diff --git a/.quixos-subtree-source.json b/.quixos-subtree-source.json
index e30aeb4..fb594f9 100644
--- a/.quixos-subtree-source.json
+++ b/.quixos-subtree-source.json
@@ -1,7 +1,7 @@
 {
   "version": 1,
   "sourceRepo": "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/quixos",
-  "sourceCommit": "a61bdda658be4878403b8d60aecb71fe5a614ac0",
+  "sourceCommit": "8014b4ba717313e1b494c59a8e2781df58bf9a85",
   "sourcePath": "quixos-protocol",
   "exportName": "quixos-protocol",
   "mirrorRemote": "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/quixos-protocol.git"
diff --git a/nix/checked-candidate.nix b/nix/checked-candidate.nix
index d657ca0..4ccb7a6 100644
--- a/nix/checked-candidate.nix
+++ b/nix/checked-candidate.nix
@@ -6,6 +6,7 @@
   kind,
   generator,
   contractOnly ? false,
+  workspaceId ? null,
   system ? builtins.currentSystem,
 }:
 let
@@ -164,6 +165,11 @@ let
               ${queryGeneratorFlags root} \
               --checked-resources ${checkedResources node} \
               --source-root-commit ${pkgs.lib.escapeShellArg node.commit} \
+              ${
+                pkgs.lib.optionalString (
+                  workspaceId != null
+                ) "--workspace-id ${pkgs.lib.escapeShellArg workspaceId}"
+              } \
               --checkout-root "$TMPDIR/checkouts" --snapshot-map ${snapshots node} \
               --graph-out "$out/graph.json" --schemas-out "$out/package-schemas.json" \
               ${
@@ -357,6 +363,13 @@ let
     )
   );
 in
+assert
+  workspaceId == null
+  || (
+    kind == "workspace"
+    && builtins.isString workspaceId
+    && builtins.match "[a-zA-Z0-9][a-zA-Z0-9:._-]{0,255}" workspaceId != null
+  );
 pkgs.runCommand (if contractOnly then "qx-contract" else "qx-checked-candidate") { } ''
   mkdir -p "$out"
   cp ${
diff --git a/src/capability-language/authoring-check.ts b/src/capability-language/authoring-check.ts
index b378075..fee9370 100644
--- a/src/capability-language/authoring-check.ts
+++ b/src/capability-language/authoring-check.ts
@@ -97,6 +97,7 @@ export async function checkAuthoring(
         (phase, ms) => {
           timings[phase] = ms;
         },
+        resource.kind === "workspace" ? context.workspaceId : undefined,
       );
     } finally {
       timings.immutableCheckMs = Math.round(performance.now() - buildStarted);
diff --git a/src/capability-language/authoring-context.ts b/src/capability-language/authoring-context.ts
index 2402292..4a88a40 100644
--- a/src/capability-language/authoring-context.ts
+++ b/src/capability-language/authoring-context.ts
@@ -20,7 +20,12 @@ export async function authoringContext(start: string) {
       if ((error as NodeJS.ErrnoException).code !== "ENOENT") throw error;
     }
     if (text !== undefined) {
-      const graph = JSON.parse(text) as { resources: AuthoringResource[] };
+      const graph = JSON.parse(text) as { resources: AuthoringResource[]; workspaceId?: string };
+      if (
+        graph.workspaceId !== undefined &&
+        (typeof graph.workspaceId !== "string" || !/^[a-zA-Z0-9][a-zA-Z0-9:._-]{0,255}$/.test(graph.workspaceId))
+      )
+        throw new Error("Managed workbench has an invalid Workspace identity");
       if (!Array.isArray(graph.resources)) throw new Error("Managed resource inventory is malformed");
       const resources: AuthoringResource[] = [{ kind: "workspace", directory: "root" }];
       const identities = new Set<string>(),
@@ -52,6 +57,7 @@ export async function authoringContext(start: string) {
       }
       return {
         workbench,
+        workspaceId: graph.workspaceId,
         resources,
         async baseline() {
           const result = await loadQuixosLock(path.join(workbench, "root/quixos.lock"));
diff --git a/src/capability-language/checked-build.ts b/src/capability-language/checked-build.ts
index 5fe2122..e7d21a0 100644
--- a/src/capability-language/checked-build.ts
+++ b/src/capability-language/checked-build.ts
@@ -112,7 +112,10 @@ export async function buildImmutableCandidate(
   logFile: string,
   contractOnly = false,
   observe?: (phase: "nixEvaluationMs" | "nixBuildMs", ms: number) => void,
+  workspaceId?: string,
 ): Promise<string> {
+  if (workspaceId !== undefined && (kind !== "workspace" || !/^[a-zA-Z0-9][a-zA-Z0-9:._-]{0,255}$/.test(workspaceId)))
+    throw new Error("Instance binding requires a valid Workspace identity and a Workspace root");
   if (!/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(source.commit))
     throw new Error("An immutable candidate requires an exact commit");
   const url = new URL(source.repository);
@@ -200,6 +203,7 @@ export async function buildImmutableCandidate(
         "--arg",
         "contractOnly",
         contractOnly ? "true" : "false",
+        ...(workspaceId === undefined ? [] : ["--argstr", "workspaceId", workspaceId]),
         "--add-root",
         gcRoot,
         "--indirect",
diff --git a/src/capability-language/development-sources.ts b/src/capability-language/development-sources.ts
new file mode 100644
index 0000000..97e8d26
--- /dev/null
+++ b/src/capability-language/development-sources.ts
@@ -0,0 +1,93 @@
+import { execFile as callback } from "node:child_process";
+import { promisify } from "node:util";
+import { randomUUID } from "node:crypto";
+import { mkdir, mkdtemp, lstat, rename, rm, writeFile } from "node:fs/promises";
+import path from "node:path";
+import { materializeWorkspaceSources, workspaceSourcePin, type WorkspaceSourcePin } from "./source-closure.js";
+
+const exec = promisify(callback);
+
+/** Developer workflow, not an ordinary Workspace Agent's implicit permission
+ * to publish against canonical repositories. Creates independent Git/jj copies,
+ * with instance binding outside committed source. No Graph is started here.
