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

Bug Description
API Error: 400 messages.1.content.56: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must
remain as they were in the original response

Dup of https://github.com/anthropics/claude-code/issues/12311

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.153
• Feedback ID: ac8742c0-36c5-484d-8067-90e42143ddfd

Errors

[{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.1.content.56: `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_011CbUkDBr3ffjhp9ajPrr8k\"}\n    at generate (/$bunfs/root/src/entrypoints/cli.js:11:63764)\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-28T09:40:16.218Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.1.content.56: `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_011CbUmqgsfZG65nyj7scwE5\"}\n    at generate (/$bunfs/root/src/entrypoints/cli.js:11:63764)\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:7694)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-28T10:01:38.483Z"}]