Introducing Precursor: Detecting Agentic Behavior With Continuous Client-Side Signals
Cloudflare, Monday, July 13th, 2026
Precursor is a session-based behavioral verification engine that detects advanced bots with less friction for real users.
Cloudflare launched Precursor, a client-side, session-based verification system that evaluates behavior across a visitor's entire journey rather than at a single challenge point.
Lightweight JavaScript collects interaction signals such as mouse movement, keyboard timing, and focus changes, which are analyzed in aggregate for automation patterns.
The premise is that while bots can mimic a human briefly or solve one CAPTCHA, consistent human behavior over a full session is far harder to fake. Cloudflare designed the system to be privacy-preserving, capturing keystroke timing rather than the keys themselves and never tying signals to user identity.
Precursor integrates with existing bot management, can run passively or enforce challenges, and is free during the rollout period.