+ */
+export async function prepareDevelopmentSources(options: {
+  source: WorkspaceSourcePin;
+  directory: string;
+  cacheDirectory: string;
+  locations?: Record<string, string>;
+}) {
+  const source = workspaceSourcePin(options.source);
+  const destination = path.resolve(options.directory);
+  const cache = path.resolve(options.cacheDirectory);
+  if (cache === destination || cache.startsWith(destination + path.sep))
+    throw Error("The retained source cache must live outside the disposable workbench");
+  if (
+    await lstat(destination).catch((error: NodeJS.ErrnoException) => {
+      if (error.code !== "ENOENT") throw error;
+      return null;
+    })
+  )
+    throw Error("Choose a new development workbench directory; existing checkouts are never overwritten");
+  const closure = await materializeWorkspaceSources({
+    source,
+    directory: options.cacheDirectory,
+    locations: options.locations,
+  });
+  const origins = new Set<string>();
+  for (const entry of closure.resources) {
+    const identity = `${entry.kind}:${entry.repository}`;
+    if (origins.has(identity)) throw Error("Multiple revisions of one repository require explicit editable selection");
+    origins.add(identity);
+  }
+  const parent = path.dirname(destination);
+  await mkdir(parent, { recursive: true });
+  const staging = await mkdtemp(path.join(parent, ".development-sources-"));
+  const workspaceId = randomUUID();
+  try {
+    const resources = [];
+    for (const entry of closure.resources) {
+      const relative = entry.kind === "workspace" ? "root" : "resources/" + entry.directory;
+      const checkout = path.join(staging, relative);
+      await mkdir(path.dirname(checkout), { recursive: true });
+      await exec("git", [
+        "clone",
+        "--no-hardlinks",
+        "--",
+        path.join(path.resolve(options.cacheDirectory), entry.directory),
+        checkout,
+      ]);
+      await exec("git", ["remote", "set-url", "origin", entry.repository], { cwd: checkout });
+      await exec("git", ["checkout", "--detach", entry.commit], { cwd: checkout });
+      await exec("jj", ["git", "init", "--colocate"], {
+        cwd: checkout,
+        env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", QUIXOS_SUBTREE_PUBLISH: "0" },
+      });
+      await exec("jj", ["describe", "-m", "Develop canonical application source"], {
+        cwd: checkout,
+        env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", QUIXOS_SUBTREE_PUBLISH: "0" },
+      });
+      if (entry.kind !== "workspace")
+        resources.push({
+          kind: entry.kind,
+          directory: relative,
+          source: { resolver: "git", repository: entry.repository, commit: entry.commit },
+        });
+    }
+    await mkdir(path.join(staging, ".quixos"), { mode: 0o700 });
+    await writeFile(
+      path.join(staging, ".quixos/resource-graph.json"),
+      JSON.stringify({ formatVersion: 1, workspaceId, resources }, null, 2) + "\n",
+      { mode: 0o600 },
+    );
+    await writeFile(
+      path.join(staging, ".quixos/development-source.json"),
+      JSON.stringify({ source, workspaceId }, null, 2) + "\n",
+      { mode: 0o600 },
+    );
+    await rename(staging, destination);
+    return { directory: destination, source, workspaceId, repositories: closure.resources.length };
+  } finally {
+    await rm(staging, { recursive: true, force: true });
+  }
+}
diff --git a/src/capability-language/source-backup.ts b/src/capability-language/source-backup.ts
new file mode 100644
index 0000000..cefa9d3
--- /dev/null
+++ b/src/capability-language/source-backup.ts
@@ -0,0 +1,117 @@
+import { execFile as callback } from "node:child_process";
+import { promisify } from "node:util";
+import { createHash } from "node:crypto";
+import { createReadStream } from "node:fs";
+import { lstat, mkdir, mkdtemp, readFile, rename, rm, writeFile } from "node:fs/promises";
+import path from "node:path";
+import { pathToFileURL } from "node:url";
+import { retentionTagForCommit } from "../resource-lock/index.js";
+import { materializeWorkspaceSources, workspaceSourcePin, type WorkspaceSourcePin } from "./source-closure.js";
+
+const exec = promisify(callback);
+type SourceBackup = {
+  formatVersion: 1;
+  root: WorkspaceSourcePin;
+  repositories: Array<{ repository: string; commits: string[]; bundle: string; sha256: string }>;
+};
+async function hash(filename: string) {
+  const digest = createHash("sha256");
+  for await (const chunk of createReadStream(filename)) digest.update(chunk);
+  return digest.digest("hex");
+}
+
+/** Source-only backup: no Graph state, checkout instructions or credentials.
+ * Git bundles retain exact commits and their ancestors without needing a forge.
+ * Storage/retention of the resulting directory belongs to the operator. */
+export async function backupWorkspaceSources(options: {
+  source: WorkspaceSourcePin;
+  directory: string;
+  output: string;
+  locations?: Record<string, string>;
+}): Promise<SourceBackup> {
+  const output = path.resolve(options.output);
+  if (
+    await lstat(output).catch((error: NodeJS.ErrnoException) => {
+      if (error.code !== "ENOENT") throw error;
+      return null;
+    })
+  )
+    throw Error("Source backup destination must not exist");
+  const closure = await materializeWorkspaceSources(options);
+  const grouped = new Map<string, Map<string, string>>();
+  for (const entry of closure.resources) {
+    const commits = grouped.get(entry.repository) ?? new Map<string, string>();
+    commits.set(entry.commit, path.join(path.resolve(options.directory), entry.directory));
+    grouped.set(entry.repository, commits);
+  }
+  await mkdir(path.dirname(output), { recursive: true });
+  const staging = await mkdtemp(path.join(path.dirname(output), ".source-backup-"));
+  const manifest: SourceBackup = { formatVersion: 1, root: closure.root, repositories: [] };
+  try {
+    for (const [repository, commits] of [...grouped].sort(([a], [b]) => a.localeCompare(b))) {
+      const bundle = createHash("sha256").update(repository).digest("hex") + ".bundle";
