Batch API Job Failed Status — Fix (2026)

The Error

Batch msg_batch_01ABC: status "ended" with 47/100 failed requests
Error in request #12: "messages[0].content exceeds maximum length for batch processing"

This error occurs when a Message Batches API job completes but some or all individual requests within the batch fail. The batch itself succeeds, but individual items have errors.

The Fix

  1. Retrieve the batch results to identify failed items:
curl -s https://api.anthropic.com/v1/messages/batches/msg_batch_01ABC/results \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  | python3 -c "
import sys, json
for line in sys.stdin:
    r = json.loads(line)
    if r['result']['type'] == 'errored':
        print(f\"ID: {r['custom_id']} Error: {r['result']['error']['message']}\")
"
  1. Fix the failing requests (usually oversized content or invalid params):
# Check message sizes before batching
python3 -c "
import json
items = json.load(open('batch-requests.json'))
for i, item in enumerate(items):
    size = len(json.dumps(item))
    if size > 100000:
        print(f'Item {i} ({item[\"custom_id\"]}): {size} bytes — TOO LARGE')
"
  1. Resubmit only the failed items:
# Extract and fix failed items, then resubmit
python3 -c "
# Filter to only failed custom_ids and rebuild batch
print('Resubmit with corrected requests')
"

Why This Happens

The Batch API processes each request independently. While the batch envelope is valid, individual requests can fail due to: content too long, invalid model specified per-request, rate limits on specific requests, or malformed message arrays. Each request is validated separately.

If That Doesn’t Work

  • Reduce batch size from 100 to 25 items to isolate failures.
  • Validate each request individually with the synchronous API before batching.
  • Check if your batch has duplicate custom_id values, which causes silent overwrites.

Prevention

Add this to your CLAUDE.md:

# Batch API
- Validate each batch item against the Messages API schema before submission.
- Keep individual messages under 80K tokens for batch processing.
- Use unique custom_id values. Log batch_id for result retrieval.
- Implement a retry pipeline for failed batch items.

See Also

This fix also applies if you see variations of this error:

  • Connection or process errors with similar root causes in the same subsystem
  • Timeout variants where the operation starts but does not complete
  • Permission variants where access is denied to the same resource
  • Configuration variants where the same setting is missing or malformed

If your specific error message differs slightly from the one shown above, the fix is likely the same. The key indicator is the operation that failed (shown in the stack trace) rather than the exact wording of the message.

Frequently Asked Questions

Does this error affect all operating systems?

This error can occur on macOS, Linux, and Windows (WSL). The exact error message may differ slightly between platforms, but the root cause and fix are the same. macOS users may see additional Gatekeeper or notarization prompts. Linux users should check that the relevant system packages are installed. Windows users should ensure they are running inside WSL2, not native Windows.

Will this error come back after updating Claude Code?

Updates can occasionally reintroduce this error if the update changes default configurations or dependency requirements. After updating Claude Code, verify your project still builds and runs correctly. If the error returns, reapply the fix and check the changelog for breaking changes.

Can this error cause data loss?

No, this error occurs before or during an operation and does not corrupt existing files. Claude Code’s edit operations are atomic — they either complete fully or not at all. However, if the error occurs during a multi-step operation, you may have partial changes that need to be reviewed with git diff before continuing.

How do I report this error to Anthropic if the fix does not work?

Open an issue at github.com/anthropics/claude-code with: (1) the full error message including stack trace, (2) your Node.js version (node --version), (3) your Claude Code version (claude --version), (4) your operating system and version, and (5) the command or operation that triggered the error.

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