 @@
+package puppet
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"context"
+	"crypto/md5"
+	"encoding/hex"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func moduleTarball(t *testing.T, dir, metadata string) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	tw := tar.NewWriter(zw)
+	for name, body := range map[string]string{dir + "/metadata.json": metadata, dir + "/manifests/init.pp": "class hello {}\n"} {
+		if err := tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(body))}); err != nil {
+			t.Fatal(err)
+		}
+		_, _ = tw.Write([]byte(body))
+	}
+	_ = tw.Close()
+	_ = zw.Close()
+	return buf.Bytes()
+}
+
+const helloMetadata = `{"name":"unkin-hello","version":"0.1.0","dependencies":[{"name":"puppetlabs/stdlib","version_requirement":">= 4.0.0"}]}`
+
+type fakeBlobs struct{ data []byte }
+
+func (f fakeBlobs) Download(context.Context, string) (io.ReadCloser, int64, error) {
+	return io.NopCloser(bytes.NewReader(f.data)), int64(len(f.data)), nil
+}
+
+type fakeStore struct{ inserted *provider.PuppetMetadata }
+
+func (f *fakeStore) InsertRPMMetadata(context.Context, *provider.RPMMetadata) error { return nil }
+func (f *fakeStore) InsertDebMetadata(context.Context, *provider.DebMetadata) error { return nil }
+func (f *fakeStore) InsertPuppetMetadata(_ context.Context, m *provider.PuppetMetadata) error {
+	f.inserted = m
+	return nil
+}
+
+type fakeReader struct{ metas []provider.PuppetMetadata }
+
+func (f fakeReader) ListPuppetMetadataEntries(_ context.Context, _, slug string) ([]provider.PuppetMetadata, error) {
+	var out []provider.PuppetMetadata
+	for _, m := range f.metas {
+		if slug == "" || m.Slug == slug {
+			out = append(out, m)
+		}
+	}
+	return out, nil
+}
+func (fakeReader) ListFilesByPrefix(context.Context, string, string) ([]provider.FileEntry, error) {
+	return nil, nil
+}
+func (fakeReader) ListPackages(context.Context, string) ([]string, error) { return nil, nil }
+
+func TestValidateUpload(t *testing.T) {
+	p := &Provider{}
+	sp, ct, err := p.ValidateUpload("some/dir/Unkin-hello-0.1.0.tar.gz")
+	if err != nil || sp != "v3/files/unkin-hello-0.1.0.tar.gz" || ct != "application/gzip" {
+		t.Errorf("sp=%q ct=%q err=%v", sp, ct, err)
+	}
+	for _, bad := range []string{"hello-0.1.0.tar.gz", "unkin-hello-0.1.tar.gz", "unkin-hello-0.1.0.zip", "unkin-Hello_x-0.1.0.tgz"} {
+		if _, _, err := p.ValidateUpload(bad); err == nil {
+			t.Errorf("%q accepted", bad)
+		}
+	}
+}
+
+func TestAfterUploadRecordsMetadata(t *testing.T) {
+	raw := moduleTarball(t, "unkin-hello-0.1.0", helloMetadata)
+	store := &fakeStore{}
+	(&Provider{}).AfterUpload(context.Background(), "forge", "v3/files/unkin-hello-0.1.0.tar.gz", "sha256:abc", fakeBlobs{raw}, store)
+	m := store.inserted
+	if m == nil {
+		t.Fatal("nothing inserted")
+	}
+	sum := md5.Sum(raw)
+	if m.Slug != "unkin-hello" || m.Version != "0.1.0" || m.MD5 != hex.EncodeToString(sum[:]) || m.Size != int64(len(raw)) || m.MetadataJSON != helloMetadata {
+		t.Errorf("got %+v", m)
+	}
+}
+
+func TestAfterUploadRejectsMismatchedFilename(t *testing.T) {
+	raw := moduleTarball(t, "unkin-hello-0.2.0", `{"name":"unkin-hello","version":"0.2.0"}`)
+	store := &fakeStore{}
+	(&Provider{}).AfterUpload(context.Background(), "forge", "v3/files/unkin-hello-0.1.0.tar.gz", "sha256:abc", fakeBlobs{raw}, store)
+	if store.inserted != nil {
+		t.Error("mismatched version indexed")
+	}
+}
+
+func TestParseModuleRequiresTopLevelMetadata(t *testing.T) {
+	if _, err := parseModule(bytes.NewReader(moduleTarball(t, "a/b", helloMetadata))); err == nil {
+		t.Error("nested metadata.json accepted")
+	}
+	if _, err := parseModule(bytes.NewReader(moduleTarball(t, "x", `{"name":"unkin-hello"}`))); err == nil {
+		t.Error("missing version accepted")
+	}
+}
+
+func tarballOf(t *testing.T, entries ...*tar.Header) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	tw := tar.NewWriter(zw)
+	for _, h := range entries {
+		if err := tw.WriteHeader(h); err != nil {
+			t.Fatal(err)
+		}
+		if h.Typeflag == tar.TypeReg {
+			body := helloMetadata
+			if !strings.HasSuffix(h.Name, "metadata.json") {
+				body = strings.Repeat("x", int(h.Size))
+			}
+			_, _ = tw.Write([]byte(body))
+		}
+	}
+	_ = tw.Close()
+	_ = zw.Close()
+	return buf.Bytes()
+}
+
+func TestParseModuleSkipsNonRegularMetadata(t *testing.T) {
+	raw := tarballOf(t,
+		&tar.Header{Name: "unkin-hello-0.1.0/metadata.json", Typeflag: tar.TypeSymlink, Linkname: "/etc/passwd"},
+		&tar.Header{Name: "unkin-hello-0.1.0/metadata.json/", Typeflag: tar.TypeDir, Mode: 0o755},
+		&tar.Header{Name: "unkin-hello-0.1.0/metadata.json", Typeflag: tar.TypeReg, Mode: 0o644, Size: int64(len(helloMetadata))},
+	)
+	meta, err := parseModule(bytes.NewReader(raw))
+	if err != nil || meta.Slug != "unkin-hello" || meta.Version != "0.1.0" {
+		t.Fatalf("got %v, %v", meta, err)
+	}
+}
+
+func TestParseModuleCapsDecompressedScan(t *testing.T) {
+	defer func(n int64) { maxModuleScan = n }(maxModuleScan)
+	maxModuleScan = 64 << 10
+	raw := tarballOf(t,
+		&tar.Header{Name: "unkin-hello-0.1.0/big", Typeflag: tar.TypeReg, Mode: 0o644, Size: 1 << 20},
+		&tar.Header{Name: "unkin-hello-0.1.0/metadata.json", Typeflag: tar.TypeReg, Mode: 0o644, Size: int64(len(helloMetadata))},
+	)
+	if _, err := parseModule(bytes.NewReader(raw)); err == nil || !strings.Contains(err.Error(), "scan limit") {
+		t.Fatalf("expected scan limit error, got %v", err)
+	}
+	maxModuleScan = 2 << 20
+	if _, err := parseModule(bytes.NewReader(raw)); err != nil {
+		t.Fatalf("under cap: %v", err)
+	}
+}
+
+func TestAfterUploadCapsTarballSize(t *testing.T) {
+	defer func(n int64) { maxModuleTarball = n }(maxModuleTarball)
+	raw := moduleTarball(t, "unkin-hello-0.1.0", helloMetadata)
+	maxModuleTarball = int64(len(raw)) - 1
+	store := &fakeStore{}
+	(&Provider{}).AfterUpload(context.Background(), "forge", "v3/files/unkin-hello-0.1.0.tar.gz", "sha256:abc", fakeBlobs{raw}, store)
+	if store.inserted != nil {
+		t.Error("oversized tarball indexed")
+	}
+	maxModuleTarball = int64(len(raw))
+	(&Provider{}).AfterUpload(context.Background(), "forge", "v3/files/unkin-hello-0.1.0.tar.gz", "sha256:abc", fakeBlobs{raw}, store)
+	if store.inserted == nil {
+		t.Error("tarball at cap not indexed")
+	}
+}
+
+func TestReleaseListClampsPagination(t *testing.T) {
+	files := releases("0.1.0", "0.2.0", "0.3.0")
+	for _, q := range []string{"offset=9223372036854775807", "offset=9223372036854775807&limit=9223372036854775807", "offset=-5&limit=-5", "limit=9223372036854775807"} {
+		code, body := get(t, files, "v3/releases?module=unkin-hello&"+q)
+		if code != http.StatusOK {
+			t.Fatalf("%s: code %d", q, code)
+		}
+		pg := body["pagination"].(map[string]any)
+		if l := pg["limit"].(float64); l < 1 || l > 100 {
+			t.Errorf("%s: limit %v", q, l)
+		}
+		if o := pg["offset"].(float64); o < 0 || o > 3 {
+			t.Errorf("%s: offset %v", q, o)
+		}
+	}
+	_, body := get(t, files, "v3/releases?module=unkin-hello&offset=9223372036854775807")
+	if len(body["results"].([]any)) != 0 || body["pagination"].(map[string]any)["next"] != nil {
+		t.Errorf("past-end page: %v", body)
+	}
+}
+
+func get(t *testing.T, files provider.FileStore, target string) (int, map[string]any) {
+	t.Helper()
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/x/"+target, nil)
+	path, _, _ := strings.Cut(target, "?")
+	if !(&Provider{}).ServeLocalIndex(rec, req, files, "forge", path) {
+		return 0, nil
+	}
+	var body map[string]any
+	_ = json.Unmarshal(rec.Body.Bytes(), &body)
+	return rec.Code, body
+}
+
+func releases(versions ...string) fakeReader {
+	var f fakeReader
+	for i, v := range versions {
+		f.metas = append(f.metas, provider.PuppetMetadata{
+			FilePath: "v3/files/unkin-hello-" + v + ".tar.gz", ContentHash: "sha256:feed", Slug: "unkin-hello",
+			Version: v, MetadataJSON: `{"name":"unkin-hello","version":"` + v + `"}`, MD5: "m" + v,
+			CreatedAt: time.Unix(int64(i), 0),
+		})
+	}
+	f.metas = append(f.metas, provider.PuppetMetadata{Slug: "other-mod", Version: "9.9.9", MetadataJSON: `{}`})
+	return f
+}
+
+func TestReleaseListPaginatesNewestFirst(t *testing.T) {
+	files := releases("0.1.0", "0.10.0", "0.2.0", "1.0.0-rc.1", "1.0.0")
+	code, body := get(t, files, "v3/releases?module=unkin/hello&limit=2")
+	if code != http.StatusOK {
+		t.Fatalf("code %d", code)
+	}
+	results := body["results"].([]any)
+	pg := body["pagination"].(map[string]any)
+	if len(results) != 2 || results[0].(map[string]any)["version"] != "1.0.0" || results[1].(map[string]any)["version"] != "1.0.0-rc.1" {
+		t.Fatalf("page 1: %v", results)
+	}
+	if pg["total"] != float64(5) || pg["next"] != "/v3/releases?limit=2&module=unkin-hello&offset=2" || pg["previous"] != nil {
+		t.Errorf("pagination: %v", pg)
+	}
+
+	_, body = get(t, files, "v3/releases?module=unkin-hello&limit=2&offset=4")
+	results = body["results"].([]any)
+	pg = body["pagination"].(map[string]any)
+	if len(results) != 1 || results[0].(map[string]any)["version"] != "0.1.0" || pg["next"] != nil || pg["previous"] != "/v3/releases?limit=2&module=unkin-hello&offset=2" {
+		t.Errorf("last page: %v %v", results, pg)
+	}
+
+	_, body = get(t, files, "v3/releases?module=nobody-none")
+	if len(body["results"].([]any)) != 0 {
+		t.Error("unknown module returned results")
+	}
+}
+
+func TestReleaseObject(t *testing.T) {
+	code, body := get(t, releases("0.1.0"), "v3/releases/unkin-hello-0.1.0")
+	if code != http.StatusOK {
+		t.Fatalf("code %d", code)
+	}
+	if body["file_uri"] != "/v3/files/unkin-hello-0.1.0.tar.gz" || body["file_md5"] != "m0.1.0" || body["file_sha256"] != "feed" {
+		t.Errorf("release: %v", body)
+	}
+	if body["metadata"].(map[string]any)["name"] != "unkin-hello" || body["module"].(map[string]any)["owner"].(map[string]any)["username"] != "unkin" {
+		t.Errorf("release refs: %v", body)
+	}
+	if code, _ := get(t, releases("0.1.0"), "v3/releases/unkin-hello-0.2.0"); code != http.StatusNotFound {
+		t.Errorf("missing version: %d", code)
+	}
+}
+
+func TestModuleObject(t *testing.T) {
+	code, body := get(t, releases("0.9.0", "0.10.0"), "v3/modules/unkin-hello")
+	if code != http.StatusOK {
+		t.Fatalf("code %d", code)
+	}
+	if body["slug"] != "unkin-hello" || body["name"] != "hello" || body["current_release"].(map[string]any)["version"] != "0.10.0" || len(body["releases"].([]any)) != 2 {
+		t.Errorf("module: %v", body)
+	}
+	if code, _ := get(t, releases(), "v3/modules/unkin-missing"); code != http.StatusNotFound {
+		t.Errorf("missing module: %d", code)
+	}
+}
+
+func TestFilesFallThrough(t *testing.T) {
+	if code, _ := get(t, releases(), "v3/files/unkin-hello-0.1.0.tar.gz"); code != 0 {
+		t.Error("file downloads must fall through to the stored file")
+	}
+}
+
+func TestCompareSemver(t *testing.T) {
+	ordered := []string{"0.1.0", "0.2.0", "0.10.0", "1.0.0-alpha", "1.0.0-alpha.1", "1.0.0-beta", "1.0.0-beta.2", "1.0.0-beta.11", "1.0.0", "1.0.1+build"}
+	for i := 1; i < len(ordered); i++ {
+		if compareSemver(ordered[i-1], ordered[i]) >= 0 || compareSemver(ordered[i], ordered[i-1]) <= 0 {
+			t.Errorf("%s should sort before %s", ordered[i-1], ordered[i])
+		}
+	}
+	if compareSemver("1.0.0+a", "1.0.0+b") != 0 {
+		t.Error("build metadata must not affect precedence")
+	}
+}
diff --git a/internal/provider/puppet/puppet.go b/internal/provider/puppet/puppet.go
index 142a431..03bf1d8 100644
--- a/internal/provider/puppet/puppet.go
+++ b/internal/provider/puppet/puppet.go
@@ -39,6 +39,8 @@ func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
 	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
 }
 
+func (p *Provider) RewritesResponse() {}
+
 func (p *Provider) RewriteResponse(body []byte, remote models.Remote, proxyBaseURL string) ([]byte, error) {
 	if proxyBaseURL == "" {
 		return nil, nil
diff --git a/internal/provider/pypi/pypi.go b/internal/provider/pypi/pypi.go
index e87e9c1..373e584 100644
--- a/internal/provider/pypi/pypi.go
+++ b/internal/provider/pypi/pypi.go
@@ -52,6 +52,8 @@ func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
 	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
 }
 
+func (p *Provider) RewritesResponse() {}
+
 func (p *Provider) RewriteResponse(body []byte, remote models.Remote, proxyBaseURL string) ([]byte, error) {
 	if proxyBaseURL == "" {
 		return nil, nil
diff --git a/internal/provider/rpm/github.go b/internal/provider/rpm/github.go
index c41d47d..707b54d 100644
--- a/internal/provider/rpm/github.go
+++ b/internal/provider/rpm/github.go
@@ -343,6 +343,9 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 		return newEtag, false, err
 	}
 
+	// A transiently failed asset fails the scan so the ETag is not advanced and
+	// the retry re-derives it; an invalid package is skipped as no retry fixes it.
+	var failed []error
 	seen := map[string]bool{}
 	for _, rel := range releases {
 		if rel.Draft {
@@ -373,10 +376,14 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			meta, err := p.deriveAsset(ctx, remote, asset, fp)
 			if err != nil {
 				slog.Warn("github_rpm: derive asset failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				if !errors.Is(err, provider.ErrInvalidPackage) {
+					failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
+				}
 				continue
 			}
 			if err := store.InsertRPMMetadata(ctx, meta); err != nil {
 				slog.Error("github_rpm: insert metadata failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
 				continue
 			}
 			slog.Info("github_rpm: derived asset", "remote", remote.Name, "name", meta.Name, "version", meta.Version, "arch", meta.Arch)
@@ -388,7 +395,7 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			_ = store.DeleteRPMMetadata(ctx, remote.Name, fp)
 		}
 	}
-	return newEtag, true, nil
+	return newEtag, true, errors.Join(failed...)
 }
 
 type ghRelease struct {
@@ -569,12 +576,12 @@ func (p *GitHubProvider) fetchHeader(ctx context.Context, remote models.Remote,
 			}
 			continue
 		}
-		return nil, fmt.Errorf("parse rpm header: %w", perr)
+		return nil, fmt.Errorf("%w: parse rpm header: %w", provider.ErrInvalidPackage, perr)
 	}
 }
 
 // rangeGet returns the first n bytes of downloadURL. full is true when the
-// response body was shorter than n (i.e. we already have the whole object).
+// response holds the whole object.
 func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, downloadURL string, n int64) ([]byte, bool, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
 	if err != nil {
@@ -596,15 +603,9 @@ func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, dow
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
-		return nil, false, fmt.Errorf("range GET %s: status %d", downloadURL, resp.StatusCode)
+		return nil, false, fmt.Errorf("range GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
-
-	body, err := io.ReadAll(io.LimitReader(resp.Body, n))
-	if err != nil {
-		return nil, false, err
-	}
-	full := int64(len(body)) < n
-	return body, full, nil
+	return provider.ReadPrefix(resp, n)
 }
 
 func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
@@ -627,7 +628,7 @@ func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK {
-		return "", fmt.Errorf("GET %s: status %d", downloadURL, resp.StatusCode)
+		return "", fmt.Errorf("GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
 
 	h := sha256.New()
diff --git a/internal/provider/rpm/github_test.go b/internal/provider/rpm/github_test.go
index 33361f5..6298c4d 100644
--- a/internal/provider/rpm/github_test.go
+++ b/internal/provider/rpm/github_test.go
@@ -1,11 +1,13 @@
 package rpm
 
 import (
+	"cmp"
 	"compress/gzip"
 	"context"
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -24,15 +26,22 @@ import (
 // fakeStore is an in-memory provider.RemoteMetadataStore keyed by file_path,
 // mirroring the (repo_name, file_path) uniqueness of the real table.
 type fakeStore struct {
-	mu   sync.Mutex
-	rows map[string]provider.RPMMetadata
+	mu         sync.Mutex
+	rows       map[string]provider.RPMMetadata
+	insertFail map[string]int // package name -> inserts left to fail
 }
 
-func newFakeStore() *fakeStore { return &fakeStore{rows: map[string]provider.RPMMetadata{}} }
+func newFakeStore() *fakeStore {
+	return &fakeStore{rows: map[string]provider.RPMMetadata{}, insertFail: map[string]int{}}
+}
 
 func (f *fakeStore) InsertRPMMetadata(_ context.Context, m *provider.RPMMetadata) error {
 	f.mu.Lock()
 	defer f.mu.Unlock()
+	if f.insertFail[m.Name] > 0 {
+		f.insertFail[m.Name]--
+		return errors.New("insert failed")
+	}
 	if _, ok := f.rows[m.FilePath]; ok {
 		return nil // ON CONFLICT DO NOTHING
 	}
@@ -79,15 +88,20 @@ type githubFixture struct {
 	releaseAuth string            // Authorization header seen on the last releases request
 	assetAuth   string            // Authorization header seen on the last asset request
 	failStatus  int               // when set, the releases list answers this status (rate-limit style)
+	assetFail   map[string]int    // asset filename -> downloads left to answer failCode
+	failCode    int               // status for assetFail downloads; 0 = 500
+	shortRead   map[string]int    // asset filename -> ranged GETs left to close early
 	mu          sync.Mutex
 }
 
 func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 	t.Helper()
 	f := &githubFixture{
-		rpmBytes: map[string][]byte{},
-		rangeHit: map[string]int{},
-		fullHit:  map[string]int{},
+		rpmBytes:  map[string][]byte{},
+		rangeHit:  map[string]int{},
+		fullHit:   map[string]int{},
+		assetFail: map[string]int{},
+		shortRead: map[string]int{},
 	}
 	f.rpmBytes["demo-1.2-3.x86_64.rpm"] = testsupport.MinimalRPM("demo", "1.2", "3", "x86_64")
 