+      const gitDirectory = await mkdtemp(path.join(staging, ".git-"));
+      try {
+        await exec("git", ["init", "--bare", gitDirectory]);
+        const refs: string[] = [];
+        for (const [commit, checkout] of commits) {
+          const ref = retentionTagForCommit(commit);
+          await exec("git", ["-C", gitDirectory, "fetch", "--no-tags", "--", checkout, `${ref}:${ref}`]);
+          refs.push(ref);
+        }
+        await exec("git", ["-C", gitDirectory, "bundle", "create", path.join(staging, bundle), ...refs]);
+      } finally {
+        await rm(gitDirectory, { recursive: true, force: true });
+      }
+      manifest.repositories.push({
+        repository,
+        commits: [...commits.keys()].sort(),
+        bundle,
+        sha256: await hash(path.join(staging, bundle)),
+      });
+    }
+    await writeFile(path.join(staging, "backup.json"), JSON.stringify(manifest, null, 2) + "\n", { mode: 0o600 });
+    await rename(staging, output);
+    return manifest;
+  } finally {
+    await rm(staging, { recursive: true, force: true });
+  }
+}
+
+export async function restoreWorkspaceSources(options: { backup: string; directory: string }) {
+  const backup = path.resolve(options.backup);
+  const filename = path.join(backup, "backup.json");
+  const info = await lstat(filename);
+  if (!info.isFile() || info.isSymbolicLink() || info.size > 1024 * 1024) throw Error("Invalid source backup manifest");
+  const manifest = JSON.parse(await readFile(filename, "utf8")) as SourceBackup;
+  if (
+    manifest.formatVersion !== 1 ||
+    !Array.isArray(manifest.repositories) ||
+    !manifest.repositories.length ||
+    manifest.repositories.length > 256
+  )
+    throw Error("Invalid source backup manifest");
+  const root = workspaceSourcePin(manifest.root);
+  const locations: Record<string, string> = {};
+  for (const entry of manifest.repositories) {
+    if (!entry || !Array.isArray(entry.commits) || !entry.commits.length || entry.commits.length > 256)
+      throw Error("Invalid source backup entry");
+    for (const commit of entry.commits) workspaceSourcePin({ repository: entry.repository, commit });
+    if (Object.hasOwn(locations, entry.repository)) throw Error("Duplicate source backup repository");
+    const expected = createHash("sha256").update(entry.repository).digest("hex") + ".bundle";
+    if (entry.bundle !== expected || !/^[a-f0-9]{64}$/.test(entry.sha256))
+      throw Error("Invalid source backup bundle identity");
+    const bundle = path.join(backup, expected);
+    const stat = await lstat(bundle);
+    if (!stat.isFile() || stat.isSymbolicLink() || (await hash(bundle)) !== entry.sha256)
+      throw Error("Source backup bundle integrity mismatch");
+    locations[entry.repository] = pathToFileURL(bundle).href;
+  }
+  if (
+    !manifest.repositories.some((entry) => entry.repository === root.repository && entry.commits.includes(root.commit))
+  )
+    throw Error("Source backup does not retain its root commit");
+  // Every discovered dependency must use the backup. Never fall through to the
+  // original forge if a manifest omits a required repository.
+  return materializeWorkspaceSources({ source: root, directory: options.directory, locations, requireLocations: true });
+}
diff --git a/src/capability-language/source-check-driver.ts b/src/capability-language/source-check-driver.ts
index 36f6350..4a4169a 100644
--- a/src/capability-language/source-check-driver.ts
+++ b/src/capability-language/source-check-driver.ts
@@ -2,7 +2,9 @@ import { buildImmutableCandidate } from "./checked-build.js";
 
 // Installed platform driver, run only inside the sealed checker's unprivileged
 // evaluator. Authored flakes never become the outer evaluator program.
-const [repository, commit, log] = process.argv.slice(2);
-if (!repository || !commit || !log || process.argv.length !== 5)
-  throw Error("source-check-driver REPOSITORY COMMIT LOG");
-process.stdout.write((await buildImmutableCandidate({ repository, commit }, "workspace", log)) + "\n");
+const [repository, commit, log, workspaceId] = process.argv.slice(2);
+if (!repository || !commit || !log || !workspaceId || process.argv.length !== 6)
+  throw Error("source-check-driver REPOSITORY COMMIT LOG WORKSPACE_ID");
+process.stdout.write(
+  (await buildImmutableCandidate({ repository, commit }, "workspace", log, false, undefined, workspaceId)) + "\n",
+);
diff --git a/src/capability-language/source-closure.ts b/src/capability-language/source-closure.ts
new file mode 100644
index 0000000..6f71763
--- /dev/null
+++ b/src/capability-language/source-closure.ts
@@ -0,0 +1,176 @@
+import { execFile as callback } from "node:child_process";
+import { promisify } from "node:util";
+import { createHash, randomUUID } from "node:crypto";
+import { mkdir, mkdtemp, lstat, realpath, rename, rm, writeFile } from "node:fs/promises";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { loadQuixosLock, retentionTagForCommit } from "../resource-lock/index.js";
+
+const exec = promisify(callback);
+import { workspaceSourcePin, type WorkspaceSourcePin } from "./source-pin.js";
+export { workspaceSourcePin, type WorkspaceSourcePin } from "./source-pin.js";
+export type SourceClosureEntry = WorkspaceSourcePin & {
+  kind: "workspace" | "interface" | "package" | "build";
+  directory: string;
+};
+export type WorkspaceSourceClosure = {
+  formatVersion: 1;
+  root: WorkspaceSourcePin;
+  resources: SourceClosureEntry[];
+};
+
+/** Trusted transport substitutions preserve source identity. A mirror or bundle
+ * is explicitly selected, never tried automatically after an origin failure.
+ * Git authentication stays in the caller's Git configuration, outside metadata.
+ */
+export async function materializeWorkspaceSources(options: {
+  source: WorkspaceSourcePin;
+  directory: string;
+  locations?: Record<string, string>;
+  concurrency?: number;
+  maxRepositories?: number;
+  requireLocations?: boolean;
+  /** Optional acquisition boundary, enforced before fetching each dependency.
