diff --git a/packages/paperclip-runner/.gitignore b/packages/paperclip-runner/.gitignore
index 6bca57979f7..7b56764a2a8 100644
--- a/packages/paperclip-runner/.gitignore
+++ b/packages/paperclip-runner/.gitignore
@@ -4,3 +4,8 @@
 /test-results/
 /dist-phase7/
 /dist-issue-thread/
+
+# The repository root ignores scratch `check-*.mjs` files and only re-includes
+# them under the root `scripts/` directory. This package's checks are real
+# source, so re-include them here instead of relying on `git add -f`.
+!scripts/check-*.mjs
diff --git a/packages/paperclip-runner/README.md b/packages/paperclip-runner/README.md
index 825aec2eb7d..e72c28af759 100644
--- a/packages/paperclip-runner/README.md
+++ b/packages/paperclip-runner/README.md
@@ -97,6 +97,7 @@ and JSON content; see the protocol-server tutorial for direct `curl` examples.
 | `typecheck` | Check TypeScript, Rust, generated schema sources, and browser types. |
 | `test` | Run Rust/TypeScript fixture, supervisor, fake-driver, live/replay, and boundary tests. |
 | `check:forbidden-imports` | Reject TypeScript imports and Cargo path dependencies that cross into Paperclip core. |
+| `check:tracked-imports` | Reject tracked imports and `package.json` entry points that only resolve against untracked files, so a clean checkout of any commit builds. |
 | `check:phase0-parity` | Require byte-for-byte equivalent Rust and TypeScript tracer output. |
 | `check:phase1-goldens` | Require all reducer snapshots and cross-language summaries to match checked goldens. |
 | `check:phase1-parity` | Run TypeScript and Rust against the same Phase 1 fixture summaries. |
diff --git a/packages/paperclip-runner/package.json b/packages/paperclip-runner/package.json
index eb7ec3418b3..45b31fb5700 100644
--- a/packages/paperclip-runner/package.json
+++ b/packages/paperclip-runner/package.json
@@ -41,7 +41,7 @@
     "typecheck:typescript": "pnpm run check:protocol-types && tsc -p tsconfig.json --noEmit",
     "typecheck:rust": "cargo check --manifest-path runner/Cargo.toml --locked --workspace",
     "typecheck:browser": "tsc -p tsconfig.browser.json --noEmit",
-    "test": "pnpm run build:phase2-binaries && pnpm run test:typescript && pnpm run test:rust && node --test scripts/check-forbidden-imports.test.mjs scripts/record-phase4-evidence.test.mjs scripts/validate-doc-links.test.mjs test/capability-contract.test.mjs",
+    "test": "pnpm run build:phase2-binaries && pnpm run test:typescript && pnpm run test:rust && node --test scripts/check-forbidden-imports.test.mjs scripts/check-tracked-imports.test.mjs scripts/record-phase4-evidence.test.mjs scripts/validate-doc-links.test.mjs test/capability-contract.test.mjs",
     "test:typescript": "vitest run",
     "test:rust": "cargo test --manifest-path runner/Cargo.toml --locked --workspace",
     "test:browser": "pnpm run build:typescript && pnpm run build:phase2-binaries && pnpm run build:browser && playwright test --config devtools/browser/playwright.config.ts",
@@ -58,6 +58,7 @@
     "check:phase1-goldens": "node scripts/generate-phase1-goldens.mjs --check",
     "check:browser-tokens": "node scripts/check-browser-tokens.mjs",
     "check:forbidden-imports": "node scripts/check-forbidden-imports.mjs",
+    "check:tracked-imports": "node scripts/check-tracked-imports.mjs",
     "generate:phase7-inventory": "node scripts/generate-phase7-inventory.mjs",
     "check:phase7-inventory": "node scripts/check-phase7-inventory.mjs",
     "test:phase7-inventory": "node scripts/check-phase7-inventory.test.mjs",
