How I Detect AI-Generated Text Without Calling an LLM

Most AI detection tools make the same mistake: they use an LLM to detect an LLM. That's expensive, slow, and ironic. You're spending money on the exact technology you're trying to filter out. For PR-Sentry — a GitHub Action that protects open source maintainers from AI-generated PR spam — I needed something different. Detection had to be free, fast, and impossible to rate-limit. Here's how I built it. The core insight: AI text has a statistical fingerprint Human writing is messy. Sentence lengths vary. Word choice is idiosyncratic. Structure is inconsistent. AI writing is suspiciously uniform. It favors certain words, certain patterns, certain rhythms. Not because it's programmed to — but because it learned from a corpus that rewards this style. This uniformity is detectable without a model. You just need the right signals. Signal 1: Buzzword density AI models consistently overuse a specific vocabulary. Not randomly — these words appear because they score well in RLHF training. "Robust