Add vcs remote type (#162 )

The generic `github` remote only allowlists URL patterns: every repo needs hand-written mutable patterns for branch archives, and a moved branch re-downloads the whole archive under a ref-named key. - add `vcs` package type for GitHub or Gitea (picked from `base_url`) tag, commit and release-download paths, cached immutable - redirect `archive/refs/heads/<branch>` to the commit archive, resolving the branch via the branch API with one shared, per-remote bounded lookup cache reused for `mutable_ttl` - cache missing branches for at least 60s and map API rate limits to `503` with `Retry-After` - reject any other path shape, escaping segments and denied redirect targets - add `docs/vcs/remote.md`, a UI type def and a vcs e2e caching case Reviewed-on: #162 Co-authored-by: unkin-agent <unkin-agent@unkin.net> Co-committed-by: unkin-agent <unkin-agent@unkin.net>
Add deb virtual repositories (#138 )
2026-10-24 17:21:05 +11:00 · 2026-10-24 16:21:33 +11:00
17 changed files with 1602 additions and 14 deletions
@@ -29,7 +29,7 @@ Each type's paths, Terraform examples and local/virtual behaviour are in `docs/<
 - `alpine`: [remote](docs/alpine/remote.md), [remote-github](docs/alpine/remote-github.md)
 - `ansible`: [remote](docs/ansible/remote.md), [local](docs/ansible/local.md), [virtual](docs/ansible/virtual.md)
 - `cargo`: [remote](docs/cargo/remote.md)
- `deb`: [remote](docs/deb/remote.md), [remote-github](docs/deb/remote-github.md)
+- `deb`: [remote](docs/deb/remote.md), [remote-github](docs/deb/remote-github.md), [virtual](docs/deb/virtual.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)
@@ -41,6 +41,7 @@ Each type's paths, Terraform examples and local/virtual behaviour are in `docs/<
 - `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)
+- `vcs`: [remote](docs/vcs/remote.md)

 ### GitHub authentication

@@ -98,4 +98,4 @@ Each type's page lists its auto-detected mutable and immutable paths:
 [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).
+[rpm github](../rpm/remote-github.md), [terraform](../terraform/remote.md), [vcs](../vcs/remote.md).
@@ -0,0 +1,32 @@
+# `deb` virtual
+
+A deb virtual serves one apt source over local and remote deb members at
+`/api/v1/virtual/<name>/`, in either the flat (`./`) or `dists/<suite>` layout.
+
+- Packages indexes are merged; on a duplicate (Package, Version, Architecture)
+  the earlier member wins.
+- The Release is generated unsigned with `Acquire-By-Hash: yes`; indexes are
+  served by name and by SHA256 from the current and previous merge.
+- `Filename` points at the virtual (`<member>/<path>`), which 302s to the
+  owning member.
+- All members must share one layout; mixing flat and suite members is
+  unsupported (suite requests fail with 502).
+- A member error fails the request with 502. Merges are cached for 60s per
+  suite, up to 32 suites per virtual.
+
+```hcl
+resource "artifactapi_virtual" "deb" {
+  name         = "deb"
+  package_type = "deb"
+  members      = [artifactapi_local_deb.internal.name, artifactapi_remote_github_deb.tool.name]
+}
+```
+
+```
+# /etc/apt/sources.list.d/artifactapi.list (flat)
+deb [trusted=yes] https://artifactapi.example.com/api/v1/virtual/deb/ ./
+# suite layout
+deb [trusted=yes] https://artifactapi.example.com/api/v1/virtual/debian/ trixie main
+```
+
+Upload to the local member directly; the virtual is read-only.
@@ -0,0 +1,29 @@
+# `vcs` remote
+
+Shared classification, TTL and eviction rules: [caching](../common/caching.md).
+
+Caches source archives and release assets from GitHub (`base_url = "https://github.com"`) or Gitea (any other `base_url`). GitHub Enterprise is not supported: a non-github.com host is treated as Gitea. Only the paths below are served; anything else is a 404.
+
+| Path | Behaviour |
+|---|---|
+| `<owner>/<repo>/archive/refs/tags/<tag>.(tar.gz\|zip)` | immutable |
+| `<owner>/<repo>/archive/<40-char sha>.(tar.gz\|zip)` | immutable |
+| `<owner>/<repo>/releases/download/<tag>/<asset>` | immutable |
+| `<owner>/<repo>/releases/latest/download/<asset>` | mutable |
+| `<owner>/<repo>/archive/refs/heads/<branch>.(tar.gz\|zip)` | `302` to the archive of the branch's current commit, resolved via the provider's branch API and reused for `mutable_ttl` |
+
+Branch archives redirect, so `curl` needs `-L`; pip and npm follow redirects. The archive is the host's commit archive (GitHub names its top-level directory `<repo>-<sha>`). `patterns` and `blocklist` match both the branch path and the commit path it redirects to, so allowlist repos by prefix (`^cli/cli/`); a branch whose commit path is denied is a `403`. A missing branch is a `404`, cached for `mutable_ttl` (at least 60s). An API rate limit (`429`, or `403` with rate-limit headers) is a `503` with `Retry-After`, unless `stale_on_error` serves the last known commit. Each remote caches up to 4096 branch lookups. GitHub API calls use the [server GitHub credential](../../README.md#github-authentication); Gitea API calls use the remote's `username`/`password`.
+
+```hcl
+resource "artifactapi_remote_vcs" "github" {
+  name        = "github-vcs"
+  base_url    = "https://github.com"
+  mutable_ttl = 600
+  patterns    = ["^cli/cli/", "^psf/requests/"]
+}
+```
+
+```bash
+curl -fsSLO https://artifactapi.example/api/v1/remote/github-vcs/cli/cli/archive/refs/tags/v2.60.0.tar.gz
+pip install https://artifactapi.example/api/v1/remote/github-vcs/psf/requests/archive/refs/tags/v2.32.3.tar.gz
+```
@@ -0,0 +1,7 @@
+//go:build dockere2e
+
+package e2edocker
+
+func init() {
+	cachingCases = append(cachingCases, cachingCase{"vcs", "octo/repo/archive/refs/tags/v1.0.0.tar.gz", "octo/repo/archive/refs/tags/v1.0.0.tar.gz"})
+}
@@ -0,0 +1,115 @@
+//go:build dockere2e
+
+package e2edocker
+
+import (
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+)
+
+// TestVirtualDebMerge merges two local deb repos carrying the same package: the
+// first member wins the duplicate, and a real apt sees both members' packages
+// and installs through the virtual.
+func TestVirtualDebMerge(t *testing.T) {
+	createRepo(t, `{"name":"vdeb-a","package_type":"deb","repo_type":"local"}`)
+	createRepo(t, `{"name":"vdeb-b","package_type":"deb","repo_type":"local"}`)
+	defer deleteRepo(t, "vdeb-a")
+	defer deleteRepo(t, "vdeb-b")
+
+	uploadFile(t, "vdeb-a", "vdeb-one_1.0.0_amd64.deb", testsupport.MinimalDeb("vdeb-one", "1.0.0", "amd64"), "application/vnd.debian.binary-package")
+	uploadFile(t, "vdeb-b", "vdeb-one_1.0.0_amd64.deb", testsupport.MinimalDeb("vdeb-one", "1.0.0", "amd64"), "application/vnd.debian.binary-package")
+	uploadFile(t, "vdeb-b", "vdeb-two_2.0.0_amd64.deb", testsupport.MinimalDeb("vdeb-two", "2.0.0", "amd64"), "application/vnd.debian.binary-package")
+
+	// Local indexes regenerate asynchronously; merge only once vdeb-b lists both.
+	deadline := time.Now().Add(15 * time.Second)
+	for {
+		resp, body := doRequest(t, http.MethodGet, api("/api/v1/local/vdeb-b/Packages"), nil, "")
+		if resp.StatusCode == http.StatusOK && strings.Contains(string(body), "vdeb-two") || time.Now().After(deadline) {
+			break
+		}
+		time.Sleep(500 * time.Millisecond)
+	}
+
+	createVirtual(t, `{"name":"vdeb","package_type":"deb","members":["vdeb-a","vdeb-b"]}`)
+	defer deleteVirtual(t, "vdeb")
+
+	_, body := doRequest(t, http.MethodGet, api("/api/v1/virtual/vdeb/Packages"), nil, "")
+	pk := string(body)
+	if strings.Count(pk, "Package: vdeb-one\n") != 1 || !strings.Contains(pk, "Filename: vdeb-a/pool/vdeb-one_1.0.0_amd64.deb") ||
+		!strings.Contains(pk, "Filename: vdeb-b/pool/vdeb-two_2.0.0_amd64.deb") {
+		t.Fatalf("merged Packages should hold vdeb-one from the first member and vdeb-two:\n%s", pk)
+	}
+
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; skipping real apt")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+	script := "set -euo pipefail; " +
+		"rm -f /etc/apt/sources.list.d/*; " +
+		"echo \"deb [trusted=yes] $URL ./\" > /etc/apt/sources.list.d/vdeb.list; " +
+		"apt-get update; " +
+		"apt-cache policy vdeb-one vdeb-two | tee /dev/stderr | grep -c virtual/vdeb | grep -qx 2; " +
+		"apt-get install -y vdeb-one vdeb-two; " +
+		"dpkg -s vdeb-one vdeb-two"
+	out, err := exec.Command("docker", "run", "--rm", "--network", network,
+		"-e", "URL="+strings.TrimRight(internal, "/")+"/api/v1/virtual/vdeb/",
+		"debian:13", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("real apt against deb virtual failed: %v\n%s", err, out)
+	}
+}
+
+// TestVirtualDebSuite merges two proxied deb.debian.org remotes and drives a
+// real apt through the virtual's dists/<suite> layout (by-hash indexes).
