An agent benchmark measures a model–harness system, not the model alone.
The authors compare OpenCode, Codex CLI, Pi CLI and DeepAgents across four core models, with native references and stress conditions. Their 111 settings yield 52,168 trajectories across six benchmarks. Rankings vary by model and task; finishing normally with an evaluable result is not the same as solving the task correctly.
Evidence & limits. This is an author-reported preprint under review, not a universal harness leaderboard. Valid Completion Rate measures operational validity, not answer quality. Pairing-level observations do not isolate a single causal component; versions, budgets, benchmark panels and task mix matter.
Make model changes a regression event for the whole harness. Track correctness, normal completion and token load including failures separately. Promote the pairing that works on your tasks, not the winner of an unrelated aggregate.