A green property suite is not a pass. If an agent patch can shrink the generator, rewrite a fixture schema, or hide a flake behind retries, the suite certifies the wrong change. Freeze the input distribution. Lock fixture schemas. Record flake identity. Score the patch on those three deltas, not on a pass count.
That rule is the whole strategy. The rest of this article is a harness you can copy, not a report of a production run.
Why pass counts fail after an agent write
Agent patches do not only edit production code. They also edit the tests that judge them. A property that used to draw integers from [-10000, 10000] can be rewritten to [-3, 3] and still be named test_invariants. A fixture that encoded a 12-field record can drop the two fields that triggered a bug. A test that failed 4 times in 50 runs can be wrapped in a retry loop until CI is green.
None of those edits show up as a red job. They show up as a quieter generator, a smaller fixture, and a flake that no longer exists on paper.
