Locke Extension by Sonomos

Locke Extension is the browser half of the Sonomos Locke desktop app. It watches a fixed list of AI websites (ChatGPT, Claude, Gemini, Perplexity, and the other in-scope chat and search surfaces) and, when a page on one of those sites sends a request with a body, it holds that request and relays it to the Locke desktop app running on your machine. The app scans it on-device and returns a verdict, which the extension enforces before anything leaves your browser:

allow — the request is sent exactly as the page issued it.
redact — the request is sent with sensitive data replaced by the desktop app's rebuilt version.
block — the request is not sent; the page sees a network error.
The failure posture is fail-closed: if the desktop app is unreachable or no clean verdict arrives, an in-scope request is blocked rather than sent unscreened. Traffic to sites outside the list is never touched.

All scanning and redaction happen locally in the Locke desktop app. The extension has no detection logic of its own, contacts no remote servers, and sends no data off your machine. Its only two endpoints are the desktop app's native-messaging host and a loopback heartbeat (127.0.0.1) that tells the app the extension is installed and connected.

Requires the Locke desktop app. Without it, in-scope AI-website requests are blocked (fail-closed) and the toolbar badge shows the connection problem.