Penmentor puts AI math hints beside your handwriting

Penmentor describes an AI math helper that marks handwritten work in Xournal++ with colored pens. Its README also discloses that the demo pen is scripted and the model’s answer is a fixed example. That disclosure matters when you’re watching a mistake get circled in exactly the right place.

I like the proposed interaction. The author describes studying calculus with a pen tablet and repeatedly sending screenshots to Claude, then reading long replies. Penmentor aims to put the feedback beside the work, where a student can connect a mark to the line that prompted it. A circle beside a sign error gives you a specific place to look while you still have the calculation in front of you.

The README describes hints that become more explicit, marks that remain while you write, and optional Manim animations for a selected expression. I’d want that control over how much help appears. Being stuck on one line shouldn’t require reading an answer that completes the rest of the exercise before you’ve had another chance.

Trying it requires the right desktop setup. Penmentor documents Linux on X11 and support for Claude Code, Codex and Antigravity. If that matches your setup, I’d start with a problem whose solution you already understand and compare each mark with your own reasoning. I’d also try a correct line that looks unusual. The fixed demo answer leaves those checks for an actual trial.

Then I’d clear the marks and see whether I can carry the calculation forward.