When to Let It Run vs. Steer Manually

The decision to let an agent run unattended comes down to three questions — a checklist you run before you walk away.

• Blast radius. If this goes wrong, how much breaks? A formatting pass across the codebase has a small blast radius. A database migration or a change to your auth logic has a large one. The bigger the radius, the more you steer by hand.
• Reversibility. Can you undo it cheaply? Work on a fresh git branch with a clean working tree is reversible — git restore . and it's gone. Work that deletes data, sends emails, charges cards, or pushes to production is not. Never let an agent run unattended over anything you can't take back.
• Verifiability. Can you tell whether the result is right? If "done" means a green test suite or a page that visibly works, you can verify it in seconds and an agent is a great fit. If "done" depends on subtle judgment — money math, security rules, race conditions — you can't gate on a quick check, so you stay close.

A simple way to combine them: let it run when the work is reversible and the result is cheap to verify; steer by hand when it isn't. Carry over the rule from the build-features chapter — the bigger the blast radius, the smaller the step — and add its sibling: the bigger the blast radius, the tighter the leash.