diff --git a/modules/gitea/README.md b/modules/gitea/README.md
new file mode 100644
index 00000000..6ef48150
--- /dev/null
+++ b/modules/gitea/README.md
@@ -0,0 +1,76 @@
+# gitea
+
+The forge, and the mesh's npm package registry: it claims the `git` and `npm-package-registry` seats.
+Its tools, its events and the provisioner of registry accounts are the TypeScript bundle (`index.ts`,
+`tools/`, `provisioner/`). This README covers the Go bundle beside it.
+
+## The package registry's retention (novox/hq ADR 0251 §4, to-be 51)
+
+Every publish adds a version to the registry, and until this nothing removed one. The Go bundle
+`cmd/npm-registry` says which versions each package holds, what keeps each one, and — asked with a why —
+deletes the versions nothing keeps.
+
+| tool | | what |
+|---|---|---|
+| `npm_packages` | r | every package of the registry's owner, each version newest first with its publish time, its size and why it is kept |
+| `npm_retention` | a | the versions retention would delete, and the bytes. **A dry run unless `dry_run` is false**; a real run needs `why` |
+
+**A version is kept when:**
+
+- a lockfile on the default branch of any repository on the forge names it — `package-lock.json`
+  (every lockfile version), `npm-shrinkwrap.json`, `yarn.lock` (classic and berry) and `pnpm-lock.yaml`
+  (by each resolved `name@version` or `name/version`), whatever the version's age;
+- it is the highest published version satisfying a range that a `package.json` there names in its
+  dependencies, development, peer or optional dependencies (an `npm:` alias counts for the package it
+  stands for; a path, a URL, git or a workspace is not a range on this registry). npm itself installs
+  the `latest` dist-tag when it satisfies the range; that version is kept by its dist-tag;
+- a dist-tag names it — and a range that *is* a dist-tag's name keeps that tag's version;
+- it is among the newest `keep` of its package, five by default (the artifact store's five builds,
+  ADR 0189 §3), by semantic-version order. **Pre-releases count** among the newest.
+
+A version that is not a semantic version is never ordered, so it is kept. A range that cannot be read,
+or a package whose dist-tags cannot be read, keeps **every** version of its package, and the answer says
+why under `keeps_all`.
+
+**Nothing is deleted on partial knowledge.** A repository whose files could not be listed, or a
+manifest or lockfile that could not be fetched, is named under `repositories_unread` in every answer,
+and a real run then deletes nothing at all. A file that was fetched but is not readable (broken JSON) is
+named under `files_not_read`; what it would have named is not known, and the operator reads that list
+before a real run. Under `node_modules` nothing is read: that is what a lockfile already says. An empty
+repository, or one without its default branch, holds nothing to read and is not a failure.
+
+A real run deletes each version through the forge's own interface (`DELETE
+/api/v1/packages/{owner}/npm/{name}/{version}`), says what it deleted and what the forge refused, and a
+version already gone counts as deleted.
+
+### How it reaches the forge
+
+Over the forge's HTTP interface on the machine (`MESH_GITEA_URL`), as the admin account the vault
+delivered (`MESH_GITEA_ADMIN_USER`, the password in `MESH_GITEA_ADMIN_PASSWORD_FILE` — the same file
+the TypeScript bundle mints its token with), by basic authentication: this bundle mints no token and
+keeps nothing. The password is read per call and never logged, answered or put in an error. The
+registry's owner is `MESH_NPM_OWNER`, the owner in the seat's `npm-path`.
+
+Calls to the forge run eight at a time, and one tool call reads for at most 50 seconds, inside a
+module's 60-second ask.
+
+### Why the manifest lists no `tools`
+
+The TypeScript bundle's tools are served without a `tools` list, and a claim without `serves` offers
+the module's `tools` as the seat's verbs — so a list here would make these two tools verbs of both the
+`git` and the `npm-package-registry` seats. The two names are kept in `ToolNames`, and a test holds them
+to this README and to what the bundle serves.
+
+### Tests
+
+```
+go test ./...
+```
+
+Against a fake forge (`httptest`): what keeps a version (a lockfile whatever its age, the highest
+version satisfying a range, a dist-tag, the newest `keep`); a dry run deleting nothing; a real run
+without why refused; a real run deleting only what nothing keeps; an unread repository stopping a real
+run before anything is deleted; an unreadable range keeping its whole package; a wrong password failing
+without saying the password. And the range matcher against npm's rules — exact, `^`, `~`, `x` and `*`,
+comparisons with partial versions, hyphen ranges, `||`, and the pre-release rule — and each lockfile
+format.
diff --git a/modules/gitea/cmd/npm-registry/forge.go b/modules/gitea/cmd/npm-registry/forge.go
new file mode 100644
index 00000000..5ce649ec
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/forge.go
@@ -0,0 +1,258 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+)
+
+// The forge as this bundle reaches it: its own HTTP interface on the machine, as the forge's admin
+// account, which the vault delivered into a file this module owns (novox/hq ADR 0086). Basic
+// authentication, so this bundle mints nothing and keeps nothing: the TypeScript bundle's token is its
+// own. The password is read when a call is made and never logged, answered or put in an error.
+
+// Forge is the forge's HTTP interface.
+type Forge struct {
+	URL          string // e.g. http://127.0.0.1:3000
+	User         string
+	PasswordFile string
+	Owner        string // the package registry's owner, as the seat serves it
+	HTTP         *http.Client
+}
+
+// ForgeFromEnv is the forge as the manifest hands it to this bundle.
+func ForgeFromEnv() (*Forge, error) {
+	f := &Forge{
+		URL:          strings.TrimRight(os.Getenv("MESH_GITEA_URL"), "/"),
+		User:         os.Getenv("MESH_GITEA_ADMIN_USER"),
+		PasswordFile: os.Getenv("MESH_GITEA_ADMIN_PASSWORD_FILE"),
+		Owner:        os.Getenv("MESH_NPM_OWNER"),
+	}
+	var missing []string
+	for name, v := range map[string]string{"MESH_GITEA_URL": f.URL, "MESH_GITEA_ADMIN_USER": f.User,
+		"MESH_GITEA_ADMIN_PASSWORD_FILE": f.PasswordFile, "MESH_NPM_OWNER": f.Owner} {
+		if v == "" {
+			missing = append(missing, name)
+		}
+	}
+	if len(missing) > 0 {
+		return nil, fmt.Errorf("the forge cannot be reached: %s not set by the manifest", strings.Join(missing, ", "))
+	}
+	return f, nil
+}
+
+// errNotFound is the forge answering 404.
+var errNotFound = errors.New("not found")
+
+// statusError is an answer the forge gave that is not a success, said without the request's credential.
+type statusError struct {
+	method, path string
+	status       int
+	said         string
+}
+
+func (e *statusError) Error() string {
+	return fmt.Sprintf("the forge answered %d to %s %s: %s", e.status, e.method, e.path, e.said)
+}
+
+func (f *Forge) client() *http.Client {
+	if f.HTTP != nil {
+		return f.HTTP
+	}
+	return &http.Client{Timeout: 20 * time.Second}
+}
+
+func (f *Forge) password() (string, error) {
+	raw, err := os.ReadFile(f.PasswordFile)
+	if err != nil {
+		// The path is the manifest's, not a secret; the content never appears.
+		return "", fmt.Errorf("the forge's admin password cannot be read from its file: %w", err)
+	}
+	return strings.TrimSpace(string(raw)), nil
+}
+
+// do sends one request and answers the body; 404 is errNotFound.
+func (f *Forge) do(ctx context.Context, method, path string) ([]byte, error) {
+	password, err := f.password()
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, method, f.URL+path, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.SetBasicAuth(f.User, password)
+	req.Header.Set("Accept", "application/json")
+	res, err := f.client().Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("the forge did not answer %s %s: %w", method, path, err)
+	}
+	defer res.Body.Close()
+	body, err := io.ReadAll(io.LimitReader(res.Body, 32<<20))
+	if err != nil {
+		return nil, err
+	}
+	switch {
+	case res.StatusCode == http.StatusNotFound:
+		return nil, fmt.Errorf("%s %s: %w", method, path, errNotFound)
+	case res.StatusCode >= 300:
+		said := strings.TrimSpace(string(body))
+		if len(said) > 300 {
+			said = said[:300] + "…"
+		}
+		return nil, &statusError{method, path, res.StatusCode, said}
+	}
+	return body, nil
+}
+
+func (f *Forge) getJSON(ctx context.Context, path string, into any) error {
+	body, err := f.do(ctx, http.MethodGet, path)
+	if err != nil {
+		return err
+	}
+	if err := json.Unmarshal(body, into); err != nil {
+		return fmt.Errorf("the forge's answer to %s is not readable: %w", path, err)
+	}
+	return nil
+}
+
+// PackageVersion is one version of one package, as the forge lists it.
+type PackageVersion struct {
+	Name      string    `json:"name"`
+	Version   string    `json:"version"`
+	CreatedAt time.Time `json:"created_at"`
+}
+
+const pageSize = 50
+
+// Packages is every npm package version of the owner, all pages.
+func (f *Forge) Packages(ctx context.Context) ([]PackageVersion, error) {
+	var all []PackageVersion
+	for page := 1; page <= 1000; page++ {
+		var batch []PackageVersion
+		path := fmt.Sprintf("/api/v1/packages/%s?type=npm&page=%d&limit=%d", url.PathEscape(f.Owner), page, pageSize)
+		if err := f.getJSON(ctx, path, &batch); err != nil {
+			return nil, err
+		}
+		all = append(all, batch...)
+		if len(batch) < pageSize {
+			return all, nil
+		}
+	}
+	return nil, errors.New("the forge listed more than 1000 pages of packages; stopped rather than read for ever")
+}
+
+func (f *Forge) versionPath(name, version string) string {
+	return fmt.Sprintf("/api/v1/packages/%s/npm/%s/%s", url.PathEscape(f.Owner), url.PathEscape(name), url.PathEscape(version))
+}
+
+// Size is the bytes of one version's files.
+func (f *Forge) Size(ctx context.Context, name, version string) (int64, error) {
+	var files []struct {
+		Size int64 `json:"size"`
+	}
+	if err := f.getJSON(ctx, f.versionPath(name, version)+"/files", &files); err != nil {
+		return 0, err
+	}
+	var total int64
+	for _, file := range files {
+		total += file.Size
+	}
+	return total, nil
+}
+
+// DistTags is the dist-tags of one package, from the registry's own metadata.
+func (f *Forge) DistTags(ctx context.Context, name string) (map[string]string, error) {
+	var meta struct {
+		DistTags map[string]string `json:"dist-tags"`
+	}
+	path := fmt.Sprintf("/api/packages/%s/npm/%s", url.PathEscape(f.Owner), url.PathEscape(name))
+	if err := f.getJSON(ctx, path, &meta); err != nil {
+		return nil, err
+	}
+	return meta.DistTags, nil
+}
+
+// Delete removes one version from the registry.
