Properties Without Witnesses Are Decorations: A Falsifiability Gate for Agent Patches

Agent-generated patches often cause failures because agents iterate until tests pass rather than ensuring code correctness. This creates a failure mode where green tests merely indicate agreement with visible checks. To prevent this, an ordered gate with three stages is required. Property checks must avoid being mere decorations by requiring a committed witness and measured detection rates. Additionally, fixtures must be isolated per sample via transcript hashing, and a flake freeze must be implemented.