How do I explain to Windsurf what my app is about so it stops guessing?

Write a CONTEXT.md once: what the app is in two sentences, then a glossary. One line per term: "Lesson: a single 50-minute session. Not a course." Windsurf reads project files at the start of a chat (check that it's included in rules). Update the glossary when it guesses wrong; that's the whole maintenance.

The glossary does more than the description. Models guess words, not architectures.