+func (f *Forge) Delete(ctx context.Context, name, version string) error {
+	_, err := f.do(ctx, http.MethodDelete, f.versionPath(name, version))
+	return err
+}
+
+// Repository is one repository on the forge, as far as reading its manifests needs.
+type Repository struct {
+	FullName      string `json:"full_name"`
+	DefaultBranch string `json:"default_branch"`
+	Empty         bool   `json:"empty"`
+}
+
+// Repositories is every repository the admin sees.
+func (f *Forge) Repositories(ctx context.Context) ([]Repository, error) {
+	var all []Repository
+	for page := 1; page <= 1000; page++ {
+		var found struct {
+			Data []Repository `json:"data"`
+		}
+		if err := f.getJSON(ctx, fmt.Sprintf("/api/v1/repos/search?page=%d&limit=%d", page, pageSize), &found); err != nil {
+			return nil, err
+		}
+		all = append(all, found.Data...)
+		if len(found.Data) < pageSize {
+			return all, nil
+		}
+	}
+	return nil, errors.New("the forge listed more than 1000 pages of repositories; stopped rather than read for ever")
+}
+
+func repoPath(fullName string) string {
+	owner, name, _ := strings.Cut(fullName, "/")
+	return url.PathEscape(owner) + "/" + url.PathEscape(name)
+}
+
+// Files is every file path on a branch, all pages of the forge's tree.
+func (f *Forge) Files(ctx context.Context, repo Repository) ([]string, error) {
+	var paths []string
+	seen := 0
+	for page := 1; page <= 1000; page++ {
+		var tree struct {
+			Tree []struct {
+				Path string `json:"path"`
+				Type string `json:"type"`
+			} `json:"tree"`
+			Truncated  bool `json:"truncated"`
+			TotalCount int  `json:"total_count"`
+		}
+		path := fmt.Sprintf("/api/v1/repos/%s/git/trees/%s?recursive=true&page=%d&per_page=1000",
+			repoPath(repo.FullName), url.PathEscape(repo.DefaultBranch), page)
+		if err := f.getJSON(ctx, path, &tree); err != nil {
+			return nil, err
+		}
+		for _, e := range tree.Tree {
+			if e.Type == "blob" {
+				paths = append(paths, e.Path)
+			}
+		}
+		seen += len(tree.Tree)
+		if len(tree.Tree) == 0 || !tree.Truncated && (tree.TotalCount == 0 || seen >= tree.TotalCount) {
+			return paths, nil
+		}
+	}
+	return nil, fmt.Errorf("%s has more than 1000 pages of files; not read whole", repo.FullName)
+}
+
+// Raw is one file's content on the repository's default branch.
+func (f *Forge) Raw(ctx context.Context, repo Repository, file string) ([]byte, error) {
+	escaped := strings.Split(file, "/")
+	for i := range escaped {
+		escaped[i] = url.PathEscape(escaped[i])
+	}
+	return f.do(ctx, http.MethodGet, fmt.Sprintf("/api/v1/repos/%s/raw/%s?ref=%s",
+		repoPath(repo.FullName), strings.Join(escaped, "/"), url.QueryEscape(repo.DefaultBranch)))
+}
diff --git a/modules/gitea/cmd/npm-registry/main.go b/modules/gitea/cmd/npm-registry/main.go
new file mode 100644
index 00000000..52d07f9e
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/main.go
@@ -0,0 +1,130 @@
+// npm-registry: the forge module's Go bundle for its package registry (novox/hq ADR 0251 §4, to-be 51).
+// A process the node's runtime launches and speaks MCP over stdio to, beside the module's TypeScript
+// bundle. It says which versions of each npm package the registry holds, what keeps each one, and —
+// asked with a why — deletes the versions nothing keeps. stdout is the protocol; it says what it says on
+// stderr, and never the forge's credential.
+package main
+
+import (
+	"context"
+	"fmt"
+	"math"
+	"os"
+	"strings"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// ToolNames are the tools this bundle serves. The module's manifest lists no `tools`: its TypeScript
+// bundle's tools are served without one, and a claim without `serves` would offer a `tools` list to both
+// of the module's seats as their verbs. The README names these two, and a test holds the two together.
+var ToolNames = []string{"npm_packages", "npm_retention"}
+
+func main() {
+	if err := stdio.Serve("", Tools(func() (*Forge, error) { return ForgeFromEnv() })); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+// Tools are the bundle's tools over the forge the function gives; asked per call, so a manifest that
+// does not set the environment is a refusal naming what is missing, not a bundle that will not start.
+func Tools(forge func() (*Forge, error)) []stdio.Tool {
+	pkg := map[string]any{"type": "string", "description": "one package, by its name (default every package)"}
+	keep := map[string]any{"type": "integer", "description": fmt.Sprintf("how many of each package's newest versions are kept whatever names them (default %d, at least 1)", DefaultKeep)}
+	return []stdio.Tool{
+		{
+			Name: "npm_packages",
+			Description: "Every npm package in the forge's package registry, each version newest first with when it was published, " +
+				"its size and what keeps it: a lockfile on a repository's default branch that names it, the highest version " +
+				"satisfying a range a package.json there names, a dist-tag, or being among the newest `keep` of its package " +
+				"(novox/hq ADR 0251). Repositories and files that could not be read are named. Changes nothing. Replaces " +
+				"npm view and npm dist-tag ls. (r)",
+			Input: map[string]any{"package": pkg, "keep": keep},
+			Run: func(args map[string]any) (any, error) {
+				f, err := forge()
+				if err != nil {
+					return nil, err
+				}
+				k, err := count(args, "keep", DefaultKeep, 1)
+				if err != nil {
+					return nil, err
+				}
+				s, err := survey(context.Background(), f, text(args, "package"), k, func(Item) bool { return true })
+				if err != nil {
+					return nil, err
+				}
+				kept, total := 0, 0
+				for _, p := range s.Packages {
+					for _, v := range p.Versions {
+						total++
+						if v.Kept {
+							kept++
+						}
+					}
+				}
+				s.Said = append(s.Said, fmt.Sprintf("%d packages, %d versions, %d kept; %d repositories read, %d unread",
+					len(s.Packages), total, kept, s.Repositories, len(s.Unread)))
+				return s, nil
+			},
+		},
+		{
+			Name: "npm_retention",
+			Description: "What retention would delete from the forge's package registry: every version nothing keeps — no lockfile " +
+				"on a repository's default branch names it, it is not the highest version satisfying any range a package.json " +
+				"there names, no dist-tag names it, and it is not among the newest `keep` of its package — with the bytes. " +
+				"A dry run unless dry_run is false; a real run needs why, and deletes nothing at all when any repository or " +
+				"file could not be read (novox/hq ADR 0251). Replaces npm unpublish. (a)",
+			Input: map[string]any{
+				"package": pkg,
+				"keep":    keep,
+				"dry_run": map[string]any{"type": "boolean", "description": "false to delete; default true"},
+				"why":     map[string]any{"type": "string", "description": "why the versions are deleted; required for a real run"},
+			},
+			Run: func(args map[string]any) (any, error) {
+				f, err := forge()
+				if err != nil {
+					return nil, err
+				}
+				k, err := count(args, "keep", DefaultKeep, 1)
+				if err != nil {
+					return nil, err
+				}
+				dry := true
+				if v, given := args["dry_run"]; given && v != nil {
+					b, ok := v.(bool)
+					if !ok {
+						if s, isText := v.(string); isText && (s == "true" || s == "false") {
+							b, ok = s == "true", true
+						}
+					}
+					if !ok {
+						return nil, fmt.Errorf("dry_run is true or false, not %v", v)
+					}
+					dry = b
+				}
+				return retention(context.Background(), f, text(args, "package"), k, dry, text(args, "why"))
+			},
+		},
+	}
+}
+
+func text(args map[string]any, key string) string {
+	s, _ := args[key].(string)
+	return strings.TrimSpace(s)
+}
+
+func count(args map[string]any, key string, fallback, least int) (int, error) {
+	v, given := args[key]
+	if !given || v == nil {
+		return fallback, nil
+	}
+	x, ok := v.(float64)
+	if !ok || x != math.Trunc(x) {
+		return 0, fmt.Errorf("%s must be a whole number", key)
+	}
+	if int(x) < least {
+		return 0, fmt.Errorf("%s must be at least %d", key, least)
+	}
+	return int(x), nil
+}
diff --git a/modules/gitea/cmd/npm-registry/refs.go b/modules/gitea/cmd/npm-registry/refs.go
new file mode 100644
index 00000000..18c86cda
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/refs.go
@@ -0,0 +1,241 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"path"
+	"regexp"
+	"strings"
+)
+
+// What the forge's repositories say they depend on (novox/hq ADR 0251 §4): every range a package
+// manifest names, and every version a lockfile pins. Read from file contents alone, so it is tested
+// without a forge.
+
+// Wanted is one range a package manifest names, and where.
+type Wanted struct {
+	Package string
+	Range   string
+	Where   string // repository:path
+}
+
+// Pinned is one version a lockfile names, and where.
+type Pinned struct {
+	Package string
+	Version string
+	Where   string
+}
+
+// Kinds of file this reads, by base name.
+var (
+	manifestNames = map[string]bool{"package.json": true}
+	lockNames     = map[string]bool{"package-lock.json": true, "npm-shrinkwrap.json": true, "yarn.lock": true,
+		"pnpm-lock.yaml": true}
+)
+
+// interesting is whether a path is a file this reads; nothing under node_modules, which is what a
+// lockfile already says and is not the repository's own.
+func interesting(p string) bool {
+	for _, part := range strings.Split(p, "/") {
+		if part == "node_modules" {
+			return false
+		}
+	}
+	base := path.Base(p)
+	return manifestNames[base] || lockNames[base]
+}
+
+var dependencyFields = []string{"dependencies", "devDependencies", "peerDependencies", "optionalDependencies"}
+
+// ReadManifest is every range a package.json names for a registry package. An `npm:` alias names the
+// package it stands for. A range that is not the registry's (a path, a URL, git, a workspace) is not
+// a range on this registry, and is left out.