+func TestVirtualDebSuite(t *testing.T) {
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; skipping real apt")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+	for _, n := range []string{"vdebs-a", "vdebs-b"} {
+		createRepo(t, `{"name":"`+n+`","package_type":"deb","repo_type":"remote","base_url":"http://deb.debian.org/debian"}`)
+		defer deleteRepo(t, n)
+	}
+	createVirtual(t, `{"name":"vdebs","package_type":"deb","members":["vdebs-a","vdebs-b"]}`)
+	defer deleteVirtual(t, "vdebs")
+
+	resp, rel := doRequest(t, http.MethodGet, api("/api/v1/virtual/vdebs/dists/trixie-updates/Release"), nil, "")
+	if resp.StatusCode != http.StatusOK || !strings.Contains(string(rel), "Acquire-By-Hash: yes\n") ||
+		!strings.Contains(string(rel), " main/binary-amd64/Packages.gz\n") {
+		t.Fatalf("merged suite Release: status %d:\n%s", resp.StatusCode, rel)
+	}
+
+	script := "set -euo pipefail; " +
+		"rm -f /etc/apt/sources.list.d/*; " +
+		"echo \"deb [trusted=yes] $URL trixie-updates main\" > /etc/apt/sources.list.d/vdebs.list; " +
+		"apt-get update; " +
+		"idx=/tmp/avail; apt-cache dumpavail > $idx; " +
+		"grep -q '^Filename: vdebs-a/pool/' $idx; if grep -q '^Filename: vdebs-b/' $idx; then echo 'vdebs-b not deduped'; exit 1; fi; " +
+		"pkg=$(awk '/^Package:/{p=$2} /^Size:/{if(!m||$2<m){m=$2;b=p}} END{print b}' $idx); " +
+		"cd /tmp && apt-get download $pkg && ls -l /tmp/*.deb"
+	out, err := exec.Command("docker", "run", "--rm", "--network", network,
+		"-e", "URL="+strings.TrimRight(internal, "/")+"/api/v1/virtual/vdebs/",
+		"debian:13", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("real apt against deb virtual suite failed: %v\n%s", err, out)
+	}
+	t.Logf("%s", out)
+	resp, _ = doRequest(t, http.MethodGet, api("/api/v1/remote/vdebs-a/dists/trixie-updates/main/binary-amd64/Packages.xz"), nil, "")
+	if src := resp.Header.Get("X-Artifact-Source"); resp.StatusCode != http.StatusOK || src != "cache" {
+		t.Fatalf("member index the virtual merged should be cached: status %d source %q", resp.StatusCode, src)
+	}
+}
@@ -0,0 +1,3 @@
+package all
+
+import _ "git.unkin.net/unkin/artifactapi/internal/provider/vcs"
@@ -71,7 +71,7 @@ func (p *Provider) AuthHeaders(ctx context.Context, remote models.Remote) (http.
 		h.Set("Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(remote.Username+":"+remote.Password)))
 		return h, nil
 	}
-	if isGitHubHost(remote.BaseURL) {
+	if IsGitHubHost(remote.BaseURL) {
 		if c := githubauth.Server(); c != nil {
 			tok, err := c.Token(ctx)
 			if err != nil {
@@ -85,11 +85,11 @@ func (p *Provider) AuthHeaders(ctx context.Context, remote models.Remote) (http.
 	return h, nil
 }

-// isGitHubHost reports whether rawURL targets a GitHub API/download host that
+// IsGitHubHost reports whether rawURL targets a GitHub API/download host that
 // accepts the server credential. objects.githubusercontent.com is deliberately
 // excluded: release-asset downloads 302-redirect there with a pre-signed URL
 // that must not carry an Authorization header.
-func isGitHubHost(rawURL string) bool {
+func IsGitHubHost(rawURL string) bool {
 	u, err := url.Parse(rawURL)
 	if err != nil {
 		return false
@@ -0,0 +1,309 @@
+// Package vcs caches source archives and release assets from GitHub or Gitea,
+// keyed by ref: tags, commits and release assets are immutable, and branch
+// archives redirect to the archive of the commit the branch currently points at.
+package vcs
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/sync/singleflight"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/provider/generic"
+	"git.unkin.net/unkin/artifactapi/internal/proxy"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func init() {
+	provider.Register(New())
+}
+
+type kind int
+
+const (
+	tagArchive kind = iota + 1
+	branchArchive
+	commitArchive
+	releaseAsset
+	latestReleaseAsset
+)
+
+// target is a parsed vcs request path.
+type target struct {
+	Kind        kind
+	Owner, Repo string
+	Name        string // tag, branch, commit or asset
+	Ext         string
+}
+
+var (
+	segmentRe = regexp.MustCompile(`^[A-Za-z0-9._+-]+$`)
+	commitRe  = regexp.MustCompile(`^[0-9a-f]{40}$`)
+)
+
+var errNotFound = errors.New("ref not found")
+
+const (
+	maxRefs     = 4096
+	negativeTTL = time.Minute
+)
+
+// Provider embeds generic for upstream URLs, content types and GitHub/Basic auth.
+type Provider struct {
+	generic.Provider
+
+	client    *http.Client
+	githubAPI string
+
+	group singleflight.Group
+	mu    sync.Mutex
+	refs  map[string]map[string]resolved
+}
+
+// resolved is a branch lookup; an empty commit records a missing branch.
+type resolved struct {
+	commit string
+	at     time.Time
+}
+
+func New() *Provider {
+	return &Provider{
+		client:    &http.Client{Timeout: 30 * time.Second},
+		githubAPI: "https://api.github.com",
+		refs:      map[string]map[string]resolved{},
+	}
+}
+
+func (p *Provider) Type() models.PackageType { return models.PackageVCS }
+
+func (p *Provider) Classify(path string) provider.Mutability {
+	if ref, ok := parsePath(path); ok && (ref.Kind == branchArchive || ref.Kind == latestReleaseAsset) {
+		return provider.Mutable
+	}
+	return provider.Immutable
+}
+
+// parsePath accepts only the archive and release-download shapes, rejecting
+// any segment that could escape owner/repo or a ref.
+func parsePath(path string) (target, bool) {
+	parts := strings.SplitN(strings.TrimPrefix(path, "/"), "/", 3)
+	if len(parts) != 3 || !validSegment(parts[0]) || !validSegment(parts[1]) {
+		return target{}, false
+	}
+	ref := target{Owner: parts[0], Repo: parts[1]}
+	rest := parts[2]
+	switch {
+	case strings.HasPrefix(rest, "archive/"):
+		name, ext, ok := archiveName(strings.TrimPrefix(rest, "archive/"))
+		if !ok {
+			return target{}, false
+		}
+		ref.Ext = ext
+		switch {
+		case strings.HasPrefix(name, "refs/tags/"):
+			ref.Kind, ref.Name = tagArchive, strings.TrimPrefix(name, "refs/tags/")
+		case strings.HasPrefix(name, "refs/heads/"):
+			ref.Kind, ref.Name = branchArchive, strings.TrimPrefix(name, "refs/heads/")
+		case commitRe.MatchString(name):
+			return target{Kind: commitArchive, Owner: ref.Owner, Repo: ref.Repo, Name: name, Ext: ext}, true
+		default:
+			return target{}, false
+		}
+		return ref, validRefName(ref.Name)
+	case strings.HasPrefix(rest, "releases/latest/download/"):
+		ref.Kind, ref.Name = latestReleaseAsset, strings.TrimPrefix(rest, "releases/latest/download/")
+		return ref, validSegment(ref.Name)
+	case strings.HasPrefix(rest, "releases/download/"):
+		tagAsset := strings.TrimPrefix(rest, "releases/download/")
+		i := strings.LastIndex(tagAsset, "/")
+		if i < 0 {
+			return target{}, false
+		}
+		ref.Kind, ref.Name = releaseAsset, tagAsset[i+1:]
+		return ref, validRefName(tagAsset[:i]) && validSegment(ref.Name)
+	}
+	return target{}, false
+}
+
+func archiveName(s string) (string, string, bool) {
+	for _, ext := range []string{".tar.gz", ".zip"} {
+		if name, ok := strings.CutSuffix(s, ext); ok && name != "" {
+			return name, ext, true
+		}
+	}
+	return "", "", false
+}
+
+func validSegment(s string) bool {
+	return segmentRe.MatchString(s) && s != "." && s != ".." && !strings.Contains(s, "..")
+}
+
+func validRefName(s string) bool {
+	for _, seg := range strings.Split(s, "/") {
+		if !validSegment(seg) || strings.HasPrefix(seg, ".") {
+			return false
+		}
+	}
+	return true
+}
+
+// ServeRemote rejects unsupported paths and redirects branch archives to the
+// immutable archive of the branch's current commit; everything else is proxied.
