RM-01: reproducible checkout — the pre-push gate fails on code, not environment (#1027)

Co-authored-by: mos-dt-0 <[email protected]>

scripts/build-web.mjs

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+#!/usr/bin/env node
+
+import { spawn } from 'node:child_process';
+import { createHash, randomUUID } from 'node:crypto';
+import { lstat, mkdir, readFile, rename, rm, writeFile } from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
+
+import { generatedSymlinkManifest, sourceFingerprint } from './preflight.mjs';
+
+const scriptRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
+
+function run(command, args, options) {
+  return new Promise((resolve, reject) => {
+    const child = spawn(command, args, options);
+    child.once('error', reject);
+    child.once('exit', (code, signal) => {
+      if (code === 0) resolve();
+      else
+        reject(
+          new Error(signal ? `next build terminated by ${signal}` : `next build exited ${code}`),
+        );
+    });
+  });
+}
+
+const delay = (milliseconds) => new Promise((resolve) => setTimeout(resolve, milliseconds));
+
+async function requireRealDirectory(target, { allowMissing = false } = {}) {
+  try {
+    const stats = await lstat(target);
+    if (!stats.isDirectory() || stats.isSymbolicLink()) {
+      throw new Error(`${target} must be a real directory, not a symbolic link.`);
+    }
+  } catch (error) {
+    if (allowMissing && error.code === 'ENOENT') return;
+    throw error;
+  }
+}
+
+async function acquireBuildLock(root) {
+  const workRoot = path.join(root, '.mosaic-test-work');
+  const lock = path.join(workRoot, 'web-build.lock');
+  const nonce = randomUUID();
+  const owner = JSON.stringify({ pid: process.pid, nonce });
+  const deadline = Date.now() + 120_000;
+  await mkdir(workRoot, { recursive: true });
+
+  while (Date.now() < deadline) {
+    try {
+      await mkdir(lock);
+      await writeFile(path.join(lock, 'owner.json'), owner, { mode: 0o600 });
+      return async () => {
+        const current = await readFile(path.join(lock, 'owner.json'), 'utf8');
+        if (current !== owner) throw new Error('Web build lock ownership changed before release.');
+        const released = `${lock}.released-${nonce}`;
+        await rename(lock, released);
+        await rm(released, { recursive: true, force: true });
+      };
+    } catch (error) {
+      if (error.code !== 'EEXIST') throw error;
+      let lockOwner;
+      try {
+        lockOwner = JSON.parse(await readFile(path.join(lock, 'owner.json'), 'utf8'));
+      } catch (ownerError) {
+        if (ownerError.code === 'ENOENT') {
+          await delay(25);
+          continue;
+        }
+        throw new Error(`Web build lock is unreadable at ${lock}.`, { cause: ownerError });
+      }
+      try {
+        process.kill(lockOwner.pid, 0);
+      } catch (processError) {
+        if (processError.code !== 'ESRCH') throw processError;
+        const stale = `${lock}.stale-${nonce}`;
+        try {
+          await rename(lock, stale);
+          await rm(stale, { recursive: true, force: true });
+        } catch (renameError) {
+          if (renameError.code !== 'ENOENT') throw renameError;
+        }
+        continue;
+      }
+      await delay(25);
+    }
+  }
+  throw new Error(`Timed out waiting for the web build lock at ${lock}.`);
+}
+
+export async function buildWeb({
+  root = scriptRoot,
+  fingerprint = sourceFingerprint,
+  runBuild = async (webDir) =>
+    run(path.join(webDir, 'node_modules', '.bin', 'next'), ['build'], {
+      cwd: webDir,
+      stdio: 'inherit',
+    }),
+} = {}) {
+  const releaseLock = await acquireBuildLock(root);
+  try {
+    const webDir = path.join(root, 'apps', 'web');
+    const nextDir = path.join(webDir, '.next');
+    const certificationMarker = path.join(nextDir, '.mosaic-source-hash');
+    const symlinkManifest = path.join(nextDir, '.mosaic-symlink-manifest');
+    const certificationTemporary = `${certificationMarker}.${randomUUID()}.tmp`;
+    const manifestTemporary = `${symlinkManifest}.${randomUUID()}.tmp`;
+    const before = await fingerprint(root);
+
+    await requireRealDirectory(nextDir, { allowMissing: true });
+    await Promise.all([
+      rm(certificationMarker, { force: true }),
+      rm(symlinkManifest, { force: true }),
+    ]);
+    await runBuild(webDir);
+    await requireRealDirectory(nextDir);
+
+    const after = await fingerprint(root);
+    if (after !== before) {
+      throw new Error(
+        'Web build inputs changed during next build; generated output was not certified.',
+      );
+    }
+
+    const manifestContents = await generatedSymlinkManifest(nextDir);
+    const certificationContents = `${JSON.stringify({
+      version: 1,
+      sourceFingerprint: before,
+      symlinkManifestHash: createHash('sha256').update(manifestContents).digest('hex'),
+    })}\n`;
+    await Promise.all([
+      writeFile(certificationTemporary, certificationContents, { mode: 0o600 }),
+      writeFile(manifestTemporary, manifestContents, { mode: 0o600 }),
+    ]);
+    // The certification marker is the commit point. Publishing the manifest first
+    // leaves interrupted builds untrusted because the marker remains absent.
+    await rename(manifestTemporary, symlinkManifest);
+    await rename(certificationTemporary, certificationMarker);
+  } finally {
+    await releaseLock();
+  }
+}
+
+if (process.argv[1] && path.resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
+  await buildWeb();
+}