+func ReadManifest(content []byte, where string, known map[string]bool) ([]Wanted, error) {
+	var m map[string]json.RawMessage
+	if err := json.Unmarshal(content, &m); err != nil {
+		return nil, err
+	}
+	var out []Wanted
+	for _, field := range dependencyFields {
+		var deps map[string]string
+		if raw, has := m[field]; !has || json.Unmarshal(raw, &deps) != nil {
+			continue
+		}
+		for name, spec := range deps {
+			if alias, ok := strings.CutPrefix(spec, "npm:"); ok {
+				at := strings.LastIndex(alias, "@")
+				if at <= 0 {
+					name, spec = alias, "*"
+				} else {
+					name, spec = alias[:at], alias[at+1:]
+				}
+			}
+			if !known[name] || notRegistry(spec) {
+				continue
+			}
+			out = append(out, Wanted{Package: name, Range: strings.TrimSpace(spec), Where: where})
+		}
+	}
+	return out, nil
+}
+
+func notRegistry(spec string) bool {
+	for _, p := range []string{"file:", "link:", "workspace:", "git+", "git:", "github:", "http:", "https:", "portal:", "patch:"} {
+		if strings.HasPrefix(spec, p) {
+			return true
+		}
+	}
+	return strings.Contains(spec, "/") && !strings.HasPrefix(spec, "npm:")
+}
+
+// ReadLock is every registry package version a lockfile names.
+func ReadLock(base string, content []byte, where string, known map[string]bool) ([]Pinned, error) {
+	switch base {
+	case "package-lock.json", "npm-shrinkwrap.json":
+		return readNpmLock(content, where, known)
+	case "yarn.lock":
+		return readYarnLock(content, where, known), nil
+	case "pnpm-lock.yaml":
+		return readTextLock(content, where, known), nil
+	}
+	return nil, nil
+}
+
+type npmLockEntry struct {
+	Name         string                  `json:"name"`
+	Version      string                  `json:"version"`
+	Dependencies map[string]npmLockEntry `json:"dependencies"`
+}
+
+func readNpmLock(content []byte, where string, known map[string]bool) ([]Pinned, error) {
+	var lock struct {
+		Packages     map[string]npmLockEntry `json:"packages"`
+		Dependencies map[string]npmLockEntry `json:"dependencies"`
+	}
+	if err := json.Unmarshal(content, &lock); err != nil {
+		return nil, err
+	}
+	var out []Pinned
+	add := func(name, version string) {
+		if known[name] && version != "" {
+			out = append(out, Pinned{Package: name, Version: version, Where: where})
+		}
+	}
+	// Version 2 and 3: keyed by the path it is installed at. An alias carries the real name.
+	for key, e := range lock.Packages {
+		_, name, found := cutLast(key, "node_modules/")
+		if !found {
+			continue
+		}
+		if e.Name != "" {
+			name = e.Name
+		}
+		add(name, e.Version)
+	}
+	// Version 1 (and 2's copy): nested by name. An alias's version is `npm:<name>@<version>`.
+	var walk func(map[string]npmLockEntry)
+	walk = func(deps map[string]npmLockEntry) {
+		for name, e := range deps {
+			if alias, ok := strings.CutPrefix(e.Version, "npm:"); ok {
+				if at := strings.LastIndex(alias, "@"); at > 0 {
+					add(alias[:at], alias[at+1:])
+				}
+			} else {
+				add(name, e.Version)
+			}
+			walk(e.Dependencies)
+		}
+	}
+	walk(lock.Dependencies)
+	return out, nil
+}
+
+func cutLast(s, sep string) (string, string, bool) {
+	i := strings.LastIndex(s, sep)
+	if i < 0 {
+		return s, "", false
+	}
+	return s[:i], s[i+len(sep):], true
+}
+
+// readYarnLock reads both yarn formats: a header of the specs it resolves (`"@a/b@^1.0.0", "@a/b@^1.1.0":`)
+// and an indented `version "1.2.3"` (classic) or `version: 1.2.3` (berry) under it.
+func readYarnLock(content []byte, where string, known map[string]bool) []Pinned {
+	var out []Pinned
+	var names []string
+	scanner := bufio.NewScanner(bytes.NewReader(content))
+	scanner.Buffer(make([]byte, 1<<20), 1<<20)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		if !strings.HasPrefix(line, " ") && strings.HasSuffix(line, ":") {
+			names = names[:0]
+			for _, spec := range strings.Split(strings.TrimSuffix(line, ":"), ",") {
+				spec = strings.Trim(strings.TrimSpace(spec), `"`)
+				// `name@range`, `name@npm:range`; the name may itself start with @.
+				at := strings.Index(spec[min(1, len(spec)):], "@")
+				if at < 0 {
+					continue
+				}
+				names = append(names, spec[:at+1])
+			}
+			continue
+		}
+		trimmed := strings.TrimSpace(line)
+		if v, ok := strings.CutPrefix(trimmed, "version "); ok && strings.HasPrefix(line, "  ") && !strings.HasPrefix(line, "    ") {
+			addYarn(&out, names, strings.Trim(v, `"`), where, known)
+		} else if v, ok := strings.CutPrefix(trimmed, "version: "); ok && strings.HasPrefix(line, "  ") && !strings.HasPrefix(line, "    ") {
+			addYarn(&out, names, strings.Trim(v, `"`), where, known)
+		}
+	}
+	return out
+}
+
+func addYarn(out *[]Pinned, names []string, version, where string, known map[string]bool) {
+	seen := map[string]bool{}
+	for _, n := range names {
+		if known[n] && !seen[n] {
+			seen[n] = true
+			*out = append(*out, Pinned{Package: n, Version: version, Where: where})
+		}
+	}
+}
+
+var versionText = regexp.MustCompile(`^\d+\.\d+\.\d+(?:-[0-9A-Za-z.-]+)?`)
+
+// readTextLock reads a lockfile whose format changes between versions (pnpm's) by what every format
+// has in common: each resolved package written as `<name>@<version>` or `<name>/<version>`. Only names
+// the registry holds are looked for, so another package whose name merely contains one is told apart by
+// the character before it.
+func readTextLock(content []byte, where string, known map[string]bool) []Pinned {
+	text := string(content)
+	var out []Pinned
+	seen := map[string]bool{}
+	for name := range known {
+		for start := 0; ; {
+			i := strings.Index(text[start:], name)
+			if i < 0 {
+				break
+			}
+			i += start
+			start = i + len(name)
+			if i > 0 && !strings.ContainsRune(" '\"/\n\t:", rune(text[i-1])) {
+				continue
+			}
+			rest := text[start:]
+			if len(rest) == 0 || (rest[0] != '@' && rest[0] != '/') {
+				continue
+			}
+			v := versionText.FindString(rest[1:])
+			if v == "" || seen[name+"@"+v] {
+				continue
+			}
+			seen[name+"@"+v] = true
+			out = append(out, Pinned{Package: name, Version: v, Where: where})
+		}
+	}
+	return out
+}
diff --git a/modules/gitea/cmd/npm-registry/refs_test.go b/modules/gitea/cmd/npm-registry/refs_test.go
new file mode 100644
index 00000000..ad75526c
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/refs_test.go
@@ -0,0 +1,92 @@
+package main
+
+import (
+	"sort"
+	"strings"
+	"testing"
+)
+
+var knownHere = map[string]bool{"@novox/mesh-sdk": true, "@novox/ui": true, "sdk": true}
+
+func pins(ps []Pinned) string {
+	var out []string
+	for _, p := range ps {
+		out = append(out, p.Package+"@"+p.Version)
+	}
+	sort.Strings(out)
+	return strings.Join(out, " ")
+}
+
+func TestAManifestNamesItsRegistryRangesAndNothingElse(t *testing.T) {
+	got, err := ReadManifest([]byte(`{
+		"dependencies": {"@novox/mesh-sdk": "^0.1.0", "left-pad": "^1.0.0", "@novox/ui": "file:../ui"},
+		"devDependencies": {"sdk": "npm:@novox/ui@~2.0.0"},
+		"peerDependencies": {"@novox/ui": "workspace:*"},
+		"optionalDependencies": {"@novox/ui": "1.x"}
+	}`), "r:package.json", knownHere)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var said []string
+	for _, w := range got {
+		said = append(said, w.Package+" "+w.Range)
+	}
+	sort.Strings(said)
+	if strings.Join(said, ",") != "@novox/mesh-sdk ^0.1.0,@novox/ui 1.x,@novox/ui ~2.0.0" {
+		t.Fatalf("read %v", said)
+	}
+}
+
+func TestAnNpmLockfileOfEveryVersionNamesWhatItPins(t *testing.T) {
+	v3 := `{"lockfileVersion":3,"packages":{"":{"name":"x"},
+		"node_modules/@novox/mesh-sdk":{"version":"0.1.3"},
+		"node_modules/a/node_modules/@novox/mesh-sdk":{"version":"0.1.1"},
+		"node_modules/sdk":{"name":"@novox/ui","version":"2.0.4"},
+		"node_modules/left-pad":{"version":"1.3.0"}}}`
+	got, err := ReadLock("package-lock.json", []byte(v3), "r:package-lock.json", knownHere)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if pins(got) != "@novox/mesh-sdk@0.1.1 @novox/mesh-sdk@0.1.3 @novox/ui@2.0.4" {
+		t.Fatalf("v3: %s", pins(got))
+	}
+	v1 := `{"lockfileVersion":1,"dependencies":{"@novox/mesh-sdk":{"version":"0.1.2","dependencies":{"@novox/ui":{"version":"1.0.0"}}},
+		"sdk":{"version":"npm:@novox/ui@2.0.1"}}}`
+	got, err = ReadLock("npm-shrinkwrap.json", []byte(v1), "r", knownHere)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if pins(got) != "@novox/mesh-sdk@0.1.2 @novox/ui@1.0.0 @novox/ui@2.0.1" {
+		t.Fatalf("v1: %s", pins(got))
+	}
+	if _, err := ReadLock("package-lock.json", []byte("{not json"), "r", knownHere); err == nil {
+		t.Fatal("a broken lockfile read as empty")
+	}
+}
+
+func TestAYarnLockOfEitherFormatNamesWhatItPins(t *testing.T) {
+	classic := "# yarn lockfile v1\n\n\"@novox/mesh-sdk@^0.1.0\", \"@novox/mesh-sdk@^0.1.2\":\n  version \"0.1.4\"\n  resolved \"x\"\n  dependencies:\n    left-pad \"^1\"\n\nleft-pad@^1:\n  version \"1.3.0\"\n"
+	if got := pins(readYarnLock([]byte(classic), "r", knownHere)); got != "@novox/mesh-sdk@0.1.4" {
+		t.Fatalf("classic: %s", got)
+	}
+	berry := "__metadata:\n  version: 6\n\n\"@novox/ui@npm:^2.0.0\":\n  version: 2.0.7\n  resolution: \"@novox/ui@npm:2.0.7\"\n"
+	if got := pins(readYarnLock([]byte(berry), "r", knownHere)); got != "@novox/ui@2.0.7" {
+		t.Fatalf("berry: %s", got)
+	}
+}
+
+func TestAPnpmLockNamesWhatItPinsInEachFormat(t *testing.T) {
+	lock := "lockfileVersion: '9.0'\npackages:\n  '@novox/mesh-sdk@0.1.5':\n    resolution: {}\n  /@novox/ui/2.0.2:\n    resolution: {}\n  /@other/novox/ui@9.9.9:\n  /x-sdk@1.0.0:\n"
+	if got := pins(readTextLock([]byte(lock), "r", knownHere)); got != "@novox/mesh-sdk@0.1.5 @novox/ui@2.0.2" {
+		t.Fatalf("pnpm: %s", got)
+	}
+}
+
+func TestOnlyTheRepositorysOwnManifestsAreRead(t *testing.T) {
+	for p, want := range map[string]bool{"package.json": true, "modules/x/package-lock.json": true, "yarn.lock": true,
+		"pnpm-lock.yaml": true, "node_modules/a/package.json": false, "README.md": false, "a/package.json.bak": false} {
+		if interesting(p) != want {
+			t.Errorf("%s: %v", p, !want)
+		}
+	}
+}
diff --git a/modules/gitea/cmd/npm-registry/retention.go b/modules/gitea/cmd/npm-registry/retention.go
new file mode 100644
index 00000000..886e2706
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/retention.go
@@ -0,0 +1,425 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"path"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Retention for the package registry (novox/hq ADR 0251 §4, to-be 51): a version is kept when a
+// lockfile on a repository's default branch names it, when it is the highest version satisfying a
+// range a package manifest there names, when a dist-tag names it, or when it is among the newest
+// `keep` of its package. Everything else is what retention would delete.
