I have yet to read the paper and I know very little about the benchmarks the authors employed but why would they even feed logs produced by the agent into the reward function instead of objectively checking (outside the agent sandbox!) what the agent does & produces? I.e. let the agent run on some code base, take the final diff produced by the agent and run it through coding benchmarks?
Or, in case the benchmarks reward certain agent behavior (tool usage etc.) on the way to its goal of producing a high-quality diff, inspect processes spawned by the agent from outside the sandbox?