@@ -97,7 +98,7 @@
     "demo:phase7": "pnpm run build:typescript && vite --config vite.phase7.config.ts --host 127.0.0.1 --port 4183",
     "browser:dev": "pnpm run build:typescript && pnpm run build:phase2-binaries && vite --config vite.config.ts",
     "browser:preview": "vite preview --config vite.config.ts",
-    "verify": "pnpm run build && pnpm run typecheck && pnpm run check:phase1-goldens && pnpm run test && pnpm run test:phase5 && pnpm run test:phase7 && pnpm run check:browser-tokens && pnpm run test:browser && pnpm run test:browser:phase5 && pnpm run test:browser:phase7 && pnpm run check:forbidden-imports && pnpm run docs:validate && pnpm run check:phase0-parity && pnpm run check:phase1-parity && pnpm run trace:phase0 && pnpm run replay:phase1 && pnpm run trace:phase2 -- --quiet && pnpm run trace:phase3",
+    "verify": "pnpm run build && pnpm run typecheck && pnpm run check:phase1-goldens && pnpm run test && pnpm run test:phase5 && pnpm run test:phase7 && pnpm run check:browser-tokens && pnpm run test:browser && pnpm run test:browser:phase5 && pnpm run test:browser:phase7 && pnpm run check:forbidden-imports && pnpm run check:tracked-imports && pnpm run docs:validate && pnpm run check:phase0-parity && pnpm run check:phase1-parity && pnpm run trace:phase0 && pnpm run replay:phase1 && pnpm run trace:phase2 -- --quiet && pnpm run trace:phase3",
     "verify:rootless": "bash scripts/verify-rootless-linux.sh"
   },
   "peerDependencies": {
diff --git a/packages/paperclip-runner/scripts/check-tracked-imports.mjs b/packages/paperclip-runner/scripts/check-tracked-imports.mjs
new file mode 100644
index 00000000000..259dd3d0ebb
--- /dev/null
+++ b/packages/paperclip-runner/scripts/check-tracked-imports.mjs
@@ -0,0 +1,20 @@
+import {
+  checkTrackedImports,
+  checkTrackedScriptEntryPoints,
+  formatTrackedImportViolation,
+} from "./lib/tracked-imports.mjs";
+
+const violations = [
+  ...(await checkTrackedImports()),
+  ...(await checkTrackedScriptEntryPoints()),
+];
+if (violations.length > 0) {
+  process.stderr.write(
+    `Tracked import check failed:\n${violations
+      .map((violation) => `- ${formatTrackedImportViolation(violation)}`)
+      .join("\n")}\n`,
+  );
+  process.exitCode = 1;
+} else {
+  process.stdout.write("Tracked import check passed.\n");
+}
diff --git a/packages/paperclip-runner/scripts/check-tracked-imports.test.mjs b/packages/paperclip-runner/scripts/check-tracked-imports.test.mjs
new file mode 100644
index 00000000000..79778857de3
--- /dev/null
+++ b/packages/paperclip-runner/scripts/check-tracked-imports.test.mjs
@@ -0,0 +1,73 @@
+import assert from "node:assert/strict";
+import { resolve } from "node:path";
+import { test } from "node:test";
+
+import {
+  checkTrackedImports,
+  checkTrackedScriptEntryPoints,
+  defaultPackageRoot,
+  listTrackedFiles,
+} from "./lib/tracked-imports.mjs";
+
+const fixtureRoot = "test-fixtures/untracked-import";
+
+test("every tracked import in the package resolves to a tracked file", async () => {
+  assert.deepEqual(await checkTrackedImports(), []);
+});
+
+test("a negative fixture proves that an untracked module is rejected", async () => {
+  const consumer = resolve(defaultPackageRoot, fixtureRoot, "consumer.ts");
+  const violations = await checkTrackedImports({
+    scanRoots: [fixtureRoot],
+    // `module.ts` is deliberately withheld from the tracked set: on disk but
+    // absent from the commit is exactly the state a clean checkout cannot build.
