Your AI forgot how your app works an hour in. That's a context problem, and it's fixable.

The short answer

When an AI coding tool seems to forget your app an hour in, it's usually not getting dumber — the early part of the conversation has fallen out of what it can see. Cursor's docs put the root cause…

The cause — the model only sees what's in its context window

The name — context engineering: deciding what the model sees

The fix — standing instructions in a file, fresh chats, decisions written down

Where it lives — Cursor rules, Claude Code's CLAUDE.md, or your tool's equivalent

The one-line version

The AI doesn't forget; it can only see what's in the window. Keep the important things where the tool loads them first, and start fresh chats often.