+func (p *Provider) ServeRemote(w http.ResponseWriter, r *http.Request, remote models.Remote, path, proxyBaseURL string, _ provider.RemoteMetadataStore) bool {
+	ref, ok := parsePath(path)
+	if !ok {
+		http.Error(w, "unsupported vcs path", http.StatusNotFound)
+		return true
+	}
+	if ref.Kind != branchArchive {
+		return false
+	}
+	classifier := proxy.NewClassifier(p)
+	if classifier.Classify(remote, path) == proxy.ClassDenied {
+		http.Error(w, "access denied", http.StatusForbidden)
+		return true
+	}
+	commit, err := p.resolve(r.Context(), remote, ref)
+	var se *provider.UpstreamStatusError
+	switch {
+	case errors.Is(err, errNotFound):
+		http.Error(w, "branch not found", http.StatusNotFound)
+		return true
+	case errors.As(err, &se) && (se.Status == http.StatusTooManyRequests || se.Status == http.StatusForbidden && !se.RetryAt.IsZero()):
+		secs := 60
+		if !se.RetryAt.IsZero() {
+			secs = max(1, int(time.Until(se.RetryAt).Seconds()+1))
+		}
+		w.Header().Set("Retry-After", strconv.Itoa(secs))
+		http.Error(w, "upstream rate limited", http.StatusServiceUnavailable)
+		return true
+	case err != nil:
+		http.Error(w, "bad gateway", http.StatusBadGateway)
+		return true
+	}
+	target := ref.Owner + "/" + ref.Repo + "/archive/" + commit + ref.Ext
+	if classifier.Classify(remote, target) == proxy.ClassDenied {
+		http.Error(w, "access denied", http.StatusForbidden)
+		return true
+	}
+	http.Redirect(w, r, strings.TrimRight(proxyBaseURL, "/")+provider.RemoteMountPath+remote.Name+"/"+target, http.StatusFound)
+	return true
+}
+
+// resolve maps a branch to its commit, reusing the answer for mutable_ttl (a
+// missing branch for at least negativeTTL) and, with stale_on_error, past an
+// upstream failure. Concurrent lookups of one branch share a single API call.
+func (p *Provider) resolve(ctx context.Context, remote models.Remote, ref target) (string, error) {
+	key := ref.Owner + "/" + ref.Repo + "\x00" + ref.Name
+	ttl := time.Duration(remote.MutableTTL) * time.Second
+	p.mu.Lock()
+	prev, ok := p.refs[remote.Name][key]
+	p.mu.Unlock()
+	if ok && prev.commit != "" && time.Since(prev.at) < ttl {
+		return prev.commit, nil
+	}
+	if ok && prev.commit == "" && time.Since(prev.at) < max(ttl, negativeTTL) {
+		return "", errNotFound
+	}
+	v, err, _ := p.group.Do(remote.Name+"\x00"+key, func() (any, error) {
+		commit, err := p.lookup(context.WithoutCancel(ctx), remote, ref)
+		if err == nil || errors.Is(err, errNotFound) {
+			p.store(remote.Name, key, commit)
+		}
+		return commit, err
+	})
+	if err != nil {
+		if ok && prev.commit != "" && remote.StaleOnError && !errors.Is(err, errNotFound) {
+			return prev.commit, nil
+		}
+		return "", err
+	}
+	return v.(string), nil
+}
+
+// store records a lookup, evicting the remote's oldest entry once it holds maxRefs.
+func (p *Provider) store(remote, key, commit string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	m := p.refs[remote]
+	if m == nil {
+		m = map[string]resolved{}
+		p.refs[remote] = m
+	}
+	if _, ok := m[key]; !ok && len(m) >= maxRefs {
+		var oldest string
+		for k, e := range m {
+			if oldest == "" || e.at.Before(m[oldest].at) {
+				oldest = k
+			}
+		}
+		delete(m, oldest)
+	}
+	m[key] = resolved{commit: commit, at: time.Now()}
+}
+
+func (p *Provider) lookup(ctx context.Context, remote models.Remote, ref target) (string, error) {
+	segs := strings.Split(ref.Name, "/")
+	for i, s := range segs {
+		segs[i] = url.PathEscape(s)
+	}
+	branch := strings.Join(segs, "/")
+	github := generic.IsGitHubHost(remote.BaseURL)
+	api := strings.TrimRight(remote.BaseURL, "/") + "/api/v1/repos/" + ref.Owner + "/" + ref.Repo + "/branches/" + branch
+	if github {
+		api = p.githubAPI + "/repos/" + ref.Owner + "/" + ref.Repo + "/git/ref/heads/" + branch
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, api, nil)
+	if err != nil {
+		return "", err
+	}
+	h, err := p.AuthHeaders(ctx, remote)
+	if err != nil {
+		return "", err
+	}
+	req.Header = h
+	if github {
+		req.Header.Set("Accept", "application/vnd.github+json")
+	}
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer func() { _ = resp.Body.Close() }()
+	if resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusUnprocessableEntity {
+		return "", errNotFound
+	}
+	if resp.StatusCode != http.StatusOK {
+		return "", provider.NewUpstreamStatusError(api, resp)
+	}
+	var b struct {
+		Commit struct {
+			ID string `json:"id"`
+		} `json:"commit"`
+		Object struct {
+			SHA string `json:"sha"`
+		} `json:"object"`
+	}
+	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&b); err != nil {
+		return "", err
+	}
+	commit := b.Commit.ID
+	if github {
+		commit = b.Object.SHA
+	}
+	if !commitRe.MatchString(commit) {
+		return "", fmt.Errorf("branch lookup %s: unexpected commit %q", api, commit)
+	}
+	return commit, nil
+}
@@ -0,0 +1,378 @@
+package vcs
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+const (
+	shaA = "4f2cfe92e3499f8581bf39db77e0a1431fa7b55c"
+	shaB = "7fa5434dbc083c853eef435d1915020345219d2f"
+)
+
+func TestParsePath(t *testing.T) {
+	tests := []struct {
+		path string
+		ok   bool
+		kind kind
+		name string
+	}{
+		{"cli/cli/archive/refs/tags/v2.60.0.tar.gz", true, tagArchive, "v2.60.0"},
+		{"/cli/cli/archive/refs/tags/v2.60.0.zip", true, tagArchive, "v2.60.0"},
+		{"o/r/archive/refs/tags/release/1.0.tar.gz", true, tagArchive, "release/1.0"},
+		{"o/r/archive/refs/heads/feature/x.tar.gz", true, branchArchive, "feature/x"},
+		{"o/r/archive/" + shaA + ".tar.gz", true, commitArchive, shaA},
+		{"o/r/releases/download/v1.0/tool_linux_amd64.tar.gz", true, releaseAsset, "tool_linux_amd64.tar.gz"},
+		{"o/r/releases/latest/download/tool.zip", true, latestReleaseAsset, "tool.zip"},
+		{"o/r/archive/main.tar.gz", false, 0, ""},
+		{"o/r/archive/" + shaA[:7] + ".tar.gz", false, 0, ""},
+		{"o/r/archive/refs/tags/v1.tar.bz2", false, 0, ""},
+		{"o/r/archive/refs/tags/.tar.gz", false, 0, ""},
+		{"../r/archive/refs/tags/v1.tar.gz", false, 0, ""},
+		{"o/../archive/refs/tags/v1.tar.gz", false, 0, ""},
+		{"o/r/archive/refs/tags/../../../etc/passwd.tar.gz", false, 0, ""},
+		{"o/r/archive/refs/heads/a//b.tar.gz", false, 0, ""},
+		{"o/r/archive/refs/heads/.hidden.tar.gz", false, 0, ""},
+		{"o/r/archive/refs/heads/a..b.tar.gz", false, 0, ""},
+		{"o/r/archive/refs/tags/v1%2f.tar.gz", false, 0, ""},
+		{"o/r/releases/download/v1/../x", false, 0, ""},
+		{"o/r/releases/download/asset", false, 0, ""},
+		{"o/r/raw/main/README.md", false, 0, ""},
+		{"o/r", false, 0, ""},
+	}
+	for _, tt := range tests {
+		ref, ok := parsePath(tt.path)
+		if ok != tt.ok || (ok && (ref.Kind != tt.kind || ref.Name != tt.name)) {
+			t.Errorf("parsePath(%q) = %+v, %v; want kind %v name %q ok %v", tt.path, ref, ok, tt.kind, tt.name, tt.ok)
+		}
+	}
+}
+
+func TestClassify(t *testing.T) {
+	p := New()
+	for path, want := range map[string]provider.Mutability{
+		"o/r/archive/refs/tags/v1.tar.gz":        provider.Immutable,
+		"o/r/archive/" + shaA + ".zip":           provider.Immutable,
+		"o/r/releases/download/v1/a.bin":         provider.Immutable,
+		"o/r/archive/refs/heads/main.tar.gz":     provider.Mutable,
+		"o/r/releases/latest/download/webui.zip": provider.Mutable,
+	} {
+		if got := p.Classify(path); got != want {
+			t.Errorf("Classify(%q) = %v, want %v", path, got, want)
+		}
+	}
+}
+
+type upstream struct {
+	srv    *httptest.Server
+	hits   atomic.Int32
+	commit atomic.Value
+	status atomic.Int32
+	header atomic.Value
+	accept atomic.Value
+	auth   atomic.Value
+	path   atomic.Value
+	gate   chan struct{}
+}
+
+func newUpstream(t *testing.T, gitea bool) *upstream {
+	u := &upstream{}
+	u.commit.Store(shaA)
+	u.status.Store(http.StatusOK)
+	u.header.Store(http.Header{})
+	u.srv = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		u.hits.Add(1)
+		if u.gate != nil {
+			<-u.gate
+		}
+		u.accept.Store(r.Header.Get("Accept"))
+		u.auth.Store(r.Header.Get("Authorization"))
+		u.path.Store(r.URL.EscapedPath())
+		for k, v := range u.header.Load().(http.Header) {
+			w.Header()[k] = v
+		}
+		if s := int(u.status.Load()); s != http.StatusOK {
+			w.WriteHeader(s)
+			return
+		}
+		if gitea {
+			_, _ = w.Write([]byte(`{"name":"main","commit":{"id":"` + u.commit.Load().(string) + `"}}`))
+			return
+		}
+		_, _ = w.Write([]byte(`{"ref":"refs/heads/main","object":{"sha":"` + u.commit.Load().(string) + `","type":"commit"}}`))
+	}))
+	t.Cleanup(u.srv.Close)
+	return u
+}
+
+func serve(p *Provider, remote models.Remote, path string) (*httptest.ResponseRecorder, bool) {
+	w := httptest.NewRecorder()
+	r := httptest.NewRequest(http.MethodGet, "/api/v1/remote/"+remote.Name+"/"+path, nil)
+	return w, p.ServeRemote(w, r, remote, path, "http://proxy", nil)
+}
+
+// age backdates every cached lookup of a remote by d.
