Multi-harness RL guide: LFM2.5 jumps 42% to 54% with 31% fewer tool calls

SergioPaniego · x · 2026-10-10

adithyask's team released 'The Ultimate Guide to Multi-Harness RL' — 50K+ reads in a week, 3 days trending on Twitter, #2 on Hugging Face. Key insight: the same model behaves differently across agent harnesses like Claude Code, Codex, and OpenCode. Their open method trains any model with RL on any task set inside the harnesses people actually use, without changing a single line of harness or training code. Trained across four harnesses, LFM2.5-2.6B went from 42% to 54% with 31% fewer tool calls.

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