# Stop gates

Everything so far fired on a single tool call. Stop gates fire on a different event entirely: the agent deciding it's done. This is the hook from the front page -- it holds the session open until edited UI files got a visual review.

The widget below simulates a session instead of a command line. Toggle what happened this session, then try to stop:


Walk the combinations. Edit `/repo/src/components/Button.tsx` without a review and the stop bounces: the agent gets the gate's message and keeps working, so you never see a "done" that isn't. Flip on `agent-browser` and `skip_if` stands down -- the gate isn't a nag, it's a condition, and the condition is satisfiable. Edit only `/repo/README.md` and the gate has no opinion at all.

[TouchedFile](../../reference/conditions.md#captain_hook.TouchedFile) and [UsedSkill](../../reference/conditions.md#captain_hook.UsedSkill) read the session's history, not the current tool call -- that's what makes gating "done" possible at all. The same machinery drives test gates (`RanCommand(r"\bpytest\b")`) and artifact checks.

[Last stop: turn the widget's cases into tests.](../../docs/tutorial/test-then-ship.md)