Heads up, agent users！
If you're using Xiaomi MiMo with thinking mode:
When thinking mode is enabled in a multi-turn agent session and the conversation history contains a tool call, any assistant message with tool calls passed back in subsequent user turns must preserve its full reasoning_content field — otherwise the API will return a 400 error.
Without it, the model's context is incomplete, which can lead to weaker instruction-following, more hallucinations, and a visibly degraded user experience.
Missing reasoning = incomplete context = degraded reasoning quality.
Affected frameworks include TRAE, Cursor, Roo Code, Codex, GitHub Copilot CLI, Zed, AutoGen. We're actively working with the maintainers to push compatibility updates.
Affected models: MiMo-V2.5-Pro, MiMo-V2.5, MiMo-V2-Pro, MiMo-V2-Omni, MiMo-V2-Flash.
See docs(https://t.co/9v7oybaW26 )for more details.
context window — The maximum amount of text a model can consider at once — its working memory for the current conversation or task.
agentic loop — The cycle an agent runs in: decide, call a tool, read the result, decide again — repeating until the goal is met or a stop condition fires.
Why it matters
If your agentic loopThe cycle an agent runs in: decide, call a tool, read the result, decide again — repeating until the goal is met or a stop condition fires.Full definition → strips reasoning traces from history, MiMo's thinking mode fails outright on tool-call turns. Several widely used harnesses including Cursor, Codex, Zed and AutoGen were affected.
