Function commitBundle

src/lib/bundle.ts:518–572

* Rename ` / ` → ` / ` for every file in `files`. * * Critical ordering for atomicity (the §3 "agent-safe" contract): * * 1. **Remove the OLD `meta.json` first.** The bundle's completion * signal is `meta.json`'s presence; an agent reading ` ` while * we're mu

(
  tmpDir: string,
  dir: string,
  files: ReadonlyArray<string>,
)

 * (per §7.3). That's what we want.
 */
async function commitBundle(
  tmpDir: string,
  dir: string,
  files: ReadonlyArray<string>,
): Promise<void> {
  // (1) Remove the prior bundle's completion signal FIRST.
  await unlink(join(dir, 'meta.json')).catch(() => undefined);

  // (2) Sweep stale top-level files that the new bundle won't write.
  // If the prior run wrote `video.mp4` and the new run has no video,
  // an in-place rename leaves the old video lingering. Enumerate
  // current top-level entries and remove anything that isn't being
  // freshly renamed in.
  const topLevel = files.filter(f => !f.startsWith('steps/'));
  const newTopLevelSet = new Set(topLevel);
  newTopLevelSet.add('meta.json'); // about to land last, do not delete
  const existing = await readdir(dir).catch(() => [] as string[]);
  for (const entry of existing) {
    // Preserve the writer's own scratch dir + the .partial marker
    // (we'll re-evaluate .partial at the end of commit). Anything else
    // not-listed in the new bundle is stale.
    if (entry === '.tmp' || entry === '.partial') continue;
    if (newTopLevelSet.has(entry)) continue;
    if (entry === 'steps') continue; // handled below
    await rm(join(dir, entry), { recursive: true, force: true });
  }

  // (3) Replace `<dir>/steps/` with `<tmp>/steps/`.
  const stepsTmp = join(tmpDir, 'steps');
  const stepsDir = join(dir, 'steps');
  await rm(stepsDir, { recursive: true, force: true });
  if (await dirExists(stepsTmp)) {
    await rename(stepsTmp, stepsDir);
  }

  // (4) Top-level files (result/failure/code/video). meta.json renames
  // LAST; track it separately.
  const metaIdx = topLevel.indexOf('meta.json');
  const beforeMeta = metaIdx >= 0 ? topLevel.filter((_, i) => i !== metaIdx) : topLevel;
  for (const file of beforeMeta) {
    await rename(join(tmpDir, file), join(dir, file));
  }

  // (5) meta.json LAST → atomic completion signal.
  if (metaIdx >= 0) {
    await rename(join(tmpDir, 'meta.json'), join(dir, 'meta.json'));
  }

  // .partial from a prior aborted run is now stale. Remove it so an
  // agent inspecting the dir sees only the fresh bundle.
  await unlink(join(dir, '.partial')).catch(() => undefined);

  // Clean up the now-empty tmp dir.
  await rm(tmpDir, { recursive: true, force: true });
}

async function dirExists(path: string): Promise<boolean> {
  try {