+   * It limits canonical identity; explicit transport substitutions remain a
+   * separate trusted operator decision. */
+  repositoryPrefix?: string;
+}): Promise<WorkspaceSourceClosure> {
+  const source = workspaceSourcePin(options.source);
+  const prefix = options.repositoryPrefix ? new URL(options.repositoryPrefix) : null;
+  if (
+    prefix &&
+    (prefix.protocol !== "https:" ||
+      prefix.username ||
+      prefix.password ||
+      prefix.search ||
+      prefix.hash ||
+      !prefix.pathname.endsWith("/") ||
+      /[%\\\\]/.test(prefix.pathname))
+  )
+    throw Error("Source repository prefix requires a credential-free HTTPS directory URL");
+  const concurrency = options.concurrency ?? 4,
+    maxRepositories = options.maxRepositories ?? 256;
+  if (
+    !Number.isInteger(concurrency) ||
+    concurrency < 1 ||
+    concurrency > 16 ||
+    !Number.isInteger(maxRepositories) ||
+    maxRepositories < 1 ||
+    maxRepositories > 4096
+  )
+    throw Error("Invalid source closure limits");
+  const locations = new Map(Object.entries(options.locations ?? {}));
+  for (const [canonical, location] of locations) {
+    workspaceSourcePin({ repository: canonical, commit: source.commit });
+    const url = new URL(location);
+    if (
+      !["https:", "file:"].includes(url.protocol) ||
+      url.username ||
+      url.password ||
+      url.search ||
+      url.hash ||
+      (url.protocol === "file:" && url.hostname !== "")
+    )
+      throw Error("Invalid source transport substitution");
+  }
+  await mkdir(options.directory, { recursive: true, mode: 0o700 });
+  const directory = await realpath(options.directory);
+  const entries = new Map<string, SourceClosureEntry>();
+  const pending: SourceClosureEntry[] = [];
+  const enqueue = (pin: WorkspaceSourcePin, kind: SourceClosureEntry["kind"]) => {
+    pin = workspaceSourcePin(pin);
+    const repository = new URL(pin.repository);
+    if (
+      prefix &&
+      (repository.origin !== prefix.origin ||
+        !repository.pathname.startsWith(prefix.pathname) ||
+        /[%\\\\]/.test(repository.pathname))
+    )
+      throw Error(`Source repository is outside the acquisition boundary: ${pin.repository}`);
+    if (options.requireLocations && !locations.has(pin.repository))
+      throw Error(`Source backup omits required repository: ${pin.repository}`);
+    const key = `${kind}\0${pin.repository}\0${pin.commit}`;
+    if (entries.has(key)) return;
+    if (entries.size >= maxRepositories) throw Error("Workspace source closure exceeds repository limit");
+    const name = `${kind}-${createHash("sha256").update(key).digest("hex").slice(0, 24)}`;
+    const entry = { ...pin, kind, directory: name };
+    entries.set(key, entry);
+    pending.push(entry);
+  };
+  enqueue(source, "workspace");
+  const git = async (cwd: string, args: string[]) =>
+    (
+      await exec("git", args, {
+        cwd,
+        env: { ...process.env, GIT_TERMINAL_PROMPT: "0" },
+        maxBuffer: 4 * 1024 * 1024,
+      })
+    ).stdout.trim();
+  const checkout = async (entry: SourceClosureEntry) => {
+    const destination = path.join(directory, entry.directory);
+    const verify = async () => {
+      const info = await lstat(destination);
+      if (!info.isDirectory() || info.isSymbolicLink() || (await realpath(destination)) !== destination)
+        throw Error("Source checkout must be a contained directory");
+      if ((await git(destination, ["rev-parse", "HEAD"])) !== entry.commit)
+        throw Error(`Source commit mismatch: ${entry.repository}`);
+      if (await git(destination, ["status", "--porcelain", "--untracked-files=all"]))
+        throw Error(`Source checkout was modified: ${entry.repository}`);
+    };
+    const existing = await lstat(destination).catch((error: NodeJS.ErrnoException) => {
+      if (error.code !== "ENOENT") throw error;
+      return null;
+    });
+    if (!existing) {
+      const staging = await mkdtemp(path.join(directory, ".fetch-"));
+      try {
+        await git(staging, ["init"]);
+        await git(staging, ["remote", "add", "origin", entry.repository]);
+        const ref = retentionTagForCommit(entry.commit);
+        // Full history supports normal jj development and independent bundles.
+        const location = locations.get(entry.repository) ?? entry.repository;
+        await git(staging, [
+          "fetch",
+          "--no-tags",
+          "--",
+          location.startsWith("file:") ? fileURLToPath(location) : location,
+          `${ref}:${ref}`,
+        ]);
+        await git(staging, ["checkout", "--detach", entry.commit]);
+        try {
+          await rename(staging, destination);
+        } catch (error) {
+          if (!["EEXIST", "ENOTEMPTY"].includes((error as NodeJS.ErrnoException).code ?? "")) throw error;
+        }
+      } finally {
+        await rm(staging, { recursive: true, force: true });
+      }
+    }
+    await verify();
+    const lock = await loadQuixosLock(path.join(destination, "quixos.lock"));
+    if (!lock.ok)
+      throw Error(`Invalid source lock in ${entry.repository}: ${lock.diagnostics.map((d) => d.message).join("; ")}`);
+    return lock.lock.resources;
+  };
+  // Bounded breadth-first batches resolve diamonds once and avoid recursive
+  // promise deadlocks. Completion order cannot affect the recorded closure.
+  while (pending.length) {
+    const batch = pending.splice(0, concurrency);
+    const results = await Promise.allSettled(batch.map(checkout));
+    for (const result of results) {
+      if (result.status === "rejected") throw result.reason;
+      for (const resource of result.value) enqueue(resource.source, resource.kind);
+    }
+  }
+  const closure: WorkspaceSourceClosure = {
+    formatVersion: 1,
+    root: source,
+    resources: [...entries.values()].sort((a, b) =>
+      `${a.kind}:${a.repository}@${a.commit}`.localeCompare(`${b.kind}:${b.repository}@${b.commit}`),
+    ),
+  };
+  const temporary = path.join(directory, `.closure-${randomUUID()}.json`);
+  await writeFile(temporary, JSON.stringify(closure, null, 2) + "\n", { flag: "wx", mode: 0o600 });
+  await rename(temporary, path.join(directory, "sources.json"));
+  return closure;
+}
diff --git a/src/capability-language/source-locks.ts b/src/capability-language/source-locks.ts
new file mode 100644
index 0000000..049bb68
--- /dev/null
+++ b/src/capability-language/source-locks.ts
