Notebook Entry 001
Silent Truncation Destroys 250 Lines of Coaching History
April 1, 2026
Why did detailed coaching history disappear from the file meant to hold it?
What happened
Over 35 sessions, CORE-01 grew to 500+ lines. Each save-progress operation used a single view call that silently truncated the file — showing the beginning and end but cutting the middle. ~250 lines of detailed coaching patterns from Sessions 14-26 were compressed into ~30 lines of summary bullets. Nobody noticed until Session 36 when Amanda realized she was repeatedly providing details that should have already been captured.
Root cause
The AI tool's file-reading function has a hidden character limit. It doesn't error — it just quietly drops the middle of long files and shows you the beginning and end. If you rewrite the file from what you see, you've permanently destroyed what you didn't see.
What changed
Hard rule — files over 150 lines must be read in explicit chunks (100 lines max per call). Line count check before every file operation. CORE-01 split into two files: one kept short (≤150 lines), one append-only in a separate system.
The lesson
Silent failures are worse than loud ones. A tool that errors on a long file is safer than a tool that pretends it read the whole thing. Always verify your AI tool actually consumed what you think it consumed. Organizations need verification layers on every AI operation that runs repeatedly — "it worked last time" is not a safety guarantee.
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