claude-code - 💡(How to fix) Fix [Bug] Anthropic API Error: Cannot modify thinking blocks in assistant messages [1 comments, 2 participants]

[{"error":"Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.8: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response."},"request_id":"req_011CbZYuUVeZmsayW2fn2ZEb"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:11:63816)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-30T22:34:59.074Z"},{"error":"Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.8: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response."},"request_id":"req_011CbZZkHvXKdQFdFQeTnD3X"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:11:63816)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-30T22:46:01.287Z"},{"error":"Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.4: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response."},"request_id":"req_011CbZbKmqLj6eDomh2rbp4k"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:11:63816)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-30T23:06:42.322Z"},{"error":"Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.15: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response."},"request_id":"req_011CbZbRgRKXj2iiaLN4RUUK"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:11:63816)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-30T23:08:02.708Z"},{"error":"Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.15: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response."},"request_id":"req_011CbZbaFDGAeHXtRNViywjo"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:11:63816)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-05-30T23:09:58.694Z"}]

TL;DR

The most likely fix is to avoid modifying thinking or redacted_thinking blocks in the latest assistant message.

Guidance

• Review the API request to ensure that thinking or redacted_thinking blocks are not being modified.
• Verify that the request complies with the API's rate limit to prevent 429 errors.
• Check the message structure to ensure that it aligns with the expected format.
• Consider implementing a retry mechanism with exponential backoff to handle rate limit errors.

Example

No code example is provided due to the lack of specific implementation details.

Notes

The issue description is truncated, which may limit the ability to provide a comprehensive solution. Additionally, the errors listed suggest multiple potential issues, including rate limiting and message structure problems.

Recommendation

Apply a workaround to handle rate limit errors and ensure compliance with the API's requirements, as the issue is likely related to exceeding the rate limit or modifying restricted blocks.