+
+// DefaultKeep is how many of each package's newest versions are kept whatever names them: the same
+// five builds the artifact store keeps (ADR 0189 §3), so "how far back" has one answer.
+const DefaultKeep = 5
+
+// workers bounds how many calls go to the forge at once; budget how long one tool call may read.
+const (
+	workers = 8
+	budget  = 50 * time.Second
+)
+
+// Item is one version, with what keeps it.
+type Item struct {
+	Version   string    `json:"version"`
+	Published time.Time `json:"published"`
+	Bytes     int64     `json:"bytes"`
+	SizeError string    `json:"size_error,omitempty"`
+	Kept      bool      `json:"kept"`
+	Why       []string  `json:"why,omitempty"`
+}
+
+// Package is one package's versions, newest first.
+type Package struct {
+	Name     string            `json:"name"`
+	DistTags map[string]string `json:"dist_tags,omitempty"`
+	// KeepsAll says why every version is kept, when something about the package could not be read.
+	KeepsAll string `json:"keeps_all,omitempty"`
+	Versions []Item `json:"versions"`
+}
+
+// Survey is the registry and what the forge's repositories say of it.
+type Survey struct {
+	Owner        string    `json:"owner"`
+	Keep         int       `json:"keep"`
+	Repositories int       `json:"repositories_read"`
+	Unread       []string  `json:"repositories_unread,omitempty"`
+	NotRead      []string  `json:"files_not_read,omitempty"`
+	Packages     []Package `json:"packages"`
+	Said         []string  `json:"said"`
+}
+
+// survey reads the registry and every repository, and decides what is kept. sizes says whether to
+// ask the forge each version's size (for these versions only, when not nil).
+func survey(ctx context.Context, f *Forge, only string, keep int, sizes func(Item) bool) (*Survey, error) {
+	ctx, cancel := context.WithTimeout(ctx, budget)
+	defer cancel()
+	listed, err := f.Packages(ctx)
+	if err != nil {
+		return nil, err
+	}
+	byName := map[string][]PackageVersion{}
+	for _, v := range listed {
+		byName[v.Name] = append(byName[v.Name], v)
+	}
+	if only != "" {
+		if _, has := byName[only]; !has {
+			return nil, fmt.Errorf("the registry of %s holds no npm package %q", f.Owner, only)
+		}
+	}
+	known := map[string]bool{}
+	for name := range byName {
+		known[name] = true
+	}
+
+	s := &Survey{Owner: f.Owner, Keep: keep, Said: []string{}}
+	wanted, pinned, err := readRepositories(ctx, f, known, s)
+	if err != nil {
+		return nil, err
+	}
+
+	names := make([]string, 0, len(byName))
+	for name := range byName {
+		if only == "" || name == only {
+			names = append(names, name)
+		}
+	}
+	sort.Strings(names)
+	tags := distTags(ctx, f, names)
+	for _, name := range names {
+		s.Packages = append(s.Packages, decide(name, byName[name], tags[name], wanted[name], pinned[name], keep))
+	}
+	if sizes != nil {
+		measure(ctx, f, s, sizes)
+	}
+	return s, nil
+}
+
+type tagAnswer struct {
+	tags map[string]string
+	err  error
+}
+
+func distTags(ctx context.Context, f *Forge, names []string) map[string]tagAnswer {
+	out := map[string]tagAnswer{}
+	var mu sync.Mutex
+	each(names, func(name string) {
+		t, err := f.DistTags(ctx, name)
+		mu.Lock()
+		out[name] = tagAnswer{t, err}
+		mu.Unlock()
+	})
+	return out
+}
+
+// each runs fn over items, workers at a time.
+func each[T any](items []T, fn func(T)) {
+	var wg sync.WaitGroup
+	gate := make(chan struct{}, workers)
+	for _, item := range items {
+		wg.Add(1)
+		gate <- struct{}{}
+		go func(item T) {
+			defer wg.Done()
+			defer func() { <-gate }()
+			fn(item)
+		}(item)
+	}
+	wg.Wait()
+}
+
+// readRepositories reads every repository's manifests and lockfiles. A repository that could not be
+// read is named in Unread: what it depends on is not known, so nothing may be deleted.
+func readRepositories(ctx context.Context, f *Forge, known map[string]bool, s *Survey) (map[string][]Wanted, map[string][]Pinned, error) {
+	repos, err := f.Repositories(ctx)
+	if err != nil {
+		return nil, nil, fmt.Errorf("the forge's repositories cannot be listed, so nothing is known to depend on anything: %w", err)
+	}
+	wanted := map[string][]Wanted{}
+	pinned := map[string][]Pinned{}
+	var mu sync.Mutex
+	each(repos, func(r Repository) {
+		if r.Empty || r.DefaultBranch == "" {
+			mu.Lock()
+			s.Repositories++
+			mu.Unlock()
+			return
+		}
+		files, err := f.Files(ctx, r)
+		if errors.Is(err, errNotFound) {
+			// A repository without its default branch holds nothing to read.
+			files, err = nil, nil
+		}
+		if err != nil {
+			mu.Lock()
+			s.Unread = append(s.Unread, fmt.Sprintf("%s: %v", r.FullName, err))
+			mu.Unlock()
+			return
+		}
+		var ws []Wanted
+		var ps []Pinned
+		var notRead, unread []string
+		for _, p := range files {
+			if !interesting(p) {
+				continue
+			}
+			where := r.FullName + ":" + p
+			content, err := f.Raw(ctx, r, p)
+			if err != nil {
+				unread = append(unread, fmt.Sprintf("%s: %v", where, err))
+				continue
+			}
+			base := path.Base(p)
+			if manifestNames[base] {
+				got, err := ReadManifest(content, where, known)
+				if err != nil {
+					notRead = append(notRead, fmt.Sprintf("%s: not JSON (%v)", where, err))
+					continue
+				}
+				ws = append(ws, got...)
+				continue
+			}
+			got, err := ReadLock(base, content, where, known)
+			if err != nil {
+				notRead = append(notRead, fmt.Sprintf("%s: not readable (%v)", where, err))
+				continue
+			}
+			ps = append(ps, got...)
+		}
+		mu.Lock()
+		defer mu.Unlock()
+		s.Repositories++
+		s.Unread = append(s.Unread, unread...)
+		s.NotRead = append(s.NotRead, notRead...)
+		for _, w := range ws {
+			wanted[w.Package] = append(wanted[w.Package], w)
+		}
+		for _, p := range ps {
+			pinned[p.Package] = append(pinned[p.Package], p)
+		}
+	})
+	sort.Strings(s.Unread)
+	sort.Strings(s.NotRead)
+	return wanted, pinned, nil
+}
+
+// decide is one package's versions, newest first, each with what keeps it.
+func decide(name string, listed []PackageVersion, tags tagAnswer, wanted []Wanted, pinned []Pinned, keep int) Package {
+	p := Package{Name: name, DistTags: tags.tags}
+	type entry struct {
+		item Item
+		v    Version
+		ok   bool
+	}
+	var entries []*entry
+	byVersion := map[string]*entry{}
+	var parsed []Version
+	for _, l := range listed {
+		e := &entry{item: Item{Version: l.Version, Published: l.CreatedAt}}
+		e.v, e.ok = mustVersion(l.Version)
+		entries = append(entries, e)
+		byVersion[l.Version] = e
+		if e.ok {
+			parsed = append(parsed, e.v)
+		}
+	}
+	why := func(version, reason string) {
+		if e := byVersion[version]; e != nil {
+			e.item.Why = append(e.item.Why, reason)
+		}
+	}
+
+	var keepsAll []string
+	if tags.err != nil {
+		keepsAll = append(keepsAll, fmt.Sprintf("its dist-tags could not be read (%v)", tags.err))
+	}
+	for tag, version := range tags.tags {
+		why(version, "dist-tag "+tag)
+	}
+	for _, pin := range pinned {
+		why(pin.Version, "a lockfile names it: "+pin.Where)
+	}
+	for _, w := range wanted {
+		if version, isTag := tags.tags[w.Range]; isTag {
+			why(version, fmt.Sprintf("dist-tag %q is the range %s names", w.Range, w.Where))
+			continue
+		}
+		r, err := ParseRange(w.Range)
+		if err != nil {
+			keepsAll = append(keepsAll, fmt.Sprintf("the range %q in %s cannot be read (%v)", w.Range, w.Where, err))
+			continue
+		}
+		if best, found := MaxSatisfying(r, parsed); found {
+			why(best.String(), fmt.Sprintf("the highest version satisfying %s in %s", w.Range, w.Where))
+		}
+	}
+
+	sort.SliceStable(entries, func(i, j int) bool {
+		a, b := entries[i], entries[j]
+		switch {
+		case a.ok && b.ok:
+			return Compare(a.v, b.v) > 0
+		case a.ok != b.ok:
+			return a.ok // a version that is not semver sorts last
+		}
+		return a.item.Published.After(b.item.Published)
+	})
+	newest := 0
+	for _, e := range entries {
+		if !e.ok {
+			e.item.Why = append(e.item.Why, "not a semantic version, so not ordered: kept")
+			continue
+		}
+		if newest < keep {
+			newest++
+			e.item.Why = append(e.item.Why, fmt.Sprintf("among the newest %d (pre-releases count)", keep))
+		}
+	}
+	if len(keepsAll) > 0 {
+		p.KeepsAll = strings.Join(keepsAll, "; ")
+	}
+	for _, e := range entries {
+		e.item.Why = dedupe(e.item.Why)
+		e.item.Kept = len(e.item.Why) > 0 || p.KeepsAll != ""
+		p.Versions = append(p.Versions, e.item)
+	}
+	return p
+}
+
+func mustVersion(s string) (Version, bool) {
+	v, err := ParseVersion(s)
+	return v, err == nil
+}
+
+// dedupe keeps each reason once and at most a few of each kind, so a version a hundred lockfiles name
+// is not a hundred lines.
