Agent adversarial captchas: captcha-spamming works surprisingly well against LLM agents

voooooogel · x · 2026-09-11

A developer watching agents grind against captchas argues captcha-spamming is an underrated, cheap defense for infrastructure against LLM agents, and predicts more LLM-adversarial captchas ahead. Also shows agents naively trusting their own notes-to-self.

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