@@ -145,6 +159,17 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 		}
 		rng := r.Header.Get("Range")
 		f.mu.Lock()
+		if f.assetFail[name] > 0 {
+			f.assetFail[name]--
+			code := cmp.Or(f.failCode, http.StatusInternalServerError)
+			f.mu.Unlock()
+			http.Error(w, "boom", code)
+			return
+		}
+		short := rng != "" && f.shortRead[name] > 0
+		if short {
+			f.shortRead[name]--
+		}
 		f.assetAuth = r.Header.Get("Authorization")
 		if rng != "" {
 			f.rangeHit[name]++
@@ -165,6 +190,9 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 			end = len(body) - 1
 		}
 		w.Header().Set("Content-Range", fmt.Sprintf("bytes 0-%d/%d", end, len(body)))
+		if short {
+			end /= 2
+		}
 		w.Header().Set("Content-Length", strconv.Itoa(end+1))
 		w.WriteHeader(http.StatusPartialContent)
 		w.Write(body[:end+1])
diff --git a/internal/provider/rpm/syncer_test.go b/internal/provider/rpm/syncer_test.go
index e368bd2..be6d9c9 100644
--- a/internal/provider/rpm/syncer_test.go
+++ b/internal/provider/rpm/syncer_test.go
@@ -399,3 +399,74 @@ func TestSyncerFailedScanRetriesAfterBackoff(t *testing.T) {
 		t.Fatalf("recovery did not refresh metadata: %d rows", len(rows))
 	}
 }
+
+// A transiently failed asset fails the scan: the ETag is not advanced, a retry
+// is scheduled, and the retry against the unchanged release list derives it. An
+// invalid package is skipped instead, since no retry can fix it.
+func TestSyncerFailedAssetRetry(t *testing.T) {
+	for _, tc := range []struct {
+		name      string
+		corrupt   bool
+		failCode  int
+		short     bool
+		insert    bool
+		wantRetry bool
+	}{
+		{name: "transient", wantRetry: true},
+		{name: "rate limited", failCode: http.StatusForbidden, wantRetry: true},
+		{name: "short read", short: true, wantRetry: true},
+		{name: "insert failure", insert: true, wantRetry: true},
+		{name: "invalid package", corrupt: true},
+		{name: "asset not found", failCode: http.StatusNotFound},
+		{name: "asset gone", failCode: http.StatusGone},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			const other = "other-9-9.aarch64.rpm"
+			fx := newGitHubFixture(t, true)
+			fx.etag = `"v1"`
+			fx.rpmBytes[other] = testsupport.MinimalRPM("other", "9", "9", "aarch64")
+			store := newFakeSyncStore()
+			switch {
+			case tc.corrupt:
+				fx.rpmBytes[other] = []byte("not a package")
+			case tc.short:
+				fx.shortRead[other] = 1
+			case tc.insert:
+				store.insertFail["other"] = 1
+			case tc.failCode != 0 && !tc.wantRetry:
+				fx.failCode, fx.assetFail[other] = tc.failCode, 1<<30
+			default:
+				fx.failCode, fx.assetFail[other] = tc.failCode, 1
+			}
+			s := newSyncer(store, newTestProvider(), testSyncConfig())
+			remote := fx.remote()
+			bg := context.Background()
+
+			s.process(bg, syncJob{remote: remote, prime: true})
+			_, pending := store.retryAt[remote.Name]
+			if pending != tc.wantRetry {
+				t.Fatalf("retry pending=%v, want %v", pending, tc.wantRetry)
+			}
+			if _, saved := store.etags[remote.Name]; saved == tc.wantRetry {
+				t.Fatalf("etag saved=%v after first scan", saved)
+			}
+			if rows, _ := store.ListRPMMetadataEntries(bg, remote.Name); len(rows) != 1 {
+				t.Fatalf("healthy asset not served: %d rows", len(rows))
+			}
+			if !tc.wantRetry {
+				return
+			}
+
+			store.mu.Lock()
+			store.retryAt[remote.Name] = time.Now().Add(-time.Second)
+			store.mu.Unlock()
+			s.process(bg, syncJob{remote: remote})
+			if _, pending := store.retryAt[remote.Name]; pending || store.etags[remote.Name] != `"v1"` {
+				t.Fatalf("retry not recorded: pending=%v etag=%q", pending, store.etags[remote.Name])
+			}
+			if rows, _ := store.ListRPMMetadataEntries(bg, remote.Name); len(rows) != 2 {
+				t.Fatalf("retry did not derive the failed asset: %d rows", len(rows))
+			}
+		})
+	}
+}
diff --git a/internal/provider/syncretry.go b/internal/provider/syncretry.go
index dff7070..1a2eb47 100644
--- a/internal/provider/syncretry.go
+++ b/internal/provider/syncretry.go
@@ -3,8 +3,10 @@ package provider
 import (
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -43,6 +45,49 @@ func NewUpstreamStatusError(url string, resp *http.Response) *UpstreamStatusErro
 	return e
 }
 
+// ErrInvalidPackage marks an asset whose bytes are not a valid package. It is
+// permanent, so a scan skips the asset instead of failing and retrying.
+var ErrInvalidPackage = errors.New("invalid package")
+
+// AssetStatusError classifies a non-success asset download. A missing or
+// unsatisfiable asset is permanent; anything else (403/429 rate limits, 5xx) is
+// transient.
+func AssetStatusError(url string, resp *http.Response) error {
+	switch resp.StatusCode {
+	case http.StatusNotFound, http.StatusGone, http.StatusRequestedRangeNotSatisfiable:
+		return fmt.Errorf("%w: %s: status %d", ErrInvalidPackage, url, resp.StatusCode)
+	}
+	return NewUpstreamStatusError(url, resp)
+}
+
+// ReadPrefix reads up to n bytes of a 200 or 206 asset response. full reports
+// that the body is the whole object (per Content-Length or the Content-Range
+// total, or a clean EOF before n when the total is unknown); a body ending before n bytes that is not the whole object is a
+// transient short read.
+func ReadPrefix(resp *http.Response, n int64) (body []byte, full bool, err error) {
+	body, err = io.ReadAll(io.LimitReader(resp.Body, n))
+	if err != nil {
+		return nil, false, err
+	}
+	total := resp.ContentLength
+	unknown := resp.StatusCode == http.StatusOK && total == -1
+	if resp.StatusCode == http.StatusPartialContent {
+		total = -1
+		if _, t, ok := strings.Cut(resp.Header.Get("Content-Range"), "/"); ok {
+			if v, perr := strconv.ParseInt(t, 10, 64); perr == nil {
+				total = v
+			}
+			unknown = t == "*"
+		}
+	}
+	// net/http errors on a premature close, so a clean EOF before n with an unknown total is the whole object.
+	full = total == int64(len(body)) || (unknown && int64(len(body)) < n)
+	if !full && int64(len(body)) < n {
+		return nil, false, fmt.Errorf("short read: got %d of %d bytes", len(body), n)
+	}
+	return body, full, nil
+}
+
 // SyncResult is a background scan's outcome, recorded when its sync lease is
 // released. A failed scan keeps the prior sync time and ETag and schedules a
 // retry after Backoff, doubled per consecutive failure up to MaxBackoff, and
diff --git a/internal/provider/syncretry_test.go b/internal/provider/syncretry_test.go
index 289a1d7..906b9e3 100644
--- a/internal/provider/syncretry_test.go
+++ b/internal/provider/syncretry_test.go
@@ -3,7 +3,9 @@ package provider
 import (
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
+	"net/http/httptest"
 	"strconv"
 	"testing"
 	"time"
@@ -61,3 +63,76 @@ func TestNewSyncResult(t *testing.T) {
 		t.Fatalf("wrapped hint not clamped to ttl: retry in %v", until)
 	}
 }
+
+func TestAssetStatusErrorClassification(t *testing.T) {
+	for status, permanent := range map[int]bool{
+		http.StatusNotFound: true, http.StatusGone: true, http.StatusRequestedRangeNotSatisfiable: true,
+		http.StatusForbidden: false, http.StatusTooManyRequests: false, http.StatusInternalServerError: false, http.StatusBadGateway: false,
+	} {
+		err := AssetStatusError("u", &http.Response{StatusCode: status, Header: http.Header{}})
+		if errors.Is(err, ErrInvalidPackage) != permanent {
+			t.Errorf("status %d: permanent=%v, want %v", status, !permanent, permanent)
+		}
+	}
+}
+
+func TestReadPrefix(t *testing.T) {
+	cases := []struct {
+		name     string
+		status   int
+		cl       int64
+		crange   string
+		body     string
+		n        int64
+		wantFull bool
+		wantErr  bool
+	}{
+		{name: "200 whole object", status: 200, cl: 5, body: "hello", n: 32, wantFull: true},
+		{name: "200 larger than n", status: 200, cl: 5, body: "hello", n: 4},
+		{name: "200 chunked shorter than n", status: 200, cl: -1, body: "hello", n: 32, wantFull: true},
+		{name: "200 chunked larger than n", status: 200, cl: -1, body: "hello", n: 4},
+		{name: "206 whole object", status: 206, crange: "bytes 0-4/5", body: "hello", n: 32, wantFull: true},
+		{name: "206 prefix", status: 206, crange: "bytes 0-3/100", body: "hell", n: 4},
+		{name: "206 short read", status: 206, crange: "bytes 0-31/100", body: "hello", n: 32, wantErr: true},
+		{name: "206 no content-range short", status: 206, body: "hello", n: 32, wantErr: true},
+		{name: "206 unknown total shorter than n", status: 206, cl: -1, crange: "bytes 0-4/*", body: "hello", n: 32, wantFull: true},
+		{name: "206 unknown total prefix", status: 206, cl: -1, crange: "bytes 0-3/*", body: "hell", n: 4},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+				if tc.cl > 0 {
+					w.Header().Set("Content-Length", strconv.FormatInt(tc.cl, 10))
+				}
+				if tc.crange != "" {
+					w.Header().Set("Content-Range", tc.crange)
+				}
+				w.WriteHeader(tc.status)
+				_, _ = io.WriteString(w, tc.body)
+				w.(http.Flusher).Flush()
+			}))
+			defer srv.Close()
+			resp, err := http.Get(srv.URL)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer resp.Body.Close()
+			if tc.cl == -1 && resp.ContentLength != -1 {
+				t.Fatalf("response not chunked: ContentLength=%d", resp.ContentLength)
+			}
+			body, full, err := ReadPrefix(resp, tc.n)
+			if (err != nil) != tc.wantErr {
+				t.Fatalf("err=%v, wantErr=%v", err, tc.wantErr)
+			}
+			if err != nil {
+				if errors.Is(err, ErrInvalidPackage) {
+					t.Fatalf("short read must be transient: %v", err)
+				}
+				return
+			}
+			if full != tc.wantFull || int64(len(body)) > tc.n {
+				t.Fatalf("full=%v len=%d, want full=%v", full, len(body), tc.wantFull)
+			}
+		})
+	}
+}
diff --git a/internal/provider/terraform/terraform.go b/internal/provider/terraform/terraform.go
index f29c33d..022d094 100644
--- a/internal/provider/terraform/terraform.go
+++ b/internal/provider/terraform/terraform.go
@@ -73,6 +73,8 @@ func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
 	return strings.TrimRight(remote.BaseURL, "/") + "/v1/providers/" + strings.TrimLeft(path, "/")
 }
 
+func (p *Provider) RewritesResponse() {}
+
 func (p *Provider) RewriteResponse(body []byte, remote models.Remote, proxyBaseURL string) ([]byte, error) {
 	if remote.ReleasesRemote == "" {
 		return nil, nil
diff --git a/internal/provider/yamlalias.go b/internal/provider/yamlalias.go
new file mode 100644
index 0000000..af6f719
--- /dev/null
+++ b/internal/provider/yamlalias.go
@@ -0,0 +1,46 @@
+package provider
+
+import (
+	"errors"
+
+	"gopkg.in/yaml.v3"
+)
+
+const MaxAliasExpandedNodes = 100000
+
+// ExpandYAMLAliases inlines alias targets and drops anchors so a node map
+// stays valid when copied away from the document that held its anchors;
+// budget caps nodes reached through aliases against alias bombs.
+func ExpandYAMLAliases(m map[string]yaml.Node, budget *int) (map[string]yaml.Node, error) {
+	var expand func(n *yaml.Node, viaAlias bool) (*yaml.Node, error)
+	expand = func(n *yaml.Node, viaAlias bool) (*yaml.Node, error) {
+		if viaAlias {
+			*budget--
+			if *budget < 0 {
+				return nil, errors.New("yaml aliases expand to too many nodes")
+			}
+		}
+		if n.Kind == yaml.AliasNode {
+			return expand(n.Alias, true)
+		}
+		c := *n
+		c.Anchor = ""
+		c.Content = make([]*yaml.Node, len(n.Content))
+		for i, ch := range n.Content {
+			var err error
+			if c.Content[i], err = expand(ch, viaAlias); err != nil {
+				return nil, err
+			}
+		}
+		return &c, nil
+	}
+	out := make(map[string]yaml.Node, len(m))
+	for k, v := range m {
+		e, err := expand(&v, false)
+		if err != nil {
+			return nil, err
+		}
+		out[k] = *e
+	}
+	return out, nil
+}
diff --git a/internal/proxy/engine.go b/internal/proxy/engine.go
index a2e82e3..779bec9 100644
--- a/internal/proxy/engine.go
+++ b/internal/proxy/engine.go
@@ -134,10 +134,11 @@ func (e *Engine) Fetch(ctx context.Context, remote models.Remote, path string, p
 		slog.Warn("cache hit but S3 miss, re-fetching", "remote", remote.Name, "path", path)
 	}
 
-	locked, err := e.cache.AcquireLock(ctx, remote.Name, path, fetchLockTTL)
+	token, err := e.cache.AcquireLock(ctx, remote.Name, path, fetchLockTTL)
 	if err != nil {
 		slog.Warn("lock acquire failed", "error", err)
 	}
+	locked := token != ""
 
 	if !locked {
 		// Another request holds the fetch lock. Poll the store until the leader
@@ -151,7 +152,7 @@ func (e *Engine) Fetch(ctx context.Context, remote models.Remote, path string, p
 	}
 
 	if locked {
-		defer e.cache.ReleaseLock(ctx, remote.Name, path)
+		defer func() { _ = e.cache.ReleaseLock(context.WithoutCancel(ctx), remote.Name, path, token) }()
 	}
 
 	if class == ClassMutable && remote.CheckMutable {
@@ -160,7 +161,7 @@ func (e *Engine) Fetch(ctx context.Context, remote models.Remote, path string, p
 			notModified, err := e.checkUpstream(ctx, remote, path, etag, prov)
 			if err == nil && notModified {
 				_ = e.cache.SetTTL(ctx, remote.Name, path, ttl)
-				_ = e.cache.SetETag(ctx, remote.Name, path, etag, ttl)
+				_ = e.cache.SetETag(ctx, remote.Name, path, etag, etagTTL(ttl))
 				result, err := e.serveFromStore(ctx, remote, path)
 				if err == nil {
 					result.Source = "cache"
@@ -229,10 +230,11 @@ func (e *Engine) Evict(ctx context.Context, remoteName, path string) error {
 		return fmt.Errorf("get remote: %w", err)
 	}
 	if !wildcard {
-		if err := e.waitForLock(ctx, remoteName, path); err != nil {
+		release, err := e.Lock(ctx, remoteName, path, e.evictLockWait, fetchLockTTL)
+		if err != nil {
 			return err
 		}
-		defer func() { _ = e.cache.ReleaseLock(context.WithoutCancel(ctx), remoteName, path) }()
+		defer release()
 		if err := e.db.DeleteArtifact(ctx, remoteName, path); err != nil {
 			return fmt.Errorf("delete artifact: %w", err)
 		}
@@ -265,28 +267,36 @@ func (e *Engine) evictPrefix(ctx context.Context, remoteName, prefix string) err
 	return e.cache.ForgetPrefix(ctx, remoteName, prefix)
 }
 
-// waitForLock takes the per-path fetch lock so an in-flight Fetch cannot
-// re-set TTL/ETag keys after an evict. It fails with a 503 when the lock
-// cannot be taken within evictLockWait or Redis errors.
-func (e *Engine) waitForLock(ctx context.Context, remoteName, path string) error {
-	deadline := time.Now().Add(e.evictLockWait)
+// Lock takes the per-path Redis lock (the one Fetch holds) and returns its
+// release. It fails with a 503 when the lock cannot be taken within wait or
+// Redis errors.
+func (e *Engine) Lock(ctx context.Context, remoteName, path string, wait, ttl time.Duration) (func(), error) {
+	token, err := e.waitForLock(ctx, remoteName, path, wait, ttl)
+	if err != nil {
+		return nil, err
+	}
+	return func() { _ = e.cache.ReleaseLock(context.WithoutCancel(ctx), remoteName, path, token) }, nil
+}
+
+func (e *Engine) waitForLock(ctx context.Context, remoteName, path string, wait, ttl time.Duration) (string, error) {
+	deadline := time.Now().Add(wait)
 	for {
-		ok, err := e.cache.AcquireLock(ctx, remoteName, path, fetchLockTTL)
-		if ok {
-			return nil
+		token, err := e.cache.AcquireLock(ctx, remoteName, path, ttl)
+		if token != "" {
+			return token, nil
 		}
 		if ctx.Err() != nil {
-			return ctx.Err()
+			return "", ctx.Err()
 		}
 		if err != nil {
-			return &ProxyError{Status: http.StatusServiceUnavailable, Message: fmt.Sprintf("fetch lock: %v", err)}
+			return "", &ProxyError{Status: http.StatusServiceUnavailable, Message: fmt.Sprintf("lock: %v", err)}
 		}
 		if time.Now().After(deadline) {
-			return &ProxyError{Status: http.StatusServiceUnavailable, Message: "fetch in progress, retry evict"}
+			return "", &ProxyError{Status: http.StatusServiceUnavailable, Message: "resource busy, retry later"}
 		}
 		select {
 		case <-ctx.Done():
-			return ctx.Err()
+			return "", ctx.Err()
 		case <-time.After(50 * time.Millisecond):
 		}
 	}
@@ -366,7 +376,7 @@ func (e *Engine) headUpstreamOnce(ctx context.Context, remote models.Remote, pat
 				req.Header.Set(k, v)
 			}
 		}
-		return http.DefaultClient.Do(req)
+		return clientForRemote(remote).Do(req)
 	}
 
 	resp, err := doHead(nil)
@@ -504,8 +514,9 @@ func (e *Engine) fetchFromUpstreamOnce(ctx context.Context, remote models.Remote
 		}
 
 		_ = e.cache.SetTTL(ctx, remote.Name, path, ttl)
-		if etag := resp.Header.Get("ETag"); etag != "" {
-			_ = e.cache.SetETag(ctx, remote.Name, path, etag, ttl)
+		// A zero TTL never expires, so it never needs revalidating.
+		if remote.CheckMutable && ttl > 0 {
+			_ = e.cache.SetETag(ctx, remote.Name, path, resp.Header.Get("ETag"), etagTTL(ttl))
 		}
 
 		return &FetchResult{
@@ -533,9 +544,6 @@ func (e *Engine) fetchFromUpstreamOnce(ctx context.Context, remote models.Remote
 	}
 
 	_ = e.cache.SetTTL(ctx, remote.Name, path, ttl)
-	if etag := resp.Header.Get("ETag"); etag != "" {
-		_ = e.cache.SetETag(ctx, remote.Name, path, etag, ttl)
-	}
 
 	reader, info, err := e.store.Download(ctx, casResult.S3Key)
 	if err != nil {
@@ -655,6 +663,12 @@ func (e *Engine) checkUpstreamOnce(ctx context.Context, remote models.Remote, pa
 	return resp.StatusCode == http.StatusNotModified, nil
 }
 
+// etagTTL keeps a mutable path's ETag well past its freshness key so an expired
+// path revalidates with a conditional HEAD, while idle paths still age out.
+func etagTTL(ttl time.Duration) time.Duration {
+	return max(10*ttl, 7*24*time.Hour)
+}
+
 func (e *Engine) ttlFor(remote models.Remote, class Classification) time.Duration {
 	switch class {
 	case ClassImmutable:
diff --git a/internal/proxy/engine_test.go b/internal/proxy/engine_test.go
index 87ce690..447de34 100644
--- a/internal/proxy/engine_test.go
+++ b/internal/proxy/engine_test.go
@@ -17,12 +17,14 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/storage"
 	"git.unkin.net/unkin/artifactapi/internal/testsupport"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
+	goredis "github.com/redis/go-redis/v9"
 )
 
 var (
 	testEngine *Engine
 	testCache  *cache.Redis
 	testDB     *database.DB
+	testRedis  string
 	upstream   *httptest.Server
 )
 
@@ -64,6 +66,7 @@ func TestMain(m *testing.M) {
 	}
 
 	testCache = redis
+	testRedis = redisURL
 	testDB = db
 	testEngine = NewEngine(db, redis, s3)
 	upstream = httptest.NewServer(http.HandlerFunc(mockUpstream))
@@ -216,6 +219,20 @@ func TestHead(t *testing.T) {
 	}
 }
 
+func TestHeadUpstreamUsesRemoteTimeout(t *testing.T) {
+	slow := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(3 * time.Second)
+	}))
+	defer slow.Close()
+	r := models.Remote{Name: "slow-head", PackageType: models.PackageGeneric, BaseURL: slow.URL, UpstreamResponseHeaderTimeout: 1}
+
+	start := time.Now()
+	_, err := (&Engine{}).headUpstreamOnce(context.Background(), r, "blob.bin", prov(t, models.PackageGeneric))
+	if err == nil || time.Since(start) > 2*time.Second {
+		t.Fatalf("HEAD ignored the remote's response header timeout: err=%v after %s", err, time.Since(start))
+	}
+}
+
 func TestStaleOnError(t *testing.T) {
 	requireStack(t)
 	ctx := context.Background()
@@ -260,30 +277,169 @@ func TestCircuitOpenServesStale(t *testing.T) {
 	res.Reader.Close()
 }
 
