Free Coding Agents Need a Refusal Contract, Not Just Better Prompts

A free coding agent tends to over-comply, producing patches that include correct code in places no one authorized, such as renamed directories or altered lockfiles. The article argues that prompt instructions like "be conservative" are unreliable, so the safeguard should instead be a checkable contract on the diff itself. It proposes a policy file defining allowed and denied paths and change budgets, plus a gate script that reads the git diff and returns allow, review, or refuse verdicts. The policy must also protect its own rules, since a policy the same process can edit provides only advisory constraint. The author presents the approach as illustrative, not a calibrated production policy.