+func dedupe(why []string) []string {
+	seen := map[string]bool{}
+	kinds := map[string]int{}
+	var out []string
+	more := map[string]int{}
+	for _, w := range why {
+		if seen[w] {
+			continue
+		}
+		seen[w] = true
+		kind, _, _ := strings.Cut(w, ":")
+		if kinds[kind] >= 3 {
+			more[kind]++
+			continue
+		}
+		kinds[kind]++
+		out = append(out, w)
+	}
+	for kind, n := range more {
+		out = append(out, fmt.Sprintf("%s: and %d more", kind, n))
+	}
+	sort.Strings(out)
+	return out
+}
+
+// measure asks the forge the size of each version sizes picks.
+func measure(ctx context.Context, f *Forge, s *Survey, sizes func(Item) bool) {
+	type at struct{ p, v int }
+	var todo []at
+	for i := range s.Packages {
+		for j := range s.Packages[i].Versions {
+			if sizes(s.Packages[i].Versions[j]) {
+				todo = append(todo, at{i, j})
+			}
+		}
+	}
+	var mu sync.Mutex
+	each(todo, func(a at) {
+		p := &s.Packages[a.p]
+		n, err := f.Size(ctx, p.Name, p.Versions[a.v].Version)
+		mu.Lock()
+		defer mu.Unlock()
+		if err != nil {
+			p.Versions[a.v].SizeError = err.Error()
+			return
+		}
+		p.Versions[a.v].Bytes = n
+	})
+}
+
+// Candidate is one version retention would delete.
+type Candidate struct {
+	Package   string    `json:"package"`
+	Version   string    `json:"version"`
+	Published time.Time `json:"published"`
+	Bytes     int64     `json:"bytes"`
+}
+
+// Plan is what retention would delete, and — for a real run — what it did.
+type Plan struct {
+	*Survey
+	DryRun     bool        `json:"dry_run"`
+	Why        string      `json:"why,omitempty"`
+	Candidates []Candidate `json:"would_delete"`
+	Bytes      int64       `json:"bytes"`
+	Deleted    []string    `json:"deleted,omitempty"`
+	Refused    []string    `json:"refused,omitempty"`
+}
+
+// retention works out the plan, and carries it out when dryRun is false.
+func retention(ctx context.Context, f *Forge, only string, keep int, dryRun bool, why string) (*Plan, error) {
+	if !dryRun && strings.TrimSpace(why) == "" {
+		return nil, errors.New("a real run deletes versions from the package registry and needs why; nothing was done")
+	}
+	s, err := survey(ctx, f, only, keep, func(i Item) bool { return !i.Kept })
+	if err != nil {
+		return nil, err
+	}
+	p := &Plan{Survey: s, DryRun: dryRun, Why: strings.TrimSpace(why), Candidates: []Candidate{}}
+	for _, pkg := range s.Packages {
+		for _, v := range pkg.Versions {
+			if !v.Kept {
+				p.Candidates = append(p.Candidates, Candidate{pkg.Name, v.Version, v.Published, v.Bytes})
+				p.Bytes += v.Bytes
+			}
+		}
+	}
+	s.Said = append(s.Said, fmt.Sprintf("%d repositories read; %d versions in %d packages; %d would be deleted, %s",
+		s.Repositories, countVersions(s), len(s.Packages), len(p.Candidates), mib(p.Bytes)))
+	if len(s.Unread) > 0 {
+		s.Said = append(s.Said, fmt.Sprintf("%d repositories or files could not be read: what they depend on is not "+
+			"known, so a real run deletes nothing", len(s.Unread)))
+	}
+	if dryRun {
+		s.Said = append(s.Said, "a dry run: nothing was deleted")
+		return p, nil
+	}
+	if len(s.Unread) > 0 {
+		return p, fmt.Errorf("refused: %d repositories or files could not be read, so what depends on what is not "+
+			"known; nothing was deleted (first: %s)", len(s.Unread), s.Unread[0])
+	}
+	del, cancel := context.WithTimeout(context.Background(), budget)
+	defer cancel()
+	for _, c := range p.Candidates {
+		if err := f.Delete(del, c.Package, c.Version); err != nil && !errors.Is(err, errNotFound) {
+			p.Refused = append(p.Refused, fmt.Sprintf("%s@%s: %v", c.Package, c.Version, err))
+			continue
+		}
+		p.Deleted = append(p.Deleted, c.Package+"@"+c.Version)
+	}
+	s.Said = append(s.Said, fmt.Sprintf("deleted %d, refused %d, because: %s", len(p.Deleted), len(p.Refused), p.Why))
+	return p, nil
+}
+
+func countVersions(s *Survey) int {
+	n := 0
+	for _, p := range s.Packages {
+		n += len(p.Versions)
+	}
+	return n
+}
+
+func mib(b int64) string { return fmt.Sprintf("%.1f MiB", float64(b)/(1<<20)) }
diff --git a/modules/gitea/cmd/npm-registry/retention_test.go b/modules/gitea/cmd/npm-registry/retention_test.go
new file mode 100644
index 00000000..d81e3c4a
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/retention_test.go
@@ -0,0 +1,393 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// fakeForge answers the forge's interface from maps, and records every delete.
+type fakeForge struct {
+	t        *testing.T
+	versions map[string][]string          // package -> versions
+	tags     map[string]map[string]string // package -> dist-tags
+	repos    map[string]map[string]string // repository -> path -> content
+	broken   map[string]bool              // repositories whose tree answers 500
+	mu       sync.Mutex
+	deleted  []string
+	password string
+}
+
+func (f *fakeForge) serve() *Forge {
+	srv := httptest.NewServer(http.HandlerFunc(f.handle))
+	f.t.Cleanup(srv.Close)
+	file := filepath.Join(f.t.TempDir(), "admin.secret")
+	if err := os.WriteFile(file, []byte(f.password+"\n"), 0o600); err != nil {
+		f.t.Fatal(err)
+	}
+	return &Forge{URL: srv.URL, User: "admin", PasswordFile: file, Owner: "acme"}
+}
+
+var (
+	versionFiles = regexp.MustCompile(`^/api/v1/packages/acme/npm/([^/]+)/([^/]+)(/files)?$`)
+	treePath     = regexp.MustCompile(`^/api/v1/repos/([^/]+)/([^/]+)/git/trees/`)
+	rawPath      = regexp.MustCompile(`^/api/v1/repos/([^/]+)/([^/]+)/raw/(.+)$`)
+)
+
+func (f *fakeForge) handle(w http.ResponseWriter, r *http.Request) {
+	user, pass, ok := r.BasicAuth()
+	if !ok || user != "admin" || pass != f.password {
+		http.Error(w, "unauthorised", http.StatusUnauthorized)
+		return
+	}
+	p := r.URL.EscapedPath()
+	q := r.URL.Query()
+	page := 1
+	fmt.Sscan(q.Get("page"), &page)
+	switch {
+	case p == "/api/v1/packages/acme" && r.Method == http.MethodGet:
+		var all []map[string]any
+		names := keys(f.versions)
+		for _, n := range names {
+			for i, v := range f.versions[n] {
+				all = append(all, map[string]any{"name": n, "version": v, "type": "npm",
+					"created_at": time.Date(2026, 1, 1+i, 0, 0, 0, 0, time.UTC)})
+			}
+		}
+		writeJSON(w, pageOf(all, page, pageSize))
+	case strings.HasPrefix(p, "/api/packages/acme/npm/"):
+		name, _ := url.PathUnescape(strings.TrimPrefix(p, "/api/packages/acme/npm/"))
+		writeJSON(w, map[string]any{"name": name, "dist-tags": f.tags[name]})
+	case versionFiles.MatchString(p):
+		m := versionFiles.FindStringSubmatch(p)
+		name, _ := url.PathUnescape(m[1])
+		version, _ := url.PathUnescape(m[2])
+		if m[3] != "" {
+			writeJSON(w, []map[string]any{{"name": "a.tgz", "size": 1 << 20}, {"name": "b", "size": 1024}})
+			return
+		}
+		if r.Method != http.MethodDelete {
+			http.Error(w, "no", http.StatusMethodNotAllowed)
+			return
+		}
+		f.mu.Lock()
+		f.deleted = append(f.deleted, name+"@"+version)
+		f.mu.Unlock()
+		w.WriteHeader(http.StatusNoContent)
+	case p == "/api/v1/repos/search":
+		var all []map[string]any
+		for _, n := range keys(f.repos) {
+			all = append(all, map[string]any{"full_name": n, "default_branch": "main", "empty": len(f.repos[n]) == 0})
+		}
+		writeJSON(w, map[string]any{"ok": true, "data": pageOf(all, page, pageSize)})
+	case treePath.MatchString(p):
+		m := treePath.FindStringSubmatch(p)
+		full := m[1] + "/" + m[2]
+		if f.broken[full] {
+			http.Error(w, "boom", http.StatusInternalServerError)
+			return
+		}
+		var tree []map[string]any
+		for _, path := range keys(f.repos[full]) {
+			tree = append(tree, map[string]any{"path": path, "type": "blob"})
+		}
+		writeJSON(w, map[string]any{"tree": tree, "truncated": false, "total_count": len(tree)})
+	case rawPath.MatchString(p):
+		m := rawPath.FindStringSubmatch(p)
+		file, _ := url.PathUnescape(m[3])
+		content, has := f.repos[m[1]+"/"+m[2]][file]
+		if !has {
+			http.NotFound(w, r)
+			return
+		}
+		w.Write([]byte(content))
+	default:
+		http.NotFound(w, r)
+	}
+}
+
+func keys[T any](m map[string]T) []string {
+	var out []string
+	for k := range m {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}
+
+func pageOf[T any](all []T, page, size int) []T {
+	lo := (page - 1) * size
+	if lo >= len(all) {
+		return []T{}
+	}
+	return all[lo:min(lo+size, len(all))]
+}
+
+func writeJSON(w http.ResponseWriter, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(v)
+}
+
+// aRegistry: the SDK with nine versions over two lines, a UI package with three, and repositories that
+// pin an old SDK in a lockfile, range onto the old line, and tag a pre-release.
