System One Harness: an open-source local agent framework for JEV

HarnessRouter @HARNESSROUTEROriginally posted 2026.09.21

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Agent Harness for JEV. We built System One Harness, an open-source harness designed specifically for System one models JEV. You can run it entirely locally. https://github.com/HarnessRouter/SystemOneHarness System One Harness observes the environment, converts its finite action space into typed questions, gates each decision by confidence, executes the selected action, and records the full trace. One model call per step. No generated actions. A probability assigned to every transition.