+func age(p *Provider, remote string, d time.Duration) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	for k, e := range p.refs[remote] {
+		e.at = e.at.Add(-d)
+		p.refs[remote][k] = e
+	}
+}
+
+type staticCred string
+
+func (s staticCred) Token(context.Context) (string, error) { return string(s), nil }
+
+func TestServeRemoteGiteaBranchRedirectsToCommit(t *testing.T) {
+	u := newUpstream(t, true)
+	p := New()
+	remote := models.Remote{Name: "gitea", BaseURL: u.srv.URL, MutableTTL: 3600, Username: "bot", Password: "pw"}
+
+	w, handled := serve(p, remote, "unkin/app/archive/refs/heads/feature/x.zip")
+	if !handled || w.Code != http.StatusFound {
+		t.Fatalf("handled=%v code=%d", handled, w.Code)
+	}
+	if got, want := w.Header().Get("Location"), "http://proxy/api/v1/remote/gitea/unkin/app/archive/"+shaA+".zip"; got != want {
+		t.Errorf("Location = %q, want %q", got, want)
+	}
+	if got := u.path.Load(); got != "/api/v1/repos/unkin/app/branches/feature/x" {
+		t.Errorf("api path = %q", got)
+	}
+	if got := u.auth.Load(); got != "Basic Ym90OnB3" {
+		t.Errorf("Authorization = %q, want remote basic auth", got)
+	}
+}
+
+func TestServeRemoteGitHubBranchUsesAPI(t *testing.T) {
+	githubauth.SetServer(staticCred("ghs_server"))
+	t.Cleanup(func() { githubauth.SetServer(nil) })
+	u := newUpstream(t, false)
+	p := New()
+	p.githubAPI = u.srv.URL
+
+	for _, base := range []string{"https://github.com", "https://www.github.com/", "https://api.github.com"} {
+		remote := models.Remote{Name: base, BaseURL: base, MutableTTL: 3600}
+		w, _ := serve(p, remote, "cli/cli/archive/refs/heads/feature/x.tar.gz")
+		if !strings.HasSuffix(w.Header().Get("Location"), "/cli/cli/archive/"+shaA+".tar.gz") {
+			t.Fatalf("%s: Location = %q", base, w.Header().Get("Location"))
+		}
+		if u.path.Load() != "/repos/cli/cli/git/ref/heads/feature/x" || u.accept.Load() != "application/vnd.github+json" {
+			t.Errorf("%s: api path %q accept %q", base, u.path.Load(), u.accept.Load())
+		}
+		if got := u.auth.Load(); got != "Bearer ghs_server" {
+			t.Errorf("%s: Authorization = %q, want server credential", base, got)
+		}
+	}
+}
+
+func TestServeRemoteBranchResolutionHonoursMutableTTL(t *testing.T) {
+	u := newUpstream(t, true)
+	p := New()
+	remote := models.Remote{Name: "g", BaseURL: u.srv.URL, MutableTTL: 600}
+	path := "o/r/archive/refs/heads/main.tar.gz"
+
+	serve(p, remote, path)
+	u.commit.Store(shaB)
+	age(p, remote.Name, 599*time.Second)
+	w, _ := serve(p, remote, path)
+	if u.hits.Load() != 1 || !strings.Contains(w.Header().Get("Location"), shaA) {
+		t.Fatalf("within ttl: hits=%d location=%q", u.hits.Load(), w.Header().Get("Location"))
+	}
+
+	age(p, remote.Name, 2*time.Second)
+	w, _ = serve(p, remote, path)
+	if u.hits.Load() != 2 || !strings.Contains(w.Header().Get("Location"), shaB) {
+		t.Fatalf("past ttl: hits=%d location=%q", u.hits.Load(), w.Header().Get("Location"))
+	}
+}
+
+func TestServeRemoteBranchUpstreamFailure(t *testing.T) {
+	path := "o/r/archive/refs/heads/main.tar.gz"
+	for _, tc := range []struct {
+		name  string
+		stale bool
+		want  int
+	}{
+		{"stale", true, http.StatusFound},
+		{"strict", false, http.StatusBadGateway},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			u := newUpstream(t, true)
+			p := New()
+			remote := models.Remote{Name: tc.name, BaseURL: u.srv.URL, StaleOnError: tc.stale}
+			serve(p, remote, path)
+			u.status.Store(http.StatusInternalServerError)
+			if w, _ := serve(p, remote, path); w.Code != tc.want {
+				t.Fatalf("code = %d, want %d", w.Code, tc.want)
+			}
+		})
+	}
+}
+
+func TestServeRemoteBranchRateLimited(t *testing.T) {
+	reset := strconv.FormatInt(time.Now().Add(120*time.Second).Unix(), 10)
+	for _, tc := range []struct {
+		name   string
+		status int
+		header http.Header
+		want   int
+		retry  [2]int
+	}{
+		{"primary 403", http.StatusForbidden, http.Header{"X-Ratelimit-Remaining": {"0"}, "X-Ratelimit-Reset": {reset}}, http.StatusServiceUnavailable, [2]int{100, 122}},
+		{"secondary 403", http.StatusForbidden, http.Header{"Retry-After": {"30"}}, http.StatusServiceUnavailable, [2]int{30, 31}},
+		{"429", http.StatusTooManyRequests, http.Header{"Retry-After": {"5"}}, http.StatusServiceUnavailable, [2]int{5, 6}},
+		{"429 no hint", http.StatusTooManyRequests, http.Header{}, http.StatusServiceUnavailable, [2]int{60, 60}},
+		{"plain 403", http.StatusForbidden, http.Header{}, http.StatusBadGateway, [2]int{}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			u := newUpstream(t, false)
+			u.status.Store(int32(tc.status))
+			u.header.Store(tc.header)
+			p := New()
+			p.githubAPI = u.srv.URL
+			w, _ := serve(p, models.Remote{Name: "gh", BaseURL: "https://github.com"}, "o/r/archive/refs/heads/main.tar.gz")
+			if w.Code != tc.want {
+				t.Fatalf("code = %d, want %d", w.Code, tc.want)
+			}
+			ra := w.Header().Get("Retry-After")
+			if tc.want != http.StatusServiceUnavailable {
+				if ra != "" {
+					t.Fatalf("Retry-After = %q on %d", ra, w.Code)
+				}
+				return
+			}
+			if n, err := strconv.Atoi(ra); err != nil || n < tc.retry[0] || n > tc.retry[1] {
+				t.Fatalf("Retry-After = %q, want %d..%d", ra, tc.retry[0], tc.retry[1])
+			}
+		})
+	}
+}
+
+func TestServeRemoteBranchNotFoundIsCached(t *testing.T) {
+	u := newUpstream(t, false)
+	u.status.Store(http.StatusNotFound)
+	p := New()
+	p.githubAPI = u.srv.URL
+	remote := models.Remote{Name: "gh", BaseURL: "https://github.com"}
+	path := "o/r/archive/refs/heads/nope.tar.gz"
+
+	for range 3 {
+		if w, _ := serve(p, remote, path); w.Code != http.StatusNotFound {
+			t.Fatalf("code = %d, want 404", w.Code)
+		}
+	}
+	if u.hits.Load() != 1 {
+		t.Fatalf("hits = %d, want 1 within negative ttl", u.hits.Load())
+	}
+	u.status.Store(http.StatusOK)
+	age(p, remote.Name, negativeTTL)
+	if w, _ := serve(p, remote, path); w.Code != http.StatusFound || u.hits.Load() != 2 {
+		t.Fatalf("after negative ttl: code=%d hits=%d", w.Code, u.hits.Load())
+	}
+}
+
+func TestServeRemoteConcurrentLookupsShareOneCall(t *testing.T) {
+	u := newUpstream(t, true)
+	u.gate = make(chan struct{})
+	p := New()
+	remote := models.Remote{Name: "g", BaseURL: u.srv.URL, MutableTTL: 600}
+
+	var wg sync.WaitGroup
+	codes := make([]int, 20)
+	for i := range codes {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			w, _ := serve(p, remote, "o/r/archive/refs/heads/main.tar.gz")
+			codes[i] = w.Code
+		}()
+	}
+	for u.hits.Load() == 0 {
+		time.Sleep(time.Millisecond)
+	}
+	time.Sleep(50 * time.Millisecond)
+	close(u.gate)
+	wg.Wait()
+	if u.hits.Load() != 1 {
+		t.Fatalf("hits = %d, want 1", u.hits.Load())
+	}
+	for i, c := range codes {
+		if c != http.StatusFound {
+			t.Fatalf("request %d: code %d", i, c)
+		}
+	}
+}
+
+func TestStoreBoundsEntriesPerRemote(t *testing.T) {
+	p := New()
+	for i := range maxRefs + 10 {
+		p.store("a", fmt.Sprint(i), "")
+	}
+	p.store("b", "x", shaA)
+	if n := len(p.refs["a"]); n != maxRefs {
+		t.Fatalf("remote a holds %d entries, want %d", n, maxRefs)
+	}
+	if len(p.refs["b"]) != 1 {
+		t.Fatalf("remote b must keep its own budget")
+	}
+	if _, ok := p.refs["a"][fmt.Sprint(maxRefs+9)]; !ok {
+		t.Fatalf("newest entry evicted")
+	}
+}
+
+func TestServeRemoteRejectsBadCommit(t *testing.T) {
+	u := newUpstream(t, true)
+	u.commit.Store("../../etc")
+	w, _ := serve(New(), models.Remote{Name: "g", BaseURL: u.srv.URL}, "o/r/archive/refs/heads/main.tar.gz")
+	if w.Code != http.StatusBadGateway {
+		t.Fatalf("code = %d, want 502", w.Code)
+	}
+}
+
+func TestServeRemoteAllowlist(t *testing.T) {
+	u := newUpstream(t, true)
+	remote := models.Remote{Name: "g", BaseURL: u.srv.URL, Patterns: []string{"^allowed/repo/"}}
+	if w, _ := serve(New(), remote, "other/repo/archive/refs/heads/main.tar.gz"); w.Code != http.StatusForbidden {