scripts/build-web.test.mjs

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+import assert from 'node:assert/strict';
+import { access, mkdir, readFile, rm, symlink, writeFile } from 'node:fs/promises';
+import path from 'node:path';
+import test from 'node:test';
+
+import { buildWeb } from './build-web.mjs';
+
+const fixtureRoot = path.join(process.cwd(), '.mosaic-test-work', `build-web-${process.pid}`);
+
+async function fixture(name) {
+  const root = path.join(fixtureRoot, name);
+  await mkdir(path.join(root, 'apps', 'web', '.next'), { recursive: true });
+  return root;
+}
+
+async function exists(target) {
+  try {
+    await access(target);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+test.after(async () => {
+  await rm(fixtureRoot, { recursive: true, force: true });
+});
+
+test('a successful web build atomically publishes its source and symlink certification', async () => {
+  const root = await fixture('success');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  const manifest = path.join(root, 'apps', 'web', '.next', '.mosaic-symlink-manifest');
+
+  await buildWeb({ root, fingerprint: async () => 'certified', runBuild: async () => {} });
+
+  assert.deepEqual(JSON.parse(await readFile(marker, 'utf8')), {
+    version: 1,
+    sourceFingerprint: 'certified',
+    symlinkManifestHash: '8a5a375cea6a55d24bd5f875856da63feba33adbefb15a92a0007719b84bcf11',
+  });
+  assert.equal(await readFile(manifest, 'utf8'), '{"version":1,"links":[]}\n');
+});
+
+test('a failed web build leaves no certification marker', async () => {
+  const root = await fixture('failure');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  const manifest = path.join(root, 'apps', 'web', '.next', '.mosaic-symlink-manifest');
+  await writeFile(marker, 'stale\n');
+  await writeFile(manifest, 'stale\n');
+
+  await assert.rejects(
+    buildWeb({
+      root,
+      fingerprint: async () => 'before',
+      runBuild: async () => {
+        throw new Error('build failed');
+      },
+    }),
+    /build failed/,
+  );
+
+  assert.equal(await exists(marker), false);
+  assert.equal(await exists(manifest), false);
+});
+
+test('overlapping web builds are serialized while the marker remains absent', async () => {
+  const root = await fixture('overlap');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  const manifest = path.join(root, 'apps', 'web', '.next', '.mosaic-symlink-manifest');
+  await writeFile(marker, 'stale\n');
+  await writeFile(manifest, 'stale\n');
+  let releaseFirst;
+  let secondEntered = false;
+  const firstEntered = new Promise((resolve) => {
+    releaseFirst = resolve;
+  });
+  let markFirstEntered;
+  const firstStarted = new Promise((resolve) => {
+    markFirstEntered = resolve;
+  });
+
+  const first = buildWeb({
+    root,
+    fingerprint: async () => 'certified',
+    runBuild: async () => {
+      markFirstEntered();
+      await firstEntered;
+    },
+  });
+  await firstStarted;
+  const second = buildWeb({
+    root,
+    fingerprint: async () => 'certified',
+    runBuild: async () => {
+      secondEntered = true;
+    },
+  });
+  await new Promise((resolve) => setTimeout(resolve, 75));
+  assert.equal(secondEntered, false);
+  assert.equal(await exists(marker), false);
+  assert.equal(await exists(manifest), false);
+
+  releaseFirst();
+  await Promise.all([first, second]);
+  assert.equal(secondEntered, true);
+  assert.equal(JSON.parse(await readFile(marker, 'utf8')).sourceFingerprint, 'certified');
+  assert.equal(await readFile(manifest, 'utf8'), '{"version":1,"links":[]}\n');
+});
+
+test('a build that replaces .next with a symbolic link cannot publish outside the checkout', async () => {
+  const root = await fixture('symbolic-next');
+  const nextDir = path.join(root, 'apps', 'web', '.next');
+  const outside = path.join(root, 'outside-generated');
+  await mkdir(outside);
+
+  await assert.rejects(
+    buildWeb({
+      root,
+      fingerprint: async () => 'certified',
+      runBuild: async () => {
+        await rm(nextDir, { recursive: true });
+        await symlink(outside, nextDir);
+      },
+    }),
+    /must be a real directory/,
+  );
+
+  assert.equal(await exists(path.join(outside, '.mosaic-source-hash')), false);
+  assert.equal(await exists(path.join(outside, '.mosaic-symlink-manifest')), false);
+});
+
+test('inputs changed during a web build are not certified', async () => {
+  const root = await fixture('changed-inputs');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  const manifest = path.join(root, 'apps', 'web', '.next', '.mosaic-symlink-manifest');
+  const fingerprints = ['before', 'after'];
+
+  await assert.rejects(
+    buildWeb({
+      root,
+      fingerprint: async () => fingerprints.shift(),
+      runBuild: async () => {},
+    }),
+    /inputs changed during next build/,
+  );
+
+  assert.equal(await exists(marker), false);
+  assert.equal(await exists(manifest), false);
+});

scripts/clean-generated.mjs

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+#!/usr/bin/env node
+
+import { access, mkdir, rename, rm } from 'node:fs/promises';
+import path from 'node:path';
+
+const root = process.cwd();
+const generated = path.join(root, 'apps', 'web', '.next');
+const quarantineRoot = path.join(root, '.mosaic-test-work', 'generated-quarantine');
+
+try {
+  await access(generated);
+} catch (error) {
+  if (error.code === 'ENOENT') process.exit(0);
+  throw error;
+}
+
+await mkdir(quarantineRoot, { recursive: true });
+const quarantine = path.join(quarantineRoot, `web-next-${Date.now()}-${process.pid}`);
+try {
+  await rename(generated, quarantine);
+} catch (error) {
+  console.error(
+    `MOSAIC_GENERATED_CLEAN_FAILED: could not quarantine apps/web/.next. Fix: sudo rm -rf '${generated}', then rerun pnpm preflight`,
+  );
+  throw error;
+}
+
+try {
+  await rm(quarantine, { recursive: true, force: true });
+} catch {
+  console.warn(
+    `Generated state was deactivated but could not be deleted; quarantined at ${quarantine}`,
+  );
+}

