Hallucinated library entry: post-mortem and safeguard
How Claude invented a book by my competitor, why it happened, and the rule added to prevent it.
What happened
During a library import session in March 2026, a Claude session added a book entry to the garden library titled “Tech skills for conversation designers” with author “Hans van Dam.” Neither the book nor the author attribution is real. Hans van Dam is a direct competitor of mine in the conversation design space.
The entry was discovered in April 2026 during a library audit triggered by an unrelated check.
Root cause
The import session scraped my public Notion library page and treated every page entry as a potential book. “Tech skills for conversation designers” is actually a Notion resource page I built myself, a curated list of courses and articles, not a book. Its Author field in Notion was empty (“Leeg”).
When Claude encountered a plausible-sounding title with no author, it did not stop or flag the gap. It generated a plausible-sounding author name instead. Hans van Dam is a known name in conversation design: that is almost certainly how his name surfaced. The hallucination was confident and structurally valid, a complete frontmatter entry with description, tags, reason, and status, which is exactly what makes it dangerous.
Why this is serious
A hallucinated book entry is bad. A hallucinated book attributed to a competitor, published on my professional site, is a professional integrity failure. The ai: assisted label on the entry was correct in form but meaningless as a safeguard: it flagged that AI helped, not that AI invented.
The safeguard
A non-negotiable rule has been added to CLAUDE.md:
NEVER generate, hallucinate, or invent factual fields for library entries. If the source has no author, write
author: "Unknown". Never generate a plausible-sounding name. Before writing any new library entry, verify the book and author exist on Open Library. If unverifiable, stop and ask.
Empty fields are always better than hallucinated ones.
Still to do
- Full audit of all
ai: assistedlibrary entries against the original Notion source - Check “Bacteria to AI” (attributed to N. Katherine Hayles, status: reading), may be real, needs verification
- Add Open Library verification step to the
/new-bookskill