Document mautrix bridge HTTP API exposure (for mautrix-manager and similar)

Add a "Expose the bridge's API" section to the common mautrix bridges
documentation page (covering the /bridges/<bridge> path, the
/.well-known/matrix/mautrix auto-discovery file, how to disable it, and
the custom-bridges hook), plus a CHANGELOG entry announcing the feature.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -1,3 +1,15 @@
+# 2026-06-29
+
+## Mautrix bridges now expose their API (for Mautrix Manager and similar tools)
+
+The playbook now exposes the HTTP API of each [mautrix](https://github.com/mautrix) bridge, so tools like [Mautrix Manager](https://github.com/mautrix/manager) can help you log into them. This is especially useful for [mautrix-gmessages](./docs/configuring-playbook-bridge-mautrix-gmessages.md): Google has removed its QR-code login, leaving a [manual cookie-extraction flow](https://docs.mau.fi/bridges/go/gmessages/authentication.html) that tools like Mautrix Manager can streamline.
+
+The API is exposed at `https://matrix.example.com/bridges/SERVICENAME` (for example, `https://matrix.example.com/bridges/gmessages`) and is advertised via a new `/.well-known/matrix/mautrix` file, so compatible tools can discover your bridges automatically. Such tools authenticate with your own Matrix access token, so no bridge secret needs to be shared with them.
+
+This affects all mautrix bridges based on the new bridge framework (bluesky, gmessages, meta-instagram, meta-messenger, signal, slack, telegram, twitter and whatsapp) and is enabled by default.
+
+To learn more (including how to turn it off), see the [Expose the bridge's API](./docs/configuring-playbook-bridge-mautrix-bridges.md#expose-the-bridges-api-for-mautrix-manager-and-similar-tools) section on our common mautrix bridges documentation page.
+
 # 2026-06-28
 
 ## baibot now supports Venice, our recommended provider

docs/configuring-playbook-bridge-mautrix-bridges.md

@@ -138,6 +138,35 @@ Replace `warn` with one of the following to control the verbosity of the logs ge
 
 If you have issues with a service, and are requesting support, the higher levels of logging (those that appear earlier in the list, like `trace`) will generally be more helpful.
 
+### Expose the bridge's API (for Mautrix Manager and similar tools)
+
+Each mautrix bridge runs an HTTP API which tools like [Mautrix Manager](https://github.com/mautrix/manager) can use to help you log into the bridge. This is especially handy for bridges where logging in manually is cumbersome (like [mautrix-gmessages](configuring-playbook-bridge-mautrix-gmessages.md)).
+
+By default, the playbook exposes this API publicly at `https://matrix.example.com/bridges/SERVICENAME` (for example, `https://matrix.example.com/bridges/gmessages`). Such tools authenticate to the bridge with your own Matrix access token, so you never need to share any bridge secret with them.
+
+To make discovery easier, the playbook also serves a `/.well-known/matrix/mautrix` file which advertises all your exposed bridges. Mautrix Manager reads this file and offers your bridges automatically, so you don't need to enter their URLs by hand.
+
+This is all enabled by default. To **disable exposing the API for all bridges**, add the following configuration to your `vars.yml` file:
+
+```yaml
+matrix_bridges_exposure_enabled: false
+```
+
+**Alternatively**, to disable it for a specific bridge:
+
+```yaml
+matrix_mautrix_SERVICENAME_exposure_enabled: false
+```
+
+If you run additional bridges on the same server which are not managed by this playbook and would like compatible tools to discover them as well, you can advertise their base URLs in the `/.well-known/matrix/mautrix` file:
+
+```yaml
+matrix_static_files_file_matrix_mautrix_property_fi_mau_bridges_custom:
+  - https://matrix.example.com/bridges/SOME_OTHER_BRIDGE
+```
+
+Only list bridges hosted on (and connected to) this server here, as compatible tools will send your Matrix access token to them. For bridges on other servers, take a look at the `fi.mau.external_bridge_servers` property described in the [Mautrix Manager](https://github.com/mautrix/manager) documentation, which you can add via `matrix_static_files_file_matrix_mautrix_configuration_extension_json`.
+
 ### Extending the configuration
 
 There are some additional things you may wish to configure about the bridge.