Discriminating Fixture Coverage in Agent-Infrastructure Verification Suites

Reusable Web-agent verification requires a rule to follow changing requirements and support subsequent execution. We introduce AgentProofBench, which connects paired tests of a frozen acceptance rule to execution from identical saved openings. The resource spans 97 tasks, 79 families, and four Web services. Experiments with DeepSeek Flash/Pro establish two linked measurements. Across 48 families, complete-panel and decision-replay tests retain 82/96 Flash and 79/96 Pro source programs; paired reuse-rebuild BA intervals are [-5.47, 1.57] and [-10.16, 0.00] percentage points. Across 22 execution families, deployment-state panel correctness separates program assignments whose two saved openings are both delivered correctly: 32/33 assignments with error-free panels, versus 1/11 with panel errors. All reference-defined program-gate regressions and withheld deliveries occur in the latter group. Neutral continuation attains the highest correct delivery under the tested generic feedback, providing a concrete baseline for measuring the value added by a gate. Released instructions, states, programs, reference rules, and trajectories connect each test failure to its execution consequences. AgentProofBench makes reusable verification assessable at both the requirement and policy levels.

Online-judge verdicts and the datasets and benchmarks built on them are treated as ground truth for evaluating and training large language models for code. Yet prior audits have sounded a warning: official suites accept buggy submissions. These audits, however, stop at the warning and offer no practical remedy. Our remedy has two parts: an off-the-shelf coding agent, serving as a test-suite auditor, both builds adversarial test suites to expose what official suites miss and supplies these suites where no official suite exists; a certification chain determines whether each agent-flagged submission is genuinely buggy without relying on the official judge: multiple independently written accepted solutions agree on the expected output for every test, brute-force solutions settle disagreements, and a per-problem validator certifies each failing input legal. One such agent identifies 589 verified accepted-but-buggy submissions among AtCoder's 20,375 audited accepted submissions; extending the same certification to all five agents yields a union floor of 906 such submissions. Five agents, scored separately, each stay within 1.7pp of official-suite coverage on logic bugs those suites catch. On post-cutoff Codeforces problems with no available official suites, the same test-building method leads all five reproduced baselines at every tested input budget. Where an official suite exists, the agent audits suite adequacy instead of assuming it; where none exists, agent suites catch the most buggy submissions among methods we reproduced and tested.

Software agents answer behavioral questions about code, such as whether a patch passes tests or which lines caused a failure. These tasks require repository-wide evidence, yet most scaffolds leave intermediate findings in free-form trajectories, making them hard to reuse and easy to disconnect from final answers. We present Agentic Interpretation (AgInt), a framework for harness-governed evidence construction. The model proposes typed records, while a deterministic harness admits, grades, and persists them, reports unresolved requirements, and licenses answers under task-specific rules. The resulting certificate gives the model persistent external state and leaves an auditable decision record. Formally, append-only certificate states form a grounding lattice ordered by record inclusion, where each admitted record extends the state by union. We evaluate AgInt with four models on SWE-bench-Live and DeepSWE for patch acceptance and Defects4J and GitBug-Java for fault localization. AgInt outperforms the plain agent and Agentic Code Reasoning on all reported patch-acceptance metrics and ranks responsible lines higher while inspecting fewer irrelevant lines in fault localization. For GLM-5, reject-class F1 rises from 0.256 to 0.543 on SWE-bench-Live, All@1 rises from 0.140 to 0.400 on Defects4J, and wasted inspected lines fall from 31.5 to 11.7 on GitBug-Java. A matched-template control separates the mechanism: the persistent scaffold drives most fault-localization gains, while the certificate body and gate govern patch-acceptance calibration. With execution licensed, AgInt produces harness-reproduced witnesses for 293 of 475 null-dereference candidates versus 253 for a matched shell agent, and 62 of 117 resource-leak candidates versus 58. Across reported efficiency measurements, it uses 35% fewer executions and reduces cost per candidate by 59%.