@@ -0,0 +1,48 @@
+import { readFile } from "node:fs/promises";
+import path from "node:path";
+import { loadQuixosLock, parseQuixosLockDocument, resolveQuixosLock } from "../resource-lock/index.js";
+import { editStructure } from "./structural-edits.js";
+import { workspaceSourcePin, type WorkspaceSourcePin } from "./source-closure.js";
+
+/** Inspect/rewrite the root and its declared imports only, using the same lock
+ * grammar as compilation. Return proposed file contents; publishing them and
+ * selecting a Graph remain the caller's separate responsibilities. */
+export async function workspaceSourceLocks(directory: string, input: unknown = []) {
+  if (!Array.isArray(input) || input.length > 256) throw Error("Invalid source lock replacements");
+  const replacements = new Map<string, WorkspaceSourcePin>();
+  const key = (source: WorkspaceSourcePin) => `${source.repository}\0${source.commit}`;
+  for (const entry of input) {
+    if (!entry || typeof entry !== "object") throw Error("Invalid source lock replacement");
+    const from = workspaceSourcePin(entry.from),
+      to = workspaceSourcePin(entry.to);
+    if (replacements.has(key(from))) throw Error("Duplicate source lock replacement");
+    replacements.set(key(from), to);
+  }
+  const lock = await loadQuixosLock(path.join(directory, "quixos.lock"));
+  if (!lock.ok) throw Error(`Invalid source lock: ${lock.diagnostics.map((d) => d.message).join("; ")}`);
+  const files = new Map<string, string>();
+  for (const filename of lock.lock.sourceFiles!) {
+    let source = await readFile(path.join(directory, filename), "utf8");
+    const parsed = parseQuixosLockDocument(source, filename);
+    if (!parsed.ok) throw Error("Source lock changed during inspection");
+    for (const dependency of parsed.document.resources) {
+      const replacement = replacements.get(key(dependency.source));
+      if (replacement)
+        source = editStructure(source, {
+          operation: "dependency",
+          kind: dependency.kind,
+          name: dependency.binding,
+          source: replacement,
+        });
+    }
+    files.set(filename, source);
+  }
+  const checked = await resolveQuixosLock(files.get("quixos.lock")!, async (filename) => {
+    const source = files.get(filename);
+    if (source === undefined) throw Error("Source lock import changed during inspection");
+    return source;
+  });
+  if (!checked.ok)
+    throw Error(`Invalid rewritten source locks: ${checked.diagnostics.map((d) => d.message).join("; ")}`);
+  return { lock: checked.lock, files: [...files].map(([path, source]) => ({ path, source })) };
+}
diff --git a/src/capability-language/source-pin.ts b/src/capability-language/source-pin.ts
new file mode 100644
index 0000000..501347c
--- /dev/null
+++ b/src/capability-language/source-pin.ts
@@ -0,0 +1,18 @@
+export type WorkspaceSourcePin = { repository: string; commit: string };
+
+export function workspaceSourcePin(value: unknown): WorkspaceSourcePin {
+  if (!value || typeof value !== "object" || Array.isArray(value)) throw Error("Invalid Workspace source pin");
+  const pin = value as WorkspaceSourcePin;
+  const url = new URL(pin.repository);
+  if (
+    url.protocol !== "https:" ||
+    url.username ||
+    url.password ||
+    url.search ||
+    url.hash ||
+    typeof pin.commit !== "string" ||
+    !/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(pin.commit)
+  )
+    throw Error("Workspace source pins require credential-free HTTPS and an exact commit");
+  return { repository: pin.repository, commit: pin.commit };
+}
diff --git a/src/capability-language/tool-cli.ts b/src/capability-language/tool-cli.ts
index 9e85703..41a382d 100644
--- a/src/capability-language/tool-cli.ts
+++ b/src/capability-language/tool-cli.ts
@@ -54,6 +54,61 @@ const planSummary = (plan: Awaited<ReturnType<typeof planStructure>>) => ({
 
 const main = async () => {
   const [command, ...args] = process.argv.slice(2);
+  if (command === "source-locks") {
+    if (!args[0] || (args.length !== 1 && (args.length !== 3 || args[1] !== "--replacements")))
+      throw Error("source-locks DIRECTORY [--replacements JSON_FILE]");
+    const { workspaceSourceLocks } = await import("./source-locks.js");
+    const replacements = args[2] ? JSON.parse(await readFile(args[2], "utf8")) : [];
+    process.stdout.write(JSON.stringify(await workspaceSourceLocks(path.resolve(args[0]), replacements)) + "\n");
+    return;
+  }
+  if (["source-checkout", "source-develop", "source-backup", "source-restore"].includes(command!)) {
+    const args = ["source", command.slice("source-".length), ...process.argv.slice(3)];
+    const { materializeWorkspaceSources } = await import("./source-closure.js");
+    if (!args[2]) throw Error("source requires a pinned source JSON file");
+    const flags = new Map<string, string>();
+    for (let i = 3; i < args.length; i += 2) {
+      if (
+        ![
+          "--dir",
+          ...(args[1] !== "restore" ? ["--locations"] : []),
+          ...(args[1] === "checkout" ? ["--repository-prefix"] : []),
+          ...(args[1] === "develop" ? ["--cache"] : []),
+          ...(args[1] === "backup" ? ["--output"] : []),
+        ].includes(args[i]) ||
+        !args[i + 1] ||
+        flags.has(args[i])
+      )
+        throw Error("Invalid source command options; use qx-workspace help source");
+      flags.set(args[i], args[i + 1]);
+    }
+    if (!flags.get("--dir")) throw Error("source requires --dir DIRECTORY");
+    if (args[1] === "restore") {
+      const { restoreWorkspaceSources } = await import("./source-backup.js");
+      const result = await restoreWorkspaceSources({ backup: args[2], directory: path.resolve(flags.get("--dir")!) });
+      process.stdout.write(JSON.stringify(result, null, 2) + "\n");
+      return;
+    }
+    const locationsFile = flags.get("--locations");
+    const options = {
+      source: JSON.parse(await readFile(args[2], "utf8")),
+      directory: path.resolve(flags.get("--dir")!),
+      ...(locationsFile ? { locations: JSON.parse(await readFile(locationsFile, "utf8")) } : {}),
+      ...(flags.has("--repository-prefix") ? { repositoryPrefix: flags.get("--repository-prefix") } : {}),
+    };
+    let result;
+    if (args[1] === "develop") {
+      if (!flags.get("--cache")) throw Error("source develop requires --cache DIRECTORY");