+// expire drops path's freshness key so the next fetch revalidates.
+func expire(t *testing.T, remote, path string) {
+	t.Helper()
+	if err := testCache.SetTTL(context.Background(), remote, path, time.Millisecond); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(5 * time.Millisecond)
+}
+
+func mutableFetch(t *testing.T, r models.Remote, path string) (string, string) {
+	t.Helper()
+	res, err := testEngine.Fetch(context.Background(), r, path, prov(t, models.PackageRPM))
+	if err != nil {
+		t.Fatalf("fetch: %v", err)
+	}
+	return readAll(t, res), res.Source
+}
+
+const repomd = "8/Everything/x86_64/repodata/repomd.xml"
+
 func TestMutableRevalidation(t *testing.T) {
+	requireStack(t)
+	srv, rev, conditional := changingUpstream(t)
+	r := seed(t, models.Remote{Name: "eng-reval", PackageType: models.PackageRPM, RepoType: models.RepoTypeRemote, BaseURL: srv.URL, CheckMutable: true, MutableTTL: 60})
+
+	if body, _ := mutableFetch(t, r, repomd); body != "rev1:/"+repomd {
+		t.Fatalf("initial fetch = %q", body)
+	}
+	expire(t, r.Name, repomd)
+	if body, src := mutableFetch(t, r, repomd); body != "rev1:/"+repomd || src != "cache" {
+		t.Errorf("after expiry = %q from %s, want cached rev1", body, src)
+	}
+	if n := conditional.Load(); n != 1 {
+		t.Errorf("conditional requests = %d, want 1 revalidation", n)
+	}
+	if fresh, _ := testCache.CheckTTL(context.Background(), r.Name, repomd); !fresh {
+		t.Error("304 should re-arm the freshness key")
+	}
+
+	rev.Store("rev2")
+	expire(t, r.Name, repomd)
+	if body, src := mutableFetch(t, r, repomd); body != "rev2:/"+repomd || src != "remote" {
+		t.Errorf("after upstream change = %q from %s, want remote rev2", body, src)
+	}
+}
+
+func etagKeyTTL(t *testing.T, remote, path string) time.Duration {
+	t.Helper()
+	opts, err := goredis.ParseURL(testRedis)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := goredis.NewClient(opts)
+	defer func() { _ = c.Close() }()
+	d, err := c.PTTL(context.Background(), "etag:"+remote+":"+path).Result()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return d
+}
+
+// The ETag is only kept when it can be used, and never without an expiry.
+func TestMutableETagStorage(t *testing.T) {
+	requireStack(t)
+	srv, _, _ := changingUpstream(t)
+	for _, tc := range []struct {
+		name  string
+		check bool
+		ttl   int
+		want  time.Duration
+	}{
+		{"eng-etag-off", false, 60, -2},
+		{"eng-etag-never", true, 0, -2},
+		{"eng-etag-short", true, 60, 7 * 24 * time.Hour},
+		{"eng-etag-long", true, 86400, 10 * 24 * time.Hour},
+	} {
+		r := seed(t, models.Remote{Name: tc.name, PackageType: models.PackageRPM, RepoType: models.RepoTypeRemote, BaseURL: srv.URL, CheckMutable: tc.check, MutableTTL: tc.ttl})
+		mutableFetch(t, r, repomd)
+		got := etagKeyTTL(t, tc.name, repomd)
+		if tc.want < 0 {
+			if got != tc.want {
+				t.Errorf("%s: etag key ttl = %v, want no key", tc.name, got)
+			}
+			continue
+		}
+		if got <= tc.want-time.Minute || got > tc.want {
+			t.Errorf("%s: etag key ttl = %v, want ~%v", tc.name, got, tc.want)
+		}
+	}
+}
+
+// Immutable paths are never revalidated, so their upstream ETag is not kept.
+func TestImmutableFetchStoresNoETag(t *testing.T) {
+	requireStack(t)
+	srv, _, _ := changingUpstream(t)
+	r := seed(t, models.Remote{Name: "eng-etag-imm", PackageType: models.PackageRPM, RepoType: models.RepoTypeRemote, BaseURL: srv.URL, CheckMutable: true, MutableTTL: 60})
+	const rpm = "Packages/e2e-1.0-1.noarch.rpm"
+	if body, src := mutableFetch(t, r, rpm); body != "rev1:/"+rpm || src != "remote" {
+		t.Fatalf("fetch = %q from %s", body, src)
+	}
+	if got := etagKeyTTL(t, r.Name, rpm); got != -2 {
+		t.Errorf("etag key ttl = %v, want no key", got)
+	}
+}
+
+// A 304 for a path whose S3 body is gone falls back to a full refetch.
+func TestNotModifiedWithEvictedBodyRefetches(t *testing.T) {
+	requireStack(t)
+	srv, _, conditional := changingUpstream(t)
+	r := seed(t, models.Remote{Name: "eng-304-gone", PackageType: models.PackageRPM, RepoType: models.RepoTypeRemote, BaseURL: srv.URL, CheckMutable: true, MutableTTL: 60})
+
+	mutableFetch(t, r, repomd)
+	if err := testEngine.store.Delete(context.Background(), storage.IndexKey(r.Name, repomd)); err != nil {
+		t.Fatal(err)
+	}
+	expire(t, r.Name, repomd)
+	if body, src := mutableFetch(t, r, repomd); body != "rev1:/"+repomd || src != "remote" {
+		t.Errorf("got %q from %s, want refetched rev1 from remote", body, src)
+	}
+	if n := conditional.Load(); n != 1 {
+		t.Errorf("conditional requests = %d, want the 304 HEAD first", n)
+	}
+}
+
+// A failing revalidation HEAD still serves the stored copy with stale_on_error.
+func TestStaleOnErrorWhenRevalidationFails(t *testing.T) {
+	requireStack(t)
+	srv, _, _ := changingUpstream(t)
+	r := seed(t, models.Remote{Name: "eng-stale-head", PackageType: models.PackageRPM, RepoType: models.RepoTypeRemote, BaseURL: srv.URL, CheckMutable: true, MutableTTL: 60, StaleOnError: true})
+
+	mutableFetch(t, r, repomd)
+	srv.Close()
+	expire(t, r.Name, repomd)
+	if body, src := mutableFetch(t, r, repomd); body != "rev1:/"+repomd || src != "cache" {
+		t.Errorf("got %q from %s, want stale rev1 from cache", body, src)
+	}
+}
+
+// After a remote is deleted and flushed, a re-created remote of the same name
+// fetches from its own upstream instead of revalidating the old ETag.
+func TestRecreatedRemoteHasNoStaleState(t *testing.T) {
 	requireStack(t)
 	ctx := context.Background()
-	r := seed(t, models.Remote{Name: "eng-npm", PackageType: models.PackageNPM, RepoType: models.RepoTypeRemote, BaseURL: upstream.URL, CheckMutable: true, MutableTTL: 3600, StaleOnError: true})
-	p := prov(t, models.PackageNPM)
+	oldSrv, _, _ := changingUpstream(t)
+	r := seed(t, models.Remote{Name: "eng-recreate", PackageType: models.PackageRPM, RepoType: models.RepoTypeRemote, BaseURL: oldSrv.URL, CheckMutable: true, MutableTTL: 60})
+	mutableFetch(t, r, repomd)
 
-	res, err := testEngine.Fetch(ctx, r, "pkg", p)
-	if err != nil {
-		t.Fatalf("initial mutable fetch: %v", err)
+	if err := testDB.DeleteRemote(ctx, r.Name); err != nil {
+		t.Fatal(err)
 	}
-	res.Reader.Close()
-
-	// Expire only the freshness marker; the ETag persists, forcing a
-	// conditional revalidation that the upstream answers with 304.
-	testCache.SetTTL(ctx, "eng-npm", "pkg", time.Millisecond)
-	time.Sleep(10 * time.Millisecond)
-	res, err = testEngine.Fetch(ctx, r, "pkg", p)
-	if err != nil {
-		t.Fatalf("revalidation fetch: %v", err)
+	if err := testCache.FlushRemote(ctx, r.Name); err != nil {
+		t.Fatal(err)
 	}
-	if res.Source != "cache" {
-		t.Errorf("revalidated response should come from cache, got %s", res.Source)
+	newSrv, rev, conditional := changingUpstream(t)
+	rev.Store("rev9")
+	r.BaseURL = newSrv.URL
+	seed(t, r)
+	if body, src := mutableFetch(t, r, repomd); body != "rev9:/"+repomd || src != "remote" {
+		t.Errorf("got %q from %s, want rev9 from the new upstream", body, src)
+	}
+	if n := conditional.Load(); n != 0 {
+		t.Errorf("conditional requests = %d, want none after flush", n)
 	}
-	res.Reader.Close()
 }
 
 func TestBearerTokenFlow(t *testing.T) {
diff --git a/internal/proxy/evict_test.go b/internal/proxy/evict_test.go
index 347de74..aa05abc 100644
--- a/internal/proxy/evict_test.go
+++ b/internal/proxy/evict_test.go
@@ -59,7 +59,7 @@ type cached struct{ row, index, ttl, etag bool }
 // Mutable indexes live in the S3 index; immutable blobs get an artifact row.
 var (
 	indexCached = cached{index: true, ttl: true, etag: true}
-	blobCached  = cached{row: true, ttl: true, etag: true}
+	blobCached  = cached{row: true, ttl: true}
 )
 
 func layers(t *testing.T, remote, path string) cached {
@@ -152,13 +152,15 @@ func TestEvictUnknownRemote(t *testing.T) {
 	}
 }
 
-func holdLock(t *testing.T, remote, path string) {
+func holdLock(t *testing.T, remote, path string) string {
 	t.Helper()
 	ctx := context.Background()
-	if ok, err := testCache.AcquireLock(ctx, remote, path, time.Minute); !ok || err != nil {
-		t.Fatalf("acquire: %v %v", ok, err)
+	token, err := testCache.AcquireLock(ctx, remote, path, time.Minute)
+	if token == "" || err != nil {
+		t.Fatalf("acquire: %q %v", token, err)
 	}
-	t.Cleanup(func() { _ = testCache.ReleaseLock(ctx, remote, path) })
+	t.Cleanup(func() { _ = testCache.ReleaseLock(ctx, remote, path, token) })
+	return token
 }
 
 func TestEvictWaitsForFetchLock(t *testing.T) {
@@ -167,7 +169,7 @@ func TestEvictWaitsForFetchLock(t *testing.T) {
 	r := rpmRemote(t, "evict-lock", srv.URL)
 	ctx := context.Background()
 	const path = "8/Everything/x86_64/repodata/repomd.xml"
-	holdLock(t, r.Name, path)
+	token := holdLock(t, r.Name, path)
 	done := make(chan error, 1)
 	go func() { done <- testEngine.Evict(ctx, r.Name, path) }()
 	select {
@@ -175,13 +177,13 @@ func TestEvictWaitsForFetchLock(t *testing.T) {
 		t.Fatalf("evict returned while fetch lock held: %v", err)
 	case <-time.After(200 * time.Millisecond):
 	}
-	_ = testCache.ReleaseLock(ctx, r.Name, path)
+	_ = testCache.ReleaseLock(ctx, r.Name, path, token)
 	if err := <-done; err != nil {
 		t.Fatalf("evict: %v", err)
 	}
-	ok, err := testCache.AcquireLock(ctx, r.Name, path, time.Second)
-	if !ok || err != nil {
-		t.Fatalf("lock still held after evict: %v %v", ok, err)
+	token, err := testCache.AcquireLock(ctx, r.Name, path, time.Second)
+	if token == "" || err != nil {
+		t.Fatalf("lock still held after evict: %q %v", token, err)
 	}
 }
 
diff --git a/internal/server/server.go b/internal/server/server.go
index 307f0e3..26a4953 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -21,20 +21,10 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/database"
 	"git.unkin.net/unkin/artifactapi/internal/gc"
 	"git.unkin.net/unkin/artifactapi/internal/githubauth"
+	_ "git.unkin.net/unkin/artifactapi/internal/provider/all"
 	"git.unkin.net/unkin/artifactapi/internal/provider/alpine"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/ansible"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/cargo"
 	"git.unkin.net/unkin/artifactapi/internal/provider/deb"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/docker"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/generic"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/goproxy"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/helm"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/npm"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/nuget"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/puppet"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/pypi"
 	"git.unkin.net/unkin/artifactapi/internal/provider/rpm"
-	_ "git.unkin.net/unkin/artifactapi/internal/provider/terraform"
 	"git.unkin.net/unkin/artifactapi/internal/proxy"
 	"git.unkin.net/unkin/artifactapi/internal/storage"
 	"git.unkin.net/unkin/artifactapi/internal/tfsign"
@@ -176,6 +166,8 @@ func (s *Server) routes() chi.Router {
 	r.Mount(tfregistry.MountPath, s.tfRegistry.Routes())
 
 	proxyHandler := v1.NewProxyHandler(s.engine, s.virtEngine, s.db, s.store, s.localHandler)
+	s.virtEngine.NPMLocal = proxyHandler.LocalNPMPackument
+	s.virtEngine.GemsLocal = proxyHandler.LocalGemsIndex
 	r.Mount("/api/v1", proxyHandler.Routes())
 	r.Mount("/v2", proxyHandler.DockerV2Routes())
 
diff --git a/internal/virtual/engine.go b/internal/virtual/engine.go
index d4c52d0..99457e2 100644
--- a/internal/virtual/engine.go
+++ b/internal/virtual/engine.go
@@ -26,18 +26,38 @@ type Engine struct {
 	proxyEngine *proxy.Engine
 	getRemote   func(context.Context, string) (*models.Remote, error)
 	rpmMember   func(context.Context, string) (*RPMMember, error)
+	npmMember   func(ctx context.Context, name, pkg string) (*NPMMember, error)
+
+	// NPMLocal returns a local npm repo's packument with tarball paths relative
+	// to the repo, or ErrNotFound.
+	NPMLocal func(ctx context.Context, repo, pkg string) ([]byte, error)
+
+	gemsMember func(ctx context.Context, name, path string) (*GemsMember, error)
+
+	// GemsLocal returns a local gems repo's versions, names or info/<gem>, or
+	// ErrNotFound.
+	GemsLocal func(ctx context.Context, repo, path string) ([]byte, error)
 
 	mergeTTL time.Duration
 
-	sf  singleflight.Group
-	mu  sync.Mutex
-	rpm map[string]*rpmGen
+	sf   singleflight.Group
+	mu   sync.Mutex
+	gens map[string]*repoGen
 }
 
-// rpmGen holds a virtual's current merge plus the previous one, so a client
-// holding the previous repomd can still fetch its content-hashed data files.
-type rpmGen struct {
-	cur, prev *RPMRepo
+// mergedRepo is a merged index document plus the files it references.
+type mergedRepo interface {
+	index() []byte
+	files() map[string][]byte
+}
+
+func (r *RPMRepo) index() []byte            { return r.Repomd }
+func (r *RPMRepo) files() map[string][]byte { return r.Files }
+
+// repoGen holds a virtual's current merge plus the previous one, so a client
+// holding the previous index can still fetch the files it references.
+type repoGen struct {
+	cur, prev mergedRepo
 	at        time.Time
 }
 
@@ -46,6 +66,8 @@ const rpmMergeTTL = 60 * time.Second
 func NewEngine(db *database.DB, proxyEngine *proxy.Engine) *Engine {
 	e := &Engine{db: db, proxyEngine: proxyEngine, getRemote: db.GetRemote, mergeTTL: rpmMergeTTL}
 	e.rpmMember = e.fetchRPMMember
+	e.npmMember = e.fetchNPMMember
+	e.gemsMember = e.fetchGemsMember
 	return e
 }
 
@@ -170,17 +192,28 @@ var (
 	ErrBadPath  = errors.New("invalid path")
 )
 
-// MemberRedirect maps an rpm virtual package path (<member>/<href>, as written
-// by MergeRPM) to the owning member's route. ok is false for any other path;
-// ErrBadPath means the path is absolute or escapes the member.
+// MemberRedirect maps an rpm or npm virtual package path (<member>/<href>, as
+// written by MergeRPM/MergeNPM) to the owning member's route. ok is false for
+// any other path; ErrBadPath means the path is absolute or escapes the member.
 func (e *Engine) MemberRedirect(ctx context.Context, virt models.Virtual, path, rawQuery, proxyBaseURL string) (string, bool, error) {
-	if virt.PackageType != models.PackageRPM || strings.HasPrefix(path, "repodata/") {
+	switch virt.PackageType {
+	case models.PackageRPM:
+		if strings.HasPrefix(path, "repodata/") {
+			return "", false, nil
+		}
+	case models.PackageNPM:
+	default:
 		return "", false, nil
 	}
 	name, rest, found := strings.Cut(path, "/")
 	if !found || !slices.Contains(virt.Members, name) {
 		return "", false, nil
 	}
+	return e.memberLocation(ctx, name, rest, rawQuery, proxyBaseURL)
+}
+
+// memberLocation returns the URL of rest on member name's own route.
+func (e *Engine) memberLocation(ctx context.Context, name, rest, rawQuery, proxyBaseURL string) (string, bool, error) {
 	segs, err := memberSegments(rest)
 	if err != nil {
 		return "", false, err
@@ -217,54 +250,57 @@ func (e *Engine) fetchRPM(ctx context.Context, virt models.Virtual, path string)
 	if !strings.HasPrefix(path, "repodata/") {
 		return nil, "", ErrNotFound
 	}
+	key := "rpm\x00" + virt.Name
 	if path != "repodata/repomd.xml" {
-		if body, ok := e.cachedRPMFile(virt.Name, path); ok {
+		if body, ok := e.cachedFile(key, path); ok {
 			return body, "application/gzip", nil
 		}
 	}
 
-	repo, err := e.mergedRPM(ctx, virt)
+	repo, err := e.merged(ctx, key, func(ctx context.Context) (mergedRepo, error) {
+		return e.mergeRPM(ctx, virt)
+	})
 	if err != nil {
 		return nil, "", err
 	}
 	if path == "repodata/repomd.xml" {
-		return repo.Repomd, "application/xml", nil
+		return repo.index(), "application/xml", nil
 	}
-	if body, ok := repo.Files[path]; ok {
+	if body, ok := repo.files()[path]; ok {
 		return body, "application/gzip", nil
 	}
 	return nil, "", ErrNotFound
 }
 
-// mergedRPM returns the virtual's merge, reusing it for mergeTTL and
-// collapsing concurrent merges of the same virtual into one.
+// merged returns the merge cached under key, reusing it for mergeTTL and
+// collapsing concurrent merges of the same key into one.
 // ponytail: per-replica cache; behind a non-sticky LB a data request landing on
 // another replica re-merges and 404s if a member changed in between. Move to the
 // shared redis cache if that shows up.
-func (e *Engine) mergedRPM(ctx context.Context, virt models.Virtual) (*RPMRepo, error) {
+func (e *Engine) merged(ctx context.Context, key string, merge func(context.Context) (mergedRepo, error)) (mergedRepo, error) {
 	e.mu.Lock()
-	g := e.rpm[virt.Name]
+	g := e.gens[key]
 	if g != nil && time.Since(g.at) < e.mergeTTL {
 		e.mu.Unlock()
 		return g.cur, nil
 	}
 	e.mu.Unlock()
 
-	v, err, _ := e.sf.Do(virt.Name, func() (any, error) {
-		repo, err := e.mergeRPM(context.WithoutCancel(ctx), virt)
+	v, err, _ := e.sf.Do(key, func() (any, error) {
+		repo, err := merge(context.WithoutCancel(ctx))
 		if err != nil {
 			return nil, err
 		}
 		e.mu.Lock()
 		defer e.mu.Unlock()
-		if e.rpm == nil {
-			e.rpm = map[string]*rpmGen{}
+		if e.gens == nil {
+			e.gens = map[string]*repoGen{}
 		}
-		g := e.rpm[virt.Name]
+		g := e.gens[key]
 		switch {
 		case g == nil:
-			e.rpm[virt.Name] = &rpmGen{cur: repo, at: time.Now()}
-		case string(g.cur.Repomd) == string(repo.Repomd):
+			e.gens[key] = &repoGen{cur: repo, at: time.Now()}
+		case string(g.cur.index()) == string(repo.index()):
 			g.at = time.Now()
 			repo = g.cur
 		default:
@@ -275,18 +311,31 @@ func (e *Engine) mergedRPM(ctx context.Context, virt models.Virtual) (*RPMRepo,
 	if err != nil {
 		return nil, err
 	}
-	return v.(*RPMRepo), nil
+	return v.(mergedRepo), nil
 }
 
 func (e *Engine) mergeRPM(ctx context.Context, virt models.Virtual) (*RPMRepo, error) {
-	members := make([]RPMMember, len(virt.Members))
+	members, err := fetchMembers(virt, func(name string) (*RPMMember, error) { return e.rpmMember(ctx, name) })
+	if err != nil {
+		return nil, err
+	}
+	repo, err := MergeRPM(members)
+	if err != nil {
+		return nil, fmt.Errorf("merge rpm repodata: %w", err)
+	}
+	return repo, nil
+}
+
+// fetchMembers reads every member in parallel, failing if any member fails.
+func fetchMembers[T any](virt models.Virtual, fetch func(name string) (*T, error)) ([]T, error) {
+	members := make([]T, len(virt.Members))
 	errs := make([]error, len(virt.Members))
 	var wg sync.WaitGroup
 	for i, name := range virt.Members {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
-			m, err := e.rpmMember(ctx, name)
+			m, err := fetch(name)
 			if err != nil {
 				errs[i] = fmt.Errorf("member %q: %w", name, err)
 				return
@@ -299,26 +348,21 @@ func (e *Engine) mergeRPM(ctx context.Context, virt models.Virtual) (*RPMRepo, e
 	if err := errors.Join(errs...); err != nil {
 		return nil, fmt.Errorf("virtual %q: %v", virt.Name, err)
 	}
-
-	repo, err := MergeRPM(members)
-	if err != nil {
-		return nil, fmt.Errorf("merge rpm repodata: %w", err)
-	}
-	return repo, nil
+	return members, nil
 }
 