scripts/install-hooks.mjs

@@ -0,0 +1,146 @@
+#!/usr/bin/env node
+
+import { access, lstat, mkdir, readFile, readdir, rename, rm } from 'node:fs/promises';
+import { execFile, spawn } from 'node:child_process';
+import { promisify } from 'node:util';
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
+
+const execFileAsync = promisify(execFile);
+
+function run(command, args, options) {
+  return new Promise((resolve, reject) => {
+    const child = spawn(command, args, options);
+    child.once('error', reject);
+    child.once('exit', (code, signal) => {
+      if (code === 0) resolve();
+      else reject(new Error(signal ? `husky terminated by ${signal}` : `husky exited ${code}`));
+    });
+  });
+}
+
+async function pathExists(target) {
+  try {
+    await access(target);
+    return true;
+  } catch (error) {
+    if (error.code === 'ENOENT') return false;
+    throw error;
+  }
+}
+
+async function directorySnapshot(root) {
+  const snapshot = [];
+  async function walk(current) {
+    const children = await readdir(current, { withFileTypes: true });
+    for (const child of children.sort((left, right) => left.name.localeCompare(right.name))) {
+      const target = path.join(current, child.name);
+      const relative = path.relative(root, target);
+      const stats = await lstat(target);
+      if (child.isDirectory()) {
+        snapshot.push([relative, 'directory', stats.mode & 0o777]);
+        await walk(target);
+      } else {
+        snapshot.push([
+          relative,
+          'file',
+          stats.mode & 0o777,
+          (await readFile(target)).toString('base64'),
+        ]);
+      }
+    }
+  }
+  await walk(root);
+  return JSON.stringify(snapshot);
+}
+
+async function directoriesMatch(left, right) {
+  return (await directorySnapshot(left)) === (await directorySnapshot(right));
+}
+
+export async function installHooks({
+  root = process.cwd(),
+  disabled = process.env.HUSKY === '0',
+  quarantineRoot = path.join(root, '.mosaic-test-work', 'husky-quarantine'),
+  runHusky = async (_stagingHooks, stagingRepo) => {
+    await execFileAsync('git', ['init', '--quiet', stagingRepo]);
+    await run(path.join(root, 'node_modules', '.bin', 'husky'), ['.husky'], {
+      cwd: stagingRepo,
+      stdio: 'inherit',
+    });
+  },
+  activateHooks = async () => {
+    await run('git', ['config', 'core.hooksPath', '.husky/_'], { cwd: root, stdio: 'inherit' });
+  },
+} = {}) {
+  if (disabled) return;
+
+  const huskyDir = path.join(root, '.husky');
+  const active = path.join(huskyDir, '_');
+  const nonce = `${Date.now()}-${process.pid}`;
+  const stagingRepo = path.join(root, '.mosaic-test-work', `husky-stage-${nonce}`);
+  const stagingHooks = path.join(stagingRepo, '.husky');
+  const quarantined = path.join(quarantineRoot, `${path.basename(root)}-${nonce}`);
+  await mkdir(huskyDir, { recursive: true });
+  await mkdir(quarantineRoot, { recursive: true });
+
+  const previousComplete = (await pathExists(active)) && (await pathExists(path.join(active, 'h')));
+  let previousQuarantined = false;
+  try {
+    if ((await pathExists(active)) && !previousComplete) {
+      await rename(active, quarantined);
+      previousQuarantined = true;
+    }
+    await mkdir(stagingRepo, { recursive: true });
+    await runHusky(stagingHooks, stagingRepo);
+    const staged = path.join(stagingHooks, '_');
+    if (!(await pathExists(path.join(staged, 'h')))) {
+      throw new Error('husky did not produce its required h shim');
+    }
+    if (previousComplete) {
+      if (!(await directoriesMatch(active, staged))) {
+        throw new Error('existing complete hook set differs from the installed Husky version');
+      }
+      await rm(stagingRepo, { recursive: true, force: true });
+    } else {
+      await rename(staged, active);
+      await rm(stagingRepo, { recursive: true, force: true });
+    }
+    await activateHooks();
+    if (previousQuarantined) {
+      try {
+        await rm(quarantined, { recursive: true, force: true });
+      } catch {
+        console.warn(
+          `Previous hook state was deactivated but remains quarantined at ${quarantined}`,
+        );
+      }
+    }
+  } catch (error) {
+    const cleanupFailures = [];
+    try {
+      if (await pathExists(stagingRepo)) {
+        await rename(stagingRepo, `${quarantined}-staging`);
+      }
+    } catch (cleanupError) {
+      cleanupFailures.push(`staging hooks: ${cleanupError.message}`);
+    }
+    const cleanup =
+      cleanupFailures.length === 0
+        ? 'No partial hook set was activated.'
+        : `Automatic cleanup was incomplete (${cleanupFailures.join('; ')}).`;
+    throw new Error(
+      `Hook installation failed: ${error.message}. ${cleanup} Fix: rm -rf .husky/_ && git config core.hooksPath .husky/_ && pnpm install --frozen-lockfile`,
+      { cause: error },
+    );
+  }
+}
+
+if (process.argv[1] && path.resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
+  try {
+    await installHooks();
+  } catch (error) {
+    console.error(error.message);
+    process.exitCode = 1;
+  }
+}