+      const { prepareDevelopmentSources } = await import("./development-sources.js");
+      result = await prepareDevelopmentSources({ ...options, cacheDirectory: path.resolve(flags.get("--cache")!) });
+    } else if (args[1] === "backup") {
+      if (!flags.get("--output")) throw Error("source backup requires --output DIRECTORY");
+      const { backupWorkspaceSources } = await import("./source-backup.js");
+      result = await backupWorkspaceSources({ ...options, output: path.resolve(flags.get("--output")!) });
+    } else result = await materializeWorkspaceSources(options);
+    process.stdout.write(JSON.stringify(result, null, 2) + "\n");
+    return;
+  }
   if (command === "source-manifest") {
     if (args.length !== 1) throw new Error("source-manifest WORKSPACE_ROOT");
     process.stdout.write(JSON.stringify(await qxSourceManifest(args[0])) + "\n");
@@ -197,10 +252,16 @@ const main = async () => {
   }
   if (command === "check-committed" && !args.includes("--help")) {
     const [kind, repository, commit, log, ...extra] = args;
-    if (!["workspace", "interface", "package", "build"].includes(kind) || !log || extra.length)
-      throw new Error("usage: quixos-qx check-committed workspace|interface|package|build REPOSITORY COMMIT LOG_FILE");
+    if (
+      !["workspace", "interface", "package", "build"].includes(kind) ||
+      !log ||
+      (extra.length !== 0 && (kind !== "workspace" || extra.length !== 2 || extra[0] !== "--workspace-id" || !extra[1]))
+    )
+      throw new Error(
+        "usage: quixos-qx check-committed workspace|interface|package|build REPOSITORY COMMIT LOG_FILE [--workspace-id ID]",
+      );
     process.stdout.write(
-      `${await buildImmutableCandidate({ repository, commit }, kind as "workspace" | "interface" | "package" | "build", log)}\n`,
+      `${await buildImmutableCandidate({ repository, commit }, kind as "workspace" | "interface" | "package" | "build", log, false, undefined, extra[1])}\n`,
     );
     return;
   }
diff --git a/src/capability-language/workspace-cli.ts b/src/capability-language/workspace-cli.ts
index 37c35c6..11b36b0 100644
--- a/src/capability-language/workspace-cli.ts
+++ b/src/capability-language/workspace-cli.ts
@@ -17,7 +17,7 @@ import {
 } from "../capability-model/index.js";
 
 const usage = `usage: quixos-workspace-compile --root DIRECTORY --checkout-root DIRECTORY
-       [--snapshot-map PATH] [--graph-out PATH] [--workspace-id ID] [--workspace-revision-id ID]
+       [--snapshot-map PATH] [--graph-out PATH] [--plan-out PATH] [--workspace-id ID] [--workspace-revision-id ID]
        [--source-root-commit GIT_REV] [--baseline PLAN_JSON] [--evolution-out PATH]
        [--reviews REVIEW_JSON] [--schemas-out PATH] [--execution-plan-out PATH] [--build-contexts-out PATH]
        [--query-generator BUILD_MODULE_PATH] [--checked-resources NIX_MAP]
@@ -41,6 +41,7 @@ const parseArgs = (args: string[]) => {
     rootDirectory,
     checkoutRoot,
     graphOut: values.get("--graph-out"),
+    planOut: values.get("--plan-out"),
     schemasOut: values.get("--schemas-out"),
     executionPlanOut: values.get("--execution-plan-out"),
     buildContextsOut: values.get("--build-contexts-out"),
@@ -84,6 +85,7 @@ const main = async () => {
       `${JSON.stringify(
         {
           formatVersion: 1,
+          workspaceId: assembled.workspace.workspaceId,
           quixos: assembled.lock.quixos,
           directResources: [...assembled.directResources.entries()].map(([bindingKey, node]) => {
             const [kind, binding] = bindingKey.split("\0");
@@ -157,7 +159,8 @@ const main = async () => {
       `${JSON.stringify(planEvolution(baseline, candidate, { reviews }), null, 2)}\n`,
     );
   }
-  process.stdout.write(`${JSON.stringify(candidate, null, 2)}\n`);
+  if (options.planOut) await writeFile(options.planOut, `${JSON.stringify(candidate)}\n`);
+  else process.stdout.write(`${JSON.stringify(candidate, null, 2)}\n`);
 };
 
 main().catch((error: unknown) => {
diff --git a/src/resource-lock/loader.ts b/src/resource-lock/loader.ts
index 7f134e9..c565d93 100644
--- a/src/resource-lock/loader.ts
+++ b/src/resource-lock/loader.ts
@@ -118,6 +118,9 @@ export const loadQuixosLock = async (fileName: string): Promise<QuixosLockParseR
   const absoluteRoot = path.resolve(fileName);
   const repositoryRoot = path.dirname(absoluteRoot);
   const rootName = path.basename(absoluteRoot);
+  const metadata = await lstat(absoluteRoot);
+  if (!metadata.isFile() || metadata.isSymbolicLink())
+    throw new Error("root locks must be ordinary files, not symbolic links");
   const rootSource = await readFile(absoluteRoot, "utf8");
   return await resolveQuixosLock(
     rootSource,
diff --git a/test/capability-assembly.test.ts b/test/capability-assembly.test.ts
index 33a16b1..44e0354 100644
--- a/test/capability-assembly.test.ts
+++ b/test/capability-assembly.test.ts
@@ -90,6 +90,28 @@ package Runtime id "package:runtime" revision "package:runtime@1" {
   );
   assert.equal(result.directResources.size, 1);
 
+  const resolveResource = async (source: { repository: string; commit: string }, kind: string) => ({
+    directory: directories.get(`${kind}\0${source.repository}\0${source.commit}`)!,
+  });
+  const bound = await Promise.all(
+    ["workspace:first", "workspace:second"].map((workspaceId) =>
+      compileWorkspaceRepository({
+        rootDirectory: root,
+        resolveResource,
+        workspaceId,
+        sourceRootCommit: "5".repeat(40),
+      }),
+    ),
+  );
+  assert.notEqual(bound[0]!.workspace.workspaceId, bound[1]!.workspace.workspaceId);
+  assert.notEqual(bound[0]!.workspace.id, bound[1]!.workspace.id);
+  for (const instance of bound) {
+    assert.equal(instance.workspace.sourceRootCommit, "5".repeat(40));
+    assert.deepEqual(instance.workspace.packageImports, result.workspace.packageImports);
+    assert.deepEqual(instance.workspace.interfaceImports, result.workspace.interfaceImports);
+    assert.deepEqual(instance.resources, result.resources, "binding does not fork resource identities");
+  }
+
   const resource = await compileCapabilityResourceRepository({
     rootDirectory: runtime,
     kind: "package",
diff --git a/test/source-closure.test.ts b/test/source-closure.test.ts
new file mode 100644
index 0000000..4fb8c3e
--- /dev/null
+++ b/test/source-closure.test.ts
@@ -0,0 +1,215 @@
+import assert from "node:assert/strict";
+import { execFile as callback } from "node:child_process";
