Two-model adversarial review under a negotiated contract — Claude and Codex each review, each verifies the other's claims, then fixes split by disjoint file set and land in one build. Use where being wrong is expensive and green CI proves little — crypto, auth, migrations, data-loss paths, backup/exfil surfaces. NOT ordinary PR review (use /code-review), not typo fixes. Costs ~3 dispatches plus a high-effort pass.