-func (e *Engine) cachedRPMFile(virt, path string) ([]byte, bool) {
+func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
-	g := e.rpm[virt]
+	g := e.gens[key]
 	if g == nil {
 		return nil, false
 	}
-	for _, r := range []*RPMRepo{g.cur, g.prev} {
+	for _, r := range []mergedRepo{g.cur, g.prev} {
 		if r == nil {
 			continue
 		}
-		if body, ok := r.Files[path]; ok {
+		if body, ok := r.files()[path]; ok {
 			return body, true
 		}
 	}
diff --git a/internal/virtual/engine_test.go b/internal/virtual/engine_test.go
index d1c28c9..cb7a334 100644
--- a/internal/virtual/engine_test.go
+++ b/internal/virtual/engine_test.go
@@ -156,3 +156,53 @@ func TestMemberRedirect(t *testing.T) {
 		}
 	}
 }
+
+type fakeRepo struct {
+	idx string
+	fs  map[string][]byte
+}
+
+func (r *fakeRepo) index() []byte            { return []byte(r.idx) }
+func (r *fakeRepo) files() map[string][]byte { return r.fs }
+
+func genRepo(gen string) func(context.Context) (mergedRepo, error) {
+	return func(context.Context) (mergedRepo, error) {
+		return &fakeRepo{idx: gen, fs: map[string][]byte{gen + ".gz": []byte(gen), "fixed": []byte(gen)}}, nil
+	}
+}
+
+func TestMergedRetainsPreviousGeneration(t *testing.T) {
+	e := fakeEngine(nil)
+	for _, gen := range []string{"g1", "g2", "g3"} {
+		if _, err := e.merged(context.Background(), "k", genRepo(gen)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for path, want := range map[string]string{"g3.gz": "g3", "g2.gz": "g2", "fixed": "g3"} {
+		if body, ok := e.cachedFile("k", path); !ok || string(body) != want {
+			t.Errorf("%s: got (%q, %v), want %q", path, body, ok, want)
+		}
+	}
+	if _, ok := e.cachedFile("k", "g1.gz"); ok {
+		t.Error("generation two merges back must be dropped")
+	}
+}
+
+func TestMergedReusesWithinTTLAndIsolatesKeys(t *testing.T) {
+	e := fakeEngine(nil)
+	e.mergeTTL = time.Minute
+	for _, step := range []struct{ key, gen, want string }{
+		{"a", "a1", "a1"}, {"b", "b1", "b1"}, {"a", "a2", "a1"},
+	} {
+		repo, err := e.merged(context.Background(), step.key, genRepo(step.gen))
+		if err != nil || string(repo.index()) != step.want {
+			t.Fatalf("%s: got %v (err %v), want %s", step.key, repo, err, step.want)
+		}
+	}
+	if _, ok := e.cachedFile("b", "a1.gz"); ok {
+		t.Error("key b served key a's file")
+	}
+	if _, ok := e.cachedFile("c", "a1.gz"); ok {
+		t.Error("unknown key served a file")
+	}
+}
diff --git a/internal/virtual/gems_merger.go b/internal/virtual/gems_merger.go
new file mode 100644
index 0000000..4fdebaf
--- /dev/null
+++ b/internal/virtual/gems_merger.go
@@ -0,0 +1,294 @@
+package virtual
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"slices"
+	"strings"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider/gems"
+	"git.unkin.net/unkin/artifactapi/internal/proxy"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+const (
+	maxGemsInfos      = 1024
+	maxGemsCandidates = 8
+)
+
+// GemsMember is one member's compact index document; Body is nil when the
+// member does not have it.
+type GemsMember struct {
+	RemoteName string
+	Body       []byte
+}
+
+// GemsDoc is a merged compact index document. Owners maps each /info
+// version[-platform] to the member serving it.
+type GemsDoc struct {
+	Body   []byte
+	Owners map[string]string
+}
+
+func (d *GemsDoc) index() []byte            { return d.Body }
+func (d *GemsDoc) files() map[string][]byte { return nil }
+
+// MergeGemsInfo unions /info lines across members; the first member wins a
+// duplicate version-platform. A gem only one member has is passed through
+// verbatim so its md5 matches that member's /versions. ErrNotFound means no
+// member has the gem.
+func MergeGemsInfo(members []GemsMember) (*GemsDoc, error) {
+	var have []GemsMember
+	for _, m := range members {
+		if m.Body != nil {
+			have = append(have, m)
+		}
+	}
+	if len(have) == 0 {
+		return nil, ErrNotFound
+	}
+	d := &GemsDoc{Owners: map[string]string{}}
+	var lines []string
+	for _, m := range have {
+		for _, l := range gems.InfoLines(m.Body) {
+			k := gems.InfoKey(l)
+			if _, dup := d.Owners[k]; dup {
+				continue
+			}
+			d.Owners[k] = m.RemoteName
+			lines = append(lines, l)
+		}
+	}
+	if len(have) == 1 {
+		d.Body = have[0].Body
+	} else {
+		d.Body = gems.InfoBody(lines)
+	}
+	return d, nil
+}
+
+// versionsLines returns the entry lines of a /versions document.
+func versionsLines(m GemsMember) ([]byte, error) {
+	if m.Body == nil {
+		return nil, fmt.Errorf("member %q has no versions", m.RemoteName)
+	}
+	if bytes.HasPrefix(m.Body, []byte("---\n")) {
+		return m.Body[4:], nil
+	}
+	_, rest, ok := bytes.Cut(m.Body, []byte("\n---\n"))
+	if !ok {
+		return nil, fmt.Errorf("member %q versions has no --- separator", m.RemoteName)
+	}
+	return rest, nil
+}
+
+func gemName(line []byte) string {
+	n, _, _ := bytes.Cut(line, []byte(" "))
+	return string(bytes.TrimSpace(n))
+}
+
+// MergeGemsVersions passes through the lines of gems only one member lists
+// and writes one regenerated line, from the merged /info, per gem that
+// several members list.
+func MergeGemsVersions(members []GemsMember, info func(name string) (*GemsDoc, error), at time.Time) ([]byte, error) {
+	bodies := make([][]byte, len(members))
+	owners := map[string]int{}
+	for i, m := range members {
+		rest, err := versionsLines(m)
+		if err != nil {
+			return nil, err
+		}
+		bodies[i] = rest
+		seen := map[string]bool{}
+		for line := range bytes.Lines(rest) {
+			if n := gemName(line); n != "" && !seen[n] {
+				seen[n] = true
+				owners[n]++
+			}
+		}
+	}
+	var b bytes.Buffer
+	b.WriteString(gems.VersionsHeader(at))
+	var shared []string
+	for _, rest := range bodies {
+		for line := range bytes.Lines(rest) {
+			n := gemName(line)
+			if n == "" {
+				continue
+			}
+			if owners[n] > 1 {
+				if !slices.Contains(shared, n) {
+					shared = append(shared, n)
+				}
+				continue
+			}
+			b.Write(bytes.TrimRight(line, "\n"))
+			b.WriteByte('\n')
+		}
+	}
+	for _, n := range shared {
+		d, err := info(n)
+		if errors.Is(err, ErrNotFound) {
+			continue
+		}
+		if err != nil {
+			return nil, err
+		}
+		b.WriteString(gems.VersionsLine(n, d.Body) + "\n")
+	}
+	return b.Bytes(), nil
+}
+
+// MergeGemsNames unions member /names documents, sorted.
+func MergeGemsNames(members []GemsMember) ([]byte, error) {
+	set := map[string]bool{}
+	for _, m := range members {
+		rest, err := versionsLines(m)
+		if err != nil {
+			return nil, err
+		}
+		for line := range bytes.Lines(rest) {
+			if n := gemName(line); n != "" {
+				set[n] = true
+			}
+		}
+	}
+	names := make([]string, 0, len(set))
+	for n := range set {
+		names = append(names, n)
+	}
+	slices.Sort(names)
+	return []byte("---\n" + strings.Join(names, "\n") + "\n"), nil
+}
+
+// FetchGems serves a gems virtual's merged versions, names or info/<gem>.
+func (e *Engine) FetchGems(ctx context.Context, virt models.Virtual, path string) ([]byte, string, error) {
+	var d *GemsDoc
+	var err error
+	switch {
+	case strings.HasPrefix(path, "info/"):
+		name := strings.TrimPrefix(path, "info/")
+		if !gems.NameRe.MatchString(name) {
+			return nil, "", ErrNotFound
+		}
+		d, err = e.gemsInfo(ctx, virt, name)
+	case path == "versions":
+		d, err = e.gemsMerged(ctx, virt, path, func(ctx context.Context, ms []GemsMember) ([]byte, error) {
+			return MergeGemsVersions(ms, func(name string) (*GemsDoc, error) { return e.gemsInfo(ctx, virt, name) }, time.Now())
+		})
+	case path == "names":
+		d, err = e.gemsMerged(ctx, virt, path, func(_ context.Context, ms []GemsMember) ([]byte, error) {
+			return MergeGemsNames(ms)
+		})
+	default:
+		return nil, "", ErrNotFound
+	}
+	if err != nil {
+		return nil, "", err
+	}
+	return d.Body, "text/plain; charset=utf-8", nil
+}
+
+func (e *Engine) gemsMerged(ctx context.Context, virt models.Virtual, path string, merge func(context.Context, []GemsMember) ([]byte, error)) (*GemsDoc, error) {
+	repo, err := e.merged(ctx, "gems\x00"+virt.Name+"\x00"+path, func(ctx context.Context) (mergedRepo, error) {
+		members, err := fetchMembers(virt, func(name string) (*GemsMember, error) { return e.gemsMember(ctx, name, path) })
+		if err != nil {
+			return nil, err
+		}
+		body, err := merge(ctx, members)
+		if err != nil {
+			return nil, err
+		}
+		return &GemsDoc{Body: body}, nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return repo.(*GemsDoc), nil
+}
+
+func (e *Engine) gemsInfo(ctx context.Context, virt models.Virtual, name string) (*GemsDoc, error) {
+	prefix := "gems\x00" + virt.Name + "\x00info/"
+	inserted := false
+	repo, err := e.merged(ctx, prefix+name, func(ctx context.Context) (mergedRepo, error) {
+		inserted = true
+		members, err := fetchMembers(virt, func(m string) (*GemsMember, error) { return e.gemsMember(ctx, m, "info/"+name) })
+		if err != nil {
+			return nil, err
+		}
+		return MergeGemsInfo(members)
+	})
+	if err != nil {
+		return nil, err
+	}
+	if inserted {
+		e.evictOldest(prefix, maxGemsInfos)
+	}
+	return repo.(*GemsDoc), nil
+}
+
+// GemsRedirect maps a gems virtual download (gems/<full>.gem or
+// quick/Marshal.4.8/<full>.gemspec.rz) to the member whose /info line won the
+// merge for that version-platform.
+func (e *Engine) GemsRedirect(ctx context.Context, virt models.Virtual, path, rawQuery, proxyBaseURL string) (string, error) {
+	full, ok := strings.CutPrefix(path, "gems/")
+	if ok {
+		full, ok = strings.CutSuffix(full, ".gem")
+	} else if full, ok = strings.CutPrefix(path, "quick/Marshal.4.8/"); ok {
+		full, ok = strings.CutSuffix(full, ".gemspec.rz")
+	}
+	if !ok || strings.Contains(full, "/") {
+		return "", ErrNotFound
+	}
+	tried := 0
+	for i := 1; i < len(full)-1 && tried < maxGemsCandidates; i++ {
+		if full[i] != '-' || full[i+1] < '0' || full[i+1] > '9' || !gems.NameRe.MatchString(full[:i]) {
+			continue
+		}
+		tried++
+		d, err := e.gemsInfo(ctx, virt, full[:i])
+		if errors.Is(err, ErrNotFound) {
+			continue
+		}
+		if err != nil {
+			return "", err
+		}
+		if owner, ok := d.Owners[full[i+1:]]; ok {
+			loc, ok, err := e.memberLocation(ctx, owner, path, rawQuery, proxyBaseURL)
+			if err == nil && !ok {
+				err = ErrNotFound
+			}
+			return loc, err
+		}
+	}
+	return "", ErrNotFound
+}
+
+// fetchGemsMember returns a nil Body when the member lacks the document.
+func (e *Engine) fetchGemsMember(ctx context.Context, name, path string) (*GemsMember, error) {
+	remote, err := e.getRemote(ctx, name)
+	if err != nil {
+		return nil, fmt.Errorf("remote %q: %w", name, err)
+	}
+	m := &GemsMember{RemoteName: name}
+	if remote.RepoType == models.RepoTypeLocal {
+		if e.GemsLocal == nil {
+			return nil, errors.New("local gems indexes are not wired")
+		}
+		m.Body, err = e.GemsLocal(ctx, name, path)
+	} else {
+		m.Body, err = e.fetchMemberPath(ctx, *remote, path)
+	}
+	var pe *proxy.ProxyError
+	if errors.Is(err, ErrNotFound) || errors.As(err, &pe) && pe.Status == http.StatusNotFound {
+		return &GemsMember{RemoteName: name}, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return m, nil
+}
diff --git a/internal/virtual/gems_merger_test.go b/internal/virtual/gems_merger_test.go
new file mode 100644
index 0000000..5b2a4bd
--- /dev/null
+++ b/internal/virtual/gems_merger_test.go
@@ -0,0 +1,180 @@
+package virtual
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider/gems"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func TestMergeGemsInfoMemberOrderWins(t *testing.T) {
+	local := GemsMember{RemoteName: "internal", Body: []byte("---\n1.0.0 |checksum:aa\n1.0.0-java |checksum:ab\n")}
+	remote := GemsMember{RemoteName: "rubygems", Body: []byte("---\n0.9.0 |checksum:99\n1.0.0 |checksum:bb\n2.0.0 rack:>= 0|checksum:cc,ruby:>= 3.0\n")}
+	d, err := MergeGemsInfo([]GemsMember{local, {RemoteName: "empty"}, remote})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "---\n1.0.0 |checksum:aa\n1.0.0-java |checksum:ab\n0.9.0 |checksum:99\n2.0.0 rack:>= 0|checksum:cc,ruby:>= 3.0\n"
+	if string(d.Body) != want {
+		t.Fatalf("merged info =\n%q\nwant\n%q", d.Body, want)
+	}
+	for k, owner := range map[string]string{"1.0.0": "internal", "1.0.0-java": "internal", "0.9.0": "rubygems", "2.0.0": "rubygems"} {
+		if d.Owners[k] != owner {
+			t.Errorf("owner of %s = %q, want %q", k, d.Owners[k], owner)
+		}
+	}
+
+	odd := GemsMember{RemoteName: "rubygems", Body: []byte("---\n1.0.0 |checksum:bb\n\n")}
+	if d, _ := MergeGemsInfo([]GemsMember{{RemoteName: "internal"}, odd}); string(d.Body) != string(odd.Body) {
+		t.Fatalf("a gem only one member has must pass through verbatim, got %q", d.Body)
+	}
+	if _, err := MergeGemsInfo([]GemsMember{{RemoteName: "a"}}); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("want ErrNotFound, got %v", err)
+	}
+}
+
+func TestMergeGemsVersions(t *testing.T) {
+	local := GemsMember{RemoteName: "internal", Body: []byte("created_at: 2026-10-18T00:00:00Z\n---\nhello 0.1.0 11\nrack 9.0.0 22\n")}
+	remote := GemsMember{RemoteName: "rubygems", Body: []byte("created_at: 2024-04-01T00:00:05Z\n---\n" +
+		"rack 1.0.0,2.0.0 33\nrails 7.0.0 44\nrack -1.0.0,3.0.0 55\n")}
+	merged := &GemsDoc{Body: []byte("---\n9.0.0 |checksum:x\n2.0.0 |checksum:y\n3.0.0 |checksum:z\n")}
+	var asked []string
+	at := time.Date(2026, 10, 18, 1, 2, 3, 0, time.UTC)
+	body, err := MergeGemsVersions([]GemsMember{local, remote}, func(name string) (*GemsDoc, error) {
+		asked = append(asked, name)
+		return merged, nil
+	}, at)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "created_at: 2026-10-18T01:02:03Z\n---\nhello 0.1.0 11\nrails 7.0.0 44\nrack 9.0.0,2.0.0,3.0.0 " + gems.MD5Hex(merged.Body) + "\n"
+	if string(body) != want {
+		t.Fatalf("versions =\n%q\nwant\n%q", body, want)
+	}
+	if len(asked) != 1 || asked[0] != "rack" {
+		t.Fatalf("merged info fetched for %v, want only the shared gem", asked)
+	}
+
+	if _, err := MergeGemsVersions([]GemsMember{{RemoteName: "x", Body: []byte("no separator")}}, nil, at); err == nil {
+		t.Fatal("malformed member versions must fail")
+	}
+	if _, err := MergeGemsVersions([]GemsMember{{RemoteName: "x"}}, nil, at); err == nil {
+		t.Fatal("a member without versions must fail")
+	}
+}
+
+func TestMergeGemsNames(t *testing.T) {
+	body, err := MergeGemsNames([]GemsMember{{RemoteName: "a", Body: []byte("---\nzeta\nalpha\n")}, {RemoteName: "b", Body: []byte("---\nalpha\nmid\n")}})
+	if err != nil || string(body) != "---\nalpha\nmid\nzeta\n" {
+		t.Fatalf("names = %q %v", body, err)
+	}
+}
+
+func gemsEngine(fetch func(name, path string) (*GemsMember, error)) *Engine {
+	return &Engine{
+		mergeTTL: time.Minute,
+		getRemote: func(_ context.Context, name string) (*models.Remote, error) {
+			rt := models.RepoTypeRemote
+			if name == "internal" {
+				rt = models.RepoTypeLocal
+			}
+			return &models.Remote{Name: name, RepoType: rt}, nil
+		},
+		gemsMember: func(_ context.Context, name, path string) (*GemsMember, error) { return fetch(name, path) },
+	}
+}
+
+func gemsVirt(members ...string) models.Virtual {
+	return models.Virtual{Name: "gems", PackageType: models.PackageGems, Members: members}
+}
+
+func TestGemsRedirectToOwner(t *testing.T) {
+	var mu sync.Mutex
+	asked := map[string]int{}
+	e := gemsEngine(func(name, path string) (*GemsMember, error) {
+		mu.Lock()
+		asked[name+" "+path]++
+		mu.Unlock()
+		switch name + " " + path {
+		case "internal info/foo-2fa":
+			return &GemsMember{RemoteName: name, Body: []byte("---\n1.0.0 |checksum:a\n")}, nil
+		case "rubygems info/foo-2fa":
+			return &GemsMember{RemoteName: name, Body: []byte("---\n1.0.0 |checksum:b\n1.1.0-x86_64-linux |checksum:c\n")}, nil
+		case "rubygems info/foo":
+			return &GemsMember{RemoteName: name, Body: []byte("---\n2.0.0 |checksum:d\n")}, nil
+		}
+		return &GemsMember{RemoteName: name}, nil
+	})
+	virt := gemsVirt("internal", "rubygems")
+	for path, want := range map[string]string{
+		"gems/foo-2fa-1.0.0.gem":                     "http://host/api/v1/local/internal/gems/foo-2fa-1.0.0.gem",
+		"gems/foo-2fa-1.1.0-x86_64-linux.gem":        "http://host/api/v1/remote/rubygems/gems/foo-2fa-1.1.0-x86_64-linux.gem",
+		"quick/Marshal.4.8/foo-2fa-1.0.0.gemspec.rz": "http://host/api/v1/local/internal/quick/Marshal.4.8/foo-2fa-1.0.0.gemspec.rz",
+		"quick/Marshal.4.8/foo-2.0.0.gemspec.rz":     "http://host/api/v1/remote/rubygems/quick/Marshal.4.8/foo-2.0.0.gemspec.rz",
+	} {
+		loc, err := e.GemsRedirect(context.Background(), virt, path, "", "http://host")
+		if err != nil || loc != want {
+			t.Errorf("%s -> %q %v, want %q", path, loc, err, want)
+		}
+	}
+	for _, path := range []string{"gems/foo-2fa-9.9.9.gem", "gems/nodash.gem", "gems/x/../foo-2.0.0.gem", "other/foo-2.0.0.gem", "specs.4.8.gz"} {
+		if _, err := e.GemsRedirect(context.Background(), virt, path, "", "http://host"); !errors.Is(err, ErrNotFound) {
+			t.Errorf("%s: want ErrNotFound, got %v", path, err)
+		}
+	}
+	if asked["internal info/foo-2fa"] != 1 {
+		t.Fatalf("merged info must be cached across redirects, internal asked %d times", asked["internal info/foo-2fa"])
+	}
+}
+
+func TestFetchGemsFailsClosed(t *testing.T) {
+	e := gemsEngine(func(name, path string) (*GemsMember, error) {
+		if name == "rubygems" {
+			return nil, errors.New("upstream down")
+		}
+		return &GemsMember{RemoteName: name, Body: []byte("created_at: x\n---\nhello 0.1.0 11\n")}, nil
+	})
+	for _, path := range []string{"versions", "names", "info/hello"} {
+		if _, _, err := e.FetchGems(context.Background(), gemsVirt("internal", "rubygems"), path); err == nil || errors.Is(err, ErrNotFound) {
+			t.Errorf("%s: want member error, got %v", path, err)
+		}
+	}
+	if _, err := e.GemsRedirect(context.Background(), gemsVirt("internal", "rubygems"), "gems/hello-0.1.0.gem", "", "http://h"); err == nil || errors.Is(err, ErrNotFound) {
+		t.Errorf("redirect: want member error, got %v", err)
+	}
+}
+
+func TestFetchGemsVersionsUsesMergedInfo(t *testing.T) {
+	e := gemsEngine(func(name, path string) (*GemsMember, error) {
+		docs := map[string]string{
+			"internal versions":  "created_at: x\n---\nrack 9.0.0 11\n",
+			"rubygems versions":  "created_at: y\n---\nrack 3.0.0 22\nrails 7.0.0 33\n",
+			"internal info/rack": "---\n9.0.0 |checksum:a\n",
+			"rubygems info/rack": "---\n3.0.0 |checksum:b\n",
+		}
+		if d, ok := docs[name+" "+path]; ok {
+			return &GemsMember{RemoteName: name, Body: []byte(d)}, nil
+		}
+		return &GemsMember{RemoteName: name}, nil
+	})
+	virt := gemsVirt("internal", "rubygems")
+	info, ct, err := e.FetchGems(context.Background(), virt, "info/rack")
+	if err != nil || !strings.HasPrefix(ct, "text/plain") {
+		t.Fatalf("info: %v %q", err, ct)
+	}
+	versions, _, err := e.FetchGems(context.Background(), virt, "versions")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(versions), "\nrails 7.0.0 33\nrack 9.0.0,3.0.0 "+gems.MD5Hex(info)+"\n") {
+		t.Fatalf("versions = %q", versions)
+	}
+	if _, _, err := e.FetchGems(context.Background(), virt, "info/../x"); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("bad name: %v", err)
+	}
+}
diff --git a/internal/virtual/helm_merger.go b/internal/virtual/helm_merger.go
index 94641d7..e7d9802 100644
--- a/internal/virtual/helm_merger.go
+++ b/internal/virtual/helm_merger.go
@@ -2,10 +2,14 @@ package virtual
 
 import (
 	"fmt"
+	"log/slog"
+	"maps"
+	"slices"
 	"strings"
 
