ProofPatch: Evidence Before Merge

AI coding assistants can generate plausible fixes quickly, but reviewing those fixes still requires developers to answer important questions: Did the patch satisfy the requirements? Were the tests changed to hide failures? Can another reviewer inspect and reproduce the evidence? ProofPatch is a working prototype that supports this review process. Built using IBM Bob IDE, it evaluates candidate patches against a fixed Git reference and protected verification files, then presents the results in an evidence dashboard. The demonstration uses a sample checkout implementation with two intentional bugs: a discount eligibility boundary error and incorrect inclusion of gift cards. Twelve requirement-derived tests evaluate three constructed candidate patches: • An incomplete fix passes nine tests but fails three. • A test-tampering patch is rejected before execution because it changes a protected test file. • A correct fix passes all twelve recorded checks. Developers run verification locally and inspect each candidate’s outcome, failed assertions, changed paths, commands, exit codes, and logs. The downloadable JSON report records the reference commit and SHA-256 hashes to identify the inputs used. Protected reference files are checked before and after patch application. ProofPatch brings patch screening, test execution, and review evidence into one workflow. It distinguishes failed checks, protected-file rejection, inconclusive execution, and success against the recorded checks. Rejected candidates retain an explanation without being presented as tested. The prototype targets developers and reviewers working with AI-assisted code changes. It automates repetitive verification and evidence collection while keeping the acceptance decision with the reviewer. The demonstration shows functional outcomes; it does not claim measured productivity gains. IBM Bob supported implementation and refinement of the verifier, automated tests, dashboard, and static export. Relevant Bob task screenshots are included in the public repository. The deployed website is clearly labelled as a recorded evidence demonstration. Live verification runs locally and is shown in the demo video. Temporary working directories provide working-copy isolation, not a security sandbox for untrusted code. Passing the recorded checks does not certify universal correctness or security.