+		t.Fatalf("code = %d, want 403", w.Code)
+	}
+	if u.hits.Load() != 0 {
+		t.Fatalf("denied branch must not hit the API")
+	}
+}
+
+func TestServeRemoteBlockedRedirectTarget(t *testing.T) {
+	u := newUpstream(t, true)
+	remote := models.Remote{Name: "g", BaseURL: u.srv.URL, Blocklist: []string{"/archive/" + shaA}}
+	w, _ := serve(New(), remote, "o/r/archive/refs/heads/main.tar.gz")
+	if w.Code != http.StatusForbidden || w.Header().Get("Location") != "" {
+		t.Fatalf("code = %d location %q, want 403 without redirect", w.Code, w.Header().Get("Location"))
+	}
+}
+
+func TestServeRemotePassesThroughAndRejects(t *testing.T) {
+	p := New()
+	remote := models.Remote{Name: "g", BaseURL: "https://github.com"}
+	if _, handled := serve(p, remote, "o/r/archive/refs/tags/v1.tar.gz"); handled {
+		t.Error("tag archives must go through the proxy engine")
+	}
+	if _, handled := serve(p, remote, "o/r/releases/download/v1/a.bin"); handled {
+		t.Error("release assets must go through the proxy engine")
+	}
+	if w, handled := serve(p, remote, "o/r/raw/main/x"); !handled || w.Code != http.StatusNotFound {
+		t.Errorf("unsupported path: handled=%v code=%d", handled, w.Code)
+	}
+}
@@ -0,0 +1,245 @@
+package virtual
+
+import (
+	"bytes"
+	"crypto/md5"
+	"encoding/hex"
+	"fmt"
+	"path"
+	"regexp"
+	"slices"
+	"strings"
+	"time"
+)
+
+// debIndexRe matches the binary Packages indexes a virtual merges: the flat
+// repo's root Packages and a suite's <component>/binary-<arch>/Packages.
+var debIndexRe = regexp.MustCompile(`^([^/]+/binary-[^/]+/)?Packages(\.[a-z0-9]+)?$`)
+
+// debByHashRe matches an index requested by its SHA256 (Acquire-By-Hash).
+var debByHashRe = regexp.MustCompile(`^([^/]+/binary-[^/]+/)?by-hash/SHA256/[0-9a-f]{64}$`)
+
+// debCompressions is the order a member's index variants are fetched in.
+var debCompressions = []string{".xz", ".gz", ".zst", ".bz2", ""}
+
+// DebMember is one member's Release plus its decompressed Packages indexes,
+// keyed by index directory relative to the Release ("" for a flat repo).
+type DebMember struct {
+	RemoteName string
+	Release    []byte
+	Packages   map[string][]byte
+}
+
+// DebRepo is a merged apt repo: Release plus the indexes it lists, keyed by
+// their path relative to the Release.
+type DebRepo struct {
+	Release []byte
+	Files   map[string][]byte
+}
+
+type debRelease struct {
+	fields map[string]string
+	files  []string
+}
+
+// parseDebRelease reads a Release file's single-line fields and the names
+// listed in its checksum sections.
+func parseDebRelease(body []byte) debRelease {
+	rel := debRelease{fields: map[string]string{}}
+	inSums := false
+	seen := map[string]bool{}
+	for line := range strings.SplitSeq(string(body), "\n") {
+		line = strings.TrimRight(line, "\r")
+		if line == "" {
+			continue
+		}
+		if line[0] == ' ' || line[0] == '\t' {
+			if f := strings.Fields(line); inSums && len(f) == 3 && !seen[f[2]] {
+				seen[f[2]] = true
+				rel.files = append(rel.files, f[2])
+			}
+			continue
+		}
+		k, v, _ := strings.Cut(line, ":")
+		v = strings.TrimSpace(v)
+		inSums = v == "" && (k == "MD5Sum" || strings.HasPrefix(k, "SHA"))
+		if _, ok := rel.fields[k]; !ok {
+			rel.fields[k] = v
+		}
+	}
+	return rel
+}
+
+// debIndexFiles returns, per index directory, the variant of its Packages file
+// to fetch from a member's Release listing.
+func debIndexFiles(rel debRelease) map[string]string {
+	listed := map[string]bool{}
+	for _, f := range rel.files {
+		listed[f] = true
+	}
+	out := map[string]string{}
+	for _, f := range rel.files {
+		m := debIndexRe.FindStringSubmatch(f)
+		if m == nil || out[m[1]] != "" {
+			continue
+		}
+		for _, c := range debCompressions {
+			if listed[m[1]+"Packages"+c] {
+				out[m[1]] = m[1] + "Packages" + c
+				break
+			}
+		}
+	}
+	return out
+}
+
+func splitStanzas(body []byte) []string {
+	var out []string
+	for s := range strings.SplitSeq(strings.ReplaceAll(string(body), "\r\n", "\n"), "\n\n") {
+		if s = strings.Trim(s, "\n"); s != "" {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
+func stanzaField(stanza, key string) string {
+	for line := range strings.SplitSeq(stanza, "\n") {
+		if k, v, ok := strings.Cut(line, ":"); ok && k == key {
+			return strings.TrimSpace(v)
+		}
+	}
+	return ""
+}
+
+func unionFields(dst []string, field string) []string {
+	for f := range strings.FieldsSeq(field) {
+		if !slices.Contains(dst, f) {
+			dst = append(dst, f)
+		}
+	}
+	return dst
+}
+
+func parseDebDate(s string) (time.Time, bool) {
+	for _, layout := range []string{time.RFC1123Z, time.RFC1123} {
+		if t, err := time.Parse(layout, s); err == nil {
+			return t, true
+		}
+	}
+	return time.Time{}, false
+}
+
+// MergeDeb merges members into one apt repo. Members are in priority order: the
+// first member to carry a (Package, Version, Architecture) in an index wins;
+// stanzas missing any of those are always kept. Filename is prefixed with the
+// owning member's name so the virtual can route downloads back to it.
+func MergeDeb(members []DebMember) *DebRepo {
+	var suite, codename string
+	var arches, comps, dirs []string
+	date := time.Unix(0, 0)
+	for _, m := range members {
+		rel := parseDebRelease(m.Release)
+		if suite == "" {
+			suite, codename = rel.fields["Suite"], rel.fields["Codename"]
+		}
+		arches = unionFields(arches, rel.fields["Architectures"])
+		comps = unionFields(comps, rel.fields["Components"])
+		if t, ok := parseDebDate(rel.fields["Date"]); ok && t.After(date) {
+			date = t
+		}
+		for d := range m.Packages {
+			if !slices.Contains(dirs, d) {
+				dirs = append(dirs, d)
+			}
+		}
+	}
+	slices.Sort(dirs)
+
+	repo := &DebRepo{Files: map[string][]byte{}}
+	for _, d := range dirs {
+		seen := map[string]bool{}
+		var b bytes.Buffer
+		for _, m := range members {
+			for _, s := range splitStanzas(m.Packages[d]) {
+				pkg, ver, arch := stanzaField(s, "Package"), stanzaField(s, "Version"), stanzaField(s, "Architecture")
+				if pkg != "" && ver != "" && arch != "" {
+					key := pkg + "\x00" + ver + "\x00" + arch
+					if seen[key] {
+						continue
+					}
+					seen[key] = true
+				}
+				if fn := stanzaField(s, "Filename"); fn != "" {
+					s = rewriteFilename(s, m.RemoteName+"/"+strings.TrimPrefix(path.Clean("/"+fn), "/"))
+				}
+				b.WriteString(s)
+				b.WriteString("\n\n")
+			}
+		}
+		gz := gzipDeterministic(b.Bytes())
+		repo.Files[d+"Packages"] = b.Bytes()
+		repo.Files[d+"Packages.gz"] = gz
+		repo.Files[d+"by-hash/SHA256/"+sha256Hex(b.Bytes())] = b.Bytes()
+		repo.Files[d+"by-hash/SHA256/"+sha256Hex(gz)] = gz
+	}
+
+	var r bytes.Buffer
+	if suite != "" {
+		fmt.Fprintf(&r, "Suite: %s\n", suite)
+	}
+	if codename != "" {
+		fmt.Fprintf(&r, "Codename: %s\n", codename)
+	}
+	fmt.Fprintf(&r, "Date: %s\n", date.UTC().Format(time.RFC1123Z))
+	fmt.Fprintf(&r, "Architectures: %s\n", strings.Join(arches, " "))
+	if len(comps) > 0 {
+		fmt.Fprintf(&r, "Components: %s\n", strings.Join(comps, " "))
+	}
+	r.WriteString("Acquire-By-Hash: yes\n")
+	for _, sec := range []struct {
+		name string
+		sum  func([]byte) string
+	}{{"MD5Sum", md5Hex}, {"SHA256", sha256Hex}} {
+		r.WriteString(sec.name + ":\n")
+		for _, d := range dirs {
+			for _, n := range []string{d + "Packages", d + "Packages.gz"} {
+				fmt.Fprintf(&r, " %s %d %s\n", sec.sum(repo.Files[n]), len(repo.Files[n]), n)
+			}
+		}
+	}
+	repo.Release = r.Bytes()
+	return repo
+}
+
+func rewriteFilename(stanza, fn string) string {
+	lines := strings.Split(stanza, "\n")
+	for i, l := range lines {
+		if strings.HasPrefix(l, "Filename:") {
+			lines[i] = "Filename: " + fn
+			break
+		}
+	}
+	return strings.Join(lines, "\n")
+}
+
+// debIndexPath splits an index request into its Release directory and the file
+// under it. ok is false for anything a deb virtual does not merge.
