Storage service returned unsupported chunk size ${created.ch

Error message

Storage service returned unsupported chunk size ${created.chunkSize}

What it means

After POSTing a new stored transfer, createStoredUpload() verifies the server's declared chunkSize equals the client's storedChunkSize (4 MiB). Chunk encryption (storeSealChunk) binds each chunk to its index and size, so a server with a different chunk size would produce ciphertext the receiving client cannot reassemble; the client aborts immediately instead of uploading garbage.

Source

Thrown at web/src/protocol/stored.ts:440

      protocol: storedProtocol,
      manifestBytes: plan.manifestJSON.byteLength + 28,
      chunkBytes: plan.chunkBytes,
      redeemVerifier: base64URL(redeemVerifier),
      files: plan.files.length,
      plaintextBytes: plan.totalSize,
      ...(downloads === 1 ? {} : { downloads }),
      ...(expiresSeconds === 24 * 60 * 60 ? {} : { expiresSeconds }),
    }),
  });
  if (!response.ok) throw await responseError(response);
  const created = (await response.json()) as {
    id: string;
    uploadToken: string;
    uploadExpiresAt: string;
    chunkSize: number;
  };
  if (created.chunkSize !== storedChunkSize) {
    throw new Error(
      `Storage service returned unsupported chunk size ${created.chunkSize}`,
    );
  }
  if (!isCapability(created.uploadToken)) {
    throw new Error("Storage service returned an invalid upload capability");
  }
  const downloadsHeader = response.headers.get("X-Croc-Downloads");
  const acceptedDownloads =
    downloadsHeader === null ? 1 : Number(downloadsHeader);
  if (!Number.isSafeInteger(acceptedDownloads) || acceptedDownloads < 1) {
    throw new Error("Storage service returned an invalid download count");
  }
  if (acceptedDownloads !== downloads) {
    throw new Error(
      `Storage service created ${acceptedDownloads} downloads instead of ${downloads}`,
    );
  }
  return {

View on GitHub (pinned to e25f1bdc04)

Solutions

Update the storage service and web client to matching versions (both must agree on the 4 MiB chunk size)
Check settings.storeAPI points at the intended service, not a stale or third-party endpoint
If you implement the service yourself, echo chunkSize: 4194304 in the create response

Defensive patterns

Strategy: try-catch

Try / catch

try { return await createStoredUpload(...); } catch (e) { if (e instanceof Error && e.message.includes("chunk size")) { alert("Client/server version mismatch — update the app and storage service"); } throw e; }

Prevention

Deploy web client and storage service in lockstep so storedChunkSize (4 MiB) always matches
Pin storeAPI to the version-matched deployment during rolling upgrades

When it happens

Trigger: The create response JSON has chunkSize !== 4194304 — typically a version skew: an older/newer storage service that chunks differently, or a misconfigured third-party implementation of the /transfers API.

Common situations: Deploying a new web client against an old storeAPI deployment (or vice versa) during a rolling upgrade; pointing storeAPI at an incompatible self-hosted relay.

Related errors

AI-assisted analysis of schollz/croc@e25f1bdc04 (2026-08-15). Data as JSON: /api/errors/7e7e65db1b68f893. Report an issue: GitHub.