It's an Overleaf-style editor with a PDF preview that compiles with TeX Live, and it installs TeX for you if you don't have it. To use the AI features, select text and press Cmd-K, and you can accept or reject the diff. If you have a handwritten formula that you want to insert, you can place your cursor where you want to insert and drop in a photo, which GLM-OCR turns into LaTeX locally since Apple's OCR doesn't handle math.
What was fun was testing out the capability of the models. Corollary uses SystemLanguageModel.default, which is Apple's general-purpose on-device model and the one built into macOS for Apple Intelligence. It's about 3B params with a 4,096 token context window on my M1 Max. When asked for plain text, it kept every \cite, \ref, \label and formula intact in 78 of 80 edits, but with structured output (@Generable) it went 0 for 20 because the JSON escaping eats the backslashes (\text comes back as a tab). While this limits capabilities like full document edits, you can already point it at Ollama or your own API key, and I'm sure the models will catch up soon.
Also, it needs an Apple silicon Mac, and the AI needs macOS 26 with Apple Intelligence. At this stage I don't have an Apple Developer ID yet, so the first launch needs System Settings > Privacy & Security > Open Anyway. Sorry about that. Please give it a try and let me know what bugs you run into or what the model struggles on!