affaan-m/ECC · error · Error

Could not allocate a snapshot filename for session

Error message

Could not allocate a snapshot filename for session ${session.sessionId}

What it means

When writing per-session snapshot files, the allocator tries to build a unique filename from the session id, retrying with an incremented attempt counter if the name collides. If it exhausts its attempts without finding a free, valid name it throws 'Could not allocate a snapshot filename for session <sessionId>'. This is a defensive invariant: in practice it indicates pathological session ids or a saturated output directory naming scheme.

Solutions

1. Inspect the reported sessionId for unusual characters or extreme length and sanitize/shorten it at the source.
2. Point --write-dir at a fresh directory to reduce name collisions from existing snapshots.
3. Update the script to increase the attempt limit or include a hash/random suffix in the filename.
4. Retry the run; a transient collision with concurrently written snapshots may resolve on the next attempt.

Example fix

// before
node scripts/loop-status.js --write-dir ./snapshots   # pathological sessionId
// after
rm -rf ./snapshots && node scripts/loop-status.js --write-dir ./snapshots  # or patch allocator to append a random suffix

if (!/^[-\w.]{1,64}$/.test(session.sessionId)) sanitize or reject the session id before snapshotting;

const isSafeSessionId = (id) => typeof id === 'string' && id.length > 0 && id.length <= 128 && !id.includes('/');

try { writeStatusSnapshots(payload, dir); } catch (e) { if (e.message.startsWith('Could not allocate a snapshot filename')) { console.error('Snapshot naming failed; clean the output dir or shorten the session id'); } else throw e; }

When it happens

Trigger: Calling writeStatusSnapshots with --write-dir where a session id produces a filename that cannot be made unique after all retry attempts (e.g. extremely long session ids colliding after truncation, or a hostile/odd sessionId string).

Common situations: Session ids containing path-unsafe or extremely long characters from a third-party tool, or thousands of snapshots in one directory hitting naming limits.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• stable source snapshot write made no progress
• all overlays must be readable local files
• all takes must be readable local files
• apply_local produced an invalid report
• artifact byte count exceeded during reading

AI-assisted analysis of affaan-m/ECC@8321021c54 (2026-09-16). Data as JSON: /api/errors/28df09f8b9de2ecc. Report an issue: GitHub.

Appendix: source

Thrown at scripts/loop-status.js:674

  }
}

function getSnapshotPath(outputDir, session, usedNames) {
  const baseName = sanitizeSnapshotName(session.sessionId);
  const hashSuffix = hashString(session.transcriptPath || session.sessionId).slice(0, 8);
  let attempt = 0;

  while (attempt < 1000) {
    const suffix = attempt === 0 ? '' : `-${hashSuffix}${attempt === 1 ? '' : `-${attempt}`}`;
    const fileName = `${baseName}${suffix}.json`;
    if (!usedNames.has(fileName)) {
      usedNames.add(fileName);
      return path.join(outputDir, fileName);
    }
    attempt += 1;
  }

  throw new Error(`Could not allocate a snapshot filename for session ${session.sessionId}`);
}

function writeStatusSnapshots(payload, writeDir) {
  if (!writeDir) {
    return null;
  }

  const outputDir = path.resolve(writeDir);
  fs.mkdirSync(outputDir, { recursive: true });

  const usedNames = new Set(['index.json']);
  const sessions = payload.sessions.map(session => {
    const snapshotPath = getSnapshotPath(outputDir, session, usedNames);
    atomicWriteJson(snapshotPath, {
      generatedAt: payload.generatedAt,
      schemaVersion: 'ecc.loop-status.session.v1',
      session,
    });

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