+func aRegistry(t *testing.T) *fakeForge {
+	return &fakeForge{
+		t:        t,
+		password: "s3cret-never-shown",
+		versions: map[string][]string{
+			"@acme/sdk": {"0.1.0", "0.1.1", "0.1.2", "0.1.3", "0.2.0", "0.2.1", "0.2.2", "0.3.0-beta.1", "0.3.0"},
+			"@acme/ui":  {"1.0.0", "1.1.0", "2.0.0"},
+		},
+		tags: map[string]map[string]string{
+			"@acme/sdk": {"latest": "0.3.0", "next": "0.3.0-beta.1"},
+			"@acme/ui":  {"latest": "2.0.0"},
+		},
+		repos: map[string]map[string]string{
+			"acme/app": {
+				"package.json":      `{"dependencies":{"@acme/sdk":"^0.1.0","left-pad":"1.0.0"}}`,
+				"package-lock.json": `{"lockfileVersion":3,"packages":{"node_modules/@acme/sdk":{"version":"0.1.0"}}}`,
+			},
+			"acme/site":  {"web/package.json": `{"devDependencies":{"@acme/ui":"~1.0.0"}}`, "README.md": "x"},
+			"acme/empty": {},
+		},
+	}
+}
+
+func decided(s *Survey) map[string]Item {
+	out := map[string]Item{}
+	for _, p := range s.Packages {
+		for _, v := range p.Versions {
+			out[p.Name+"@"+v.Version] = v
+		}
+	}
+	return out
+}
+
+func TestWhatKeepsAVersionIsWhatNamesIt(t *testing.T) {
+	f := aRegistry(t)
+	s, err := survey(context.Background(), f.serve(), "", 3, func(Item) bool { return true })
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.Repositories != 3 || len(s.Unread) != 0 {
+		t.Fatalf("read %d, unread %v", s.Repositories, s.Unread)
+	}
+	d := decided(s)
+	wantKept := map[string]string{
+		"@acme/sdk@0.1.0":        "a lockfile names it: acme/app:package-lock.json", // old, but pinned
+		"@acme/sdk@0.1.3":        "the highest version satisfying ^0.1.0 in acme/app:package.json",
+		"@acme/sdk@0.3.0-beta.1": "dist-tag next",
+		"@acme/sdk@0.3.0":        "dist-tag latest",
+		"@acme/sdk@0.2.2":        "among the newest 3 (pre-releases count)",
+		"@acme/ui@1.0.0":         "the highest version satisfying ~1.0.0 in acme/site:web/package.json",
+		"@acme/ui@1.1.0":         "among the newest 3 (pre-releases count)",
+	}
+	for v, why := range wantKept {
+		item := d[v]
+		if !item.Kept || !contains(item.Why, why) {
+			t.Errorf("%s: kept %v, why %v; want %q", v, item.Kept, item.Why, why)
+		}
+	}
+	for _, v := range []string{"@acme/sdk@0.1.1", "@acme/sdk@0.1.2", "@acme/sdk@0.2.0", "@acme/sdk@0.2.1"} {
+		if d[v].Kept {
+			t.Errorf("%s kept for %v", v, d[v].Why)
+		}
+	}
+	if d["@acme/sdk@0.1.1"].Bytes != 1<<20+1024 {
+		t.Errorf("size %d", d["@acme/sdk@0.1.1"].Bytes)
+	}
+	// Newest first.
+	if s.Packages[0].Versions[0].Version != "0.3.0" || s.Packages[0].Versions[1].Version != "0.3.0-beta.1" {
+		t.Errorf("order %v", s.Packages[0].Versions[:2])
+	}
+}
+
+func contains(list []string, s string) bool {
+	for _, x := range list {
+		if x == s {
+			return true
+		}
+	}
+	return false
+}
+
+func TestADryRunDeletesNothingAndSaysWhatWouldGo(t *testing.T) {
+	f := aRegistry(t)
+	p, err := retention(context.Background(), f.serve(), "", 3, true, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(f.deleted) != 0 {
+		t.Fatalf("a dry run deleted %v", f.deleted)
+	}
+	var would []string
+	for _, c := range p.Candidates {
+		would = append(would, c.Package+"@"+c.Version)
+	}
+	sort.Strings(would)
+	if strings.Join(would, " ") != "@acme/sdk@0.1.1 @acme/sdk@0.1.2 @acme/sdk@0.2.0 @acme/sdk@0.2.1" {
+		t.Fatalf("would delete %v", would)
+	}
+	if p.Bytes != 4*(1<<20+1024) {
+		t.Errorf("bytes %d", p.Bytes)
+	}
+	raw, _ := json.Marshal(p)
+	if strings.Contains(string(raw), f.password) {
+		t.Fatal("the answer carries the forge's password")
+	}
+}
+
+func TestARealRunWithoutWhyIsRefusedBeforeAnythingIsRead(t *testing.T) {
+	f := aRegistry(t)
+	if _, err := retention(context.Background(), f.serve(), "", 3, false, "  "); err == nil || !strings.Contains(err.Error(), "needs why") {
+		t.Fatalf("got %v", err)
+	}
+	if len(f.deleted) != 0 {
+		t.Fatal("deleted without a why")
+	}
+}
+
+func TestARealRunDeletesOnlyWhatNothingKeeps(t *testing.T) {
+	f := aRegistry(t)
+	p, err := retention(context.Background(), f.serve(), "", 3, false, "the registry keeps what is named")
+	if err != nil {
+		t.Fatal(err)
+	}
+	sort.Strings(f.deleted)
+	if strings.Join(f.deleted, " ") != "@acme/sdk@0.1.1 @acme/sdk@0.1.2 @acme/sdk@0.2.0 @acme/sdk@0.2.1" {
+		t.Fatalf("deleted %v", f.deleted)
+	}
+	if len(p.Deleted) != 4 || len(p.Refused) != 0 {
+		t.Fatalf("answered %v / %v", p.Deleted, p.Refused)
+	}
+}
+
+func TestAnUnreadRepositoryStopsARealRunBeforeAnythingIsDeleted(t *testing.T) {
+	f := aRegistry(t)
+	f.broken = map[string]bool{"acme/site": true}
+	p, err := retention(context.Background(), f.serve(), "", 3, false, "tidy")
+	if err == nil || !strings.Contains(err.Error(), "nothing was deleted") {
+		t.Fatalf("got %v", err)
+	}
+	if len(f.deleted) != 0 {
+		t.Fatalf("deleted %v while a repository was unread", f.deleted)
+	}
+	if p == nil || len(p.Unread) != 1 || !strings.HasPrefix(p.Unread[0], "acme/site") {
+		t.Fatalf("unread %v", p)
+	}
+	// And the dry run says so, without failing.
+	dry, err := retention(context.Background(), f.serve(), "", 3, true, "")
+	if err != nil || len(dry.Unread) != 1 {
+		t.Fatalf("dry run: %v %v", err, dry)
+	}
+}
+
+func TestARangeThatCannotBeReadKeepsEveryVersionOfItsPackage(t *testing.T) {
+	f := aRegistry(t)
+	f.repos["acme/odd"] = map[string]string{"package.json": `{"dependencies":{"@acme/sdk":"^not.a.range"}}`}
+	p, err := retention(context.Background(), f.serve(), "@acme/sdk", 1, true, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(p.Candidates) != 0 || !strings.Contains(p.Packages[0].KeepsAll, "^not.a.range") {
+		t.Fatalf("candidates %v, keeps all %q", p.Candidates, p.Packages[0].KeepsAll)
+	}
+}
+
+func TestADistTagNamedAsARangeKeepsItsVersion(t *testing.T) {
+	f := aRegistry(t)
+	f.repos["acme/tagged"] = map[string]string{"package.json": `{"dependencies":{"@acme/sdk":"next"}}`}
+	s, err := survey(context.Background(), f.serve(), "@acme/sdk", 1, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.Packages[0].KeepsAll != "" || !decided(s)["@acme/sdk@0.3.0-beta.1"].Kept {
+		t.Fatalf("%+v", s.Packages[0])
+	}
+}
+
+func TestAWrongPasswordIsAFailureThatDoesNotSayThePassword(t *testing.T) {
+	f := aRegistry(t)
+	forge := f.serve()
+	f.password = "rotated"
+	_, err := survey(context.Background(), forge, "", 3, nil)
+	if err == nil || !strings.Contains(err.Error(), "401") || strings.Contains(err.Error(), "s3cret") {
+		t.Fatalf("got %v", err)
+	}
+}
+
+func TestToolsAreTheOnesTheReadmeNamesAndSayWhatTheyDo(t *testing.T) {
+	tools := Tools(func() (*Forge, error) { return nil, fmt.Errorf("unset") })
+	var served []string
+	for _, tl := range tools {
+		served = append(served, tl.Name)
+		suffix := "(r)"
+		if tl.Name == "npm_retention" {
+			suffix = "(a)"
+		}
+		if !strings.HasSuffix(tl.Description, suffix) {
+			t.Errorf("%s does not end with %s", tl.Name, suffix)
+		}
+	}
+	if strings.Join(served, ",") != strings.Join(ToolNames, ",") {
+		t.Fatalf("served %v, named %v", served, ToolNames)
+	}
+	readme, err := os.ReadFile("../../README.md")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, n := range ToolNames {
+		if !strings.Contains(string(readme), "`"+n+"`") {
+			t.Errorf("the README does not name %s", n)
+		}
+	}
+	raw, err := os.ReadFile("../../module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var m struct {
+		Tools []string `json:"tools"`
+		Build struct {
+			Artifacts []struct {
+				From  string            `json:"from"`
+				Loads []string          `json:"loads"`
+				Env   map[string]string `json:"env"`
+			} `json:"artifacts"`
+		} `json:"build"`
+	}
+	if err := json.Unmarshal(raw, &m); err != nil {
+		t.Fatal(err)
+	}
+	if len(m.Tools) != 0 {
+		t.Error("the manifest lists tools: its claims would offer them as both seats' verbs")
+	}
+	found := false
+	for _, a := range m.Build.Artifacts {
+		if a.From == "cmd/npm-registry" {
+			found = true
+			for _, k := range []string{"MESH_GITEA_URL", "MESH_GITEA_ADMIN_USER", "MESH_GITEA_ADMIN_PASSWORD_FILE", "MESH_NPM_OWNER"} {
+				if a.Env[k] == "" {
+					t.Errorf("the bundle is not given %s", k)
+				}
+			}
+		}
+	}
+	if !found {
+		t.Error("the manifest builds no cmd/npm-registry bundle")
+	}
+	// Refused cleanly when the environment is missing, not a crash.
