Unlike on desktop, where the Nostr ID is a browser extension, in Keychat, the browser (WebView) is an extension of the ID and BTC wallet.

Vanadium is Chromium based but with a lot of security and privacy changes. Because Vanadium is also the OS WebView you can run apps using WebView in a safer fashion, they benefit from such features:

Features overview | GrapheneOS

Also a control for WebView JIT per app to reduce a large JS JIT attack surface for them. Our PDF viewer is an example of a WebView app.