Hey, thanks for the report. This isn’t a bug, it’s a current design limitation.
For custom OpenAI-compatible models that aren’t in our catalog, Cursor uses a fixed default context. Right now we can’t auto-detect the real context window from the provider side (in your case, Z.AI), and there’s no UI to set it manually. That’s why the advertised 1M for GLM-5.2 isn’t picked up.
One small note: a Z.AI developer mentioned in one of the threads Context Size & Reasoning Mode Adaptation for Z.ai GLM via Chat Completions that the practical context for GLM models is closer to 200K, even if 1M is used in marketing, so 200K isn’t necessarily wrong.
The same topic is discussed in more detail here: Custom Models Set The Context Window to 1M
Being able to set the context window for custom models manually is a valid request, and it’s being tracked here: Unlock Full Context Window with Own API Keys. Please add your GLM-5.2 case there. The more specific the setup details are, the better it is for prioritization. I can’t share an ETA for this option yet.