Finicky is a macOS app that acts as your default browser. When you click a link anywhere on your system (Slack, email, terminal, etc.), Finicky intercepts it, evaluates rules from ~/.finicky.js, and opens the URL in the right browser — or the right profile of a browser.
This is useful when you work across multiple organizations and want to keep sessions, cookies, and bookmarks separated.
Finicky's official documentation covers the profile property for Chromium browsers only (e.g. browser: { name: "Google Chrome", profile: "Work" }). Firefox profile routing is undocumented, and the args property that makes it possible isn't mentioned in the wiki at all. This guide fills that gap.