Hey, quick answer: you can’t turn on Max Mode via ACP right now, for the same reason as the thinking levels and non-Fast options mentioned earlier in the thread.
When the ACP client (Zed, Neovim, etc.) doesn’t declare the capability for parameterized model selection, the backend only returns one default option per model (defaultNonMax). Max Mode is a separate model variant, so it just doesn’t show up in the ACP selector.
The current workaround is to use Cursor CLI directly, outside ACP. Model variants and Max Mode work there as expected.
The proper fix is on our tracking list. We need to move to the standard ACP Session Config Options so clients can set thinking level, variant, and Max. I can’t share an ETA yet, but I’ll post an update in the thread when I have one.