scripts/install-hooks.test.mjs

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+import assert from 'node:assert/strict';
+import { access, mkdir, readFile, readdir, rm, writeFile } from 'node:fs/promises';
+import path from 'node:path';
+import test from 'node:test';
+
+import { installHooks } from './install-hooks.mjs';
+
+const fixtureRoot = path.join(process.cwd(), '.mosaic-test-work', `hooks-${process.pid}`);
+const quarantineRoot = path.join(fixtureRoot, 'quarantine');
+
+async function fixture(name) {
+  const root = path.join(fixtureRoot, name);
+  await mkdir(path.join(root, '.husky'), { recursive: true });
+  return root;
+}
+
+async function exists(target) {
+  try {
+    await access(target);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+test.after(async () => {
+  await rm(fixtureRoot, { recursive: true, force: true });
+});
+
+test('an interrupted install quarantines the partial active hook set and fails loudly', async () => {
+  const root = await fixture('interrupted');
+  let restoredHooksPath = 'not-called';
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot,
+      runHusky: async (stagingHooks) => {
+        await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+        await writeFile(path.join(stagingHooks, '_', 'h'), 'partial');
+        throw new Error('simulated interruption');
+      },
+      activateHooks: async () => {},
+      readHooksPath: async () => null,
+      restoreHooksPath: async (value) => {
+        restoredHooksPath = value;
+      },
+    }),
+    (error) => {
+      assert.match(error.message, /Hook installation failed/);
+      assert.match(error.message, /pnpm install --frozen-lockfile/);
+      return true;
+    },
+  );
+
+  assert.equal(await exists(path.join(root, '.husky', '_')), false);
+  assert.equal(restoredHooksPath, 'not-called');
+  const quarantined = await readdir(quarantineRoot);
+  assert.equal(quarantined.length, 1);
+});
+
+test('a failed replacement restores a previously complete active hook set', async () => {
+  const root = await fixture('rollback');
+  const activeShim = path.join(root, '.husky', '_', 'h');
+  await mkdir(path.dirname(activeShim), { recursive: true });
+  await writeFile(activeShim, 'previous-complete');
+  let previousRemainedActiveDuringStaging = false;
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot: path.join(fixtureRoot, 'rollback-quarantine'),
+      runHusky: async () => {
+        previousRemainedActiveDuringStaging =
+          (await readFile(activeShim, 'utf8')) === 'previous-complete';
+        throw new Error('simulated replacement failure');
+      },
+      activateHooks: async () => {},
+      readHooksPath: async () => '.husky/_',
+      restoreHooksPath: async () => {},
+    }),
+    /Hook installation failed/,
+  );
+
+  assert.equal(previousRemainedActiveDuringStaging, true);
+  assert.equal(await readFile(activeShim, 'utf8'), 'previous-complete');
+});
+
+test('a mismatched complete hook set fails loudly instead of reporting a stale install as current', async () => {
+  const root = await fixture('mismatch');
+  const activeShim = path.join(root, '.husky', '_', 'h');
+  await mkdir(path.dirname(activeShim), { recursive: true });
+  await writeFile(activeShim, 'old-complete');
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot: path.join(fixtureRoot, 'mismatch-quarantine'),
+      runHusky: async (stagingHooks) => {
+        await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+        await writeFile(path.join(stagingHooks, '_', 'h'), 'new-complete');
+      },
+      activateHooks: async () => {},
+      readHooksPath: async () => '.husky/_',
+      restoreHooksPath: async () => {},
+    }),
+    /Hook installation failed.*pnpm install --frozen-lockfile/,
+  );
+
+  assert.equal(await readFile(activeShim, 'utf8'), 'old-complete');
+});
+
+test('a competing successful installer is not removed by the losing process', async () => {
+  const root = await fixture('concurrent');
+  const activeShim = path.join(root, '.husky', '_', 'h');
+  let restored = false;
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot: path.join(fixtureRoot, 'concurrent-quarantine'),
+      runHusky: async (stagingHooks) => {
+        await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+        await writeFile(path.join(stagingHooks, '_', 'h'), 'ours');
+        await mkdir(path.dirname(activeShim), { recursive: true });
+        await writeFile(activeShim, 'peer');
+      },
+      activateHooks: async () => {},
+      readHooksPath: async () => null,
+      restoreHooksPath: async () => {
+        restored = true;
+      },
+    }),
+    /Hook installation failed/,
+  );
+
+  assert.equal(await readFile(activeShim, 'utf8'), 'peer');
+  assert.equal(restored, false);
+});
+
+test("a competing installer that replaces this installer's active set is preserved", async () => {
+  const root = await fixture('concurrent-after-rename');
+  const active = path.join(root, '.husky', '_');
+  const activeShim = path.join(active, 'h');
+  let restored = false;
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot: path.join(fixtureRoot, 'concurrent-after-rename-quarantine'),
+      runHusky: async (stagingHooks) => {
+        await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+        await writeFile(path.join(stagingHooks, '_', 'h'), 'ours');
+      },
+      activateHooks: async () => {
+        await rm(active, { recursive: true, force: true });
+        await mkdir(active, { recursive: true });
+        await writeFile(activeShim, 'peer');
+        throw new Error('our activation lost to peer');
+      },
+      readHooksPath: async () => null,
+      restoreHooksPath: async () => {
+        restored = true;
+      },
+    }),
+    /Hook installation failed/,
+  );
+
+  assert.equal(await readFile(activeShim, 'utf8'), 'peer');
+  assert.equal(restored, false);
+});
+
+test('an explicit interactive HUSKY=0 opt-out preserves existing hooks without running installer', async () => {
+  const root = await fixture('disabled');
+  const activeShim = path.join(root, '.husky', '_', 'h');
+  await mkdir(path.dirname(activeShim), { recursive: true });
+  await writeFile(activeShim, 'preserved');
+  let ran = false;
+
+  await installHooks({
+    root,
+    disabled: true,
+    runHusky: async () => {
+      ran = true;
+    },
+  });
+
+  assert.equal(ran, false);
+  assert.equal(await readFile(activeShim, 'utf8'), 'preserved');
+});
+
+test('a successful install leaves a complete active hook set', async () => {
+  const root = await fixture('success');
+
+  await installHooks({
+    root,
+    quarantineRoot,
+    runHusky: async (stagingHooks) => {
+      await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+      await writeFile(path.join(stagingHooks, '_', 'h'), 'complete');
+    },
+    activateHooks: async () => {},
+    readHooksPath: async () => null,
+    restoreHooksPath: async () => {},
+  });
+
+  assert.equal(await exists(path.join(root, '.husky', '_', 'h')), true);
+});