+func debIndexPath(p string) (base, name string, ok bool) {
+	if rest, found := strings.CutPrefix(p, "dists/"); found {
+		suite, n, found := strings.Cut(rest, "/")
+		if !found || suite == "" {
+			return "", "", false
+		}
+		base, p = "dists/"+suite+"/", n
+	}
+	if p != "Release" && !debIndexRe.MatchString(p) && !debByHashRe.MatchString(p) {
+		return "", "", false
+	}
+	return base, p, true
+}
+
+func md5Hex(data []byte) string {
+	h := md5.Sum(data)
+	return hex.EncodeToString(h[:])
+}
@@ -0,0 +1,179 @@
+package virtual
+
+import (
+	"bytes"
+	"crypto/md5"
+	"encoding/hex"
+	"fmt"
+	"maps"
+	"path"
+	"slices"
+	"strings"
+	"testing"
+)
+
+func debStanza(pkg, ver, arch, filename string) string {
+	return fmt.Sprintf("Package: %s\nVersion: %s\nArchitecture: %s\nDescription: test\n multi-line body\nFilename: %s\nSize: 1\n", pkg, ver, arch, filename)
+}
+
+func flatDebMember(name, date string, stanzas ...string) DebMember {
+	rel := "Date: " + date + "\nArchitectures: amd64\nAcquire-By-Hash: no\nSHA256:\n x 1 Packages\n x 1 Packages.gz\n"
+	return DebMember{RemoteName: name, Release: []byte(rel), Packages: map[string][]byte{"": []byte(strings.Join(stanzas, "\n"))}}
+}
+
+func TestMergeDebDedupesByMemberOrder(t *testing.T) {
+	repo := MergeDeb([]DebMember{
+		flatDebMember("a", "Mon, 05 Oct 2026 10:00:00 +0000",
+			debStanza("foo", "1.0", "amd64", "pool/foo_1.0_amd64.deb"),
+			debStanza("bar", "2.0", "amd64", "/pool/bar.deb"),
+			debStanza("dot", "1.0", "amd64", "./dot.deb"),
+			"Package: noversion\nFilename: nv1.deb\n",
+			"Package: noversion\nFilename: nv2.deb\n"),
+		flatDebMember("b", "Tue, 06 Oct 2026 10:00:00 UTC",
+			debStanza("foo", "1.0", "amd64", "pool/foo-from-b.deb"),
+			debStanza("foo", "1.0", "arm64", "pool/foo_arm64.deb"),
+			debStanza("foo", "1.1", "amd64", "o/r/releases/download/v1/foo.deb")),
+	})
+	pk := string(repo.Files["Packages"])
+	stanzas := splitStanzas(repo.Files["Packages"])
+	if len(stanzas) != 7 {
+		t.Fatalf("want 7 stanzas (one duplicate dropped), got %d:\n%s", len(stanzas), pk)
+	}
+	for _, want := range []string{
+		"Filename: a/pool/foo_1.0_amd64.deb",
+		"Filename: a/pool/bar.deb",
+		"Filename: a/dot.deb",
+		"Filename: a/nv1.deb",
+		"Filename: a/nv2.deb",
+		"Filename: b/pool/foo_arm64.deb",
+		"Filename: b/o/r/releases/download/v1/foo.deb",
+		" multi-line body",
+	} {
+		if !strings.Contains(pk, want) {
+			t.Errorf("merged Packages missing %q:\n%s", want, pk)
+		}
+	}
+	if strings.Contains(pk, "foo-from-b") {
+		t.Fatalf("second member's duplicate must lose:\n%s", pk)
+	}
+	if !bytes.Equal(gunzip(t, repo.Files["Packages.gz"]), repo.Files["Packages"]) {
+		t.Fatal("Packages.gz does not match Packages")
+	}
+	if !strings.Contains(string(repo.Release), "Date: Tue, 06 Oct 2026 10:00:00 +0000\n") {
+		t.Fatalf("Date should be the newest member date:\n%s", repo.Release)
+	}
+}
+
+func TestMergeDebReleaseHashesFiles(t *testing.T) {
+	repo := MergeDeb([]DebMember{flatDebMember("a", "", debStanza("foo", "1", "amd64", "pool/foo.deb"))})
+	rel := parseDebRelease(repo.Release)
+	if got := slices.Sorted(slices.Values(rel.files)); !slices.Equal(got, []string{"Packages", "Packages.gz"}) {
+		t.Fatalf("Release lists %v", got)
+	}
+	inSHA := false
+	checked := 0
+	for line := range strings.SplitSeq(string(repo.Release), "\n") {
+		if !strings.HasPrefix(line, " ") {
+			inSHA = line == "SHA256:"
+			continue
+		}
+		var sum, name string
+		var size int
+		if _, err := fmt.Sscan(line, &sum, &size, &name); err != nil {
+			t.Fatal(err)
+		}
+		body := repo.Files[name]
+		want := sha256Hex(body)
+		if !inSHA {
+			h := md5.Sum(body)
+			want = hex.EncodeToString(h[:])
+		}
+		if sum != want || size != len(body) {
+			t.Errorf("%s: Release has %s %d, file is %s %d", name, sum, size, want, len(body))
+		}
+		checked++
+	}
+	if checked != 4 {
+		t.Fatalf("checked %d Release entries, want 4:\n%s", checked, repo.Release)
+	}
+	if !bytes.Equal(MergeDeb([]DebMember{flatDebMember("a", "", debStanza("foo", "1", "amd64", "pool/foo.deb"))}).Release, repo.Release) {
+		t.Fatal("merge must be deterministic")
+	}
+}
+
+func TestMergeDebSuiteLayout(t *testing.T) {
+	rel := func(comps string) []byte {
+		return []byte("Suite: stable\nCodename: trixie\nArchitectures: amd64 arm64\nComponents: " + comps + "\nSHA256:\n x 1 main/binary-amd64/Packages.xz\n")
+	}
+	repo := MergeDeb([]DebMember{
+		{RemoteName: "deb1", Release: rel("main"), Packages: map[string][]byte{"main/binary-amd64/": []byte(debStanza("foo", "1", "amd64", "pool/main/f/foo.deb"))}},
+		{RemoteName: "deb2", Release: rel("main contrib"), Packages: map[string][]byte{
+			"main/binary-amd64/":    []byte(debStanza("bar", "1", "amd64", "pool/main/b/bar.deb")),
+			"contrib/binary-amd64/": []byte(debStanza("baz", "1", "amd64", "pool/contrib/b/baz.deb")),
+		}},
+	})
+	for _, want := range []string{"Suite: stable\n", "Codename: trixie\n", "Components: main contrib\n", "Architectures: amd64 arm64\n"} {
+		if !strings.Contains(string(repo.Release), want) {
+			t.Errorf("Release missing %q:\n%s", want, repo.Release)
+		}
+	}
+	want := []string{"contrib/binary-amd64/Packages", "contrib/binary-amd64/Packages.gz", "main/binary-amd64/Packages", "main/binary-amd64/Packages.gz"}
+	if got := slices.Sorted(slices.Values(parseDebRelease(repo.Release).files)); !slices.Equal(got, want) {
+		t.Fatalf("Release lists %v, want %v", got, want)
+	}
+	if !strings.Contains(string(repo.Release), "Acquire-By-Hash: yes\n") {
+		t.Fatalf("Release must advertise by-hash:\n%s", repo.Release)
+	}
+	for _, n := range want {
+		byHash := path.Dir(n) + "/by-hash/SHA256/" + sha256Hex(repo.Files[n])
+		if !bytes.Equal(repo.Files[byHash], repo.Files[n]) {
+			t.Errorf("%s not served at %s", n, byHash)
+		}
+	}
+	if len(repo.Files) != 2*len(want) {
+		t.Fatalf("files %v, want each index plus its by-hash copy", slices.Sorted(maps.Keys(repo.Files)))
+	}
+	if n := len(splitStanzas(repo.Files["main/binary-amd64/Packages"])); n != 2 {
+		t.Fatalf("main/binary-amd64 should merge both members, got %d stanzas", n)
+	}
+}
+
+func TestDebIndexFiles(t *testing.T) {
+	rel := parseDebRelease([]byte("Origin: Debian\nMD5Sum:\n a 1 main/binary-amd64/Packages\n a 1 main/binary-amd64/Packages.gz\nSHA256:\n" +
+		" a 1 main/binary-amd64/Packages\n a 1 main/binary-amd64/Packages.xz\n a 1 main/binary-amd64/Packages.gz\n" +
+		" a 1 main/debian-installer/binary-amd64/Packages.xz\n a 1 main/i18n/Translation-en.xz\n a 1 contrib/binary-all/Packages\n"))
+	got := debIndexFiles(rel)
+	want := map[string]string{"main/binary-amd64/": "main/binary-amd64/Packages.xz", "contrib/binary-all/": "contrib/binary-all/Packages"}
+	if !maps.Equal(got, want) {
+		t.Fatalf("got %v, want %v", got, want)
+	}
+	if flat := debIndexFiles(parseDebRelease([]byte("SHA256:\n a 1 Packages\n a 1 Packages.gz\n"))); flat[""] != "Packages.gz" {
+		t.Fatalf("flat repo should fetch Packages.gz, got %v", flat)
