Hugging Face Daily PapersRuishuo Chen, Xun Wang, Yu Chen1 min readpaperadvanced
The Router Within: Eliciting Native Skill Routing from a Frozen LLM
Summary
The paper introduces Gavel, a method that extracts a frozen LLM's internal routing signal via two trained linear maps, eliminating the need to embed skill descriptions in the prompt. Experiments on Qwen3‑32B show up to 13.4‑point improvements on task benchmarks and higher skill‑use accuracy compared to larger retrieval‑based systems.
- Gavel uses a "glance" step: projects mid‑layer activations of the task and each skill through two linear maps to score a full skill library.
- A "verdict" step resumes forward passes for top‑k skills, combining the model's own likelihood with the glance score as a product of experts.
- Only the two linear maps are trained; the backbone LLM remains frozen, and per‑skill activation banks are built once at installation.
- Zero‑shot transfer to three public benchmarks and a new 372‑trajectory SkillTraj benchmark outperforms retrieval‑and‑rerank pipelines that add up to 16 B external parameters.
LLM‑agent developers can achieve accurate skill selection without inflating model size or context, saving compute and simplifying deployment.
8/10