scripts/preflight.mjs

@@ -0,0 +1,254 @@
+#!/usr/bin/env node
+
+import { constants } from 'node:fs';
+import { access, lstat, readFile, readdir, readlink } from 'node:fs/promises';
+import { createHash } from 'node:crypto';
+import { createRequire } from 'node:module';
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
+
+export const MISSING_DEPS_EXIT = 42;
+export const GENERATED_STATE_EXIT = 43;
+
+const scriptRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
+
+async function entries(root) {
+  const result = [];
+  async function walk(current) {
+    let children;
+    try {
+      children = await readdir(current, { withFileTypes: true });
+    } catch (error) {
+      if (error.code === 'ENOENT') return;
+      throw error;
+    }
+    for (const child of children) {
+      const target = path.join(current, child.name);
+      result.push(target);
+      if (child.isDirectory() && !child.isSymbolicLink()) await walk(target);
+    }
+  }
+  await walk(root);
+  return result;
+}
+
+export async function generatedSymlinkManifest(nextDir) {
+  const links = [];
+  for (const target of (await entries(nextDir)).sort()) {
+    const stats = await lstat(target);
+    if (!stats.isSymbolicLink()) continue;
+    links.push({
+      path: path.relative(nextDir, target).split(path.sep).join('/'),
+      target: await readlink(target),
+    });
+  }
+  return `${JSON.stringify({ version: 1, links })}\n`;
+}
+
+const webSourceRoots = (root) => [
+  path.join(root, 'apps', 'web', 'src'),
+  path.join(root, 'apps', 'web', 'public'),
+  path.join(root, 'apps', 'web', 'next-env.d.ts'),
+  path.join(root, 'apps', 'web', 'next.config.ts'),
+  path.join(root, 'apps', 'web', 'postcss.config.mjs'),
+  path.join(root, 'apps', 'web', 'package.json'),
+  path.join(root, 'apps', 'web', 'tsconfig.json'),
+  path.join(root, 'packages', 'design-tokens', 'src'),
+  path.join(root, 'packages', 'design-tokens', 'package.json'),
+  path.join(root, 'packages', 'design-tokens', 'tsconfig.json'),
+  path.join(root, 'package.json'),
+  path.join(root, 'tsconfig.base.json'),
+  path.join(root, 'pnpm-lock.yaml'),
+  path.join(root, 'pnpm-workspace.yaml'),
+  path.join(root, 'turbo.json'),
+];
+
+// next.config.ts currently reads no server-only environment. Add any future
+// server-side build inputs here; all resolved NEXT_PUBLIC_* inputs are automatic.
+const serverBuildEnvironmentKeys = [];
+
+function publicBuildEnvironment(root) {
+  const webDir = path.join(root, 'apps', 'web');
+  const requireFromWeb = createRequire(path.join(scriptRoot, 'apps', 'web', 'package.json'));
+  const requireFromNext = createRequire(requireFromWeb.resolve('next/package.json'));
+  const { loadEnvConfig, resetEnv, updateInitialEnv } = requireFromNext('@next/env');
+  const originalEnvironment = { ...process.env };
+  updateInitialEnv(originalEnvironment);
+  try {
+    const { combinedEnv } = loadEnvConfig(webDir, false, { info() {}, error() {} }, true);
+    return Object.fromEntries(
+      Object.entries(combinedEnv).filter(
+        ([key, value]) =>
+          value !== undefined &&
+          (key.startsWith('NEXT_PUBLIC_') || serverBuildEnvironmentKeys.includes(key)),
+      ),
+    );
+  } finally {
+    resetEnv();
+  }
+}
+
+export async function sourceFingerprint(root = process.cwd()) {
+  const files = [];
+  for (const sourceRoot of webSourceRoots(root)) {
+    try {
+      const stats = await lstat(sourceRoot);
+      if (stats.isSymbolicLink()) {
+        throw new Error(
+          `Web build input must not be a symbolic link: ${path.relative(root, sourceRoot)}`,
+        );
+      }
+      if (stats.isFile()) files.push(sourceRoot);
+      if (stats.isDirectory()) {
+        for (const target of await entries(sourceRoot)) {
+          const targetStats = await lstat(target);
+          if (targetStats.isSymbolicLink()) {
+            throw new Error(
+              `Web build input must not be a symbolic link: ${path.relative(root, target)}`,
+            );
+          }
+          if (targetStats.isFile()) files.push(target);
+        }
+      }
+    } catch (error) {
+      if (error.code !== 'ENOENT') throw error;
+    }
+  }
+
+  const digest = createHash('sha256');
+  for (const [key, value] of Object.entries(publicBuildEnvironment(root)).sort()) {
+    digest.update(`env:${key}\0${value.length}\0${value}\0`);
+  }
+  for (const target of files.sort()) {
+    const contents = await readFile(target);
+    digest.update(path.relative(root, target).split(path.sep).join('/'));
+    digest.update('\0');
+    digest.update(String(contents.length));
+    digest.update('\0');
+    digest.update(contents);
+    digest.update('\0');
+  }
+  return digest.digest('hex');
+}
+
+export async function runPreflight({ root = process.cwd(), uid = process.getuid?.() } = {}) {
