Error: Invalid signature in thinking block #6418

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1. rdvo

   added

   bugSomething isn't workingSomething isn't working

   on Dec 30, 2025
2. github-actions

   assigned

   rekram1-node

   on Dec 30, 2025
3. github-actions commented on Dec 30, 2025

   

   github-actionsBot

   on Dec 30, 2025 – with GitHub Actions

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

   • [BUG]: Gemini 3 Pro function calling fails - missing thoughtSignature support #4832: [BUG]: Gemini 3 Pro function calling fails - missing thoughtSignature support - Similar issue with signature in thinking blocks when using models with reasoning
   • Response terminates prematurely when using Gemini 3 via LiteLLM #6244: Response terminates prematurely when using Gemini 3 via LiteLLM - Related issue with thinking/reasoning blocks and signature validation
   • SSE Stream Bug: Out-of-Order thinking_delta via LiteLLM → AWS Bedrock #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.
4. rekram1-node commented on Dec 30, 2025

   

   rekram1-node

   on Dec 30, 2025

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

   👍React with 👍3Reacted by rob, Kai H. Meder and Hanasaki
5. rdvo commented on Dec 30, 2025

   

   rdvo

   on Dec 30, 2025

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   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?
6. mastternick commented on Jan 2, 2026

   

   mastternick

   on Jan 2, 2026

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   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
7. vieenrose commented on Jan 6, 2026

   

   vieenrose

   on Jan 6, 2026

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   I made a Session Repair Tool on this issue.
8. mounan commented on Jan 18, 2026

   

   mounan

   on Jan 18, 2026

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   I hit this Corrupted thought signature. error when I switch from google provider to manul api token
9. MrGuardian commented on Feb 2, 2026

   

   MrGuardian

   on Feb 2, 2026

   Last edited by MrGuardian

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   I have this too. I'm not using Anthropic subscription directly, I do it via Github Copilot subscription.

   Steps I did before getting the same error (all models from Github Copilot):

   1. Plan with Gemini 3 Pro Preview
   2. Switch to Build Claude Sonnet 4.5 thinking.
   3. Type "Build it".

   Got this error messages.1.content.0: Invalid `signature` in `thinking` block.
   Using opencode version 1.1.48 in vs code.
10. DerekCorniello commented on Feb 3, 2026

    

    DerekCorniello

    on Feb 3, 2026

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    just now getting this same error on opus 4.5 and sonnet through github copilot sub. Using v1.1.48 on kitty with hyprland/arch
11. d-init-d

    added a commit that references this issue on Feb 3, 2026

    fix: strip incompatible thinking blocks when switching to Claude

    ...

    This issue will close once commit f1baa87 is merged into the 'dev' branch.

    f1baa87
12. rekram1-node commented on Feb 3, 2026

    

    rekram1-node

    on Feb 3, 2026

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    This was fixed for all models a while ago, but for github copilot there was a separate issue that is fixed in dev.

    Release should go out tonight

    ❤️React with ❤️2Reacted by Derek Corniello and CC
13. rekram1-node

    closed this as completedon Feb 3, 2026
14. Wenbobobo commented on Feb 10, 2026

    

    Wenbobobo

    on Feb 10, 2026

    Last edited by Wenbobobo

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    This was fixed for all models a while ago, but for github copilot there was a separate issue that is fixed in dev.

    Release should go out tonight

    hi，After GitHub crashed and was restored, I just restarted and seemed to encounter this [Error: Invalid signature in thinking block] issue again.

    👍React with 👍1Reacted by Gileade C. Valente
15. geekgil commented on Feb 10, 2026

    

    geekgil

    on Feb 10, 2026

    Last edited by geekgil

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    I can confirm that this bug in switching between models in the same session with Github Copilot subscription integration came back. I've got an error similar to @Wenbobobo 's one (messages.21.content.0: Invalid 'signature' in 'thinking' block) when switching from gemini-3-pro-preview to claude-opus-4.6 in opencode 1.1.53 installed in Pop!_OS 24.04 running in Cosmic Terminal.

    

    The issue seems to happen only in the same execution. I closed opencode CLI client, opened it again, resumed the session, and resent the last prompt and it worked fine.