Trailblaze is Block's open-source CLI for driving real apps with AI on Android, iOS, and web. No more clicking through your own app to check a change. AI is slow, expensive, and non-deterministic — fine for exploration, painful in CI. So save what the agent did as a trail: a YAML record, replayable forever with no LLM calls. Map your app with waypoints and agents take the fast path next time. For teams who want AI-driven flows without rewriting what works. Explore once, replay forever.