 	"gopkg.in/yaml.v3"
 
+	"git.unkin.net/unkin/artifactapi/internal/provider"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
@@ -16,22 +20,17 @@ func init() {
 type HelmMerger struct{}
 
 type helmIndex struct {
-	APIVersion string                        `yaml:"apiVersion"`
-	Entries    map[string][]helmChartVersion `yaml:"entries"`
-	Generated  string                        `yaml:"generated,omitempty"`
-}
-
-type helmChartVersion struct {
-	Name    string   `yaml:"name"`
-	Version string   `yaml:"version"`
-	URLs    []string `yaml:"urls"`
-	rest    map[string]any
+	APIVersion string                            `yaml:"apiVersion"`
+	Entries    map[string][]map[string]yaml.Node `yaml:"entries"`
+	Generated  string                            `yaml:"generated,omitempty"`
 }
 
+// MergeIndexes keeps each chart version's fields as raw nodes so digest,
+// apiVersion and the rest survive the merge untouched; only urls are rewritten.
 func (m *HelmMerger) MergeIndexes(members []MemberIndex, proxyBaseURL string) ([]byte, error) {
 	merged := &helmIndex{
 		APIVersion: "v1",
-		Entries:    make(map[string][]helmChartVersion),
+		Entries:    make(map[string][]map[string]yaml.Node),
 	}
 
 	seen := map[string]map[string]bool{}
@@ -42,47 +41,38 @@ func (m *HelmMerger) MergeIndexes(members []MemberIndex, proxyBaseURL string) ([
 			continue
 		}
 
-		for chart, versions := range idx.Entries {
+		budget := provider.MaxAliasExpandedNodes
+		for _, chart := range slices.Sorted(maps.Keys(idx.Entries)) {
+			versions := idx.Entries[chart]
 			if seen[chart] == nil {
 				seen[chart] = map[string]bool{}
 			}
-			for _, ver := range versions {
-				key := chart + ":" + ver.Version
-				if seen[chart][ver.Version] {
+			for _, raw := range versions {
+				ver, err := provider.ExpandYAMLAliases(raw, &budget)
+				if err != nil {
+					slog.Warn("helm merge: dropping chart entry", "member", member.RemoteName, "chart", chart, "error", err)
 					continue
 				}
-				seen[chart][ver.Version] = true
+				version := ver["version"].Value
+				if seen[chart][version] {
+					continue
+				}
+				seen[chart][version] = true
 
-				if proxyBaseURL != "" {
-					routePrefix := "remote"
-					if member.RepoType == "local" {
-						routePrefix = "local"
+				if urlsNode, ok := ver["urls"]; ok && proxyBaseURL != "" {
+					var urls []string
+					if err := urlsNode.Decode(&urls); err != nil {
+						continue
 					}
-					baseHost := extractHost(member.BaseURL)
-
-					for i, u := range ver.URLs {
-						if strings.HasPrefix(u, "http://") || strings.HasPrefix(u, "https://") {
-							if baseHost != "" && extractHost(u) != baseHost {
-								continue
-							}
-							relPath := extractPathRelativeToBase(u, member.BaseURL)
-							ver.URLs[i] = fmt.Sprintf("%s/api/v1/%s/%s/%s",
-								strings.TrimRight(proxyBaseURL, "/"),
-								routePrefix,
-								member.RemoteName,
-								relPath)
-						} else {
-							ver.URLs[i] = fmt.Sprintf("%s/api/v1/%s/%s/%s",
-								strings.TrimRight(proxyBaseURL, "/"),
-								routePrefix,
-								member.RemoteName,
-								u)
-						}
+					rewriteHelmURLs(urls, member, proxyBaseURL)
+					var n yaml.Node
+					if err := n.Encode(urls); err != nil {
+						return nil, err
 					}
+					ver["urls"] = n
 				}
 
 				merged.Entries[chart] = append(merged.Entries[chart], ver)
-				_ = key
 			}
 		}
 	}
@@ -90,6 +80,34 @@ func (m *HelmMerger) MergeIndexes(members []MemberIndex, proxyBaseURL string) ([
 	return yaml.Marshal(merged)
 }
 
+func rewriteHelmURLs(urls []string, member MemberIndex, proxyBaseURL string) {
+	routePrefix := "remote"
+	if member.RepoType == "local" {
+		routePrefix = "local"
+	}
+	baseHost := extractHost(member.BaseURL)
+
+	for i, u := range urls {
+		if strings.HasPrefix(u, "http://") || strings.HasPrefix(u, "https://") {
+			if baseHost != "" && extractHost(u) != baseHost {
+				continue
+			}
+			relPath := extractPathRelativeToBase(u, member.BaseURL)
+			urls[i] = fmt.Sprintf("%s/api/v1/%s/%s/%s",
+				strings.TrimRight(proxyBaseURL, "/"),
+				routePrefix,
+				member.RemoteName,
+				relPath)
+		} else {
+			urls[i] = fmt.Sprintf("%s/api/v1/%s/%s/%s",
+				strings.TrimRight(proxyBaseURL, "/"),
+				routePrefix,
+				member.RemoteName,
+				u)
+		}
+	}
+}
+
 func extractHost(rawURL string) string {
 	idx := strings.Index(rawURL, "://")
 	if idx == -1 {
diff --git a/internal/virtual/helm_merger_test.go b/internal/virtual/helm_merger_test.go
index 857074d..c7908be 100644
--- a/internal/virtual/helm_merger_test.go
+++ b/internal/virtual/helm_merger_test.go
@@ -1,9 +1,12 @@
 package virtual_test
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
+	"gopkg.in/yaml.v3"
+
 	"git.unkin.net/unkin/artifactapi/internal/virtual"
 )
 
