Prime Agent is an open-source harness designed for long-horizon evaluation and coding-agent workflows, utilizing a persistent IPython REPL and recursive subagents to manage context and computation beyond model weights.
The system employs a Continual Harness to preserve histories, memories, and skills across trajectories, while allowing direct agent-to-agent communication. It standardizes execution, recovery, and verification processes, preventing harness failures from impacting the model's performance.
In benchmarks, Prime Agent increased ARC-AGI-3 RHAE Best@1 scores from 30% to 95.5%, matching or exceeding native harnesses in long-context coding and autonomous tasks. On Factorio, the framework enabled continuous technology progression through refinement and parallelized work via dedicated subagents.