PrimeIntellect's Prime Agent: a self-improving RLM agent

PrimeIntellect open-sources Prime Agent, a recursive-language-model agent whose harness runs sub-agents as function calls inside a persistent IPython REPL. The launch post reports its harness taking Opus 5 from ~30% to 95.5% on ARC-AGI-3 — the sharpest evidence yet that harness engineering can beat model selection.