+	if _, err := tools[0].Run(map[string]any{}); err == nil {
+		t.Error("ran without a forge")
+	}
+}
diff --git a/modules/gitea/cmd/npm-registry/semver.go b/modules/gitea/cmd/npm-registry/semver.go
new file mode 100644
index 00000000..5e21bf2e
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/semver.go
@@ -0,0 +1,362 @@
+package main
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Versions and ranges as npm reads them (node-semver), small enough to read whole: a version, the
+// order of two, and whether a version satisfies a range. Only what retention needs — which published
+// version a range resolves to — and nothing npm does beyond that (no coercion, no loose mode).
+
+// Version is one semantic version.
+type Version struct {
+	Major, Minor, Patch int
+	Pre                 []string // the pre-release identifiers; none for a release
+	raw                 string
+}
+
+func (v Version) String() string { return v.raw }
+
+var versionPattern = regexp.MustCompile(`^v?(\d+)\.(\d+)\.(\d+)(?:-([0-9A-Za-z.-]+))?(?:\+[0-9A-Za-z.-]+)?$`)
+
+// ParseVersion reads a full version; a partial one (1.2) is not a version.
+func ParseVersion(s string) (Version, error) {
+	s = strings.TrimSpace(s)
+	m := versionPattern.FindStringSubmatch(s)
+	if m == nil {
+		return Version{}, fmt.Errorf("%q is not a version", s)
+	}
+	v := Version{raw: strings.TrimPrefix(s, "v")}
+	v.Major, _ = strconv.Atoi(m[1])
+	v.Minor, _ = strconv.Atoi(m[2])
+	v.Patch, _ = strconv.Atoi(m[3])
+	if m[4] != "" {
+		v.Pre = strings.Split(m[4], ".")
+	}
+	return v, nil
+}
+
+// Compare is -1, 0 or 1 as a is lower than, equal to or higher than b, by semver precedence.
+func Compare(a, b Version) int {
+	for _, d := range [][2]int{{a.Major, b.Major}, {a.Minor, b.Minor}, {a.Patch, b.Patch}} {
+		if d[0] != d[1] {
+			if d[0] < d[1] {
+				return -1
+			}
+			return 1
+		}
+	}
+	switch {
+	case len(a.Pre) == 0 && len(b.Pre) == 0:
+		return 0
+	case len(a.Pre) == 0:
+		return 1 // a release is higher than any of its pre-releases
+	case len(b.Pre) == 0:
+		return -1
+	}
+	for i := 0; i < len(a.Pre) && i < len(b.Pre); i++ {
+		if c := compareIdentifier(a.Pre[i], b.Pre[i]); c != 0 {
+			return c
+		}
+	}
+	switch {
+	case len(a.Pre) < len(b.Pre):
+		return -1
+	case len(a.Pre) > len(b.Pre):
+		return 1
+	}
+	return 0
+}
+
+func compareIdentifier(a, b string) int {
+	an, aerr := strconv.Atoi(a)
+	bn, berr := strconv.Atoi(b)
+	switch {
+	case aerr == nil && berr == nil:
+		switch {
+		case an < bn:
+			return -1
+		case an > bn:
+			return 1
+		}
+		return 0
+	case aerr == nil:
+		return -1 // a numeric identifier is lower than an alphanumeric one
+	case berr == nil:
+		return 1
+	}
+	return strings.Compare(a, b)
+}
+
+// comparator is one `<op> <version>`; ANY when the version is the zero bound of `*`.
+type comparator struct {
+	op string // ">", ">=", "<", "<=", "="
+	v  Version
+}
+
+func (c comparator) test(v Version) bool {
+	d := Compare(v, c.v)
+	switch c.op {
+	case ">":
+		return d > 0
+	case ">=":
+		return d >= 0
+	case "<":
+		return d < 0
+	case "<=":
+		return d <= 0
+	}
+	return d == 0
+}
+
+// Range is a set of comparator sets, any one of which a version must satisfy (`||`).
+type Range struct {
+	sets [][]comparator
+	raw  string
+}
+
+func (r Range) String() string { return r.raw }
+
+// partial is a version that may stop early or carry x/X/*: -1 for a missing or wild part.
+type partial struct {
+	major, minor, patch int
+	pre                 []string
+}
+
+var partialPattern = regexp.MustCompile(`^v?(\d+|[xX*])?(?:\.(\d+|[xX*]))?(?:\.(\d+|[xX*]))?(?:-([0-9A-Za-z.-]+))?(?:\+[0-9A-Za-z.-]+)?$`)
+
+func parsePartial(s string) (partial, error) {
+	m := partialPattern.FindStringSubmatch(s)
+	if m == nil {
+		return partial{}, fmt.Errorf("%q is not a version or a partial one", s)
+	}
+	num := func(x string) int {
+		if x == "" || x == "x" || x == "X" || x == "*" {
+			return -1
+		}
+		n, _ := strconv.Atoi(x)
+		return n
+	}
+	p := partial{major: num(m[1]), minor: num(m[2]), patch: num(m[3])}
+	// Nothing below a wild part counts: 1.x.3 is 1.x.
+	if p.major < 0 {
+		p.minor, p.patch = -1, -1
+	} else if p.minor < 0 {
+		p.patch = -1
+	}
+	if m[4] != "" {
+		if p.patch < 0 {
+			return partial{}, fmt.Errorf("%q has a pre-release on a partial version", s)
+		}
+		p.pre = strings.Split(m[4], ".")
+	}
+	return p, nil
+}
+
+func ver(major, minor, patch int, pre ...string) Version {
+	raw := fmt.Sprintf("%d.%d.%d", major, minor, patch)
+	if len(pre) > 0 {
+		raw += "-" + strings.Join(pre, ".")
+	}
+	return Version{Major: major, Minor: minor, Patch: patch, Pre: pre, raw: raw}
+}
+
+// lower is the lowest version a partial names; upperExclusive the first version above it (with -0, so
+// no pre-release of that next version slips in), and whether it has one.
+func (p partial) lower() Version {
+	switch {
+	case p.major < 0:
+		return ver(0, 0, 0)
+	case p.minor < 0:
+		return ver(p.major, 0, 0)
+	case p.patch < 0:
+		return ver(p.major, p.minor, 0)
+	}
+	return ver(p.major, p.minor, p.patch, p.pre...)
+}
+
+func (p partial) upperExclusive() (Version, bool) {
+	switch {
+	case p.major < 0:
+		return Version{}, false
+	case p.minor < 0:
+		return ver(p.major+1, 0, 0, "0"), true
+	case p.patch < 0:
+		return ver(p.major, p.minor+1, 0, "0"), true
+	}
+	return Version{}, false
+}
+
+var (
+	hyphenPattern = regexp.MustCompile(`^\s*(\S+)\s+-\s+(\S+)\s*$`)
+	opSpace       = regexp.MustCompile(`(>=|<=|>|<|=|\^|~>?)\s+`)
+)
+
+// ParseRange reads a range as npm does: exact, `^`, `~`, x-ranges, comparisons, hyphen ranges, sets
+// joined by spaces, and `||`.
+func ParseRange(s string) (Range, error) {
+	r := Range{raw: s}
+	for _, part := range strings.Split(s, "||") {
+		set, err := parseSet(strings.TrimSpace(part))
+		if err != nil {
+			return Range{}, err
+		}
+		r.sets = append(r.sets, set)
+	}
+	return r, nil
+}
+
+func parseSet(s string) ([]comparator, error) {
+	if m := hyphenPattern.FindStringSubmatch(s); m != nil {
+		from, err := parsePartial(m[1])
+		if err != nil {
+			return nil, err
+		}
+		to, err := parsePartial(m[2])
+		if err != nil {
+			return nil, err
+		}
+		set := []comparator{{">=", from.lower()}}
+		if up, has := to.upperExclusive(); has {
+			set = append(set, comparator{"<", up})
+		} else if to.major >= 0 {
+			set = append(set, comparator{"<=", to.lower()})
+		}
+		return set, nil
+	}
+	s = opSpace.ReplaceAllString(s, "$1")
+	if s == "" {
+		return []comparator{{">=", ver(0, 0, 0)}}, nil
+	}
+	var set []comparator
+	for _, word := range strings.Fields(s) {
+		cs, err := parseComparator(word)
+		if err != nil {
+			return nil, err
+		}
+		set = append(set, cs...)
+	}
+	return set, nil
+}
+
+func parseComparator(w string) ([]comparator, error) {
+	var op string
+	for _, o := range []string{">=", "<=", "~>", ">", "<", "=", "^", "~"} {
+		if strings.HasPrefix(w, o) {
+			op, w = o, w[len(o):]
+			break
+		}
+	}
+	p, err := parsePartial(w)
+	if err != nil {
+		return nil, err
+	}
+	lo := p.lower()
+	up, bounded := p.upperExclusive()
+	switch op {
+	case "", "=":
+		if !bounded && p.major >= 0 {
+			return []comparator{{"=", lo}}, nil
+		}
+		return xrange(lo, up, bounded), nil
+	case "^":
+		var hi Version
+		switch {
+		case p.major < 0:
+			return []comparator{{">=", ver(0, 0, 0)}}, nil
+		case p.major > 0 || p.minor < 0:
+			hi = ver(p.major+1, 0, 0, "0")
+		case p.minor > 0 || p.patch < 0:
+			hi = ver(0, p.minor+1, 0, "0")
+		default:
+			hi = ver(0, 0, p.patch+1, "0")
+		}
+		return []comparator{{">=", lo}, {"<", hi}}, nil
+	case "~", "~>":
+		var hi Version
+		switch {
+		case p.major < 0:
+			return []comparator{{">=", ver(0, 0, 0)}}, nil
+		case p.minor < 0:
+			hi = ver(p.major+1, 0, 0, "0")
+		default:
+			hi = ver(p.major, p.minor+1, 0, "0")
+		}
+		return []comparator{{">=", lo}, {"<", hi}}, nil
+	case ">":
+		if p.major < 0 {
+			return []comparator{{"<", ver(0, 0, 0, "0")}}, nil // nothing
+		}
+		if bounded {
+			return []comparator{{">=", up}}, nil
+		}
+		return []comparator{{">", lo}}, nil
+	case ">=":
+		return []comparator{{">=", lo}}, nil
+	case "<":
+		if p.major < 0 {
+			return []comparator{{"<", ver(0, 0, 0, "0")}}, nil
+		}
+		return []comparator{{"<", lo}}, nil
+	case "<=":
+		if p.major < 0 {
+			return []comparator{{">=", ver(0, 0, 0)}}, nil
+		}
+		if bounded {
+			return []comparator{{"<", up}}, nil
+		}
+		return []comparator{{"<=", lo}}, nil
+	}
+	return nil, fmt.Errorf("%q is not a comparator", w)
+}
+
+func xrange(lo, up Version, bounded bool) []comparator {
+	if !bounded {
+		return []comparator{{">=", lo}}
+	}
+	return []comparator{{">=", lo}, {"<", up}}
+}
+
+// Satisfies is whether v is in the range. A pre-release satisfies a set only when one of its
+// comparators names the same major.minor.patch with a pre-release of its own — npm's rule, so that
+// `^1.2.0` never resolves to 1.3.0-beta.
