Why git checkout can't undo an AI agent's code changes, and a better checkpoint approach

When an AI agent edits project files and breaks something, developers often reach for git checkout or git stash, but these answer a different question than the one they face. Git restores the last commit or a snapshot of tracked files, which mixes the user's uncommitted work with the agent's changes and ignores gitignored files. The osFoundry desktop app instead stores each file's prior bytes in a content-addressed store before the agent writes to it, enabling a precise rewind. In a timed test on a 4,686-file TypeScript tree, the checkpoint restore returned the project exactly to its pre-turn state, while all four git-based methods left leftover or lost files. The author also notes that git-based snapshots pollute the real index by staging all user work on every turn.