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

Resolved 💬 1 comment Opened May 29, 2026 by mdwitr0 Closed Jul 2, 2026

Bug Description
API Error: 400 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.

Environment Info

  • Platform: darwin
  • Terminal: vscode
  • Version: 2.1.154
  • Feedback ID: 10a96613-6310-40ed-8eb6-5d4cf7d2e0fd

Errors

[{"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_011CbX7MvGP8Tuf8ejWSdoSj\"}\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":"2026-05-29T15:38:49.134Z"}]

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