Extension API overview

The FKN browser extension runs @fkn/lib capabilities inside the user’s browser: requests leave from that browser, and frames can use its logged-in sessions. Sensitive operations use per-app consent. Permission decisions, plus the first automatic or covered use of each capability and scope during a visit, are kept in a 30-day on-device activity log. In the backend model these APIs live under extension.*.

This section covers the extension-specific surfaces:

• Locators and actions: the shared extension and cloud frame API, using Playwright-style selectors.
• Permissions and consent: the consent model behind every gated capability, and how to ask well.
• fetch() and cookies: cross-origin fetch from the user’s browser, optionally carrying their session.

Frames themselves are attached with attachFrame(), a platform API rather than an extension one. The extension backend can either seed the frame from the user’s browser session or use a clean partition. When no extension is exposed, the cloud render proxy serves the frame instead, with its own persistent or per-attach cookie jar. The consent prompts and activity log described in this section belong to the extension backend.

Detecting the extension from your app - and prompting the user to install it - is covered in Getting started.