API Error 400: Invalid signature in thinking block during session interactions

Dear Support Team,

I am experiencing a recurring API error during my session interactions with the platform, and I would appreciate your assistance in resolving this issue.

Error Message:

API Error: 400 messages.21.content.0: Invalid signature in thinking block

Issue Description:

This error occurs consistently under the following circumstances:

1. When the conversation context becomes longer - After multiple exchanges in a session, the error starts appearing

2. After switching models - Specifically when switching from MiniMax to Sonnet model during an active session

Impact:

The error prevents me from continuing the conversation and disrupts my workflow, requiring me to restart the session.

Expected Behavior:

The system should handle longer contexts and model switches gracefully without throwing validation errors related to thinking block signatures.

Additional Context:

The error references "messages.21.content.0", suggesting it may be related to how thinking blocks are being formatted or validated when context grows or models change

The issue appears to be related to thinking block signature validation in the API request processing

Request:

Could you please investigate this issue and provide guidance on:

• Whether this is a known limitation or bug

• Any workarounds available while a fix is implemented

• Expected timeline for resolution if this is a known issue

Thank you for your attention to this matter. Please let me know if you need any additional information or logs to help diagnose the problem.

B.R.

Jesse Zhu