@@ -122,3 +125,129 @@ entries:
 		t.Error("expected fallback repo to be excluded for duplicate")
 	}
 }
+
+func TestHelmMerger_PreservesChartFields(t *testing.T) {
+	m := &virtual.HelmMerger{}
+	body := []byte(`apiVersion: v1
+entries:
+  app:
+    - apiVersion: v2
+      name: app
+      version: "1.0"
+      appVersion: "3.1"
+      description: in-house
+      digest: deadbeef
+      urls:
+        - app-1.0.tgz
+`)
+	result, err := m.MergeIndexes([]virtual.MemberIndex{{RemoteName: "charts", RepoType: "local", Body: body}}, "https://proxy.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := string(result)
+	for _, want := range []string{
+		"digest: deadbeef",
+		"apiVersion: v2",
+		`appVersion: "3.1"`,
+		"description: in-house",
+		`version: "1.0"`,
+		"https://proxy.example.com/api/v1/local/charts/app-1.0.tgz",
+	} {
+		if !strings.Contains(out, want) {
+			t.Errorf("merged index missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestHelmMerger_ExpandsAliasesAcrossDedupe(t *testing.T) {
+	m := &virtual.HelmMerger{}
+	first := []byte(`apiVersion: v1
+entries:
+  app:
+    - version: "1.0"
+      urls: [app-1.0.tgz]
+`)
+	second := []byte(`apiVersion: v1
+entries:
+  app:
+    - version: "1.0"
+      maintainers: &team
+        - name: ops
+      urls: [app-1.0.tgz]
+    - version: "2.0"
+      maintainers: *team
+      urls: [app-2.0.tgz]
+`)
+	result, err := m.MergeIndexes([]virtual.MemberIndex{
+		{RemoteName: "a", RepoType: "local", Body: first},
+		{RemoteName: "b", RepoType: "local", Body: second},
+	}, "https://proxy.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var idx struct {
+		Entries map[string][]struct {
+			Version     string `yaml:"version"`
+			Maintainers []struct {
+				Name string `yaml:"name"`
+			} `yaml:"maintainers"`
+		} `yaml:"entries"`
+	}
+	if err := yaml.Unmarshal(result, &idx); err != nil {
+		t.Fatalf("merged index does not parse: %v\n%s", err, result)
+	}
+	app := idx.Entries["app"]
+	if len(app) != 2 || app[1].Version != "2.0" || len(app[1].Maintainers) != 1 || app[1].Maintainers[0].Name != "ops" {
+		t.Errorf("alias not expanded: %+v\n%s", app, result)
+	}
+}
+
+func TestHelmMerger_DropsAliasBomb(t *testing.T) {
+	m := &virtual.HelmMerger{}
+	body := []byte(`apiVersion: v1
+entries:
+  app:
+    - version: "1.0"
+      a: &a [x, x, x, x, x, x, x, x, x, x]
+      b: &b [*a, *a, *a, *a, *a, *a, *a, *a, *a, *a]
+      c: &c [*b, *b, *b, *b, *b, *b, *b, *b, *b, *b]
+      d: &d [*c, *c, *c, *c, *c, *c, *c, *c, *c, *c]
+      e: &e [*d, *d, *d, *d, *d, *d, *d, *d, *d, *d]
+      urls: [app-1.0.tgz]
+`)
+	result, err := m.MergeIndexes([]virtual.MemberIndex{{RemoteName: "a", RepoType: "local", Body: body}}, "https://proxy.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(result), "app-1.0.tgz") {
+		t.Errorf("alias bomb entry was kept")
+	}
+}
+
+func TestHelmMerger_LargeIndexWithoutAliasesIsComplete(t *testing.T) {
+	var b strings.Builder
+	b.WriteString("apiVersion: v1\nentries:\n")
+	for c := 0; c < 100; c++ {
+		fmt.Fprintf(&b, "  chart%d:\n", c)
+		for v := 0; v < 100; v++ {
+			fmt.Fprintf(&b, "    - name: chart%d\n      version: \"1.0.%d\"\n      description: d\n      maintainers: [{name: ops, email: ops@example.com}]\n      urls: [chart%d-1.0.%d.tgz]\n", c, v, c, v)
+		}
+	}
+	result, err := (&virtual.HelmMerger{}).MergeIndexes([]virtual.MemberIndex{{RemoteName: "a", RepoType: "local", Body: []byte(b.String())}}, "https://proxy.example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var idx struct {
+		Entries map[string][]map[string]any `yaml:"entries"`
+	}
+	if err := yaml.Unmarshal(result, &idx); err != nil {
+		t.Fatal(err)
+	}
+	total := 0
+	for _, vs := range idx.Entries {
+		total += len(vs)
+	}
+	if len(idx.Entries) != 100 || total != 10000 {
+		t.Errorf("got %d charts, %d versions; want 100, 10000", len(idx.Entries), total)
+	}
+}
diff --git a/internal/virtual/npm_merger.go b/internal/virtual/npm_merger.go
new file mode 100644
index 0000000..844059f
--- /dev/null
+++ b/internal/virtual/npm_merger.go
@@ -0,0 +1,271 @@
+package virtual
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"regexp"
+	"slices"
+	"strings"
+
+	"git.unkin.net/unkin/artifactapi/internal/proxy"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+const (
+	NPMAbbreviatedType = "application/vnd.npm.install-v1+json"
+	npmAbbreviatedFile = "install-v1"
+	maxNPMPackuments   = 1024
+)
+
+var npmVirtualNameRe = regexp.MustCompile(`^(@[A-Za-z0-9][A-Za-z0-9._~-]*/)?[A-Za-z0-9][A-Za-z0-9._~-]*$`)
+
+// npmAbbreviatedFields are the version fields kept in an install-v1 packument.
+var npmAbbreviatedFields = []string{
+	"name", "version", "deprecated", "dependencies", "optionalDependencies",
+	"devDependencies", "bundleDependencies", "peerDependencies", "peerDependenciesMeta",
+	"bin", "directories", "dist", "engines", "_hasShrinkwrap", "hasInstallScript",
+	"cpu", "os", "libc",
+}
+
+// NPMMember is one member's full packument for a package; Doc is nil when the
+// member does not have the package. Tarball URLs under one of Bases are
+// rewritten to go via the virtual; with no Bases (a local) they are relative.
+type NPMMember struct {
+	RemoteName string
+	Bases      []string
+	Doc        []byte
+}
+
+// NPMPackument is a merged packument in full and install-v1 form.
+type NPMPackument struct {
+	Full, Abbreviated []byte
+}
+
+func (p *NPMPackument) index() []byte { return p.Full }
+func (p *NPMPackument) files() map[string][]byte {
+	return map[string][]byte{npmAbbreviatedFile: p.Abbreviated}
+}
+
+// MergeNPM unions versions across members (first member wins a duplicate),
+// keeps the first member's value for each dist-tag, drops tags naming versions
+// outside the merged set and points every owned tarball at
+// tarballBase + <member>/<path>. ErrNotFound means no member has the package.
+func MergeNPM(members []NPMMember, tarballBase string) (*NPMPackument, error) {
+	var base map[string]json.RawMessage
+	versions := map[string]map[string]json.RawMessage{}
+	tags := map[string]string{}
+	times := map[string]json.RawMessage{}
+	var modified string
+	for _, m := range members {
+		if m.Doc == nil {
+			continue
+		}
+		var doc map[string]json.RawMessage
+		var vs map[string]map[string]json.RawMessage
+		var dt map[string]string
+		var tm map[string]json.RawMessage
+		if err := json.Unmarshal(m.Doc, &doc); err != nil {
+			return nil, fmt.Errorf("member %q packument: %w", m.RemoteName, err)
+		}
+		for field, dst := range map[string]any{"versions": &vs, "dist-tags": &dt, "time": &tm} {
+			if raw, ok := doc[field]; ok {
+				if err := json.Unmarshal(raw, dst); err != nil {
+					return nil, fmt.Errorf("member %q %s: %w", m.RemoteName, field, err)
+				}
+			}
+		}
+		if base == nil {
+			base = doc
+		}
+		for v, man := range vs {
+			if _, dup := versions[v]; dup || man == nil {
+				continue
+			}
+			if err := rewriteNPMTarball(man, m, tarballBase); err != nil {
+				return nil, fmt.Errorf("member %q %s: %w", m.RemoteName, v, err)
+			}
+			versions[v] = man
+		}
+		for tag, v := range dt {
+			if _, ok := tags[tag]; !ok {
+				tags[tag] = v
+			}
+		}
+		for k, v := range tm {
+			if k == "modified" {
+				var s string
+				if json.Unmarshal(v, &s) == nil && s > modified {
+					modified = s
+				}
+				continue
+			}
+			if _, ok := times[k]; !ok {
+				times[k] = v
+			}
+		}
+	}
+	if base == nil {
+		return nil, ErrNotFound
+	}
+	for tag, v := range tags {
+		if _, ok := versions[v]; !ok {
+			delete(tags, tag)
+		}
+	}
+	if modified != "" {
+		times["modified"], _ = json.Marshal(modified)
+	}
+
+	full := map[string]any{}
+	for k, v := range base {
+		full[k] = v
+	}
+	full["versions"], full["dist-tags"] = versions, tags
+	delete(full, "time")
+	if len(times) > 0 {
+		full["time"] = times
+	}
+
+	abbrevVersions := make(map[string]map[string]json.RawMessage, len(versions))
+	for v, man := range versions {
+		a := map[string]json.RawMessage{}
+		for _, f := range npmAbbreviatedFields {
+			if raw, ok := man[f]; ok {
+				a[f] = raw
+			}
+		}
+		abbrevVersions[v] = a
+	}
+	abbrev := map[string]any{"name": base["name"], "dist-tags": tags, "versions": abbrevVersions}
+	if modified != "" {
+		abbrev["modified"] = modified
+	}
+
+	fullJSON, err := json.Marshal(full)
+	if err != nil {
+		return nil, err
+	}
+	abbrevJSON, err := json.Marshal(abbrev)
+	if err != nil {
+		return nil, err
+	}
+	return &NPMPackument{Full: fullJSON, Abbreviated: abbrevJSON}, nil
+}
+
+// rewriteNPMTarball leaves a tarball outside the member's bases untouched.
+func rewriteNPMTarball(man map[string]json.RawMessage, m NPMMember, tarballBase string) error {
+	raw, ok := man["dist"]
+	if !ok {
+		return nil
+	}
+	var dist map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &dist); err != nil {
+		return fmt.Errorf("dist: %w", err)
+	}
+	var tarball string
+	if err := json.Unmarshal(dist["tarball"], &tarball); err != nil {
+		return nil
+	}
+	rel, ok := npmMemberPath(tarball, m.Bases)
+	if !ok {
+		return nil
+	}
+	dist["tarball"], _ = json.Marshal(tarballBase + url.PathEscape(m.RemoteName) + "/" + rel)
+	man["dist"], _ = json.Marshal(dist)
+	return nil
+}
+
+func npmMemberPath(tarball string, bases []string) (string, bool) {
+	if len(bases) == 0 {
+		return tarball, tarball != "" && !strings.Contains(tarball, "://") && !strings.HasPrefix(tarball, "/")
+	}
+	for _, b := range bases {
+		if rel, ok := strings.CutPrefix(tarball, strings.TrimRight(b, "/")+"/"); ok && rel != "" {
+			return rel, true
+		}
+	}
+	return "", false
+}
+
+// FetchNPM serves the merged packument for the package named by path, full or
+// abbreviated (install-v1).
+func (e *Engine) FetchNPM(ctx context.Context, virt models.Virtual, path, proxyBaseURL string, abbreviated bool) ([]byte, string, error) {
+	pkg, err := url.PathUnescape(strings.TrimSuffix(path, "/"))
+	if err != nil || !npmVirtualNameRe.MatchString(pkg) {
+		return nil, "", ErrNotFound
+	}
+	prefix := "npm\x00" + virt.Name + "\x00"
+	tarballBase := strings.TrimRight(proxyBaseURL, "/") + "/api/v1/virtual/" + url.PathEscape(virt.Name) + "/"
+	inserted := false
+	repo, err := e.merged(ctx, prefix+pkg+"\x00"+proxyBaseURL, func(ctx context.Context) (mergedRepo, error) {
+		inserted = true
+		members, err := fetchMembers(virt, func(name string) (*NPMMember, error) { return e.npmMember(ctx, name, pkg) })
+		if err != nil {
+			return nil, err
+		}
+		p, err := MergeNPM(members, tarballBase)
+		if err != nil {
+			return nil, err
+		}
+		return p, nil
+	})
+	if err != nil {
+		return nil, "", err
+	}
+	if inserted {
+		e.evictOldest(prefix, maxNPMPackuments)
+	}
+	if abbreviated {
+		return repo.files()[npmAbbreviatedFile], NPMAbbreviatedType, nil
+	}
+	return repo.index(), "application/json", nil
+}
+
+// fetchNPMMember returns a member with a nil Doc when it lacks the package.
+func (e *Engine) fetchNPMMember(ctx context.Context, name, pkg string) (*NPMMember, error) {
+	remote, err := e.getRemote(ctx, name)
+	if err != nil {
+		return nil, fmt.Errorf("remote %q: %w", name, err)
+	}
+	m := &NPMMember{RemoteName: name}
+	if remote.RepoType == models.RepoTypeLocal {
+		if e.NPMLocal == nil {
+			return nil, errors.New("local npm packuments are not wired")
+		}
+		m.Doc, err = e.NPMLocal(ctx, name, pkg)
+	} else {
+		m.Bases = remote.UpstreamPool()
+		m.Doc, err = e.fetchMemberPath(ctx, *remote, strings.Replace(pkg, "/", "%2f", 1))
+	}
+	var pe *proxy.ProxyError
+	if errors.Is(err, ErrNotFound) || errors.As(err, &pe) && pe.Status == http.StatusNotFound {
+		return &NPMMember{RemoteName: name}, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+// evictOldest drops the oldest merges under prefix beyond keep.
+func (e *Engine) evictOldest(prefix string, keep int) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	var keys []string
+	for k := range e.gens {
+		if strings.HasPrefix(k, prefix) {
+			keys = append(keys, k)
+		}
+	}
+	if len(keys) <= keep {
+		return
+	}
+	slices.SortFunc(keys, func(a, b string) int { return e.gens[b].at.Compare(e.gens[a].at) })
+	for _, k := range keys[keep:] {
+		delete(e.gens, k)
+	}
+}
diff --git a/internal/virtual/npm_merger_test.go b/internal/virtual/npm_merger_test.go
new file mode 100644
index 0000000..9536e0d
--- /dev/null
+++ b/internal/virtual/npm_merger_test.go
@@ -0,0 +1,289 @@
+package virtual
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+type npmDoc struct {
+	Name     string                    `json:"name"`
+	Readme   string                    `json:"readme,omitempty"`
+	Modified string                    `json:"modified,omitempty"`
+	DistTags map[string]string         `json:"dist-tags"`
+	Versions map[string]map[string]any `json:"versions"`
+	Time     map[string]string         `json:"time,omitempty"`
+}
+
+func npmVersion(name, v, tarball string) map[string]any {
+	return map[string]any{"name": name, "version": v, "readme": "long", "scripts": map[string]string{"test": "x"},
+		"dependencies": map[string]string{"dep": "^1"}, "dist": map[string]any{"tarball": tarball, "shasum": "abc"}}
+}
+
+func mustJSON(t *testing.T, v any) []byte {
+	t.Helper()
+	b, err := json.Marshal(v)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return b
+}
+
+func decodeNPM(t *testing.T, b []byte) npmDoc {
+	t.Helper()
+	var d npmDoc
+	if err := json.Unmarshal(b, &d); err != nil {
+		t.Fatalf("decode %s: %v", b, err)
+	}
+	return d
+}
+
+func tarballOf(d npmDoc, v string) string {
+	dist, _ := d.Versions[v]["dist"].(map[string]any)
+	s, _ := dist["tarball"].(string)
+	return s
+}
+
+func npmMembersFixture(t *testing.T) []NPMMember {
+	local := npmDoc{Name: "pkg", DistTags: map[string]string{"latest": "1.0.0", "beta": "9.9.9"},
+		Versions: map[string]map[string]any{"1.0.0": npmVersion("pkg", "1.0.0", "pkg/-/pkg-1.0.0.tgz")}}
+	remote := npmDoc{Name: "pkg", Readme: "remote readme",
+		DistTags: map[string]string{"latest": "2.0.0", "next": "2.0.0", "beta": "1.0.0"},
+		Versions: map[string]map[string]any{
+			"1.0.0": npmVersion("pkg", "1.0.0", "https://registry.npmjs.org/pkg/-/pkg-1.0.0.tgz"),
+			"2.0.0": npmVersion("pkg", "2.0.0", "https://registry.npmjs.org/pkg/-/pkg-2.0.0.tgz"),
+			"3.0.0": npmVersion("pkg", "3.0.0", "https://cdn.example/pkg-3.0.0.tgz"),
+		},
+		Time: map[string]string{"modified": "2024-01-01T00:00:00.000Z", "2.0.0": "2023-01-01T00:00:00.000Z"}}
+	return []NPMMember{
+		{RemoteName: "internal", Doc: mustJSON(t, local)},
+		{RemoteName: "absent"},
+		{RemoteName: "npmjs", Bases: []string{"https://registry.npmjs.org/"}, Doc: mustJSON(t, remote)},
+	}
+}
+
+func TestMergeNPMUnionsVersionsMemberOrderWins(t *testing.T) {
+	p, err := MergeNPM(npmMembersFixture(t), "http://aa/api/v1/virtual/npm/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	d := decodeNPM(t, p.Full)
+	if len(d.Versions) != 3 {
+		t.Fatalf("want 3 merged versions, got %v", d.Versions)
+	}
+	for v, want := range map[string]string{
+		"1.0.0": "http://aa/api/v1/virtual/npm/internal/pkg/-/pkg-1.0.0.tgz",
+		"2.0.0": "http://aa/api/v1/virtual/npm/npmjs/pkg/-/pkg-2.0.0.tgz",
+		"3.0.0": "https://cdn.example/pkg-3.0.0.tgz",
+	} {
+		if got := tarballOf(d, v); got != want {
+			t.Errorf("%s tarball = %q, want %q", v, got, want)
+		}
+	}
+	if d.Readme != "" {
+		t.Errorf("top-level fields come from the first member with the package, got readme %q", d.Readme)
+	}
+	if d.Time["modified"] != "2024-01-01T00:00:00.000Z" || d.Time["2.0.0"] == "" {
+		t.Errorf("time not merged: %v", d.Time)
+	}
+}
+
+func TestMergeNPMDistTags(t *testing.T) {
+	members := npmMembersFixture(t)
+	members[0].Doc = mustJSON(t, npmDoc{Name: "pkg", DistTags: map[string]string{"latest": "1.0.0", "gone": "0.0.1"},
+		Versions: map[string]map[string]any{"1.0.0": npmVersion("pkg", "1.0.0", "pkg/-/pkg-1.0.0.tgz")}})
+	p, err := MergeNPM(members, "http://aa/v/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := decodeNPM(t, p.Full).DistTags
+	want := map[string]string{"latest": "1.0.0", "next": "2.0.0", "beta": "1.0.0"}
+	if fmt.Sprint(got) != fmt.Sprint(want) {
+		t.Fatalf("dist-tags = %v, want %v", got, want)
+	}
+}
+
+func TestMergeNPMDropsFirstTagNamingMissingVersion(t *testing.T) {
+	// internal claims beta=9.9.9 first; it wins over npmjs's beta, and is then
+	// dropped because no member has 9.9.9.
+	p, err := MergeNPM(npmMembersFixture(t), "http://aa/v/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tag, ok := decodeNPM(t, p.Full).DistTags["beta"]; ok {
+		t.Fatalf("beta should be dropped, got %q", tag)
+	}
+}
+
+func TestMergeNPMAbbreviated(t *testing.T) {
+	p, err := MergeNPM(npmMembersFixture(t), "http://aa/v/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var a map[string]any
+	if err := json.Unmarshal(p.Abbreviated, &a); err != nil {
+		t.Fatal(err)
+	}
+	if a["modified"] != "2024-01-01T00:00:00.000Z" || a["name"] != "pkg" || a["readme"] != nil || a["time"] != nil {
+		t.Fatalf("bad abbreviated top level: %v", a)
+	}
+	v := a["versions"].(map[string]any)["2.0.0"].(map[string]any)
+	if v["readme"] != nil || v["scripts"] != nil {
+		t.Errorf("abbreviated version keeps non-install fields: %v", v)
+	}
+	if v["dependencies"] == nil || v["dist"].(map[string]any)["tarball"] != "http://aa/v/npmjs/pkg/-/pkg-2.0.0.tgz" {
+		t.Errorf("abbreviated version lost install fields: %v", v)
+	}
+}
+
+func TestMergeNPMNoMemberHasPackage(t *testing.T) {
+	if _, err := MergeNPM([]NPMMember{{RemoteName: "a"}, {RemoteName: "b"}}, "http://aa/v/"); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("want ErrNotFound, got %v", err)
+	}
+}
+
+func TestNPMMemberPath(t *testing.T) {
+	for _, c := range []struct {
+		tarball string
+		bases   []string
+		want    string
+		ok      bool
+	}{
+		{"@s/n/-/n-1.0.0.tgz", nil, "@s/n/-/n-1.0.0.tgz", true},
+		{"https://evil.example/x.tgz", nil, "", false},
+		{"/abs/x.tgz", nil, "", false},
+		{"https://r.example/@s/n/-/n-1.0.0.tgz", []string{"https://m.example", "https://r.example"}, "@s/n/-/n-1.0.0.tgz", true},
+		{"https://r.example.evil/x.tgz", []string{"https://r.example"}, "", false},
+	} {
+		got, ok := npmMemberPath(c.tarball, c.bases)
+		if ok != c.ok || ok && got != c.want {
+			t.Errorf("npmMemberPath(%q, %v) = %q,%v want %q,%v", c.tarball, c.bases, got, ok, c.want, c.ok)
+		}
+	}
+}
+
+func npmEngine(fetch func(name, pkg string) (*NPMMember, error)) *Engine {
+	return &Engine{
+		mergeTTL: time.Minute,
+		getRemote: func(_ context.Context, name string) (*models.Remote, error) {
+			return &models.Remote{Name: name, RepoType: models.RepoTypeRemote}, nil
+		},
+		npmMember: func(_ context.Context, name, pkg string) (*NPMMember, error) { return fetch(name, pkg) },
+	}
+}
+
+func npmVirt(members ...string) models.Virtual {
+	return models.Virtual{Name: "npm", PackageType: models.PackageNPM, Members: members}
+}
+
+func TestFetchNPMScopedAndAbbreviated(t *testing.T) {
+	var mu sync.Mutex
+	var asked []string
+	e := npmEngine(func(name, pkg string) (*NPMMember, error) {
+		mu.Lock()
+		asked = append(asked, pkg)
+		mu.Unlock()
+		if name == "b" {
+			return &NPMMember{RemoteName: name}, nil
+		}
+		return &NPMMember{RemoteName: name, Doc: mustJSON(t, npmDoc{Name: pkg, DistTags: map[string]string{"latest": "1.0.0"},
+			Versions: map[string]map[string]any{"1.0.0": npmVersion(pkg, "1.0.0", pkg+"/-/n-1.0.0.tgz")}})}, nil
+	})
+	body, ct, err := e.FetchNPM(context.Background(), npmVirt("a", "b"), "@s%2fn", "http://host", true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ct != NPMAbbreviatedType || !strings.Contains(string(body), `"tarball":"http://host/api/v1/virtual/npm/a/@s/n/-/n-1.0.0.tgz"`) {
+		t.Fatalf("ct %q body %s", ct, body)
+	}
+	if asked[0] != "@s/n" {
+		t.Fatalf("member asked for %q, want decoded scoped name", asked[0])
+	}
+	full, ct, err := e.FetchNPM(context.Background(), npmVirt("a", "b"), "@s%2fn", "http://host", false)
+	if err != nil || ct != "application/json" || string(full) == string(body) {
+		t.Fatalf("full packument: ct %q err %v", ct, err)
+	}
+	if len(asked) != 2 {
+		t.Fatalf("second fetch should be served from the merge cache, members asked %d times", len(asked))
+	}
+}
+
+func TestFetchNPMFailsClosed(t *testing.T) {
+	e := npmEngine(func(name, pkg string) (*NPMMember, error) {
+		if name == "b" {
+			return nil, errors.New("upstream down")
+		}
+		return &NPMMember{RemoteName: name, Doc: []byte(`{"name":"x","versions":{}}`)}, nil
+	})
+	_, _, err := e.FetchNPM(context.Background(), npmVirt("a", "b"), "x", "http://host", false)
+	if err == nil || errors.Is(err, ErrNotFound) {
+		t.Fatalf("want upstream error with a member down, got %v", err)
+	}
+}
+
+func TestFetchNPMNotFound(t *testing.T) {
+	e := npmEngine(func(name, _ string) (*NPMMember, error) { return &NPMMember{RemoteName: name}, nil })
+	for _, path := range []string{"missing", "-/npm/v1/security/advisories/bulk", "a/../b", "@s"} {
+		if _, _, err := e.FetchNPM(context.Background(), npmVirt("a"), path, "http://host", false); !errors.Is(err, ErrNotFound) {
+			t.Errorf("%q: want ErrNotFound, got %v", path, err)
+		}
+	}
+}
+
+func TestFetchNPMMemberLocalNotFound(t *testing.T) {
+	e := &Engine{getRemote: func(_ context.Context, name string) (*models.Remote, error) {
+		return &models.Remote{Name: name, RepoType: models.RepoTypeLocal}, nil
+	}}
+	e.NPMLocal = func(_ context.Context, _, pkg string) ([]byte, error) {
+		if pkg == "boom" {
+			return nil, errors.New("db down")
+		}
+		return nil, fmt.Errorf("wrapped: %w", ErrNotFound)
+	}
+	m, err := e.fetchNPMMember(context.Background(), "internal", "nope")
+	if err != nil || m.Doc != nil {
+		t.Fatalf("missing package must be an empty member, got %v %v", m, err)
+	}
+	if _, err := e.fetchNPMMember(context.Background(), "internal", "boom"); err == nil {
+		t.Fatal("local read errors must surface")
+	}
+}
+
+func TestMemberRedirectNPM(t *testing.T) {
+	e := npmEngine(nil)
+	virt := npmVirt("internal", "npmjs")
+	loc, ok, err := e.MemberRedirect(context.Background(), virt, "npmjs/@s/n/-/n-1.0.0.tgz", "", "http://host")
+	if err != nil || !ok || loc != "http://host/api/v1/remote/npmjs/@s/n/-/n-1.0.0.tgz" {
+		t.Fatalf("got %q %v %v", loc, ok, err)
+	}
+	if _, ok, _ := e.MemberRedirect(context.Background(), virt, "@s/n", "", "http://host"); ok {
+		t.Fatal("scoped packument path must not redirect")
+	}
+	if _, _, err := e.MemberRedirect(context.Background(), virt, "npmjs/%2e%2e/x.tgz", "", "http://host"); !errors.Is(err, ErrBadPath) {
+		t.Fatalf("want ErrBadPath, got %v", err)
+	}
+}
+
+func TestEvictOldestBoundsNPMMerges(t *testing.T) {
+	e := npmEngine(func(name, pkg string) (*NPMMember, error) {
+		return &NPMMember{RemoteName: name, Doc: mustJSON(t, npmDoc{Name: pkg, Versions: map[string]map[string]any{}})}, nil
+	})
+	for i := range maxNPMPackuments + 5 {
+		if _, _, err := e.FetchNPM(context.Background(), npmVirt("a"), fmt.Sprintf("p%d", i), "http://host", false); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if len(e.gens) != maxNPMPackuments {
+		t.Fatalf("cached merges = %d, want %d", len(e.gens), maxNPMPackuments)
+	}
+	if _, ok := e.gens["npm\x00npm\x00p0\x00http://host"]; ok {
+		t.Fatal("oldest merge should be evicted")
+	}
+}
diff --git a/migrations/0003_github_sync_state_cascade.sql b/migrations/0003_github_sync_state_cascade.sql
new file mode 100644
index 0000000..90b9a1a
--- /dev/null
+++ b/migrations/0003_github_sync_state_cascade.sql
@@ -0,0 +1,12 @@
+-- Sync state is dropped with its remote, so a recreated remote of the same name
+-- starts with no inherited ETag or timing. NOT VALID skips checking rows left by
+-- remotes deleted before this migration, which would otherwise fail it.
+ALTER TABLE github_rpm_sync_state    DROP CONSTRAINT IF EXISTS github_rpm_sync_state_remote_fk;
+ALTER TABLE github_rpm_sync_state    ADD CONSTRAINT github_rpm_sync_state_remote_fk
+	FOREIGN KEY (remote_name) REFERENCES remotes(name) ON DELETE CASCADE NOT VALID;
+ALTER TABLE github_deb_sync_state    DROP CONSTRAINT IF EXISTS github_deb_sync_state_remote_fk;
+ALTER TABLE github_deb_sync_state    ADD CONSTRAINT github_deb_sync_state_remote_fk
+	FOREIGN KEY (remote_name) REFERENCES remotes(name) ON DELETE CASCADE NOT VALID;
+ALTER TABLE github_alpine_sync_state DROP CONSTRAINT IF EXISTS github_alpine_sync_state_remote_fk;
+ALTER TABLE github_alpine_sync_state ADD CONSTRAINT github_alpine_sync_state_remote_fk
+	FOREIGN KEY (remote_name) REFERENCES remotes(name) ON DELETE CASCADE NOT VALID;
diff --git a/migrations/0004_puppet_metadata.sql b/migrations/0004_puppet_metadata.sql
new file mode 100644
index 0000000..a3bd85e
--- /dev/null
+++ b/migrations/0004_puppet_metadata.sql
@@ -0,0 +1,15 @@
+CREATE TABLE IF NOT EXISTS puppet_metadata (
+	id            BIGSERIAL PRIMARY KEY,
+	repo_name     TEXT NOT NULL,
+	file_path     TEXT NOT NULL,
+	content_hash  TEXT NOT NULL,
+	slug          TEXT NOT NULL,
+	version       TEXT NOT NULL,
+	metadata_json TEXT NOT NULL,
+	file_size     BIGINT NOT NULL DEFAULT 0,
+	file_md5      TEXT NOT NULL,
+	created_at    TIMESTAMPTZ DEFAULT NOW(),
+	UNIQUE(repo_name, file_path)
+);
+
+CREATE INDEX IF NOT EXISTS idx_puppet_metadata_repo_slug ON puppet_metadata(repo_name, slug);
diff --git a/migrations/0005_helm_metadata.sql b/migrations/0005_helm_metadata.sql
new file mode 100644
index 0000000..cd20389
--- /dev/null
+++ b/migrations/0005_helm_metadata.sql
@@ -0,0 +1,13 @@
+CREATE TABLE IF NOT EXISTS helm_metadata (
+	id           BIGSERIAL PRIMARY KEY,
+	repo_name    TEXT NOT NULL,
+	file_path    TEXT NOT NULL,
+	content_hash TEXT NOT NULL,
+	name         TEXT NOT NULL,
+	version      TEXT NOT NULL,
+	chart_yaml   TEXT NOT NULL,
+	created_at   TIMESTAMPTZ DEFAULT NOW(),
+	UNIQUE(repo_name, file_path)
+);
+
+CREATE INDEX IF NOT EXISTS idx_helm_metadata_repo ON helm_metadata(repo_name);
diff --git a/pkg/models/package_type.go b/pkg/models/package_type.go
index bb81ef3..7fb1b8f 100644
--- a/pkg/models/package_type.go
+++ b/pkg/models/package_type.go
@@ -4,44 +4,10 @@ import "fmt"
 
 type PackageType string
 
-const (
-	PackageGeneric      PackageType = "generic"
-	PackageDocker       PackageType = "docker"
-	PackageHelm         PackageType = "helm"
-	PackagePyPI         PackageType = "pypi"
-	PackageNPM          PackageType = "npm"
-	PackageRPM          PackageType = "rpm"
-	PackageDeb          PackageType = "deb"
-	PackageAlpine       PackageType = "alpine"
-	PackagePuppet       PackageType = "puppet"
-	PackageTerraform    PackageType = "terraform"
-	PackageGoProxy      PackageType = "goproxy"
-	PackageCargo        PackageType = "cargo"
-	PackageAnsible      PackageType = "ansible"
-	PackageNuGet        PackageType = "nuget"
-	PackageGitHubRPM    PackageType = "github_rpm"
-	PackageGitHubDeb    PackageType = "github_deb"
-	PackageGitHubAlpine PackageType = "github_alpine"
-)
+var validPackageTypes = map[PackageType]bool{}
 
