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

Bug Description
API Error: 400 messages.5.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.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.154
• Feedback ID: a71a0a2f-175d-49e7-b25f-3211314dbcc6

Errors

[{"error":"The socket connection was closed unexpectedly. For more information, pass `verbose: true` in the second argument to fetch()","timestamp":"2026-05-28T19:50:31.864Z"},{"error":"The socket connection was closed unexpectedly. For more information, pass `verbose: true` in the second argument to fetch()","timestamp":"2026-05-28T19:50:35.090Z"},{"error":"The socket connection was closed unexpectedly. For more information, pass `verbose: true` in the second argument to fetch()","timestamp":"2026-05-28T19:54:42.611Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.5.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_011CbVZXiENt7JTqYthaozWM\"}\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":"2026-05-28T20:00:48.205Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.5.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_011CbVZcz5Wahbw7HMCXBMPg\"}\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":"2026-05-28T20:01:59.494Z"}]