+  const binDir = path.join(root, 'node_modules', '.bin');
+  const requiredBinaries = ['eslint', 'husky', 'prettier', 'tsc', 'turbo', 'vitest'];
+  const missingBinaries = [];
+  for (const binary of requiredBinaries) {
+    try {
+      await access(path.join(binDir, binary), constants.X_OK);
+    } catch {
+      missingBinaries.push(binary);
+    }
+  }
+  if (missingBinaries.length > 0) {
+    return {
+      code: MISSING_DEPS_EXIT,
+      message: `MOSAIC_PREFLIGHT_MISSING_DEPS: dependency installation is missing ${missingBinaries.join(', ')}; run pnpm install --frozen-lockfile`,
+    };
+  }
+
+  const buildLock = path.join(root, '.mosaic-test-work', 'web-build.lock');
+  try {
+    await lstat(buildLock);
+    return {
+      code: GENERATED_STATE_EXIT,
+      message: `MOSAIC_PREFLIGHT_GENERATED_STATE: web build is in progress or interrupted at ${buildLock}; wait for it to finish or rerun pnpm build to recover the stale lock`,
+    };
+  } catch (error) {
+    if (error.code !== 'ENOENT') throw error;
+  }
+
+  const nextDir = path.join(root, 'apps', 'web', '.next');
+  let generated = [];
+  try {
+    const nextStats = await lstat(nextDir);
+    if (!nextStats.isDirectory() || nextStats.isSymbolicLink()) {
+      return {
+        code: GENERATED_STATE_EXIT,
+        message:
+          'MOSAIC_PREFLIGHT_GENERATED_STATE: apps/web/.next must be a real directory, not a symbolic link, and is not trustworthy; run pnpm clean:generated, then rerun the gate',
+      };
+    }
+    generated = [nextDir, ...(await entries(nextDir))];
+  } catch (error) {
+    if (error.code !== 'ENOENT') throw error;
+  }
+
+  if (generated.length > 0) {
+    const foreign = [];
+    for (const target of generated) {
+      const stats = await lstat(target);
+      if (uid !== undefined && stats.uid !== uid) foreign.push(path.relative(root, target));
+    }
+
+    // Detects accidental, independent, stale, and foreign-residue mutation of
+    // generated state: the class this check was born from was a five-month-stale
+    // .next whose validator referenced deleted pages and produced 19 phantom TS2307
+    // errors indistinguishable from real type errors.
+    //
+    // Does NOT defend against an actor with same-UID write access to the generated
+    // tree, which can regenerate both the manifest and marker consistently
+    // (CWE-345). No local construction can, absent a trust anchor outside that
+    // actor's authority. RM-59 tracks executor/spine-side attestation.
+    let certification = null;
+    let certifiedManifest = null;
+    try {
+      const [certificationContents, manifestContents] = await Promise.all([
+        readFile(path.join(nextDir, '.mosaic-source-hash'), 'utf8'),
+        readFile(path.join(nextDir, '.mosaic-symlink-manifest'), 'utf8'),
+      ]);
+      try {
+        const parsed = JSON.parse(certificationContents);
+        if (
+          parsed.version === 1 &&
+          typeof parsed.sourceFingerprint === 'string' &&
+          typeof parsed.symlinkManifestHash === 'string'
+        ) {
+          certification = parsed;
+          certifiedManifest = manifestContents;
+        }
+      } catch {
+        // Invalid certification is handled as untrusted generated state below.
+      }
+    } catch (error) {
+      if (error.code !== 'ENOENT') throw error;
+    }
+    const stale = certification?.sourceFingerprint !== (await sourceFingerprint(root));
+    const actualManifest = await generatedSymlinkManifest(nextDir);
+    const certifiedManifestHash =
+      certifiedManifest === null
+        ? null
+        : createHash('sha256').update(certifiedManifest).digest('hex');
+    const changedSymlinks =
+      certification?.symlinkManifestHash !== certifiedManifestHash ||
+      certifiedManifest !== actualManifest;
+    if (foreign.length > 0 || stale || changedSymlinks) {
+      const reasons = [
+        foreign.length > 0 ? `foreign-owned paths: ${foreign.slice(0, 3).join(', ')}` : '',
+        stale ? 'generated source fingerprint does not match web source/configuration' : '',
+        changedSymlinks
+          ? 'generated symbolic-link manifest does not match the certified build'
+          : '',
+      ].filter(Boolean);
+      return {
+        code: GENERATED_STATE_EXIT,
+        message: `MOSAIC_PREFLIGHT_GENERATED_STATE: apps/web/.next is not trustworthy (${reasons.join('; ')}); run pnpm clean:generated, then rerun the gate`,
+      };
+    }
+  }
+
+  return { code: 0, message: 'checkout preflight passed' };
+}
+
+async function main() {
+  const result = await runPreflight();
+  const stream = result.code === 0 ? process.stdout : process.stderr;
+  stream.write(`${result.message}\n`);
+  process.exitCode = result.code;
+}
+
+if (process.argv[1] && path.resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
+  await main();
+}

