What causes "Duplicate filename: ${name}" in schollz/croc?

Rename one of the colliding files before selecting, or move them into a single folder with unique names

Duplicate filename: ${name}

Error message

Duplicate filename: ${name}

What it means

Stored manifests are flat (no directory structure), so prepareStoredFiles() normalizes each name with normalizeOutgoingFileName and rejects any second file that normalizes to an already-seen name. Two different inputs (a/report.pdf and b/report.pdf, or names that differ only in characters the normalizer strips) collide and throw.

Source

Thrown at web/src/protocol/stored.ts:309

  settings: StoredSettings,
  callbacks: { onStatus?(status: string): void } = {},
  signal?: AbortSignal,
) {
  if (selected.length === 0) throw new Error("Choose at least one file");
  if (selected.length > settings.maxFiles) {
    throw new Error(`Stored transfers can contain at most ${settings.maxFiles} files`);
  }
  const total = selected.reduce((sum, file) => sum + file.size, 0);
  if (!Number.isSafeInteger(total) || total > settings.maxTransferBytes) {
    throw new Error(`Stored transfer exceeds the ${settings.maxTransferBytes} byte limit`);
  }
  const names = new Set<string>();
  const prepared: StoredPreparedFile[] = [];
  let firstChunk = 0;
  for (let index = 0; index < selected.length; index += 1) {
    const file = selected[index];
    const name = normalizeOutgoingFileName(file.name);
    if (names.has(name)) throw new Error(`Duplicate filename: ${name}`);
    names.add(name);
    callbacks.onStatus?.(`Hashing ${index + 1}/${selected.length}: ${name}`);
    const chunkCount = Math.ceil(file.size / storedChunkSize);
    prepared.push({
      file,
      name,
      size: file.size,
      hash: new Uint8Array(),
      sha256: await sha256Blob(file, signal),
      modified: new Date(file.lastModified).toISOString(),
      firstChunk,
      chunkCount,
    });
    firstChunk += chunkCount;
  }
  return prepared;
}

View on GitHub (pinned to e25f1bdc04)

Solutions

Rename one of the colliding files before selecting, or move them into a single folder with unique names
Send folders via the direct (relay) transfer mode, which preserves structure, instead of stored mode
Pre-scan the selection for post-normalization duplicates and surface them in the UI before prepareStoredFiles runs

Example fix

// pre-flight duplicate check
const seen = new Set<string>();
for (const f of selected) {
  const name = normalizeOutgoingFileName(f.name);
  if (seen.has(name)) throw new Error(`Duplicate filename: ${name}`);
  seen.add(name);
}

Defensive patterns

Strategy: validation

Validate before calling

const seen = new Set<string>();
for (const f of selected) { const n = normalizeOutgoingFileName(f.name); if (seen.has(n)) { showError(`Duplicate filename: ${n}`); return; } seen.add(n); }

Prevention

Warn when a multi-folder selection contains equal basenames
Use direct relay transfer when folder structure must be preserved; stored transfers flatten it

When it happens

Trigger: Selecting two files with the same basename from different folders; names that are distinct on disk but identical after normalization (case folding, reserved-character stripping, or path removal).

Common situations: Users selecting multiple folders each containing README or invoice.pdf; case-insensitive filesystems where Photo.jpg and photo.jpg coexist but would collide on download targets.

Related errors

AI-assisted analysis of schollz/croc@e25f1bdc04 (2026-08-15). Data as JSON: /api/errors/a27c7bef7aa0b689. Report an issue: GitHub.