+	}
+}
+
+func TestDebIndexPath(t *testing.T) {
+	for _, tc := range []struct {
+		in, base, name string
+		ok             bool
+	}{
+		{"Release", "", "Release", true},
+		{"Packages.gz", "", "Packages.gz", true},
+		{"dists/trixie/Release", "dists/trixie/", "Release", true},
+		{"dists/trixie/main/binary-amd64/Packages", "dists/trixie/", "main/binary-amd64/Packages", true},
+		{"by-hash/SHA256/abababababababababababababababababababababababababababababababab", "", "by-hash/SHA256/abababababababababababababababababababababababababababababababab", true},
+		{"dists/trixie/main/binary-amd64/by-hash/SHA256/abababababababababababababababababababababababababababababababab", "dists/trixie/", "main/binary-amd64/by-hash/SHA256/abababababababababababababababababababababababababababababababab", true},
+		{"dists/trixie/main/binary-amd64/by-hash/MD5Sum/abababababababababababababababab", "", "", false},
+		{"InRelease", "", "", false},
+		{"Release.gpg", "", "", false},
+		{"dists/trixie/InRelease", "", "", false},
+		{"dists/trixie/main/i18n/Translation-en", "", "", false},
+		{"dists/Release", "", "", false},
+		{"pool/foo.deb", "", "", false},
+	} {
+		base, name, ok := debIndexPath(tc.in)
+		if base != tc.base || name != tc.name || ok != tc.ok {
+			t.Errorf("%s: got (%q, %q, %v), want (%q, %q, %v)", tc.in, base, name, ok, tc.base, tc.name, tc.ok)
+		}
+	}
+}
@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"path"
 	"slices"
 	"strings"
 	"sync"
@@ -26,6 +27,7 @@ type Engine struct {
 	proxyEngine *proxy.Engine
 	getRemote   func(context.Context, string) (*models.Remote, error)
 	rpmMember   func(context.Context, string) (*RPMMember, error)
+	debMember   func(ctx context.Context, name, base string) (*DebMember, error)
 	npmMember   func(ctx context.Context, name, pkg string) (*NPMMember, error)

 	// NPMLocal returns a local npm repo's packument with tarball paths relative
@@ -62,19 +64,25 @@ type mergedRepo interface {

 func (r *RPMRepo) index() []byte            { return r.Repomd }
 func (r *RPMRepo) files() map[string][]byte { return r.Files }
+func (r *DebRepo) index() []byte            { return r.Release }
+func (r *DebRepo) 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
+	at, used  time.Time
 }

 const rpmMergeTTL = 60 * time.Second

+// maxDebSuites bounds the client-chosen suites cached per deb virtual.
+const maxDebSuites = 32
+
 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.debMember = e.fetchDebMember
 	e.npmMember = e.fetchNPMMember
 	e.gemsMember = e.fetchGemsMember
 	e.ansibleDoc = e.ansibleMemberDoc
@@ -84,8 +92,11 @@ func NewEngine(db *database.DB, proxyEngine *proxy.Engine) *Engine {
 }

 func (e *Engine) Fetch(ctx context.Context, virt models.Virtual, path string, proxyBaseURL string) ([]byte, string, error) {
-	if virt.PackageType == models.PackageRPM {
+	switch virt.PackageType {
+	case models.PackageRPM:
 		return e.fetchRPM(ctx, virt, path)
+	case models.PackageDeb:
+		return e.fetchDeb(ctx, virt, path)
 	}

 	merger, err := GetMerger(virt.PackageType)
@@ -204,16 +215,22 @@ var (
 	ErrBadPath  = errors.New("invalid path")
 )

-// MemberRedirect maps an rpm, npm or ansible virtual package path
-// (<member>/<href>, as written by MergeRPM/MergeNPM/AnsibleVersion) 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, deb, npm or ansible virtual package path
+// (<member>/<href>, as written by MergeRPM/MergeDeb/MergeNPM/AnsibleVersion)
+// 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) {
 	switch virt.PackageType {
 	case models.PackageRPM:
 		if strings.HasPrefix(path, "repodata/") {
 			return "", false, nil
 		}
+	case models.PackageDeb:
+		// apt requests a flat repo's files under its "./" dist verbatim.
+		path = strings.TrimPrefix(path, "./")
+		if strings.HasPrefix(path, "dists/") {
+			return "", false, nil
+		}
 	case models.PackageNPM, models.PackageAnsible:
 	default:
 		return "", false, nil
@@ -294,6 +311,7 @@ func (e *Engine) merged(ctx context.Context, key string, merge func(context.Cont
 	e.mu.Lock()
 	g := e.gens[key]
 	if g != nil && time.Since(g.at) < e.mergeTTL {
+		g.used = time.Now()
 		e.mu.Unlock()
 		return g.cur, nil
 	}
@@ -312,12 +330,12 @@ func (e *Engine) merged(ctx context.Context, key string, merge func(context.Cont
 		g := e.gens[key]
 		switch {
 		case g == nil:
-			e.gens[key] = &repoGen{cur: repo, at: time.Now()}
+			e.gens[key] = &repoGen{cur: repo, at: time.Now(), used: time.Now()}
 		case string(g.cur.index()) == string(repo.index()):
-			g.at = time.Now()
+			g.at, g.used = time.Now(), time.Now()
 			repo = g.cur
 		default:
-			g.prev, g.cur, g.at = g.cur, repo, time.Now()
+			g.prev, g.cur, g.at, g.used = g.cur, repo, time.Now(), time.Now()
 		}
 		return repo, nil
 	})
@@ -364,6 +382,85 @@ func fetchMembers[T any](virt models.Virtual, fetch func(name string) (*T, error
 	return members, nil
 }

+func (e *Engine) fetchDeb(ctx context.Context, virt models.Virtual, reqPath string) ([]byte, string, error) {
+	base, name, ok := debIndexPath(strings.TrimPrefix(path.Clean("/"+reqPath), "/"))
+	if !ok {
+		return nil, "", ErrNotFound
+	}
+	key := "deb\x00" + virt.Name + "\x00" + base
+	if name != "Release" {
+		if body, ok := e.cachedFile(key, name); ok {
+			return body, debContentType(name), nil
+		}
+	}
+
+	repo, err := e.merged(ctx, key, func(ctx context.Context) (mergedRepo, error) {
+		members, err := fetchMembers(virt, func(name string) (*DebMember, error) { return e.debMember(ctx, name, base) })
+		if err != nil {
+			return nil, err
+		}
+		return MergeDeb(members), nil
+	})
+	if err != nil {
+		return nil, "", err
+	}
+	e.evictLRU("deb\x00"+virt.Name+"\x00", maxDebSuites)
+	if name == "Release" {
+		return repo.index(), "text/plain", nil
+	}
+	if body, ok := repo.files()[name]; ok {
+		return body, debContentType(name), nil
+	}
+	return nil, "", ErrNotFound
+}
+
+func debContentType(name string) string {
+	if strings.HasSuffix(name, ".gz") {
+		return "application/gzip"
+	}
+	return "text/plain"
+}
+
+// fetchDebMember reads a member's Release under base and each binary Packages
+// index it lists.
+func (e *Engine) fetchDebMember(ctx context.Context, name, base string) (*DebMember, error) {
+	remote, err := e.getRemote(ctx, name)
+	if err != nil {
+		return nil, fmt.Errorf("remote %q: %w", name, err)
+	}
+	rel, err := e.fetchMemberPath(ctx, *remote, base+"Release")
+	if err != nil {
+		return nil, err
+	}
+	m := &DebMember{RemoteName: name, Release: rel, Packages: map[string][]byte{}}
+	for dir, file := range debIndexFiles(parseDebRelease(rel)) {
+		raw, err := e.fetchMemberPath(ctx, *remote, base+file)
+		if err != nil {
+			return nil, err
+		}
+		if m.Packages[dir], err = decompress(file, raw); err != nil {
+			return nil, fmt.Errorf("decompress %s: %w", file, err)
+		}
+	}
+	return m, nil
+}
+
+// evictLRU drops the least recently used merges under prefix beyond keep.
