Hi William!
The model picker in the agents window has multiple code paths that can silently override your selection — both the revert to “auto” and the 200k->1m context switch are part of this known issue class. Several fixes have shipped in recent versions, but the problem persists in 3.1.17.
You may also find this related thread helpful — another user reported the same symptoms and there’s additional context there: Cursor AI agent constantly reverts to “Auto” model
Could you share a Request ID from a session where the model switched on you? (Chat menu in the top-right corner > Copy Request ID.) That helps narrow down which specific code path is triggering in your case.
As a workaround, double-check the model in the picker before sending each prompt, if it’s reverted, switch it back.