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

Bug Description
I was using the claude code web interface sucessfuly for a day and a half. We were working on a branch, claude created a PR and we were iterating over some changes. Then I started getting the below error. I can't send any more messages, I just get this error. Same thing happens when I join that same session in my terminal.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.0.76
• Feedback ID: b82f9b10-2b15-45a4-9c5b-407b5175097c

Errors

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.11.content.29: 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_011CX4LEFLuHNv9yH6vAKT4U"}