scripts/preflight.test.mjs

@@ -0,0 +1,274 @@
+import assert from 'node:assert/strict';
+import { createHash } from 'node:crypto';
+import { chmod, mkdir, rm, symlink, utimes, writeFile } from 'node:fs/promises';
+import path from 'node:path';
+import test from 'node:test';
+
+import { runPreflight, sourceFingerprint } from './preflight.mjs';
+
+const fixtureRoot = path.join(process.cwd(), '.mosaic-test-work', `preflight-${process.pid}`);
+
+const requiredBins = ['eslint', 'husky', 'prettier', 'tsc', 'turbo', 'vitest'];
+
+async function fixture(name) {
+  const root = path.join(fixtureRoot, name);
+  await mkdir(path.join(root, 'apps', 'web', 'src', 'app'), { recursive: true });
+  await writeFile(path.join(root, 'apps', 'web', 'src', 'app', 'page.tsx'), 'export default 1;\n');
+  return root;
+}
+
+async function installRequiredBins(root) {
+  const binDir = path.join(root, 'node_modules', '.bin');
+  await mkdir(binDir, { recursive: true });
+  await Promise.all(
+    requiredBins.map(async (name) => {
+      const target = path.join(binDir, name);
+      await writeFile(target, '');
+      await chmod(target, 0o755);
+    }),
+  );
+}
+
+async function certifyGeneratedState(root, links = []) {
+  const nextDir = path.join(root, 'apps', 'web', '.next');
+  await mkdir(nextDir, { recursive: true });
+  const manifest = `${JSON.stringify({ version: 1, links })}\n`;
+  const manifestHash = createHash('sha256').update(manifest).digest('hex');
+  await writeFile(path.join(nextDir, '.mosaic-symlink-manifest'), manifest);
+  await writeFile(
+    path.join(nextDir, '.mosaic-source-hash'),
+    `${JSON.stringify({
+      version: 1,
+      sourceFingerprint: await sourceFingerprint(root),
+      symlinkManifestHash: manifestHash,
+    })}\n`,
+  );
+}
+
+test.after(async () => {
+  await rm(fixtureRoot, { recursive: true, force: true });
+});
+
+test('missing dependencies have a dedicated exit code and install remediation', async () => {
+  const root = await fixture('missing-deps');
+  const result = await runPreflight({ root });
+
+  assert.equal(result.code, 42);
+  assert.match(result.message, /MOSAIC_PREFLIGHT_MISSING_DEPS/);
+  assert.match(result.message, /run pnpm install/i);
+});
+
+test('a partial dependency install keeps the dedicated missing-deps result', async () => {
+  const root = await fixture('partial-deps');
+  await mkdir(path.join(root, 'node_modules', '.bin'), { recursive: true });
+  await writeFile(path.join(root, 'node_modules', '.bin', 'tsc'), '', { mode: 0o755 });
+
+  const result = await runPreflight({ root });
+  assert.equal(result.code, 42);
+  assert.match(result.message, /turbo/);
+});
+
+test('a dangling required dependency shim keeps the dedicated missing-deps result', async () => {
+  const root = await fixture('dangling-deps');
+  await installRequiredBins(root);
+  const turbo = path.join(root, 'node_modules', '.bin', 'turbo');
+  await rm(turbo);
+  await symlink(path.join(root, 'node_modules', 'missing-turbo'), turbo);
+
+  const result = await runPreflight({ root });
+  assert.equal(result.code, 42);
+  assert.match(result.message, /turbo/);
+});
+
+test('installed dependencies pass when generated state is absent', async () => {
+  const root = await fixture('clean');
+  await installRequiredBins(root);
+
+  assert.deepEqual(await runPreflight({ root }), { code: 0, message: 'checkout preflight passed' });
+});
+
+test('foreign-owned generated Next state is identified separately from source errors', async () => {
+  const root = await fixture('foreign-next');
+  await installRequiredBins(root);
+  const generated = path.join(root, 'apps', 'web', '.next', 'types', 'validator.ts');
+  await mkdir(path.dirname(generated), { recursive: true });
+  await writeFile(generated, 'generated output');
+
+  const result = await runPreflight({ root, uid: (process.getuid?.() ?? 0) + 1 });
+  assert.equal(result.code, 43);
+  assert.match(result.message, /MOSAIC_PREFLIGHT_GENERATED_STATE/);
+  assert.match(result.message, /foreign-owned/);
+});
+
+test('a generated marker mismatch is identified separately from source errors', async () => {
+  const root = await fixture('stale-next');
+  await installRequiredBins(root);
+  const generated = path.join(root, 'apps', 'web', '.next', 'types', 'validator.ts');
+  await mkdir(path.dirname(generated), { recursive: true });
+  await writeFile(generated, 'stale generated output');
+  await writeFile(path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash'), 'old-source');
+
+  const result = await runPreflight({ root });
+  assert.equal(result.code, 43);
+  assert.match(result.message, /MOSAIC_PREFLIGHT_GENERATED_STATE/);
+  assert.match(result.message, /apps\/web\/\.next/);
+  assert.match(result.message, /pnpm clean:generated/);
+});
+
+test('generated-state symbolic links are accepted only when exactly build-certified', async (t) => {
+  await t.test('apps/web/.next itself is rejected when it is a symbolic link', async () => {
+    const root = await fixture('symbolic-next-root');
+    await installRequiredBins(root);
+    await writeFile(path.join(root, 'outside-generated'), 'not a Next build\n');
+    await symlink(path.join(root, 'outside-generated'), path.join(root, 'apps', 'web', '.next'));
+
+    const result = await runPreflight({ root });
+    assert.equal(result.code, 43);
+    assert.match(result.message, /MOSAIC_PREFLIGHT_GENERATED_STATE/);
+    assert.match(result.message, /symbolic link/);
+  });
+
+  await t.test('apps/web/.next is rejected when it is not a directory', async () => {
+    const root = await fixture('non-directory-next-root');
+    await installRequiredBins(root);
+    await writeFile(path.join(root, 'apps', 'web', '.next'), 'not a Next build\n');
+
