Problem with AWS Bedrock #24648

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1. franjorub

   added

   bugSomething isn't workingSomething isn't working

   on Apr 27, 2026
2. github-actions

   assigned

   rekram1-node

   on Apr 27, 2026
3. github-actions

   added

   coreAnything pertaining to core functionality of the application (opencode server stuff)Anything pertaining to core functionality of the application (opencode server stuff)

   on Apr 27, 2026
4. github-actions commented on Apr 27, 2026

   

   github-actionsBot

   on Apr 27, 2026 – with GitHub Actions

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

   • Bedrock Claude Opus 4.7 replays thinking blocks through interleaved OpenAI-compatible transform #23926: Bedrock Claude replays thinking blocks through wrong transform, causing the same thinking.signature: Field required error
   • fix: thinking block signature lost when model differs, breaking multi-turn with extended thinking #22813: Thinking block signature lost when switching models mid-session, also causing signature validation failures on Bedrock/Anthropic

   If your issue is not fully covered by those, please add details (OpenCode version, OS, terminal) so it can be tracked separately.
5. shakedlokits commented on Apr 28, 2026

   

   shakedlokits

   on Apr 28, 2026

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   I think it might be possible to resolve this with something like:

   
   export const plugin: Plugin = async () => {
     let isAnthropicBedrock = false;
   
     return {
       "chat.params": async (input, _output) => {
         isAnthropicBedrock =
           input.model.providerID === "amazon-bedrock" &&
           input.model.api.id.includes("anthropic");
       },
       "experimental.chat.messages.transform": async (_input, output) => {
         if (!isAnthropicBedrock) return;
         for (const msg of output.messages) {
           msg.parts = msg.parts.filter((part) => part.type !== "reasoning");
         }
       },
     };
   };
   
6. rekram1-node commented on Apr 28, 2026

   

   rekram1-node

   on Apr 28, 2026

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   ill try fixing this today

   👍React with 👍4Reacted by Francisco Rubial, Shaked Lokits, Jose Chirivella and Drew Miller
7. Dulani commented on Apr 29, 2026

   

   Dulani

   on Apr 29, 2026

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   We hit the same messages.1.content.0.thinking.signature: Field required error when switching models mid-session (Azure OpenAI GPT-5.4 → AWS Bedrock Claude Opus) and after investigating we've identified the same root cause you're encountering with Plan(Opus) ↔ Build(Sonnet) on Bedrock.

   Root Cause

   packages/opencode/src/session/message-v2.ts in toModelMessages() replays assistant parts when building conversation history. For type: "reasoning" it currently does:

   assistantMessage.parts.push({
     type: "reasoning",
     text: part.text,
     ...(differentModel ? {} : { providerMetadata: part.metadata }),
   })

   When differentModel is true (either different provider or different model), it strips providerMetadata but keeps the reasoning part. The downstream Anthropic/Bedrock path then serializes that part as a Claude thinking block without a valid signature, and Bedrock rejects the request with exactly the error you're seeing.

   For your Plan(Opus) ↔ Build(Sonnet) case, differentModel is true (same provider, different model), so Claude's own signature gets stripped on replay — even though it would have been valid to pass through unchanged.

   Fix Applied

   We introduced differentProvider and split the behavior:

   • different provider → drop the reasoning part entirely (can't translate foreign reasoning into Anthropic thinking safely)
   • same provider, different model → preserve the reasoning part and its providerMetadata, so signatures from one Claude model can round-trip into the next

   const differentProvider = model.providerID !== msg.info.providerID
   // ...
   if (part.type === "reasoning") {
     if (differentProvider) continue
     assistantMessage.parts.push({
       type: "reasoning",
       text: part.text,
       providerMetadata: part.metadata,
     })
   }

   Verification

   • Two-turn repro (GPT-5.4 → Bedrock Opus) reproduced the failure deterministically before the fix, passes cleanly after
   • Switching a live session with existing Claude thinking blocks also works
   • Added focused tests for both cross-provider drop and same-provider preservation

   Related Issues

   This issue appears related in symptom to #22813 (which focuses on Anthropic thinking block signature validation) and #23926 (which identifies a different code path in transform.ts). All three converge on the same family of errors when mixing providers or models with extended thinking enabled.

   Ready to submit as a PR if helpful.
8. rekram1-node commented on Apr 29, 2026

   

   rekram1-node

   on Apr 29, 2026

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   @Dulani im going to fix it, this solution u propose "works" but it is poor. Also please dont paste giant AI messages

   👍React with 👍2Reacted by Dulani Woods and Jose Chirivella
9. rekram1-node

   marked bug: Anthropic thinking block signature lost when switching between Claude models #25005 as a duplicate of this issue on Apr 29, 2026
10. Dulani commented on Apr 30, 2026

    

    Dulani

    on Apr 30, 2026

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    @rekram1-node - Apologies for the "giant AI message." I do most of my patching/PRs with LLMs and the larger messages are super helpful for giving the LLM the context it needs to do the job (I don't really have the Typescript expertise needed to write the code all on my own, but I still want to be helpful).

    I will keep them shorter in the future (wish I could attach more context instead). In any case, thanks for your GREAT work on this harness, it's been a pleasure to work in/with.
11. xer0x commented on May 1, 2026

    

    xer0x

    on May 1, 2026

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    Thanks for working on this. As a Bedrock user it's been a frustrating surprise to get stuck on this. Running /compact on this history is my workaround at the moment.
12. josechirivella commented on May 1, 2026

    

    josechirivella

    on May 1, 2026

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    I'm planning with Opus, and my executor is with Sonnet, but when I do the switching, that's when I get the error. My solution at the moment is to get the planning in Markdown and copy-paste to a new chat with Sonnet, but I've been getting mixed results.
13. rekram1-node commented on May 1, 2026

    

    rekram1-node

    on May 1, 2026

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    My open pr fixes this, will prolly release today

    ❤️React with ❤️2Reacted by Benjamin Bartels and Drew Miller
14. rekram1-node

    closed this as completedin #25303on May 1, 2026