How to Limit AI Agent Patch Damage with a Strict Side-Effect Gate

A proposed software engineering method outlines a fail-closed security envelope to restrict what an AI agent patch can do during a run. The gate monitors four categories of side effects: filesystem writes, tool invocations, environment variable reads, and outbound network connections. If an agent touches anything outside a pre-declared, hash-verified allowlist in any of these categories, the gate fails immediately without retry. The author argues that passing unit tests alone is insufficient verification, since a green test suite may never observe writes to temp directories, environment access, or open sockets. The envelope configuration is treated as a pinned fixture, and any drift in its hash without a review note blocks execution entirely.