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+.docname {Teams for Linux}
+.include {docs}
+
+Microsoft does not publish a native Teams client for Linux. [Teams for Linux][teams-for-linux] is an
+unofficial [Electron][electron] wrapper around the Teams web app that provides a standalone desktop
+client, system tray integration and native notifications.
+
+Install it with `yay -S teams-for-linux-bin`.
+
+## Configuration
+
+The configuration is stored in `~/.config/teams-for-linux/config.json`.
+
+```json
+{
+	"notificationMethod": "web",
+	"electronCLIFlags": [
+		["enable-features", "WebRtcPipeWireCamera"]
+	]
+}
+```
+
+- `notificationMethod: web` uses the browser notification API of the embedded web app instead of the
+  Electron notification API.
+- `WebRtcPipeWireCamera` enables the PipeWire camera backend, which is required for the webcam to
+  work under Wayland.
+
+## Opening meeting links in the app
+
+Clicking a Teams meeting link in the [Thunderbird](002-thunderbird.qd) or Outlook web interface opens
+the meeting in the browser instead of in Teams for Linux. Getting the handover to work requires a
+userscript, because the desktop integration alone is not sufficient.
+
+### Verify the protocol handler
+
+The package registers the `msteams:` URI scheme through its desktop entry, so this part usually works
+out of the box:
+
+```sh
+gio mime x-scheme-handler/msteams
+```
+
+The output must name `teams-for-linux.desktop` as the default application. If it does not, register it
+with `xdg-mime default teams-for-linux.desktop x-scheme-handler/msteams`.
+
+A deep link can be tested directly from a shell. This opens the meeting in Teams for Linux:
+
+```sh
+xdg-open 'msteams:/meet/<meeting-id>?p=<passcode>'
+```
+
+### Why the browser never asks
+
+Meeting invitations do not contain `msteams:` links. They contain plain HTTPS links in the form
+`https://teams.microsoft.com/meet/<meeting-id>?p=<passcode>`. An HTTPS URL belongs to the browser,
+so nothing is ever handed to an external application.
+
+That URL answers with a redirect to a launcher page:
+
+```txt
+HTTP/2 302
+location: /dl/launcher/launcher.html?url=%2F_%23%2Fmeet%2F<meeting-id>%3Fp%3D<passcode>%26anon%3Dtrue&type=meet&directDl=true&msLaunch=true
+```
+
+Because the redirect happens on the server, no document is ever created for the `/meet/` URL and a
+userscript cannot match on it. The launcher page is the first document that actually loads, and its
+`url` query parameter carries the deep link path, prefixed with `/_#`. Stripping that prefix yields
+exactly the path the `msteams:` scheme expects.
+
+### Userscript
+
+Install [Tampermonkey][tampermonkey] in [Librewolf](001-librewolf.qd) and add the following userscript.
+
+```js
+// ==UserScript==
+// @name         Teams links to teams-for-linux
+// @match        https://teams.microsoft.com/dl/launcher/launcher.html*
+// @match        https://teams.microsoft.com/meet/*
+// @match        https://teams.microsoft.com/l/*
+// @run-at       document-start
+// @grant        GM_info
+// ==/UserScript==
+(() => {
+  let path;
+  if (location.pathname.startsWith('/dl/launcher/')) {
+    const u = new URLSearchParams(location.search).get('url');
+    if (!u) return;
+    path = u.replace(/^\/_#/, '');
+  } else {
+    path = location.pathname + location.search;
+  }
+  if (!/^\/(meet|l)\//.test(path)) return;
+
+  window.stop();
+  location.href = 'msteams:' + path;
+  setTimeout(() => {
+    window.close();
+    location.replace('about:blank');
+  }, 1500);
+})();
+```
+
+Three details in this script are not obvious and the script silently stops working without them:
+
+- `@grant GM_info` forces Tampermonkey to run the script in its sandboxed content script scope. With
+  `@grant none` the script is injected into the page as an inline `<script>` element and is then
+  blocked by the launcher page, which sends a `script-src 'nonce-...'` content security policy.
+  The script still matches, but never executes.
+- `window.stop()` aborts the launcher page before its own scripts are parsed. Otherwise the page
+  navigates on to `https://teams.microsoft.com/v2/`, which destroys the document and discards the
+  pending timeout, so the tab is never cleaned up. It must be called **before** the `msteams:`
+  assignment, because calling it afterwards cancels the handover itself.
+- `@run-at document-start` is what makes the above possible in the first place.
+
+On the first meeting link the browser asks which application should open the link. Select Teams for
+Linux and enable `Always allow teams.microsoft.com to open links of this type`. The dialog is
+tab-modal, so if it is still open when the tab closes it disappears together with the tab.
+
+> Tip: The tab is closed by `window.close()` even though `dom.allow_scripts_to_close_windows` is
+> `false` by default. Outlook opens meeting links through `window.open()`, and Firefox permits a
+> script to close windows that were opened by a script. The `location.replace('about:blank')` call
+> is the fallback for tabs that were opened another way.
+
+### Maintenance
+
+Two upstream changes can break this and are worth checking first if meeting links stop working:
+
+- Microsoft changing the launcher URL layout. The `.replace(/^\/_#/, '')` call encodes the current
+  `/_#/meet/...` format of the `url` query parameter.
+- Teams for Linux tightening its deep link validation. The accepted schemes are defined by these
+  regular expressions in the application:
+
+```txt
+^msteams:/(?:meet/|l/(?:app|call|channel|chat|entity|file|meet(?:ing|up-join)|message|task|team)/)
+^msteams://teams\.(?:microsoft\.com|live\.com|cloud\.microsoft)/(?:meet/|l/(?:app|call|channel|chat|entity|file|meet(?:ing|up-join)|message|task|team)/)
+```
+
+[teams-for-linux]: https://github.com/IsmaelMartinez/teams-for-linux
+[electron]: https://www.electronjs.org
+[tampermonkey]: https://www.tampermonkey.net