+import { promisify } from "node:util";
+import { mkdtemp, mkdir, writeFile, readFile, rm, symlink } from "node:fs/promises";
+import path from "node:path";
+import os from "node:os";
+import test from "node:test";
+import { pathToFileURL } from "node:url";
+import { materializeWorkspaceSources, workspaceSourcePin } from "../src/capability-language/source-closure.js";
+import { prepareDevelopmentSources } from "../src/capability-language/development-sources.js";
+import { backupWorkspaceSources, restoreWorkspaceSources } from "../src/capability-language/source-backup.js";
+
+const exec = promisify(callback);
+const lock = (resources: string) => `quixos-lock version 1 {
+ quixos source { repository "https://unavailable.test/toolchain.git"; commit "${"a".repeat(40)}"; }
+ ${resources}
+}`;
+test("exact source closure recovers through explicitly selected bundles, preserves history and rejects edits", async (context) => {
+  const temporary = await mkdtemp(path.join(os.tmpdir(), "qx-closure-"));
+  context.after(() => rm(temporary, { recursive: true, force: true }));
+  const locations: Record<string, string> = {};
+  const repository = async (name: string, resources: string) => {
+    const directory = path.join(temporary, name);
+    await mkdir(directory);
+    const git = async (...args: string[]) => (await exec("git", args, { cwd: directory })).stdout.trim();
+    await git("init");
+    await writeFile(path.join(directory, "quixos.lock"), lock(""));
+    await git("add", ".");
+    const commit = async () => {
+      await git("-c", "user.name=Test", "-c", "user.email=test@example.test", "commit", "-am", "Source");
+      return await git("rev-parse", "HEAD");
+    };
+    const parent = await commit();
+    await writeFile(path.join(directory, "quixos.lock"), lock(resources));
+    await writeFile(path.join(directory, "marker"), name);
+    await git("add", ".");
+    const rev = await commit();
+    await git("tag", `quixos-reachability/${rev}`);
+    const bundle = path.join(temporary, `${name}.bundle`);
+    await git("bundle", "create", bundle, `refs/tags/quixos-reachability/${rev}`);
+    const source = { repository: `https://unavailable.test/${name}.git`, commit: rev };
+    locations[source.repository] = pathToFileURL(bundle).href;
+    return { ...source, parent };
+  };
+  const common = await repository("common", "");
+  const dependency = `interface Common source { repository "${common.repository}"; commit "${common.commit}"; }`;
+  const left = await repository("left", dependency),
+    right = await repository("right", dependency);
+  const root = await repository(
+    "root",
+    `
+    package Left source { repository "${left.repository}"; commit "${left.commit}"; }
+    package Right source { repository "${right.repository}"; commit "${right.commit}"; }`,
+  );
+  const directory = path.join(temporary, "checkout");
+  const closure = await materializeWorkspaceSources({ source: root, directory, locations, concurrency: 2 });
+  assert.deepEqual(
+    await materializeWorkspaceSources({ source: root, directory, repositoryPrefix: "https://unavailable.test/" }),
+    closure,
+  );
+  // Allow this root but not its dependencies: reject them before Git acquisition.
+  const scopedRoot = { ...root, repository: "https://unavailable.test/selected/root.git" };
+  await assert.rejects(
+    materializeWorkspaceSources({
+      source: scopedRoot,
+      directory: path.join(temporary, "scoped"),
+      locations: { ...locations, [scopedRoot.repository]: locations[root.repository] },
+      repositoryPrefix: "https://unavailable.test/selected/",
+    }),
+    /outside the acquisition boundary/,
+  );
+  await assert.rejects(
+    materializeWorkspaceSources({ source: root, directory, repositoryPrefix: "https://unavailable.test/root.git/" }),
+    /outside the acquisition boundary/,
+  );
+  assert.equal(closure.resources.length, 4, "diamond dependency is materialized once");
+  assert.deepEqual(JSON.parse(await readFile(path.join(directory, "sources.json"), "utf8")), closure);
+  const rootEntry = closure.resources.find((entry) => entry.kind === "workspace")!;
+  const rootDirectory = path.join(directory, rootEntry.directory);
+  const rootLock = path.join(rootDirectory, "quixos.lock");
+  const rootBody = await readFile(rootLock, "utf8");
+  const outsideLock = path.join(temporary, "outside.lock");
+  await writeFile(outsideLock, rootBody);
+  // Exercise the shared loader directly: committed root symlinks must not let
+  // privileged source inspection read outside the acquired repository.
+  const { loadQuixosLock } = await import("../src/resource-lock/index.js");
+  const linkedLock = path.join(temporary, "linked.lock");
+  await symlink(outsideLock, linkedLock);
+  await assert.rejects(loadQuixosLock(linkedLock), /root locks must be ordinary/);
+  const backup = path.join(temporary, "retained");
+  const manifest = await backupWorkspaceSources({ source: root, directory, output: backup });
+  assert.equal(manifest.repositories.length, 4);
+  const restored = await restoreWorkspaceSources({ backup, directory: path.join(temporary, "restored") });
+  assert.deepEqual(restored, closure, "Source-only recovery retains canonical identity without an available forge");
+  await assert.rejects(backupWorkspaceSources({ source: root, directory, output: backup }), /must not exist/);
+  const missing = {
+    ...manifest,
+    repositories: manifest.repositories.filter((entry) => entry.repository !== common.repository),
+  };
+  await writeFile(path.join(backup, "backup.json"), JSON.stringify(missing));
+  await assert.rejects(
+    restoreWorkspaceSources({ backup, directory: path.join(temporary, "incomplete") }),
+    /omits required repository/,
+  );
+  await writeFile(path.join(backup, "backup.json"), JSON.stringify(manifest));
+  await writeFile(path.join(backup, manifest.repositories[0].bundle), "damaged backup");
+  await assert.rejects(
+    restoreWorkspaceSources({ backup, directory: path.join(temporary, "damaged") }),
+    /integrity mismatch/,
+  );
+  assert.equal((await exec("git", ["rev-parse", "HEAD^"], { cwd: rootDirectory })).stdout.trim(), root.parent);
+  assert.equal(
+    (await exec("git", ["remote", "get-url", "origin"], { cwd: rootDirectory })).stdout.trim(),
+    root.repository,
+  );
+  // Cached recovery does not need the primary or the backup.
