[Bug] Anthropic API Error: Cannot modify thinking blocks in assistant message

Bug Description
Update(package.json)
File not found

Read 7 files, listed 1 directory, ran 18 shell commands

⏺ Write(/tmp/cn_t3.mjs)
Error writing file

Read 1 file, ran 2 shell commands

⏺ Update(README.md)
Error editing file

⏺ Update(README.md)
Error editing file

Read 1 file

⏺ Update(README.md)
Error editing file

⏺ Update(RUNBOOK.md)
Error editing file

⏺ Update(RUNBOOK.md)
Error editing file

Ran 3 shell commands
API Error: 400 messages.1.content.19: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.154
• Feedback ID: 1585aadf-92ec-4e1f-8003-2c30dcdbcec1

Errors

[{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.1.content.7: `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_011CbVQ3SFNfE9D8FRwDUhMt\"}\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":"2026-05-28T17:56:23.026Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.1.content.19: `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_011CbVQYfvwr3Urh8mRgVbpr\"}\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":"2026-05-28T18:02:59.587Z"}]