+func (r Range) Satisfies(v Version) bool {
+	for _, set := range r.sets {
+		if testSet(set, v) {
+			return true
+		}
+	}
+	return false
+}
+
+func testSet(set []comparator, v Version) bool {
+	for _, c := range set {
+		if !c.test(v) {
+			return false
+		}
+	}
+	if len(v.Pre) == 0 {
+		return true
+	}
+	for _, c := range set {
+		if len(c.v.Pre) > 0 && c.v.Major == v.Major && c.v.Minor == v.Minor && c.v.Patch == v.Patch {
+			return true
+		}
+	}
+	return false
+}
+
+// MaxSatisfying is the highest of the versions in the range; false when none is.
+func MaxSatisfying(r Range, versions []Version) (Version, bool) {
+	var best Version
+	found := false
+	for _, v := range versions {
+		if r.Satisfies(v) && (!found || Compare(v, best) > 0) {
+			best, found = v, true
+		}
+	}
+	return best, found
+}
diff --git a/modules/gitea/cmd/npm-registry/semver_test.go b/modules/gitea/cmd/npm-registry/semver_test.go
new file mode 100644
index 00000000..84ac934d
--- /dev/null
+++ b/modules/gitea/cmd/npm-registry/semver_test.go
@@ -0,0 +1,117 @@
+package main
+
+import "testing"
+
+func TestVersionsAreOrderedAsSemverSays(t *testing.T) {
+	// Each is lower than the next (semver.org §11's own example, and the edges around it).
+	ordered := []string{"0.0.1", "0.1.0", "1.0.0-0", "1.0.0-alpha", "1.0.0-alpha.1", "1.0.0-alpha.beta", "1.0.0-beta",
+		"1.0.0-beta.2", "1.0.0-beta.11", "1.0.0-rc.1", "1.0.0", "1.0.1", "1.2.0", "1.10.0", "2.0.0"}
+	for i := 0; i+1 < len(ordered); i++ {
+		a, _ := ParseVersion(ordered[i])
+		b, _ := ParseVersion(ordered[i+1])
+		if Compare(a, b) >= 0 || Compare(b, a) <= 0 {
+			t.Errorf("%s should be lower than %s", ordered[i], ordered[i+1])
+		}
+	}
+	a, _ := ParseVersion("1.2.3+build.1")
+	b, _ := ParseVersion("1.2.3")
+	if Compare(a, b) != 0 {
+		t.Error("build metadata does not order")
+	}
+	for _, bad := range []string{"1.2", "x", "1.2.3.4", "latest", ""} {
+		if _, err := ParseVersion(bad); err == nil {
+			t.Errorf("%q read as a version", bad)
+		}
+	}
+}
+
+func TestRangesAreReadAsNpmReadsThem(t *testing.T) {
+	cases := []struct {
+		r   string
+		in  []string
+		out []string
+	}{
+		{"1.2.3", []string{"1.2.3"}, []string{"1.2.4", "1.2.3-beta"}},
+		{"=1.2.3", []string{"1.2.3"}, []string{"1.2.2"}},
+		{"^1.2.3", []string{"1.2.3", "1.9.9"}, []string{"2.0.0", "1.2.2", "1.3.0-beta", "2.0.0-0"}},
+		{"^0.2.3", []string{"0.2.3", "0.2.9"}, []string{"0.3.0", "0.2.2"}},
+		{"^0.0.3", []string{"0.0.3"}, []string{"0.0.4"}},
+		{"^1.2", []string{"1.2.0", "1.9.0"}, []string{"2.0.0", "1.1.9"}},
+		{"^0.x", []string{"0.0.1", "0.9.9"}, []string{"1.0.0"}},
+		{"^0.0", []string{"0.0.9"}, []string{"0.1.0"}},
+		{"^1.2.3-beta.2", []string{"1.2.3-beta.2", "1.2.3-beta.4", "1.2.3", "1.5.0"}, []string{"1.2.3-beta.1", "1.2.4-beta.1", "2.0.0"}},
+		{"~1.2.3", []string{"1.2.3", "1.2.9"}, []string{"1.3.0", "1.2.2"}},
+		{"~1.2", []string{"1.2.0", "1.2.9"}, []string{"1.3.0"}},
+		{"~1", []string{"1.0.0", "1.9.9"}, []string{"2.0.0"}},
+		{"~0.2.3", []string{"0.2.5"}, []string{"0.3.0"}},
+		{"*", []string{"0.0.0", "9.9.9"}, []string{"1.0.0-beta"}},
+		{"", []string{"1.0.0"}, nil},
+		{"x", []string{"1.0.0"}, nil},
+		{"1.x", []string{"1.0.0", "1.9.9"}, []string{"2.0.0", "0.9.9"}},
+		{"1.2.*", []string{"1.2.0", "1.2.9"}, []string{"1.3.0"}},
+		{"1", []string{"1.5.0"}, []string{"2.0.0"}},
+		{">1.2.3", []string{"1.2.4"}, []string{"1.2.3"}},
+		{">1.2", []string{"1.3.0"}, []string{"1.2.9"}},
+		{">=1.2.3", []string{"1.2.3", "5.0.0"}, []string{"1.2.2"}},
+		{"<1.2.3", []string{"1.2.2"}, []string{"1.2.3", "1.2.3-beta"}},
+		{"<1.2", []string{"1.1.9"}, []string{"1.2.0"}},
+		{"<=1.2.3", []string{"1.2.3"}, []string{"1.2.4"}},
+		{"<=1.2", []string{"1.2.9"}, []string{"1.3.0"}},
+		{">= 1.2.3 < 2", []string{"1.2.3", "1.9.9"}, []string{"2.0.0", "1.2.2"}},
+		{">=1.2.3 <1.5.0", []string{"1.4.9"}, []string{"1.5.0"}},
+		{"1.2.3 - 2.3.4", []string{"1.2.3", "2.3.4"}, []string{"2.3.5", "1.2.2"}},
+		{"1.2 - 2.3", []string{"1.2.0", "2.3.9"}, []string{"2.4.0", "1.1.9"}},
+		{"1.2.3 - 2", []string{"2.9.9"}, []string{"3.0.0"}},
+		{"^1.0.0 || ^3.0.0", []string{"1.5.0", "3.1.0"}, []string{"2.0.0"}},
+		{"1.2.3 || >=2.5.0 <3", []string{"1.2.3", "2.6.0"}, []string{"2.0.0", "3.0.0"}},
+		{"v1.2.3", []string{"1.2.3"}, nil},
+		{"~>1.2.3", []string{"1.2.9"}, []string{"1.3.0"}},
+		{">=1.0.0-rc.1 <1.0.0", []string{"1.0.0-rc.2"}, []string{"0.9.0-rc.1"}},
+	}
+	for _, c := range cases {
+		r, err := ParseRange(c.r)
+		if err != nil {
+			t.Errorf("%q: %v", c.r, err)
+			continue
+		}
+		for _, s := range c.in {
+			v, err := ParseVersion(s)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !r.Satisfies(v) {
+				t.Errorf("%q should hold %s", c.r, s)
+			}
+		}
+		for _, s := range c.out {
+			v, _ := ParseVersion(s)
+			if r.Satisfies(v) {
+				t.Errorf("%q should not hold %s", c.r, s)
+			}
+		}
+	}
+}
+
+func TestARangeThatIsNotOneIsRefused(t *testing.T) {
+	for _, bad := range []string{"latest", "^abc", "1.2.3.4", ">=x.y.z", "1.x-beta"} {
+		if _, err := ParseRange(bad); err == nil {
+			t.Errorf("%q read as a range", bad)
+		}
+	}
+}
+
+func TestTheHighestSatisfyingVersionIsTheOneARangeResolvesTo(t *testing.T) {
+	var vs []Version
+	for _, s := range []string{"0.1.0", "0.1.4", "0.2.0", "0.2.1-beta", "1.0.0"} {
+		v, _ := ParseVersion(s)
+		vs = append(vs, v)
+	}
+	r, _ := ParseRange("^0.1.0")
+	if best, ok := MaxSatisfying(r, vs); !ok || best.String() != "0.1.4" {
+		t.Fatalf("^0.1.0 resolved to %v", best)
+	}
+	r, _ = ParseRange("^2.0.0")
+	if _, ok := MaxSatisfying(r, vs); ok {
+		t.Fatal("^2.0.0 resolved to something")
+	}
+}
diff --git a/modules/gitea/go.mod b/modules/gitea/go.mod
new file mode 100644
index 00000000..c05b9bd6
--- /dev/null
+++ b/modules/gitea/go.mod
@@ -0,0 +1,5 @@
+module gitea
+
+go 1.22
+
+require git.novox.be/novox/mesh-sdk/go v0.1.7
diff --git a/modules/gitea/go.sum b/modules/gitea/go.sum
new file mode 100644
index 00000000..b474419e
--- /dev/null
+++ b/modules/gitea/go.sum
@@ -0,0 +1,2 @@
+git.novox.be/novox/mesh-sdk/go v0.1.7 h1:C0sTQmtTiyYH7bnqZb7PusXnqA37gKuT7Nqjn9gG47w=
+git.novox.be/novox/mesh-sdk/go v0.1.7/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
diff --git a/modules/gitea/module.json b/modules/gitea/module.json
index 20a52ec6..1088a76b 100644
--- a/modules/gitea/module.json
+++ b/modules/gitea/module.json
@@ -239,6 +239,23 @@
           "MESH_GITEA_STATE_DIR": "${dir:runtime-state}",
           "MESH_RECEIVES": "${dir:grants}/npm.json"
         }
+      },
+      {
+        "name": "npm-registry",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/npm-registry",
+        "binary": "npm-registry",
+        "loads": [
+          "npm-registry"
+        ],
+        "env": {
+          "MESH_GITEA_URL": "http://127.0.0.1:${port:3000}",
+          "MESH_GITEA_ADMIN_USER": "mesh-admin",
+          "MESH_GITEA_ADMIN_PASSWORD_FILE": "${dir:state}/admin.secret",
+          "MESH_NPM_OWNER": "novox"
+        }
       }
     ]
   },
diff --git a/modules/gitea/npm-registry b/modules/gitea/npm-registry
new file mode 100755
index 00000000..37c988b7
Binary files /dev/null and b/modules/gitea/npm-registry differ