+func (e *Engine) evictLRU(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)
+		}
+	}
+	slices.SortFunc(keys, func(a, b string) int { return e.gens[b].used.Compare(e.gens[a].used) })
+	for _, k := range keys[min(len(keys), keep):] {
+		delete(e.gens, k)
+	}
+}
+
 func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
@@ -376,6 +473,7 @@ func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 			continue
 		}
 		if body, ok := r.files()[path]; ok {
+			g.used = time.Now()
 			return body, true
 		}
 	}
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"regexp"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"testing"
@@ -157,6 +158,97 @@ func TestMemberRedirect(t *testing.T) {
 	}
 }

+func debEngine(members map[string]*DebMember) *Engine {
+	e := fakeEngine(nil)
+	e.debMember = func(_ context.Context, name, base string) (*DebMember, error) {
+		if m := members[name]; m != nil && base == "" {
+			return m, nil
+		}
+		return nil, errors.New("upstream down")
+	}
+	return e
+}
+
+func debVirt(members ...string) models.Virtual {
+	return models.Virtual{Name: "v", PackageType: models.PackageDeb, Members: members}
+}
+
+func TestFetchDebFailsClosed(t *testing.T) {
+	a := flatDebMember("a", "", debStanza("foo", "1", "amd64", "pool/foo.deb"))
+	e := debEngine(map[string]*DebMember{"a": &a})
+	for _, p := range []string{"Release", "./Packages.gz", "dists/trixie/Release"} {
+		if _, _, err := e.Fetch(context.Background(), debVirt("a", "b"), p, ""); err == nil || errors.Is(err, ErrNotFound) {
+			t.Errorf("%s: want upstream error with a member down, got %v", p, err)
+		}
+	}
+	for _, p := range []string{"InRelease", "./Release.gpg", "Packages.xz"} {
+		if _, _, err := e.Fetch(context.Background(), debVirt("a"), p, ""); !errors.Is(err, ErrNotFound) {
+			t.Errorf("%s: want not found, got %v", p, err)
+		}
+	}
+}
+
+func TestFetchDebRemergesAfterTTL(t *testing.T) {
+	a := flatDebMember("a", "", debStanza("foo", "1", "amd64", "pool/foo_1.deb"))
+	e := debEngine(map[string]*DebMember{"a": &a})
+	virt := debVirt("a")
+
+	rel, _, err := e.Fetch(context.Background(), virt, "./Release", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	a.Packages[""] = []byte(debStanza("foo", "2", "amd64", "pool/foo_2.deb"))
+	e.mergeTTL = 0
+	newRel, _, err := e.Fetch(context.Background(), virt, "Release", "")
+	if err != nil || string(newRel) == string(rel) {
+		t.Fatalf("Release should reflect the member change (err %v)", err)
+	}
+	pk, ct, err := e.Fetch(context.Background(), virt, "./Packages", "")
+	if err != nil || ct != "text/plain" || !strings.Contains(string(pk), "Version: 2") {
+		t.Fatalf("Packages should be the current merge (ct %q, err %v):\n%s", ct, err, pk)
+	}
+}
+
+func TestFetchDebMergeIsSharedPerSuite(t *testing.T) {
+	var calls atomic.Int32
+	e := fakeEngine(nil)
+	e.mergeTTL = time.Minute
+	e.debMember = func(_ context.Context, name, base string) (*DebMember, error) {
+		calls.Add(1)
+		m := flatDebMember(name, "", debStanza("foo", "1", "amd64", "pool/foo.deb"))
+		return &m, nil
+	}
+	for _, p := range []string{"Release", "Packages", "Packages.gz", "./Release", "dists/a/Release", "dists/b/Release"} {
+		if _, _, err := e.Fetch(context.Background(), debVirt("a"), p, ""); err != nil && !errors.Is(err, ErrNotFound) {
+			t.Fatal(err)
+		}
+	}
+	if n := calls.Load(); n != 3 {
+		t.Fatalf("member fetched %d times, want once per Release dir (3)", n)
+	}
+}
+
+func TestMemberRedirectDeb(t *testing.T) {
+	e := fakeEngine(nil)
+	virt := debVirt("gh", "loc")
+	for _, tc := range []struct {
+		path, want string
+		ok         bool
+		err        error
+	}{
+		{path: "gh/o/r/releases/download/v1/foo_1.0_amd64.deb", ok: true, want: "http://h/api/v1/remote/gh/o/r/releases/download/v1/foo_1.0_amd64.deb"},
+		{path: "./gh/pool/a+b.deb", ok: true, want: "http://h/api/v1/remote/gh/pool/a+b.deb"},
+		{path: "gh/../loc/x.deb", err: ErrBadPath},
+		{path: "dists/trixie/Release"},
+		{path: "Packages"},
+	} {
+		got, ok, err := e.MemberRedirect(context.Background(), virt, tc.path, "", "http://h/")
+		if got != tc.want || ok != tc.ok || !errors.Is(err, tc.err) {
+			t.Errorf("%s: got (%q, %v, %v), want (%q, %v, %v)", tc.path, got, ok, err, tc.want, tc.ok, tc.err)
+		}
+	}
+}
+
 type fakeRepo struct {
 	idx string
 	fs  map[string][]byte
@@ -206,3 +298,72 @@ func TestMergedReusesWithinTTLAndIsolatesKeys(t *testing.T) {
 		t.Error("unknown key served a file")
 	}
 }
+
+func suiteDebMember(name, version string) *DebMember {
+	return &DebMember{RemoteName: name, Release: []byte("Suite: s\nSHA256:\n x 1 main/binary-amd64/Packages.gz\n"),
+		Packages: map[string][]byte{"main/binary-amd64/": []byte(debStanza("foo", version, "amd64", "pool/foo_"+version+".deb"))}}
+}
+
+func TestFetchDebByHashSurvivesRemerge(t *testing.T) {
+	version := "1"
+	e := fakeEngine(nil)
+	e.debMember = func(_ context.Context, name, _ string) (*DebMember, error) { return suiteDebMember(name, version), nil }
+	virt := debVirt("a")
+	fetch := func(p string) []byte {
+		body, _, err := e.Fetch(context.Background(), virt, p, "")
+		if err != nil {
+			t.Fatalf("%s: %v", p, err)
+		}
+		return body
+	}
+	byHash := func(rel []byte) string {
+		m := regexp.MustCompile(`(?m)^SHA256:\n(?: .*\n)*? ([0-9a-f]{64}) \d+ main/binary-amd64/Packages.gz$`).FindSubmatch(rel)
+		if m == nil {
+			t.Fatalf("no Packages.gz SHA256 in Release:\n%s", rel)
+		}
+		return "dists/trixie/main/binary-amd64/by-hash/SHA256/" + string(m[1])
+	}
+
+	oldRel := fetch("dists/trixie/Release")
+	version, e.mergeTTL = "2", 0
+	if newRel := fetch("dists/trixie/Release"); string(newRel) == string(oldRel) {
+		t.Fatal("Release should reflect the member change")
+	}
+	if got := string(gunzip(t, fetch(byHash(oldRel)))); !strings.Contains(got, "Version: 1\n") {
+		t.Fatalf("by-hash from the previous Release served the wrong index:\n%s", got)
+	}
+	if got := string(fetch("dists/trixie/main/binary-amd64/Packages")); !strings.Contains(got, "Version: 2\n") {
+		t.Fatalf("fixed-name Packages should be the current merge:\n%s", got)
+	}
+}
+
+func TestFetchDebBoundsSuitesPerVirtual(t *testing.T) {
+	e := fakeEngine(nil)
+	e.mergeTTL = time.Minute
+	e.debMember = func(_ context.Context, name, _ string) (*DebMember, error) { return suiteDebMember(name, "1"), nil }
+	other := models.Virtual{Name: "other", PackageType: models.PackageDeb, Members: []string{"a"}}
+	if _, _, err := e.Fetch(context.Background(), other, "dists/keep/Release", ""); err != nil {
+		t.Fatal(err)
+	}
+	for i := range maxDebSuites + 5 {
+		if _, _, err := e.Fetch(context.Background(), debVirt("a"), fmt.Sprintf("dists/s%d/Release", i), ""); err != nil {
+			t.Fatal(err)
+		}
+		time.Sleep(time.Microsecond)
+	}
+	n := 0
+	for k := range e.gens {
+		if strings.HasPrefix(k, "deb\x00v\x00") {
+			n++
+		}
+	}
+	if n != maxDebSuites {
+		t.Fatalf("virtual v caches %d suites, want %d", n, maxDebSuites)
+	}
+	if e.gens["deb\x00v\x00dists/s0/"] != nil || e.gens["deb\x00v\x00dists/s4/"] != nil {
+		t.Fatal("least recently used suites should be evicted first")
+	}
+	if e.gens["deb\x00other\x00dists/keep/"] == nil {
+		t.Fatal("another virtual's suites must not be evicted")
+	}
+}
@@ -0,0 +1,5 @@
+package models
+
+const PackageVCS PackageType = "vcs"
+
+func init() { registerPackageType(PackageVCS) }
@@ -0,0 +1,26 @@
+import type { PackageTypeUI } from '../types';
+
+const def: PackageTypeUI = {
+  color: 'default',
+  snippets: ({ proxy }) => {
+    return [
+      {
+        title: 'Download a tag archive',
+        language: 'bash',
+        code: `curl -fsSLO ${proxy}/<owner>/<repo>/archive/refs/tags/<tag>.tar.gz`,
+      },
+      {
+        title: 'Download a branch archive (redirects to its current commit)',
+        language: 'bash',
+        code: `curl -fsSL -o src.tar.gz ${proxy}/<owner>/<repo>/archive/refs/heads/<branch>.tar.gz`,
+      },
+      {
+        title: 'Download a release asset',
+        language: 'bash',
+        code: `curl -fsSLO ${proxy}/<owner>/<repo>/releases/download/<tag>/<asset>`,
+      },
+    ];
+  },
+};
+
+export default def;