ArXiv paper: 'The Harness as the Only Mutable Surface' — admission-gated self-evolution for LLM agents in credit pipelines
The paper argues that LLM agents may only be reviewable if self-modification is confined to a mutable runtime harness (instructions, tool-call logic, primitive composition) while model weights remain fixed, and it presents a dual-loop engine with a single admission gate that writes a hash-chained record before deployment. In simulation (simulated agent and seeded proposer) across three families of supervisory re-interpretation and 10 seeds each, the gated loop admitted 144 of 7,449 candidate changes and did not worsen held-out error, while an unbounded check admitted 309 harmful changes and left missed flags >10% in 49 of 90 runs; the gate rejected every candidate when evaluated on pre-shift labels and had mixed outcomes on high-severity structural shifts.