Harness adapters: per-agent-framework LoRAs cut tool calls, $5 for 1,350 eval sessions

LysandreJik · x · 2026-11-06

Liquid AI's Lysandre shares progress on making models work better with agent harnesses: "harness adapters" — small LoRAs trained with RL inside the actual harness they'll be used with (pi, opencode, hermes, etc.).

The insight: the same base model behaves very differently depending on surrounding tools, prompts, and control flow, so specializing a tiny part of the weights per environment beats one-size-fits-all weights.

Early results are encouraging — adapters make fewer tool calls than the base model while keeping or improving accuracy on held-out tasks. And since they're LoRAs, operations are cheap: one LFM2.5-24B-A2B experiment evaluated 9 checkpoints / 1,350 agent sessions on a single H200 in under an hour, for about $5 total.

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