Passkeys

A passkey is made once, only for a site you armed and only with your approval, and after that it signs the agent in by itself. Its private key stays in the computer's service and never enters the browser.

Signing in

The browser's pinned Hotline extension takes every passkey request a page makes, with the page's origin, and the service signs it for that origin. It signs in without a prompt; nothing types it and no tool answers it. A site's passkey autofill is never answered: with the extension as the WebAuthn proxy, Chromium offers none, so it cannot race the passkey button.

Registration

• The client arms the computer for one site: PUT /passkeys/registration {"rpId":"github.com"}. Arming lasts ten minutes, covers one site, answers {"state":"armed","rpId":…,"expiresAt":…}, and starts the browser on that site if none is open.
• While armed, a navigator.credentials.create() for that site waits. The service records what the site asked for: the site, the origin, and the account's name and display name.
• GET /passkeys/registration answers asked with that request (id, rpId, origin, rpName, userName, userDisplayName, askedAt). The client shows you a card.
• Your answer goes back with POST /passkeys/registration/answer {"id":…,"approved":true}.
• Approved, the service mints a P-256 key and answers the site. GET then answers approved, and registered with the new credential, until the client stores it, sends the secret set with it, and ends the arming with DELETE.

Denied, the site gets a NotAllowedError, as if you had cancelled the browser's own prompt, and the arming ends, so neither the site nor the agent can keep asking. An answer to a request that is not waiting is a 409. A create() for any other site, or with nothing armed, is refused with a NotAllowedError that says so. The browser holds one request at a time, and a site that gives up withdraws its request.

Limits

The registration answer is the one time a private key leaves the computer, over the bearer-guarded loopback route the client already uses. The extension's line to the service is a socket only the container's user can open, but jobs run as that user too: until jobs and the browser have separate identities, that line is a convenience, not a wall.

HOTLINE_COMPUTER_PASSKEYS=virtual keeps the older arrangement, Chromium's virtual authenticator filled over DevTools on port 9222.