todo/.agents/skills/avoid-ai-writing/detector

Detector engine

patterns.js is the executable expression of this skill's pattern rules — a zero-dependency, build-step-free detection engine that scores text for AI-writing tells. It runs identically in Node (>=18) and in the browser.

The skill's SKILL.md is the human-readable catalog of rules; this engine is the deterministic, testable implementation of the regex-detectable subset, plus stylometric and AI-tool-fingerprint detectors that don't make sense as prose. See CATEGORIES.md for the rule ↔ category mapping that keeps the two in sync.

Run it

npm test          # runs detector/patterns.test.js (no deps to install)
# or directly:
node detector/patterns.test.js

const AIDetector = require("./detector/patterns.js");
const result = AIDetector.analyzeText("Your text here…");
console.log(result.score, result.label, result.issues.length);

In the browser, load patterns.js as a plain script — it self-registers as a global AIDetector (the module.exports block is guarded and only runs under CommonJS).

analyzeText(text, options?) → result

Field	Type	Meaning
score	0–100	0 = clean, 100 = heavy AI
label	string	Minimal / Some / Strong / Heavy (or Empty / Too short / Text too long)
issues[]	{type, text, severity, …}	one entry per detected pattern; type keys map to CATEGORIES.md
stats	object	wordCount, per-tier counts, contextMode, denseAIVocab, normalization flags, etc.
document_classification	string	trinary HUMAN_ONLY / MIXED / AI_ONLY (shape mirrors GPTZero for swap-in)
class_probabilities	{human, mixed, ai}	sums to exactly 1.0
confidence_category	low / medium / high
highlight_sentence_for_ai	region[]	sentence spans with byte offsets + per-region score, for UI highlighting

options.contextMode accepts general (default) or technical; technical mode suppresses flags that are legitimate in code-adjacent prose (e.g. Title Case headers). Invalid modes fall back to general and set stats.contextModeFallback.

Design notes

• FN-biased. False positives damage trust more than false negatives, so MIXED is wide and AI_ONLY requires multiple corroborating signals.
• Scoring is non-linear. Repeated hits of the same phrase are deduplicated; category weights live in the ISSUE_WEIGHTS table.
• Length gates. Under ~10 words → Too short (unscorable); over 10k words → Text too long.