-var validPackageTypes = map[PackageType]bool{
-	PackageGeneric:      true,
-	PackageDocker:       true,
-	PackageHelm:         true,
-	PackagePyPI:         true,
-	PackageNPM:          true,
-	PackageRPM:          true,
-	PackageDeb:          true,
-	PackageAlpine:       true,
-	PackagePuppet:       true,
-	PackageTerraform:    true,
-	PackageGoProxy:      true,
-	PackageCargo:        true,
-	PackageAnsible:      true,
-	PackageNuGet:        true,
-	PackageGitHubRPM:    true,
-	PackageGitHubDeb:    true,
-	PackageGitHubAlpine: true,
+func registerPackageType(p PackageType) {
+	validPackageTypes[p] = true
 }
 
 func (p PackageType) Valid() bool {
diff --git a/pkg/models/package_type_alpine.go b/pkg/models/package_type_alpine.go
new file mode 100644
index 0000000..93bbe28
--- /dev/null
+++ b/pkg/models/package_type_alpine.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageAlpine PackageType = "alpine"
+
+func init() { registerPackageType(PackageAlpine) }
diff --git a/pkg/models/package_type_ansible.go b/pkg/models/package_type_ansible.go
new file mode 100644
index 0000000..976a1b1
--- /dev/null
+++ b/pkg/models/package_type_ansible.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageAnsible PackageType = "ansible"
+
+func init() { registerPackageType(PackageAnsible) }
diff --git a/pkg/models/package_type_cargo.go b/pkg/models/package_type_cargo.go
new file mode 100644
index 0000000..2c83925
--- /dev/null
+++ b/pkg/models/package_type_cargo.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageCargo PackageType = "cargo"
+
+func init() { registerPackageType(PackageCargo) }
diff --git a/pkg/models/package_type_deb.go b/pkg/models/package_type_deb.go
new file mode 100644
index 0000000..5dd67de
--- /dev/null
+++ b/pkg/models/package_type_deb.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageDeb PackageType = "deb"
+
+func init() { registerPackageType(PackageDeb) }
diff --git a/pkg/models/package_type_docker.go b/pkg/models/package_type_docker.go
new file mode 100644
index 0000000..c9f72d9
--- /dev/null
+++ b/pkg/models/package_type_docker.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageDocker PackageType = "docker"
+
+func init() { registerPackageType(PackageDocker) }
diff --git a/pkg/models/package_type_gems.go b/pkg/models/package_type_gems.go
new file mode 100644
index 0000000..58e0bd1
--- /dev/null
+++ b/pkg/models/package_type_gems.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageGems PackageType = "gems"
+
+func init() { registerPackageType(PackageGems) }
diff --git a/pkg/models/package_type_generic.go b/pkg/models/package_type_generic.go
new file mode 100644
index 0000000..f59b49d
--- /dev/null
+++ b/pkg/models/package_type_generic.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageGeneric PackageType = "generic"
+
+func init() { registerPackageType(PackageGeneric) }
diff --git a/pkg/models/package_type_github_alpine.go b/pkg/models/package_type_github_alpine.go
new file mode 100644
index 0000000..7da0913
--- /dev/null
+++ b/pkg/models/package_type_github_alpine.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageGitHubAlpine PackageType = "github_alpine"
+
+func init() { registerPackageType(PackageGitHubAlpine) }
diff --git a/pkg/models/package_type_github_deb.go b/pkg/models/package_type_github_deb.go
new file mode 100644
index 0000000..6f96cee
--- /dev/null
+++ b/pkg/models/package_type_github_deb.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageGitHubDeb PackageType = "github_deb"
+
+func init() { registerPackageType(PackageGitHubDeb) }
diff --git a/pkg/models/package_type_github_rpm.go b/pkg/models/package_type_github_rpm.go
new file mode 100644
index 0000000..2ae19bf
--- /dev/null
+++ b/pkg/models/package_type_github_rpm.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageGitHubRPM PackageType = "github_rpm"
+
+func init() { registerPackageType(PackageGitHubRPM) }
diff --git a/pkg/models/package_type_goproxy.go b/pkg/models/package_type_goproxy.go
new file mode 100644
index 0000000..50c0eb6
--- /dev/null
+++ b/pkg/models/package_type_goproxy.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageGoProxy PackageType = "goproxy"
+
+func init() { registerPackageType(PackageGoProxy) }
diff --git a/pkg/models/package_type_helm.go b/pkg/models/package_type_helm.go
new file mode 100644
index 0000000..4ce80b4
--- /dev/null
+++ b/pkg/models/package_type_helm.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageHelm PackageType = "helm"
+
+func init() { registerPackageType(PackageHelm) }
diff --git a/pkg/models/package_type_npm.go b/pkg/models/package_type_npm.go
new file mode 100644
index 0000000..4c8929c
--- /dev/null
+++ b/pkg/models/package_type_npm.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageNPM PackageType = "npm"
+
+func init() { registerPackageType(PackageNPM) }
diff --git a/pkg/models/package_type_nuget.go b/pkg/models/package_type_nuget.go
new file mode 100644
index 0000000..ca14590
--- /dev/null
+++ b/pkg/models/package_type_nuget.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageNuGet PackageType = "nuget"
+
+func init() { registerPackageType(PackageNuGet) }
diff --git a/pkg/models/package_type_puppet.go b/pkg/models/package_type_puppet.go
new file mode 100644
index 0000000..1b02dd2
--- /dev/null
+++ b/pkg/models/package_type_puppet.go
@@ -0,0 +1,5 @@
+package models
+
+const PackagePuppet PackageType = "puppet"
+
+func init() { registerPackageType(PackagePuppet) }
diff --git a/pkg/models/package_type_pypi.go b/pkg/models/package_type_pypi.go
new file mode 100644
index 0000000..f30806e
--- /dev/null
+++ b/pkg/models/package_type_pypi.go
@@ -0,0 +1,5 @@
+package models
+
+const PackagePyPI PackageType = "pypi"
+
+func init() { registerPackageType(PackagePyPI) }
diff --git a/pkg/models/package_type_rpm.go b/pkg/models/package_type_rpm.go
new file mode 100644
index 0000000..50b3270
--- /dev/null
+++ b/pkg/models/package_type_rpm.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageRPM PackageType = "rpm"
+
+func init() { registerPackageType(PackageRPM) }
diff --git a/pkg/models/package_type_terraform.go b/pkg/models/package_type_terraform.go
new file mode 100644
index 0000000..38c6746
--- /dev/null
+++ b/pkg/models/package_type_terraform.go
@@ -0,0 +1,5 @@
+package models
+
+const PackageTerraform PackageType = "terraform"
+
+func init() { registerPackageType(PackageTerraform) }
diff --git a/pkg/models/package_type_test.go b/pkg/models/package_type_test.go
index fec32f8..c902264 100644
--- a/pkg/models/package_type_test.go
+++ b/pkg/models/package_type_test.go
@@ -1,34 +1,54 @@
 package models_test
 
 import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"path/filepath"
+	"strings"
 	"testing"
 
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
+// TestPackageTypeValid parses every package_type_<type>.go and asserts the
+// const it declares is registered, so a type file missing its init() fails.
 func TestPackageTypeValid(t *testing.T) {
-	valid := []models.PackageType{
-		models.PackageGeneric,
-		models.PackageDocker,
-		models.PackageHelm,
-		models.PackagePyPI,
-		models.PackageNPM,
-		models.PackageRPM,
-		models.PackageAlpine,
-		models.PackagePuppet,
-		models.PackageTerraform,
-		models.PackageGoProxy,
-		models.PackageCargo,
-		models.PackageAnsible,
-		models.PackageNuGet,
-		models.PackageGitHubRPM,
-		models.PackageGitHubDeb,
-		models.PackageGitHubAlpine,
+	files, err := filepath.Glob("package_type_*.go")
+	if err != nil {
+		t.Fatal(err)
 	}
-	for _, pt := range valid {
-		if !pt.Valid() {
-			t.Errorf("expected %q to be valid", pt)
+	seen := 0
+	for _, f := range files {
+		if strings.HasSuffix(f, "_test.go") {
+			continue
 		}
+		file, err := parser.ParseFile(token.NewFileSet(), f, nil, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, decl := range file.Decls {
+			gd, ok := decl.(*ast.GenDecl)
+			if !ok || gd.Tok != token.CONST {
+				continue
+			}
+			for _, spec := range gd.Specs {
+				for _, v := range spec.(*ast.ValueSpec).Values {
+					lit := v.(*ast.BasicLit)
+					pt := models.PackageType(strings.Trim(lit.Value, `"`))
+					if !pt.Valid() {
+						t.Errorf("%s: %q is not registered", f, pt)
+					}
+					if want := "package_type_" + pt.String() + ".go"; f != want {
+						t.Errorf("%s declares %q, want it in %s", f, pt, want)
+					}
+					seen++
+				}
+			}
+		}
+	}
+	if seen == 0 {
+		t.Fatal("found no package types")
 	}
 }
 
diff --git a/ui/src/components/UsageInstructions.tsx b/ui/src/components/UsageInstructions.tsx
index 943ac79..1059f53 100644
--- a/ui/src/components/UsageInstructions.tsx
+++ b/ui/src/components/UsageInstructions.tsx
@@ -1,37 +1,16 @@
 import { useState } from 'react';
 import './UsageInstructions.css';
+import { packageTypes } from '../packagetypes';
+import type { RepoClass, Snippet } from '../packagetypes/types';
 
-// repoClass distinguishes the three ways a repository is consumed. remotes are
-// caching proxies, locals are real registries you also publish to, virtuals are
-// merged read-only indexes.
-type RepoClass = 'remote' | 'local' | 'virtual';
-
-interface Snippet {
-  title: string;
-  language: string;
-  code: string;
-  note?: string;
-}
-
-// baseURL resolves the externally reachable origin of this artifactapi instance.
-// The UI is served on the same origin as the API (client BASE is ''), so
-// window.location.origin is the address a host would actually curl/pull against
-// — no hardcoded hostname, works in prod and in `npm run dev` behind a proxy.
+// The UI is served on the same origin as the API, so this is the address clients use.
 function baseURL(): string {
-  if (typeof window !== 'undefined' && window.location?.origin) {
-    return window.location.origin.replace(/\/$/, '');
-  }
-  return 'https://artifactapi.k8s.syd1.au.unkin.net';
+  return window.location.origin;
 }
 
-// hostOnly is the bare host[:port] with no scheme, for docker/terraform source
-// addresses which are scheme-less.
+// hostOnly is host[:port] for scheme-less docker/terraform addresses.
 function hostOnly(): string {
-  try {
-    return new URL(baseURL()).host;
-  } catch {
-    return 'artifactapi.k8s.syd1.au.unkin.net';
-  }
+  return window.location.host;
 }
 
 // remoteProxyBase is where a remote (or virtual) repo's proxied artifacts live.
@@ -46,303 +25,8 @@ export function buildSnippets(packageType: string, repoClass: RepoClass, name: s
   const proxy = remoteProxyBase(repoClass, name);
   const isLocal = repoClass === 'local';
 
-  switch (packageType) {
-    case 'rpm':
-      return [
-        {
-          title: isLocal
-            ? 'Add the yum repo (real yum repo, repodata auto-regenerated)'
-            : 'Add the yum repo (caching proxy)',
-          language: 'bash',
-          code: `sudo tee /etc/yum.repos.d/${name}.repo >/dev/null <<'EOF'
-[${name}]
-name=${name} (artifactapi)
-baseurl=${isLocal ? `${url}/api/v2/remotes/${name}/files/` : `${proxy}/`}
-enabled=1
-gpgcheck=0
-repo_gpgcheck=0
-EOF
-
-sudo dnf install <package>`,
-          note: isLocal
-            ? 'gpgcheck=0: artifactapi serves the repo unsigned. If you sign your RPMs, import your key and set gpgcheck=1.'
-            : 'gpgcheck=0 trusts upstream over the proxy. To verify package signatures, import the upstream GPG key and set gpgcheck=1.',
-        },
-        ...(isLocal
-          ? [
-              {
-                title: 'Publish an RPM (repodata regenerates automatically)',
-                language: 'bash',
-                code: `curl -fsSL --upload-file ./my-package-1.0-1.el9.x86_64.rpm \\
-  ${url}/api/v2/remotes/${name}/files/my-package-1.0-1.el9.x86_64.rpm`,
-              },
-            ]
-          : []),
-      ];
-
-    case 'pypi':
-      return [
-        {
-          title: 'Install a package (one-off)',
-          language: 'bash',
-          code: `pip install --index-url ${proxy}/simple/ <package>`,
-        },
-        {
-          title: 'Configure pip persistently',
-          language: 'bash',
-          code: `mkdir -p ~/.config/pip
-cat > ~/.config/pip/pip.conf <<'EOF'
-[global]
-index-url = ${proxy}/simple/
-EOF
-
-pip install <package>`,
-        },
-      ];
-
-    case 'npm':
-      return [
-        {
-          title: 'Point npm at this registry',
-          language: 'bash',
-          code: `npm config set registry ${proxy}/
-npm install <package>`,
-        },
-        {
-          title: 'Per-project (.npmrc)',
-          language: 'bash',
-          code: `echo 'registry=${proxy}/' >> .npmrc
-npm install`,
-        },
-      ];
-
-    case 'docker':
-      return [
-        {
-          title: 'Pull an image',
-          language: 'bash',
-          code: `docker pull ${host}/${name}/<image>:<tag>`,
-          note: 'The first path segment after the host is the artifactapi repo name; the rest is the image name.',
-        },
-        ...(isLocal
-          ? [
-              {
-                title: 'Push an image (this is a real Registry V2)',
-                language: 'bash',
-                code: `docker tag myapp:latest ${host}/${name}/myapp:latest
-docker push        ${host}/${name}/myapp:latest`,
-                note: 'Works with docker, podman, skopeo and buildah. If the registry requires auth, run `docker login ' + host + '` first.',
-              },
-            ]
-          : []),
-      ];
-
-    case 'terraform':
-      return [
-        {
-          title: 'Use as a provider source (bare address, no mirror config)',
-          language: 'hcl',
-          code: `terraform {
-  required_providers {
-    ${name} = {
-      source  = "${host}/${name}/<type>"
-      version = ">= 0.1.0"
-    }
-  }
-}`,
-          note: 'The namespace segment is this repo name; <type> is the provider type. artifactapi signs SHA256SUMS server-side with its GPG key, so `terraform init` installs with no .terraformrc.',
-        },
-        ...(isLocal
-          ? [
-              {
-                title: 'Publish a provider build',
-                language: 'bash',
-                code: `curl -fsSL --upload-file terraform-provider-<type>_0.1.0_linux_amd64.zip \\
-  ${url}/api/v2/remotes/${name}/files/${name}/<type>/terraform-provider-<type>_0.1.0_linux_amd64.zip`,
-              },
-            ]
-          : []),
-      ];
-
-    case 'helm':
-      return [
-        {
-          title: 'Add the Helm repo',
-          language: 'bash',
-          code: `helm repo add ${name} ${proxy}/
-helm repo update
-helm install <release> ${name}/<chart>`,
-        },
-      ];
-
-    case 'alpine':
-      return isLocal
-        ? [
-            {
-              title: 'Add the apk repo (real apk repo, APKINDEX auto-generated)',
-              language: 'bash',
-              code: `echo '${url}/api/v1/local/${name}' | sudo tee -a /etc/apk/repositories
-sudo apk update --allow-untrusted
-sudo apk add --allow-untrusted <package>`,
-              note: `Served unsigned (parity with the rpm repo's gpgcheck=0) — use --allow-untrusted, or install a signing key. apk fetches <arch>/APKINDEX.tar.gz under this base.`,
-            },
-            {
-              title: 'Publish a .apk (index regenerates automatically)',
-              language: 'bash',
-              code: `curl -fsSL --upload-file ./mypkg-1.0-r0.apk \\
-  ${url}/api/v2/remotes/${name}/files/x86_64/mypkg-1.0-r0.apk`,
-              note: 'Upload each package at <arch>/<name>-<version>.apk — apk reconstructs that exact path from the index (APKINDEX carries no filename), so a mismatched path will 404 on install.',
-            },
-          ]
-        : [
-            {
-              title: 'Add the APK repository',
-              language: 'bash',
-              code: `echo '${proxy}/' | sudo tee -a /etc/apk/repositories
-sudo apk update
-sudo apk add <package>`,
-              note: 'If the index is unsigned over the proxy, add --allow-untrusted or install the signing key into /etc/apk/keys.',
-            },
-          ];
-
-    case 'github_alpine':
-      return [
-        {
-          title: 'Add the apk repo (metadata-only, from GitHub releases)',
-          language: 'bash',
-          code: `echo '${proxy}' | sudo tee -a /etc/apk/repositories
-sudo apk update --allow-untrusted
-sudo apk add --allow-untrusted <package>`,
-          note: "The per-arch APKINDEX is synthesized from the configured GitHub repo's release .apk assets; package downloads are redirected to the backing releases remote. Served unsigned, so --allow-untrusted.",
-        },
-      ];
-
-    case 'goproxy':
-      return [
-        {
-          title: 'Point the Go module proxy here',
-          language: 'bash',
-          code: `export GOPROXY=${proxy}
-go mod download`,
-          note: 'Append ,direct to fall back to VCS for modules this proxy does not cover.',
-        },
-      ];
-
-    case 'cargo':
-      return [
-        {
-          title: 'Point crates.io at this sparse registry',
-          language: 'toml',
-          code: `# ~/.cargo/config.toml
-[source.crates-io]
-replace-with = "${name}"
-
-[registries.${name}]
-index = "sparse+${proxy}/"`,
-          note: 'config.json is served by artifactapi so crate downloads also go through this remote.',
-        },
-      ];
-
-    case 'ansible':
-      return [
-        {
-          title: 'Install collections through this Galaxy proxy',
-          language: 'bash',
-          code: `ansible-galaxy collection install community.general -s ${proxy}/api/`,
-        },
-      ];
-
-    case 'nuget':
-      return [
-        {
-          title: 'Use this feed instead of nuget.org',
-          language: 'xml',
-          code: `<!-- nuget.config -->
-<configuration>
-  <packageSources>
-    <clear />
-    <add key="${name}" value="${proxy}/index.json" protocolVersion="3" />
-  </packageSources>
-</configuration>`,
-          note: 'Serve artifactapi over HTTPS: NuGet rejects the repository signatures resource over plain HTTP.',
-        },
-      ];
-
-    case 'puppet':
-      return [
-        {
-          title: 'Install a module from the Forge proxy',
-          language: 'bash',
-          code: `puppet module install <author>-<module> \\
-  --module_repository ${proxy}`,
-        },
-      ];
-
-    case 'deb':
-      return isLocal
-        ? [
-            {
-              title: 'Add the apt repo (real apt repo, flat — Packages/Release auto-generated)',
-              language: 'bash',
-              code: `echo 'deb [trusted=yes] ${url}/api/v1/local/${name}/ ./' | sudo tee /etc/apt/sources.list.d/${name}.list
-sudo apt-get update
-sudo apt-get install <package>`,
-              note: '[trusted=yes]: artifactapi serves the flat repo unsigned (matches the rpm repo\'s gpgcheck=0). The `./` is the flat-repo suite — apt fetches Packages/Release from the repo root.',
-            },
-            {
-              title: 'Publish a .deb (index regenerates automatically)',
-              language: 'bash',
-              code: `curl -fsSL --upload-file ./my-package_1.0_amd64.deb \\
-  ${url}/api/v2/remotes/${name}/files/my-package_1.0_amd64.deb`,
-            },
-          ]
-        : [
-            {
-              title: 'Add the apt repo (caching proxy)',
-              language: 'bash',
-              code: `echo 'deb ${proxy} <suite> <component>' | sudo tee /etc/apt/sources.list.d/${name}.list
-sudo apt-get update
-sudo apt-get install <package>`,
-              note: "Signatures are verified against the upstream mirror's real signed Release through the proxy (no [trusted=yes] needed). Example suite/component: bookworm main.",
-            },
-          ];
-
-    case 'github_deb':
-      return [
-        {
-          title: 'Add the apt repo (metadata-only, from GitHub releases)',
-          language: 'bash',
-          code: `echo 'deb [trusted=yes] ${proxy}/ ./' | sudo tee /etc/apt/sources.list.d/${name}.list
-sudo apt-get update
-sudo apt-get install <package>`,
-          note: "The apt index is synthesized from the configured GitHub repo's release .deb assets; package downloads are redirected to the backing releases remote. Served unsigned, so [trusted=yes].",
-        },
-      ];
-
-    case 'generic':
-    default:
-      return [
-        {
-          title: 'Download a file',
-          language: 'bash',
-          code: `curl -fsSLO ${proxy}/<path>`,
-          note:
-            packageType === 'generic'
-              ? 'Generic repos are fetched as plain files at their upstream path.'
-              : `No tailored client instructions for "${packageType}" yet — fetch artifacts directly by path.`,
-        },
-        ...(isLocal
-          ? [
-              {
-                title: 'Publish a file',
-                language: 'bash',
-                code: `curl -fsSL --upload-file ./myfile \\
-  ${url}/api/v2/remotes/${name}/files/<path>/myfile`,
-              },
-            ]
-          : []),
-      ];
-  }
+  const def = packageTypes[packageType] ?? packageTypes.generic;
+  return def.snippets({ packageType, name, url, host, proxy, isLocal });
 }
 
