[Bug] Harness modifying thinking blocks causes Anthropic API rejection

Bug Description
there's a bug in the harness, looks like it's modifying he thinking blocks, which the API then rejects.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.154
• Feedback ID: 388a01f3-a8fe-4eaf-8718-042bd717b62d

Errors

[{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.1.content.14: `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_011CbWiEzyXg2TTqhRVccYea\"}\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":"2026-05-29T10:35:38.706Z"}]