+  assert.deepEqual(await materializeWorkspaceSources({ source: root, directory }), closure);
+  const pinFile = path.join(temporary, "source.json");
+  await writeFile(pinFile, JSON.stringify(root));
+  const cli = path.resolve(import.meta.dirname, "../src/capability-language/tool-cli.js");
+  const command = await exec(process.execPath, [cli, "source-checkout", pinFile, "--dir", directory]);
+  assert.deepEqual(JSON.parse(command.stdout), closure, "Protocol CLI preserves exact cached source identity");
+  const scoped = await exec(process.execPath, [
+    cli,
+    "source-checkout",
+    pinFile,
+    "--dir",
+    directory,
+    "--repository-prefix",
+    "https://unavailable.test/",
+  ]);
+  assert.deepEqual(JSON.parse(scoped.stdout), closure);
+  const cliBackup = path.join(temporary, "cli-backup");
+  const backupCommand = await exec(process.execPath, [
+    cli,
+    "source-backup",
+    pinFile,
+    "--dir",
+    directory,
+    "--output",
+    cliBackup,
+  ]);
+  assert.equal(JSON.parse(backupCommand.stdout).repositories.length, 4);
+  const restoreCommand = await exec(process.execPath, [
+    cli,
+    "source-restore",
+    cliBackup,
+    "--dir",
+    path.join(temporary, "cli-restore"),
+  ]);
+  assert.deepEqual(JSON.parse(restoreCommand.stdout), closure);
+  const developmentCommand = await exec(process.execPath, [
+    cli,
+    "source-develop",
+    pinFile,
+    "--dir",
+    path.join(temporary, "cli-developer"),
+    "--cache",
+    directory,
+  ]);
+  const developmentResult = JSON.parse(developmentCommand.stdout);
+  assert.equal(developmentResult.repositories, 4);
+  assert.deepEqual(developmentResult.source, closure.root);
+  const a = await prepareDevelopmentSources({
+    source: root,
+    cacheDirectory: directory,
+    directory: path.join(temporary, "a"),
+  });
+  const b = await prepareDevelopmentSources({
+    source: root,
+    cacheDirectory: directory,
+    directory: path.join(temporary, "b"),
+  });
+  assert.notEqual(a.workspaceId, b.workspaceId);
+  const aRoot = path.join(a.directory, "root"),
+    bRoot = path.join(b.directory, "root");
+  assert.equal((await exec("git", ["remote", "get-url", "origin"], { cwd: aRoot })).stdout.trim(), root.repository);
+  assert.equal(
+    await readFile(path.join(aRoot, "quixos.lock"), "utf8"),
+    await readFile(path.join(rootDirectory, "quixos.lock"), "utf8"),
+  );
+  await exec("git", ["cat-file", "-e", root.parent], { cwd: aRoot });
+  await writeFile(path.join(aRoot, "marker"), "Independent developer change");
+  assert.equal(await readFile(path.join(bRoot, "marker"), "utf8"), "root");
+  assert.equal(await readFile(path.join(rootDirectory, "marker"), "utf8"), "root");
+  await assert.rejects(
+    prepareDevelopmentSources({ source: root, cacheDirectory: directory, directory: a.directory }),
+    /never overwritten/,
+  );
+  await writeFile(path.join(rootDirectory, "marker"), "edited");
+  await assert.rejects(materializeWorkspaceSources({ source: root, directory, locations }), /modified/);
+  await assert.rejects(
+    materializeWorkspaceSources({
+      source: root,
+      directory: path.join(temporary, "bounded"),
+      locations,
+      maxRepositories: 2,
+    }),
+    /repository limit/,
+  );
+  await assert.rejects(
+    materializeWorkspaceSources({
+      source: root,
+      directory,
+      locations: { [root.repository]: "https://secret:password@example.test/root.git" },
+    }),
+    /transport substitution/,
+  );
+});
+test("Workspace pins reject floating revisions and embedded credentials", () => {
+  assert.throws(() => workspaceSourcePin({ repository: "https://example.test/root.git", commit: "main" }));
+  assert.throws(() =>
+    workspaceSourcePin({ repository: "https://user:password@example.test/root.git", commit: "a".repeat(40) }),
+  );
+});
diff --git a/test/source-locks.test.ts b/test/source-locks.test.ts
new file mode 100644
index 0000000..d4da479
--- /dev/null
+++ b/test/source-locks.test.ts
@@ -0,0 +1,46 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { mkdtemp, writeFile, readFile, rm } from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { workspaceSourceLocks } from "../src/capability-language/source-locks.js";
+
+test("fork lock proposals follow declared fragments and ignore comments and unrelated lock files", async (context) => {
+  const directory = await mkdtemp(path.join(os.tmpdir(), "qx-lock-fork-"));
+  context.after(() => rm(directory, { recursive: true, force: true }));
+  const from = { repository: "https://source.test/app/runtime.git", commit: "b".repeat(40) };
+  const to = { repository: "https://source.test/fork/runtime.git", commit: "c".repeat(40) };
+  const root = `quixos-lock version 1 {
+    quixos source { repository "https://source.test/quixos.git"; commit "${"a".repeat(40)}"; }
+    import "resources.lock";
+    // package Fake source { repository "https://unrelated.test/secret.git"; commit "${"d".repeat(40)}"; }
+  }`;
+  const fragment = `quixos-lock fragment version 1 {
+    // Preserve this note: 雨 📚
+    package Runtime source { repository "${from.repository}"; commit "${from.commit}"; }
+  }`;
+  await writeFile(path.join(directory, "quixos.lock"), root);
+  await writeFile(path.join(directory, "resources.lock"), fragment);
+  await writeFile(path.join(directory, "unrelated.lock"), "This is not a Quixos lock.");
+  const result = await workspaceSourceLocks(directory, [{ from, to }]);
+  assert.equal(result.lock.resources.length, 1);
+  assert.deepEqual(result.lock.resources[0].source, { resolver: "git", ...to });
+  assert.equal(result.files.find((file) => file.path === "quixos.lock")!.source, root);
+  assert.match(result.files.find((file) => file.path === "resources.lock")!.source, /Preserve this note: 雨 📚/);
+  assert.deepEqual(result.files.map((file) => file.path).sort(), ["quixos.lock", "resources.lock"]);
+  assert.equal(
+    await readFile(path.join(directory, "resources.lock"), "utf8"),
+    fragment,
+    "Proposing a fork does not edit selected source",
+  );
+  await assert.rejects(
+    workspaceSourceLocks(directory, [
+      { from, to },
+      { from, to },
+    ]),
+    /Duplicate/,
+  );
+  await assert.rejects(workspaceSourceLocks(directory, [{ from, to: { ...to, commit: "main" } }]), /exact commit/);
+  await writeFile(path.join(directory, "quixos.lock"), root.replace('"resources.lock"', '"../outside.lock"'));
+  await assert.rejects(workspaceSourceLocks(directory), /Invalid source lock/);
+});