Error: Invalid `signature` in `thinking` block

[rdvo]

Description

When changing model mid session from GLM 4.7 or MinMax 2.1 i get this error

messages.19.content.0: Invalid signatureinthinking block

Not sure why, if I toggle back to the first model I was using it works fine.

OpenCode version

1.0.207

Steps to reproduce

1. Start a new sesson
2. Send few messages with GLM 4.7 or MinMax 2.1
3. Switch model to Opus 4.5 via Anthropic
4. Send message

Will error

Screenshot and/or share link

Operating System

mac os x

Terminal

ghostty

[github-actions[bot]]

This issue might be a duplicate of existing issues. Please check:

• #4832: [BUG]: Gemini 3 Pro function calling fails - missing thoughtSignature support - Similar issue with signature in thinking blocks when using models with reasoning
• #6244: Response terminates prematurely when using Gemini 3 via LiteLLM - Related issue with thinking/reasoning blocks and signature validation
• #3596: SSE Stream Bug: Out-of-Order thinking_delta via LiteLLM → AWS Bedrock - Addresses thinking block ordering issues that could relate to signature problems

Feel free to ignore if none of these address your specific case.

[rekram1-node]

Yeah ik why, I think we have to filter out all reasoning from old model when u switch

[rdvo]

would there be a way to transform it to the right format or somethin without just stripping it? or is the default behavior to strip thoughts from subsequent messages?

[mastternick]

I can confirm this issue as well:

Description: An error occurs when switching to Anthropic models during an active session and sending a message after switching.|

Steps to reproduce:

1. Connect to the Anthropic provider using the Pro subscription option
2. Start chat with non-Anthropic model (e.g., Grok)
3. Switch to any Anthropic model (Claude Sonnet 4.5 or Opus)
4. Try to send a message or switch models

Error message: messages.1.content.0: Invalid signature in thinking block

[vieenrose]

I made a Session Repair Tool on this issue.