no-fake-stats

A Claude Code Stop hook that blocks fabricated-looking statistics — specific decimal percentages, large dollar amounts in $B/$M, "% of users" claims — when no source citation appears in the same message.

no-fake-stats is one bash file (~80 lines, depends only on jq) wired into Claude Code's Stop and SubagentStop events. It pattern-matches three classes of statistics that look authoritative and require sourcing:

• Decimal percentages — 73.4%, 19.9%, 91.7%. The decimal claims precision; precision needs a source.
• <N>% of <noun> claims — 73% of users, 45% of enterprises. The noun-attached form is the single most common LLM stat-fabrication pattern.
• Large dollar amounts — $67.4 billion, $145M. Loud-sounding economic claims.
• 4+-digit user/customer counts — 30000 developers, 12000 companies. (Comma-separated 30,000 is a known false negative; PRs welcome.)

Why this exists

LLM hallucination rates on numeric claims run 14–94% (2026 benchmark across 37 models).

• GPTZero found 50+ hallucinations in ICLR 2026 submissions, each missed by 3-5 peer reviewers.
• Q1 2026 legal sanctions hit $145,000 for AI-fake citations and stats in court filings — the highest quarterly total in legal history.
• Enterprise losses from AI hallucinations reached $67.4 billion in 2024; 47% of enterprise AI users reported business decisions made on hallucinated information.

Loose hedges ("approximately", "roughly", "around", "about") do not make a precise decimal honest. If the model writes "approximately 73.4%" — the decimal contradicts the hedge.

What gets blocked

A message containing any of the four trigger classes above without any of:

• A URL (https://...) in the same message.
• An academic citation: (YYYY) parenthetical year, <Author> et al., doi:, arXiv:.
• An attribution: "according to ", "per ", "source: ".
• A strong neutral hedge: unverified, unknown, insufficient_data, order of magnitude, "I do not have a verified figure here", "could be anywhere".

Install

mkdir -p .claude/hooks
curl -fsSL https://raw.githubusercontent.com/waitdeadai/no-fake-stats/main/no-fake-stats.sh \
  -o .claude/hooks/no-fake-stats.sh
chmod +x .claude/hooks/no-fake-stats.sh

Merge settings.example.json into .claude/settings.json. Requires jq.

Receipts

Four reproducible local tests in RECEIPTS.md. Four for four.

Sister tools

Part of the LLM Dark Patterns Hooks suite.

• no-vibes, time-anchor, no-curfew, no-sycophancy, no-cliffhanger, honest-eta
• no-fake-recall, no-fake-cite (sister fact-fabrication hooks)
• minmaxing — parent harness

License

Apache-2.0.