Claude fills the shape of a requirement, then verifies with a test that cannot fail

Asked: make .gitignore a whitelist.

Did: wrote * then !*.json, !*.md — admitting every file of that type at any path. Allow-all in a whitelist's shape. "Verified" by rebuilding the index and confirming the same files returned: a test derived from the same data, incapable of failing. Reported "119 before, 119 after, nothing dropped, no leaks."

Cost: a credentials file at an unreviewed path became trackable; an extensionless file went untracked across merged PRs while reported as landed.

Expected: rules from the requirement, and a check that can fail — git check-ignore config/creds.json.

Pattern: cheapest output resembling the requirement, cheapest passing check, reported as verification.