+    const result = await runPreflight({ root });
+    assert.equal(result.code, 43);
+    assert.match(result.message, /MOSAIC_PREFLIGHT_GENERATED_STATE/);
+    assert.match(result.message, /real directory/);
+  });
+
+  await t.test('an added descendant symlink is rejected', async () => {
+    const root = await fixture('symbolic-next-added');
+    await installRequiredBins(root);
+    await certifyGeneratedState(root);
+    await symlink('/etc/hosts', path.join(root, 'apps', 'web', '.next', 'reviewer-symlink'));
+
+    const result = await runPreflight({ root });
+    assert.equal(result.code, 43);
+    assert.match(result.message, /symbolic-link manifest/);
+  });
+
+  await t.test('a removed certified descendant symlink is rejected', async () => {
+    const root = await fixture('symbolic-next-removed');
+    await installRequiredBins(root);
+    const link = path.join(root, 'apps', 'web', '.next', 'dependency-link');
+    await mkdir(path.dirname(link), { recursive: true });
+    await symlink('../dependency-one', link);
+    await certifyGeneratedState(root, [{ path: 'dependency-link', target: '../dependency-one' }]);
+    await rm(link);
+
+    const result = await runPreflight({ root });
+    assert.equal(result.code, 43);
+    assert.match(result.message, /symbolic-link manifest/);
+  });
+
+  await t.test('a retargeted certified descendant symlink is rejected', async () => {
+    const root = await fixture('symbolic-next-retargeted');
+    await installRequiredBins(root);
+    const link = path.join(root, 'apps', 'web', '.next', 'dependency-link');
+    await mkdir(path.dirname(link), { recursive: true });
+    await symlink('../dependency-one', link);
+    await certifyGeneratedState(root, [{ path: 'dependency-link', target: '../dependency-one' }]);
+    await rm(link);
+    await symlink('../dependency-two', link);
+
+    const result = await runPreflight({ root });
+    assert.equal(result.code, 43);
+    assert.match(result.message, /symbolic-link manifest/);
+  });
+
+  await t.test('a manifest edited to whitelist a rogue symlink is rejected', async () => {
+    const root = await fixture('symbolic-next-tampered-manifest');
+    await installRequiredBins(root);
+    await certifyGeneratedState(root);
+    const nextDir = path.join(root, 'apps', 'web', '.next');
+    await symlink('/etc/hosts', path.join(nextDir, 'reviewer-symlink'));
+    await writeFile(
+      path.join(nextDir, '.mosaic-symlink-manifest'),
+      `${JSON.stringify({
+        version: 1,
+        links: [{ path: 'reviewer-symlink', target: '/etc/hosts' }],
+      })}\n`,
+    );
+
+    const result = await runPreflight({ root });
+    assert.equal(result.code, 43);
+    assert.match(result.message, /symbolic-link manifest/);
+  });
+
+  await t.test('unchanged canonical-style descendant symlinks are accepted', async () => {
+    const root = await fixture('symbolic-next-certified');
+    await installRequiredBins(root);
+    const link = path.join(
+      root,
+      'apps',
+      'web',
+      '.next',
+      'standalone',
+      'node_modules',
+      'dependency',
+    );
+    await mkdir(path.dirname(link), { recursive: true });
+    await symlink('../.pnpm/dependency', link);
+    await certifyGeneratedState(root, [
+      { path: 'standalone/node_modules/dependency', target: '../.pnpm/dependency' },
+    ]);
+
+    assert.deepEqual(await runPreflight({ root }), {
+      code: 0,
+      message: 'checkout preflight passed',
+    });
+  });
+});
+
+test('the source fingerprint includes inherited TypeScript configuration', async () => {
+  const root = await fixture('inherited-typescript-config');
+  const config = path.join(root, 'tsconfig.base.json');
+  await writeFile(config, '{"compilerOptions":{"strict":true}}\n');
+  const first = await sourceFingerprint(root);
+  await writeFile(config, '{"compilerOptions":{"strict":false}}\n');
+  const second = await sourceFingerprint(root);
+
+  assert.notEqual(first, second);
+});
+
+test('the source fingerprint rejects symbolic-link build inputs', async () => {
+  const root = await fixture('symbolic-source');
+  await writeFile(path.join(root, 'outside.ts'), 'export default 1;\n');
+  await symlink(path.join(root, 'outside.ts'), path.join(root, 'apps', 'web', 'src', 'linked.ts'));
+
+  await assert.rejects(sourceFingerprint(root), /must not be a symbolic link/);
+});
+
+test('the source fingerprint includes expanded public web build environment', async () => {
+  const root = await fixture('public-build-environment');
+  const envFile = path.join(root, 'apps', 'web', '.env.production');
+  await writeFile(
+    envFile,
+    'RM01_GATEWAY_URL=https://one.example\nNEXT_PUBLIC_RM01_URL=$RM01_GATEWAY_URL\n',
+  );
+  const first = await sourceFingerprint(root);
+  await writeFile(
+    envFile,
+    'RM01_GATEWAY_URL=https://two.example\nNEXT_PUBLIC_RM01_URL=$RM01_GATEWAY_URL\n',
+  );
+  const second = await sourceFingerprint(root);
+
+  assert.notEqual(first, second);
+});
+
+test('a matching generation marker accepts incremental output with mixed mtimes', async () => {
+  const root = await fixture('incremental-next');
+  await installRequiredBins(root);
+  const generated = path.join(root, 'apps', 'web', '.next', 'types', 'validator.ts');
+  await mkdir(path.dirname(generated), { recursive: true });
+  await writeFile(generated, 'unchanged generated output');
+  await utimes(generated, new Date('2020-01-01T00:00:00Z'), new Date('2020-01-01T00:00:00Z'));
+  const fresh = path.join(root, 'apps', 'web', '.next', 'types', 'routes.ts');
+  await writeFile(fresh, 'fresh generated output');
+  await certifyGeneratedState(root);
+
+  assert.deepEqual(await runPreflight({ root }), { code: 0, message: 'checkout preflight passed' });
+});