+    trackedFiles: [consumer],
+  });
+
+  assert.deepEqual(
+    violations.map(({ specifier, reason }) => ({ specifier, reason })),
+    [
+      {
+        specifier: "./module.js",
+        reason: "resolves only to an untracked file, so a clean checkout cannot build it",
+      },
+      {
+        specifier: "./absent.js",
+        reason: "does not resolve to any tracked file",
+      },
+    ],
+  );
+  assert.ok(violations.every((violation) => violation.file === consumer));
+});
+
+test("every package.json script entry point is tracked", async () => {
+  assert.deepEqual(await checkTrackedScriptEntryPoints(), []);
+});
+
+test("a negative case proves that an untracked script entry point is rejected", async () => {
+  const violations = await checkTrackedScriptEntryPoints({
+    // Withholding the check script itself reproduces the repository-root
+    // `check-*.mjs` ignore rule that kept these entry points out of commits.
+    trackedFiles: (await listTrackedFiles()).filter(
+      (file) => !file.endsWith("/scripts/check-tracked-imports.mjs"),
+    ),
+  });
+
+  assert.deepEqual(
+    violations.map(({ specifier, reason }) => ({ specifier, reason })),
+    [
+      {
+        specifier: "scripts/check-tracked-imports.mjs",
+        reason:
+          'the "check:tracked-imports" script runs a file that is not tracked, so a clean checkout cannot run it',
+      },
+    ],
+  );
+});
+
+test("the fixture itself is tracked so the package-wide check stays green", async () => {
+  const tracked = new Set(await listTrackedFiles());
+  for (const name of ["consumer.ts", "module.ts"]) {
+    assert.ok(tracked.has(resolve(defaultPackageRoot, fixtureRoot, name)), name);
+  }
+});
diff --git a/packages/paperclip-runner/scripts/lib/forbidden-imports.mjs b/packages/paperclip-runner/scripts/lib/forbidden-imports.mjs
index 1c3c822bfe2..f9bea61dc82 100644
--- a/packages/paperclip-runner/scripts/lib/forbidden-imports.mjs
+++ b/packages/paperclip-runner/scripts/lib/forbidden-imports.mjs
@@ -44,7 +44,7 @@ async function collectSourceFiles(target) {
   return files;
 }
 
-function findSpecifiers(source) {
+export function findSpecifiers(source) {
   const found = [];
   for (const pattern of IMPORT_PATTERNS) {
     pattern.lastIndex = 0;
diff --git a/packages/paperclip-runner/scripts/lib/tracked-imports.mjs b/packages/paperclip-runner/scripts/lib/tracked-imports.mjs
new file mode 100644
index 00000000000..d11dd14e93f
--- /dev/null
+++ b/packages/paperclip-runner/scripts/lib/tracked-imports.mjs
@@ -0,0 +1,214 @@
+import { execFile, spawnSync } from "node:child_process";
+import { existsSync } from "node:fs";
+import { readFile } from "node:fs/promises";
+import { dirname, relative, resolve } from "node:path";
+import { promisify } from "node:util";
+
+import { defaultPackageRoot, findSpecifiers } from "./forbidden-imports.mjs";
+
+export { defaultPackageRoot };
+
+const execFileAsync = promisify(execFile);
+
+const SCANNED_EXTENSIONS = new Set([".cjs", ".js", ".jsx", ".mjs", ".ts", ".tsx"]);
+// TypeScript resolves an ESM ".js" specifier against its ".ts" source sibling,
+// so a tracked import may legitimately name a file that never exists on disk.
+const JS_TO_SOURCE_EXTENSIONS = new Map([
+  [".js", [".ts", ".tsx", ".d.ts"]],
+  [".jsx", [".tsx", ".d.ts"]],
+  [".mjs", [".mts", ".d.mts"]],
+  [".cjs", [".cts", ".d.cts"]],
+]);
+const EXTENSIONLESS_CANDIDATES = [
+  ".ts",
+  ".tsx",
+  ".mts",
+  ".cts",
+  ".d.ts",
+  ".js",
+  ".jsx",
+  ".mjs",
+  ".cjs",
+  "/index.ts",
+  "/index.tsx",
+  "/index.js",
+  "/index.mjs",
+];
+
+function extension(path) {
+  const match = path.match(/\.[^./\\]+$/);
+  return match?.[0] ?? "";
+}
+
+function isScannable(path) {
+  return SCANNED_EXTENSIONS.has(extension(path));
+}
+
+function isRelative(specifier) {
+  return specifier.startsWith("./") || specifier.startsWith("../");
+}
+
+/**
+ * Every on-disk path a bundler or `tsc` could pick for this specifier. The
+ * check only needs one of them to be tracked.
