Browser-agent demos usually show the happy path. The harder question is what the runtime itself should prove before an agent trusts the result.
For Jet Browser, we made the acceptance check deliberately boring: a local fixture loads, JavaScript runs, native input reaches the page, semantic DOM agrees with what was typed, a fresh screenshot is captured, outbound browser networking stays off, and cleanup succeeds.
Jet Browser packages WPE WebKit as a portable browser runtime for AI agents. Each container owns one isolated session and accepts ordered JSONL commands for navigation, native keyboard and pointer input, semantic DOM inspection, screenshots, and clean shutdown. It ships a deterministic offline smoke test, versioned tool declarations, and reproducible benchmark data without bundling a model, agent loop, or hosted control plane.
