Backport: fix(cerebras): serialize reasoning parts as 'reasoning' on assistant messages#15425
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…messages (#15416) ## Background #15042 alternate solution to #15383 `@ai-sdk/openai-compatible` serializes the assistant reasoning as `reasoning_content` but cerebras's chat-completions API doesnt accept `reasoning_content` on input. their assistant-message schema uses a `reasoning` field instead ## Summary made the change specific to cerebras so that assistant message reasoning parts are branded as `reasoning` instead of `reasoning_content` ## Manual Verification verified by running the following repro: ```ts import { isStepCount, tool, streamText } from "ai"; import z from "zod"; import { cerebras } from "@ai-sdk/cerebras"; import { run } from '../../lib/run'; run(async () => { const result = streamText({ model: cerebras('zai-glm-4.7'), tools: { create_thing: tool({ inputSchema: z.object({ name: z.string() }), execute: async ({ name }) => ({ id: 'abc', name }), }), }, stopWhen: isStepCount(5), messages: [{ role: 'user', content: 'create a thing called foo, then say done' }], }); for await (const _ of result.fullStream) {} console.log('steps:', (await result.steps).length); }); ``` it will fail after the first step before the fix ## Checklist - [x] All commits are signed (PRs with unsigned commits cannot be merged) - [x] Tests have been added / updated (for bug fixes / features) - [ ] Documentation has been added / updated (for bug fixes / features) - [x] A _patch_ changeset for relevant packages has been added (for bug fixes / features - run `pnpm changeset` in the project root) - [x] I have reviewed this pull request (self-review) ## Future Work look into the error seen in #15349 ## Related Issues fixes #15402
aayush-kapoor
approved these changes
May 19, 2026
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This is an automated backport of #15416 to the release-v6.0 branch. FYI @aayush-kapoor