彻底揭示LLM Agent为何会‘平静地撒谎’
论文对自2026年3月持续生产的个人助手LLM Agent运行时进行8周纵向研究，系统包含约40个定时任务、8个LLM供应商、4286个单元测试和827个治理检查。记录22起事故，识别出至少28次“静默故障”实例，归纳为5类机制导向分类（A环境平台异常、B设计假设不匹配、C错误吞噬稀释、D链式幻觉与捏造、E操作遗漏与取证盲点）。D类为LLM特有且最危险——系统不仅不报告错误，还将其转化为流畅可信的叙事呈现给用户，作者称为“fail-plausible”。关键发现：约70%静默故障由人类用户视角观察发现而非测试或审计捕获；事故延迟从13小时到60天不等，与故障机制相关而非代码复杂度。
When Errors Become Narratives: A Longitudinal Taxonomy of Silent Failures in a Production LLM Agent Runtime
LLM agent systems increasingly run as long-lived autonomous runtimes: scheduling jobs, calling tools, maintaining memory, and pushing results to humans. We present a longitudinal study of silent failures in one such system: a personal-assistant agent runtime in continuous production since March 2026, with roughly 40 scheduled jobs, 8 LLM providers, a tool-governance proxy, and a knowledge-base memory plane, defended by 4,286 unit tests and 827 governance checks. Over eight weeks we documented 22 incidents with full root-cause postmortems, in which one meta-pattern -- a failure whose error signal never reaches a human in actionable form -- manifested at least 28 times. We derive a five-class, mechanism-oriented taxonomy: (A) environment and platform quirks, (B) design-assumption mismatches, (C) error swallowing and dilution, (D) chained hallucination and fabrication, (E) operational omission and forensic blind spots. Class D is unique to LLM systems and the most dangerous: the system does not merely fail to report an error -- the LLM transforms it into fluent, plausible narrative delivered to the user. We term this fail-plausible: gray failure's differential observability escalated -- the observer is not just blind, it is convincingly lied to by the failure itself. Three findings: about 70% of silent failures were caught by human user-view observation, not tests or audits; a retrospective audit of 15 incidents found 0% ex-ante prevention but 87% regression blocking -- audits are regression engines, not prediction engines; incident latency (13 hours to 60 days) tracks failure mechanism, not code complexity -- the longest-lived failures lived in the seams between components, where no test runs. We describe the resulting defense framework and distill design principles for agent systems whose failures are loud, attributable, and boring. All postmortems and artifacts are public.