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

Bug Description
I just had to compact because I hit this error on opus 4.8:

API Error: 400 messages.9.content.23: th blocks in the latest assistant messagecannot be modified. These blocks must remain as they were in the original response.

Environment Info

• Platform: darwin
• Terminal: xterm-256color
• Version: 2.1.154
• Feedback ID: ba5281a0-a64b-4d07-a333-688dec0c6611

Errors

[{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.7.content.45: `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_011CbVV2SZXnWkSStzcPmEU3\"}\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":"2026-05-28T19:01:44.045Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.9.content.23: `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_011CbVVEpYStWtqVAcGGHTZj\"}\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":"2026-05-28T19:04:31.666Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.9.content.23: `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_011CbVVFN3muXtifxGNVonCZ\"}\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":"2026-05-28T19:04:38.995Z"},{"error":"Error: Error during compaction: API Error: 400 messages.9.content.23: `thinking` or `redacted_thinking` blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response.\n    at Vn3 (/$bunfs/root/src/entrypoints/cli.js:7737:1645)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-28T19:04:38.997Z"}]