Exploit Resistance: Separating Bug Repair from Verifier Manipulation

A coding agent can make a test runner report success without repairing the target function. Exploit Resistance separates functional repair from verifier manipulation in 46 seeded tasks spanning 23 scenarios. Independent semantic checks and integrity checks define success. We run 9 scripted control policies through the benchmark, yielding 828 episodes including exact semantic repeats. Reference repairs solve all tasks (95% Wilson interval 92.3-100.0%). Scripted verifier attacks pass every visible suite (95% Wilson interval 92.3-100.0%) but solve none (0.0-7.7%). Repair followed by tampering also loses all solved credit. A simulated population sweep compares visible-only, semantic-only, and full acceptance on identical measured traces. It isolates the contribution of integrity checks under a stated mixture, without estimating real agent behavior. These results validate selected scoring boundaries, not learned-model resistance, attack completeness, or deployment safety.