How Filesystem Timestamps Silently Misled Three AI Agent Subsystems

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A developer discovered that three separate AI agent subsystems were incorrectly using file modification times (mtime) as proxies for meaningful events such as task completion, audio capture, and capability sweeps. When 54 knowledge files were copied to a new machine on July 14, 2026, their mtimes reset to the transfer moment, causing a sweep gate to falsely treat weeks-old files as freshly updated. Separately, a room audio daemon's transcript file was being touched by a cron job on schedule even when the recording process was inactive, making liveness checks appear green while the system had been deaf for hours. A strand-tracking tool also closed out a work item 71 seconds before the actual commit, because a file save reset its mtime and triggered an early 'done' signal. The author concludes that mtime answers only one question — when bytes were last written — and cannot reliably stand in for claims about whether meaningful work actually occurred.

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