+ */
+function resolutionCandidates(file, specifier) {
+  const base = resolve(dirname(file), specifier);
+  const specifierExtension = extension(specifier);
+  const sourceExtensions = JS_TO_SOURCE_EXTENSIONS.get(specifierExtension);
+  if (sourceExtensions !== undefined) {
+    const withoutExtension = base.slice(0, base.length - specifierExtension.length);
+    return [base, ...sourceExtensions.map((suffix) => `${withoutExtension}${suffix}`)];
+  }
+  if (specifierExtension !== "") {
+    return [base];
+  }
+  return [base, ...EXTENSIONLESS_CANDIDATES.map((suffix) => `${base}${suffix}`)];
+}
+
+/**
+ * Build output is untracked on purpose, so an import that points into an
+ * ignored path is not evidence of a missing source file.
+ */
+async function listIgnoredPaths(packageRoot, paths) {
+  if (paths.length === 0) {
+    return new Set();
+  }
+  const result = spawnSync("git", ["check-ignore", "-z", "--stdin"], {
+    cwd: packageRoot,
+    input: paths.join("\0"),
+    encoding: "utf8",
+    maxBuffer: 64 * 1024 * 1024,
+  });
+  if (result.error !== undefined) {
+    throw result.error;
+  }
+  // `git check-ignore` exits 1 when nothing matched, which is not a failure.
+  if (result.status !== 0 && result.status !== 1) {
+    throw new Error(`git check-ignore failed: ${result.stderr}`);
+  }
+  return new Set(
+    result.stdout
+      .split("\0")
+      .filter((entry) => entry !== "")
+      .map((entry) => resolve(packageRoot, entry)),
+  );
+}
+
+export async function listTrackedFiles(packageRoot = defaultPackageRoot) {
+  const { stdout } = await execFileAsync("git", ["ls-files", "-z", "--", "."], {
+    cwd: packageRoot,
+    maxBuffer: 64 * 1024 * 1024,
+  });
+  return stdout
+    .split("\0")
+    .filter((entry) => entry !== "")
+    .map((entry) => resolve(packageRoot, entry));
+}
+
+function isInside(parent, candidate) {
+  const pathFromParent = relative(parent, candidate);
+  return pathFromParent !== "" && !pathFromParent.startsWith("..");
+}
+
+/**
+ * Reject tracked sources whose relative imports only resolve against files git
+ * does not carry. A shared worktree happily builds such a tree while a clean
+ * clone of the same commit cannot, so this guard runs on the tracked set only.
+ */
+export async function checkTrackedImports({
+  packageRoot = defaultPackageRoot,
+  scanRoots = ["src", "scripts", "devtools", "examples"],
+  trackedFiles,
+} = {}) {
+  const tracked = trackedFiles ?? (await listTrackedFiles(packageRoot));
+  const trackedSet = new Set(tracked);
+  const roots = scanRoots.map((root) => resolve(packageRoot, root));
+  const files = tracked
+    .filter((file) => isScannable(file) && roots.some((root) => isInside(root, file)))
+    .sort();
+
+  const suspects = [];
+  for (const file of files) {
+    const source = await readFile(file, "utf8");
+    for (const { specifier, offset } of findSpecifiers(source)) {
+      if (!isRelative(specifier) || /[?*]|\$\{/.test(specifier)) {
+        continue;
+      }
+      const candidates = resolutionCandidates(file, specifier);
+      if (candidates.some((candidate) => trackedSet.has(candidate))) {
+        continue;
+      }
+      suspects.push({
+        file,
+        line: source.slice(0, offset).split("\n").length,
+        specifier,
+        candidates,
+      });
+    }
+  }
+
+  const ignored = await listIgnoredPaths(
+    packageRoot,
+    [...new Set(suspects.flatMap((suspect) => suspect.candidates))],
+  );
+  return suspects
+    .filter((suspect) => !suspect.candidates.some((candidate) => ignored.has(candidate)))
+    .map(({ file, line, specifier, candidates }) => ({
+      file,
+      line,
+      specifier,
+      reason: candidates.some((candidate) => existsSync(candidate))
+        ? "resolves only to an untracked file, so a clean checkout cannot build it"
+        : "does not resolve to any tracked file",
+    }));
+}
+
+const ENTRY_POINT_TOKEN = /^[A-Za-z0-9._@/-]+\.(?:mjs|cjs|js|jsx|ts|tsx|sh|toml)$/;
+
+/**
+ * `package.json` scripts are the other way a commit can depend on a file git
+ * does not carry: an ignored or never-added entry point runs fine locally and
+ * fails immediately in a clean checkout.
