Mastra•3w ago

toAISDKStream Not Returning Reasoning Output

I’ve configured a simple agent with reasoning enabled in the provider options. When I test it in Studio, I can see the reasoning coming through correctly. However, when I call it via toAISDKStream, there doesn’t appear to be any reasoning in the response. Does toAISDKStream support reasoning, or am I missing a configuration step?

4 Replies

rickyh3OP•3w ago

I ended up adding the options to directly and now it passes a reasoning step - but still doesn't stream the reasoning-delta chunks for the reasoning step (only sends the reasoning-start and reasoning-end).

Mastra Triager•3w ago

📝 Created GitHub issue: https://github.com/mastra-ai/mastra/issues/10398 🔍 If you're experiencing an error, please provide a minimal reproducible example whenever possible to help us resolve it quickly. 🙏 Thank you for helping us improve Mastra!

Abhi Aiyer•3w ago

Hey @rickyh3 let me look into this. Its probably missing a transform somewhere!

Grayson•3w ago

I think this can be solved with the sendReasoning option, but looks like we need to update some docs on this!

const agentStream = await generalAgent.stream(message, {
  requestContext,
  memory: {
    thread: id, 
    resource: session.user.id, 
  },
  providerOptions: {
    openai: { reasoningEffort: "high", reasoningSummary: "detailed" },
  }
});

// Create a Response that streams the UI message stream to the client
return createUIMessageStreamResponse({
  stream: toAISdkStream(agentStream, { 
    from: "agent",
    sendReasoning: true  // ← Add this!
  }),
});

const agentStream = await generalAgent.stream(message, {
  requestContext,
  memory: {
    thread: id, 
    resource: session.user.id, 
  },
  providerOptions: {
    openai: { reasoningEffort: "high", reasoningSummary: "detailed" },
  }
});

// Create a Response that streams the UI message stream to the client
return createUIMessageStreamResponse({
  stream: toAISdkStream(agentStream, { 
    from: "agent",
    sendReasoning: true  // ← Add this!
  }),
});

Adding some docs here: https://github.com/mastra-ai/mastra/pull/10404

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toAISDKStream Not Returning Reasoning Output

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