I built this because every time I asked Claude to help me interact with a website, it would rediscover the same
things from scratch — is this a React SPA? Does it have an API? Which selectors work?
Foxhole is a Firefox sidebar extension where Claude learns and remembers how each site works across sessions.
It saves site profiles (UI-only vs API-driven), working selectors, endpoints, and workflows. Next visit, it
reads those specs before doing anything.
Key things it does differently:
- Site profiles: knows whether to click buttons or call APIs
- Spec staleness: flags old knowledge, Claude can delete broken specs
- Not QA automation: asks the user to handle age gates, logins, CAPTCHAs instead of flailing
- Prompt injection defense: sanitizes page content before Claude sees it
- Context compression: strips screenshots and raw payloads from old turns, keeps semantic summaries
Firefox-only (Manifest V2), no build step, raw JS. Uses your own Anthropic API key.
I built this because every time I asked Claude to help me interact with a website, it would rediscover the same things from scratch — is this a React SPA? Does it have an API? Which selectors work?