+ */
+export async function checkTrackedScriptEntryPoints({
+  packageRoot = defaultPackageRoot,
+  trackedFiles,
+} = {}) {
+  const manifestPath = resolve(packageRoot, "package.json");
+  const manifest = JSON.parse(await readFile(manifestPath, "utf8"));
+  const trackedSet = new Set(trackedFiles ?? (await listTrackedFiles(packageRoot)));
+
+  const suspects = [];
+  for (const [name, body] of Object.entries(manifest.scripts ?? {})) {
+    for (const token of new Set(body.split(/\s+/))) {
+      if (!ENTRY_POINT_TOKEN.test(token) || token.startsWith("@")) {
+        continue;
+      }
+      const path = resolve(packageRoot, token);
+      if (trackedSet.has(path) || !isInside(packageRoot, path)) {
+        continue;
+      }
+      suspects.push({ file: manifestPath, script: name, specifier: token, candidates: [path] });
+    }
+  }
+
+  const ignored = await listIgnoredPaths(
+    packageRoot,
+    suspects.map((suspect) => suspect.candidates[0]),
+  );
+  return suspects
+    .filter((suspect) => !ignored.has(suspect.candidates[0]))
+    .map(({ file, script, specifier }) => ({
+      file,
+      line: 1,
+      specifier,
+      reason: `the "${script}" script runs a file that is not tracked, so a clean checkout cannot run it`,
+    }));
+}
+
+export function formatTrackedImportViolation(violation, packageRoot = defaultPackageRoot) {
+  return `${relative(packageRoot, violation.file)}:${violation.line} imports ${JSON.stringify(
+    violation.specifier,
+  )}: ${violation.reason}`;
+}
diff --git a/packages/paperclip-runner/src/index.ts b/packages/paperclip-runner/src/index.ts
index c720ca9befc..6d566d05f87 100644
--- a/packages/paperclip-runner/src/index.ts
+++ b/packages/paperclip-runner/src/index.ts
@@ -15,7 +15,6 @@ export * from "./drivers/codex/codex-app-server-driver.js";
 export * from "./mock-core/mock-control-plane-adapter.js";
 export * from "./mock-core/phase7-control-plane-types.js";
 export * from "./mock-core/phase7-mock-control-plane-adapter.js";
-export * from "./standalone/phase6-demo.js";
 export * from "./mock-core/phase4-codex-runner.js";
 export * from "./mock-core/phase4b-demo-server.js";
 export * from "./mock-core/phase4b-demo-manifests.js";
diff --git a/packages/paperclip-runner/test-fixtures/untracked-import/consumer.ts b/packages/paperclip-runner/test-fixtures/untracked-import/consumer.ts
new file mode 100644
index 00000000000..e4eb60e5b11
--- /dev/null
+++ b/packages/paperclip-runner/test-fixtures/untracked-import/consumer.ts
@@ -0,0 +1,5 @@
+// Negative fixture for scripts/check-tracked-imports.mjs. Both files here are
+// tracked; the test supplies a tracked set that omits `module.ts` to stand in
+// for a source file that only exists in a contributor's worktree.
+export * from "./module.js";
+export * from "./absent.js";
diff --git a/packages/paperclip-runner/test-fixtures/untracked-import/module.ts b/packages/paperclip-runner/test-fixtures/untracked-import/module.ts
new file mode 100644
index 00000000000..e0f11d75eff
--- /dev/null
+++ b/packages/paperclip-runner/test-fixtures/untracked-import/module.ts
@@ -0,0 +1 @@
+export const untrackedImportFixture = "present on disk";