 function CodeBox({ snippet }: { snippet: Snippet }) {
diff --git a/ui/src/packagetypes/defs/alpine.ts b/ui/src/packagetypes/defs/alpine.ts
new file mode 100644
index 0000000..fc70a84
--- /dev/null
+++ b/ui/src/packagetypes/defs/alpine.ts
@@ -0,0 +1,37 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'green',
+  snippets: ({ name, url, proxy, isLocal }) => {
+    return isLocal
+      ? [
+          {
+            title: 'Add the apk repo (real apk repo, APKINDEX auto-generated)',
+            language: 'bash',
+            code: `echo '${url}/api/v1/local/${name}' | sudo tee -a /etc/apk/repositories
+sudo apk update --allow-untrusted
+sudo apk add --allow-untrusted <package>`,
+            note: `Served unsigned (parity with the rpm repo's gpgcheck=0) — use --allow-untrusted, or install a signing key. apk fetches <arch>/APKINDEX.tar.gz under this base.`,
+          },
+          {
+            title: 'Publish a .apk (index regenerates automatically)',
+            language: 'bash',
+            code: `curl -fsSL --upload-file ./mypkg-1.0-r0.apk \\
+  ${url}/api/v2/remotes/${name}/files/x86_64/mypkg-1.0-r0.apk`,
+            note: 'Upload each package at <arch>/<name>-<version>.apk — apk reconstructs that exact path from the index (APKINDEX carries no filename), so a mismatched path will 404 on install.',
+          },
+        ]
+      : [
+          {
+            title: 'Add the APK repository',
+            language: 'bash',
+            code: `echo '${proxy}/' | sudo tee -a /etc/apk/repositories
+sudo apk update
+sudo apk add <package>`,
+            note: 'If the index is unsigned over the proxy, add --allow-untrusted or install the signing key into /etc/apk/keys.',
+          },
+        ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/ansible.ts b/ui/src/packagetypes/defs/ansible.ts
new file mode 100644
index 0000000..653b9ed
--- /dev/null
+++ b/ui/src/packagetypes/defs/ansible.ts
@@ -0,0 +1,16 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'red',
+  snippets: ({ proxy }) => {
+    return [
+      {
+        title: 'Install collections through this Galaxy proxy',
+        language: 'bash',
+        code: `ansible-galaxy collection install community.general -s ${proxy}/api/`,
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/cargo.ts b/ui/src/packagetypes/defs/cargo.ts
new file mode 100644
index 0000000..af4f5da
--- /dev/null
+++ b/ui/src/packagetypes/defs/cargo.ts
@@ -0,0 +1,22 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'yellow',
+  snippets: ({ name, proxy }) => {
+    return [
+      {
+        title: 'Point crates.io at this sparse registry',
+        language: 'toml',
+        code: `# ~/.cargo/config.toml
+[source.crates-io]
+replace-with = "${name}"
+
+[registries.${name}]
+index = "sparse+${proxy}/"`,
+        note: 'config.json is served by artifactapi so crate downloads also go through this remote.',
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/deb.ts b/ui/src/packagetypes/defs/deb.ts
new file mode 100644
index 0000000..644dd3e
--- /dev/null
+++ b/ui/src/packagetypes/defs/deb.ts
@@ -0,0 +1,35 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  snippets: ({ name, url, proxy, isLocal }) => {
+    return isLocal
+      ? [
+          {
+            title: 'Add the apt repo (real apt repo, flat — Packages/Release auto-generated)',
+            language: 'bash',
+            code: `echo 'deb [trusted=yes] ${url}/api/v1/local/${name}/ ./' | sudo tee /etc/apt/sources.list.d/${name}.list
+sudo apt-get update
+sudo apt-get install <package>`,
+            note: '[trusted=yes]: artifactapi serves the flat repo unsigned (matches the rpm repo\'s gpgcheck=0). The `./` is the flat-repo suite — apt fetches Packages/Release from the repo root.',
+          },
+          {
+            title: 'Publish a .deb (index regenerates automatically)',
+            language: 'bash',
+            code: `curl -fsSL --upload-file ./my-package_1.0_amd64.deb \\
+  ${url}/api/v2/remotes/${name}/files/my-package_1.0_amd64.deb`,
+          },
+        ]
+      : [
+          {
+            title: 'Add the apt repo (caching proxy)',
+            language: 'bash',
+            code: `echo 'deb ${proxy} <suite> <component>' | sudo tee /etc/apt/sources.list.d/${name}.list
+sudo apt-get update
+sudo apt-get install <package>`,
+            note: "Signatures are verified against the upstream mirror's real signed Release through the proxy (no [trusted=yes] needed). Example suite/component: bookworm main.",
+          },
+        ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/docker.ts b/ui/src/packagetypes/defs/docker.ts
new file mode 100644
index 0000000..6a3ef9e
--- /dev/null
+++ b/ui/src/packagetypes/defs/docker.ts
@@ -0,0 +1,28 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'blue',
+  snippets: ({ name, host, isLocal }) => {
+    return [
+      {
+        title: 'Pull an image',
+        language: 'bash',
+        code: `docker pull ${host}/${name}/<image>:<tag>`,
+        note: 'The first path segment after the host is the artifactapi repo name; the rest is the image name.',
+      },
+      ...(isLocal
+        ? [
+            {
+              title: 'Push an image (this is a real Registry V2)',
+              language: 'bash',
+              code: `docker tag myapp:latest ${host}/${name}/myapp:latest
+docker push        ${host}/${name}/myapp:latest`,
+              note: 'Works with docker, podman, skopeo and buildah. If the registry requires auth, run `docker login ' + host + '` first.',
+            },
+          ]
+        : []),
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/gems.ts b/ui/src/packagetypes/defs/gems.ts
new file mode 100644
index 0000000..68cbffb
--- /dev/null
+++ b/ui/src/packagetypes/defs/gems.ts
@@ -0,0 +1,36 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'red',
+  snippets: ({ name, url, proxy, isLocal }) => {
+    if (isLocal) {
+      const src = `${url}/api/v1/local/${name}`;
+      return [
+        {
+          title: 'Push and yank',
+          language: 'bash',
+          code: `GEM_HOST_API_KEY=unused gem push --host ${src} <gem>-<version>.gem
+GEM_HOST_API_KEY=unused gem yank <gem> -v <version> --host ${src}`,
+          note: 'gem push needs an API key; any value works. Pushing an existing version is rejected.',
+        },
+        {
+          title: 'Install',
+          language: 'bash',
+          code: `gem install <gem> --source ${src}/
+# Gemfile
+source "${src}/"`,
+        },
+      ];
+    }
+    return [
+      {
+        title: 'Use this remote as the RubyGems source',
+        language: 'bash',
+        code: `gem sources --clear-all --add ${proxy}/
+bundle config mirror.https://rubygems.org ${proxy}`,
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/generic.ts b/ui/src/packagetypes/defs/generic.ts
new file mode 100644
index 0000000..40939d5
--- /dev/null
+++ b/ui/src/packagetypes/defs/generic.ts
@@ -0,0 +1,30 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'default',
+  snippets: ({ packageType, name, url, proxy, isLocal }) => {
+    return [
+      {
+        title: 'Download a file',
+        language: 'bash',
+        code: `curl -fsSLO ${proxy}/<path>`,
+        note:
+          packageType === 'generic'
+            ? 'Generic repos are fetched as plain files at their upstream path.'
+            : `No tailored client instructions for "${packageType}" yet — fetch artifacts directly by path.`,
+      },
+      ...(isLocal
+        ? [
+            {
+              title: 'Publish a file',
+              language: 'bash',
+              code: `curl -fsSL --upload-file ./myfile \\
+  ${url}/api/v2/remotes/${name}/files/<path>/myfile`,
+            },
+          ]
+        : []),
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/github_alpine.ts b/ui/src/packagetypes/defs/github_alpine.ts
new file mode 100644
index 0000000..bd32c97
--- /dev/null
+++ b/ui/src/packagetypes/defs/github_alpine.ts
@@ -0,0 +1,18 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  snippets: ({ proxy }) => {
+    return [
+      {
+        title: 'Add the apk repo (metadata-only, from GitHub releases)',
+        language: 'bash',
+        code: `echo '${proxy}' | sudo tee -a /etc/apk/repositories
+sudo apk update --allow-untrusted
+sudo apk add --allow-untrusted <package>`,
+        note: "The per-arch APKINDEX is synthesized from the configured GitHub repo's release .apk assets; package downloads are redirected to the backing releases remote. Served unsigned, so --allow-untrusted.",
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/github_deb.ts b/ui/src/packagetypes/defs/github_deb.ts
new file mode 100644
index 0000000..63b8bc7
--- /dev/null
+++ b/ui/src/packagetypes/defs/github_deb.ts
@@ -0,0 +1,18 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  snippets: ({ name, proxy }) => {
+    return [
+      {
+        title: 'Add the apt repo (metadata-only, from GitHub releases)',
+        language: 'bash',
+        code: `echo 'deb [trusted=yes] ${proxy}/ ./' | sudo tee /etc/apt/sources.list.d/${name}.list
+sudo apt-get update
+sudo apt-get install <package>`,
+        note: "The apt index is synthesized from the configured GitHub repo's release .deb assets; package downloads are redirected to the backing releases remote. Served unsigned, so [trusted=yes].",
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/goproxy.ts b/ui/src/packagetypes/defs/goproxy.ts
new file mode 100644
index 0000000..44c803b
--- /dev/null
+++ b/ui/src/packagetypes/defs/goproxy.ts
@@ -0,0 +1,18 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'green',
+  snippets: ({ proxy }) => {
+    return [
+      {
+        title: 'Point the Go module proxy here',
+        language: 'bash',
+        code: `export GOPROXY=${proxy}
+go mod download`,
+        note: 'Append ,direct to fall back to VCS for modules this proxy does not cover.',
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/helm.ts b/ui/src/packagetypes/defs/helm.ts
new file mode 100644
index 0000000..c2f9ea6
--- /dev/null
+++ b/ui/src/packagetypes/defs/helm.ts
@@ -0,0 +1,29 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'green',
+  snippets: ({ name, url, proxy, isLocal }) => {
+    return [
+      {
+        title: isLocal ? 'Add the Helm repo (index.yaml auto-generated)' : 'Add the Helm repo',
+        language: 'bash',
+        code: `helm repo add ${name} ${isLocal ? `${url}/api/v1/local/${name}` : proxy}/
+helm repo update
+helm install <release> ${name}/<chart>`,
+      },
+      ...(isLocal
+        ? [
+            {
+              title: 'Publish a chart',
+              language: 'bash',
+              code: `helm package ./mychart
+curl -fsSL --upload-file mychart-0.1.0.tgz \\
+  ${url}/api/v2/remotes/${name}/files/mychart-0.1.0.tgz`,
+            },
+          ]
+        : []),
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/npm.ts b/ui/src/packagetypes/defs/npm.ts
new file mode 100644
index 0000000..a10af90
--- /dev/null
+++ b/ui/src/packagetypes/defs/npm.ts
@@ -0,0 +1,44 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'red',
+  snippets: ({ name, url, host, proxy, isLocal }) => {
+    if (isLocal) {
+      const reg = `${url}/api/v1/local/${name}/`;
+      return [
+        {
+          title: 'Configure .npmrc (registry + publish token)',
+          language: 'bash',
+          code: `cat >> .npmrc <<'EOF'
+registry=${reg}
+//${host}/api/v1/local/${name}/:_authToken=unused
+EOF`,
+          note: 'npm refuses to publish without an _authToken for the registry; any value works. For a scope only, use @<scope>:registry=… instead of registry=.',
+        },
+        {
+          title: 'Publish and install',
+          language: 'bash',
+          code: `npm publish
+npm install <package>`,
+          note: 'Versions are immutable: republishing an existing version is rejected. The dist-tags sent with the publish (latest, or --tag) move to the new version.',
+        },
+      ];
+    }
+    return [
+      {
+        title: 'Point npm at this registry',
+        language: 'bash',
+        code: `npm config set registry ${proxy}/
+npm install <package>`,
+      },
+      {
+        title: 'Per-project (.npmrc)',
+        language: 'bash',
+        code: `echo 'registry=${proxy}/' >> .npmrc
+npm install`,
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/nuget.ts b/ui/src/packagetypes/defs/nuget.ts
new file mode 100644
index 0000000..ba70200
--- /dev/null
+++ b/ui/src/packagetypes/defs/nuget.ts
@@ -0,0 +1,23 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'blue',
+  snippets: ({ name, proxy }) => {
+    return [
+      {
+        title: 'Use this feed instead of nuget.org',
+        language: 'xml',
+        code: `<!-- nuget.config -->
+<configuration>
+  <packageSources>
+    <clear />
+    <add key="${name}" value="${proxy}/index.json" protocolVersion="3" />
+  </packageSources>
+</configuration>`,
+        note: 'Serve artifactapi over HTTPS: NuGet rejects the repository signatures resource over plain HTTP.',
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/puppet.ts b/ui/src/packagetypes/defs/puppet.ts
new file mode 100644
index 0000000..99f7d6c
--- /dev/null
+++ b/ui/src/packagetypes/defs/puppet.ts
@@ -0,0 +1,27 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'yellow',
+  snippets: ({ name, url, proxy, isLocal }) => {
+    return [
+      {
+        title: isLocal ? 'Install a module from this forge' : 'Install a module from the Forge proxy',
+        language: 'bash',
+        code: `puppet module install <author>-<module> \\
+  --module_repository ${isLocal ? `${url}/api/v1/local/${name}` : proxy}`,
+      },
+      ...(isLocal
+        ? [
+            {
+              title: 'Publish a module (versions are immutable)',
+              language: 'bash',
+              code: `puppet module build && curl -fsSL --upload-file pkg/<author>-<module>-<version>.tar.gz \\
+  ${url}/api/v2/remotes/${name}/files/<author>-<module>-<version>.tar.gz`,
+            },
+          ]
+        : []),
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/pypi.ts b/ui/src/packagetypes/defs/pypi.ts
new file mode 100644
index 0000000..003ce9c
--- /dev/null
+++ b/ui/src/packagetypes/defs/pypi.ts
@@ -0,0 +1,27 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'blue',
+  snippets: ({ proxy }) => {
+    return [
+      {
+        title: 'Install a package (one-off)',
+        language: 'bash',
+        code: `pip install --index-url ${proxy}/simple/ <package>`,
+      },
+      {
+        title: 'Configure pip persistently',
+        language: 'bash',
+        code: `mkdir -p ~/.config/pip
+cat > ~/.config/pip/pip.conf <<'EOF'
+[global]
+index-url = ${proxy}/simple/
+EOF
+
+pip install <package>`,
+      },
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/rpm.ts b/ui/src/packagetypes/defs/rpm.ts
new file mode 100644
index 0000000..d83e813
--- /dev/null
+++ b/ui/src/packagetypes/defs/rpm.ts
@@ -0,0 +1,40 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'yellow',
+  snippets: ({ name, url, proxy, isLocal }) => {
+    return [
+      {
+        title: isLocal
+          ? 'Add the yum repo (real yum repo, repodata auto-regenerated)'
+          : 'Add the yum repo (caching proxy)',
+        language: 'bash',
+        code: `sudo tee /etc/yum.repos.d/${name}.repo >/dev/null <<'EOF'
+[${name}]
+name=${name} (artifactapi)
+baseurl=${isLocal ? `${url}/api/v2/remotes/${name}/files/` : `${proxy}/`}
+enabled=1
+gpgcheck=0
+repo_gpgcheck=0
+EOF
+
+sudo dnf install <package>`,
+        note: isLocal
+          ? 'gpgcheck=0: artifactapi serves the repo unsigned. If you sign your RPMs, import your key and set gpgcheck=1.'
+          : 'gpgcheck=0 trusts upstream over the proxy. To verify package signatures, import the upstream GPG key and set gpgcheck=1.',
+      },
+      ...(isLocal
+        ? [
+            {
+              title: 'Publish an RPM (repodata regenerates automatically)',
+              language: 'bash',
+              code: `curl -fsSL --upload-file ./my-package-1.0-1.el9.x86_64.rpm \\
+  ${url}/api/v2/remotes/${name}/files/my-package-1.0-1.el9.x86_64.rpm`,
+            },
+          ]
+        : []),
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/defs/terraform.ts b/ui/src/packagetypes/defs/terraform.ts
new file mode 100644
index 0000000..07cf3e1
--- /dev/null
+++ b/ui/src/packagetypes/defs/terraform.ts
@@ -0,0 +1,34 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'blue',
+  snippets: ({ name, url, host, isLocal }) => {
+    return [
+      {
+        title: 'Use as a provider source (bare address, no mirror config)',
+        language: 'hcl',
+        code: `terraform {
+  required_providers {
+    ${name} = {
+      source  = "${host}/${name}/<type>"
+      version = ">= 0.1.0"
+    }
+  }
+}`,
+        note: 'The namespace segment is this repo name; <type> is the provider type. artifactapi signs SHA256SUMS server-side with its GPG key, so `terraform init` installs with no .terraformrc.',
+      },
+      ...(isLocal
+        ? [
+            {
+              title: 'Publish a provider build',
+              language: 'bash',
+              code: `curl -fsSL --upload-file terraform-provider-<type>_0.1.0_linux_amd64.zip \\
+  ${url}/api/v2/remotes/${name}/files/${name}/<type>/terraform-provider-<type>_0.1.0_linux_amd64.zip`,
+            },
+          ]
+        : []),
+    ];
+  },
+};
+
+export default def;
diff --git a/ui/src/packagetypes/index.ts b/ui/src/packagetypes/index.ts
new file mode 100644
index 0000000..e638865
--- /dev/null
+++ b/ui/src/packagetypes/index.ts
@@ -0,0 +1,11 @@
+import type { BadgeColor, PackageTypeUI } from './types';
+
+const defs = import.meta.glob<PackageTypeUI>('./defs/*.ts', { eager: true, import: 'default' });
+
+export const packageTypes: Record<string, PackageTypeUI> = Object.fromEntries(
+  Object.entries(defs).map(([path, def]) => [path.slice('./defs/'.length, -'.ts'.length), def]),
+);
+
+export function typeColor(packageType: string): BadgeColor {
+  return packageTypes[packageType]?.color || 'default';
+}
diff --git a/ui/src/packagetypes/types.ts b/ui/src/packagetypes/types.ts
new file mode 100644
index 0000000..bc4fbb5
--- /dev/null
+++ b/ui/src/packagetypes/types.ts
@@ -0,0 +1,27 @@
+// repoClass distinguishes the three ways a repository is consumed. remotes are
+// caching proxies, locals are real registries you also publish to, virtuals are
+// merged read-only indexes.
+export type RepoClass = 'remote' | 'local' | 'virtual';
+
+export interface Snippet {
+  title: string;
+  language: string;
+  code: string;
+  note?: string;
+}
+
+export interface SnippetContext {
+  packageType: string;
+  name: string;
+  url: string;
+  host: string;
+  proxy: string;
+  isLocal: boolean;
+}
+
+export type BadgeColor = 'blue' | 'green' | 'yellow' | 'red' | 'default';
+
+export interface PackageTypeUI {
+  color?: BadgeColor;
+  snippets: (ctx: SnippetContext) => Snippet[];
+}
diff --git a/ui/src/pages/Locals.tsx b/ui/src/pages/Locals.tsx
index ba895ee..01ebae9 100644
--- a/ui/src/pages/Locals.tsx
+++ b/ui/src/pages/Locals.tsx
@@ -4,23 +4,9 @@ import { api } from '../api/client';
 import type { Remote } from '../api/types';
 import { Badge } from '../components/Badge';
 import { DataTable } from '../components/DataTable';
+import { typeColor } from '../packagetypes';
 import './Remotes.css';
 
-const typeColors: Record<string, 'blue' | 'green' | 'yellow' | 'red' | 'default'> = {
-  docker: 'blue',
-  helm: 'green',
-  rpm: 'yellow',
-  pypi: 'blue',
-  npm: 'red',
-  generic: 'default',
-  alpine: 'green',
-  puppet: 'yellow',
-  terraform: 'blue',
-  goproxy: 'green',
-  cargo: 'yellow',
-  nuget: 'blue',
-};
-
 export function Locals() {
   const navigate = useNavigate();
   const [remotes, setRemotes] = useState<Remote[]>([]);
@@ -66,7 +52,7 @@ export function Locals() {
               key: 'type',
               header: 'Type',
               render: (r: Remote) => (
-                <Badge variant={typeColors[r.package_type] || 'default'}>
+                <Badge variant={typeColor(r.package_type)}>
                   {r.package_type}
                 </Badge>
               ),
diff --git a/ui/src/pages/Remotes.tsx b/ui/src/pages/Remotes.tsx
index 0fcbd44..53bfe63 100644
--- a/ui/src/pages/Remotes.tsx
+++ b/ui/src/pages/Remotes.tsx
@@ -4,24 +4,9 @@ import { api } from '../api/client';
 import type { Remote } from '../api/types';
 import { Badge } from '../components/Badge';
 import { DataTable } from '../components/DataTable';
+import { typeColor } from '../packagetypes';
 import './Remotes.css';
 
-const typeColors: Record<string, 'blue' | 'green' | 'yellow' | 'red' | 'default'> = {
-  docker: 'blue',
-  helm: 'green',
-  rpm: 'yellow',
-  pypi: 'blue',
-  npm: 'red',
-  generic: 'default',
-  alpine: 'green',
-  puppet: 'yellow',
-  terraform: 'blue',
-  goproxy: 'green',
-  cargo: 'yellow',
-  ansible: 'red',
-  nuget: 'blue',
-};
-
 export function Remotes() {
   const navigate = useNavigate();
   const [remotes, setRemotes] = useState<Remote[]>([]);
@@ -82,7 +67,7 @@ export function Remotes() {
               key: 'type',
               header: 'Type',
               render: (r: Remote) => (
-                <Badge variant={typeColors[r.package_type] || 'default'}>
+                <Badge variant={typeColor(r.package_type)}>
                   {r.package_type}
                 </Badge>
               ),