Add an admin API to get the space hierarchy (#19021)

It is often useful when investigating a space to get information about that space and it's children. This PR adds an Admin API to return information about a space and it's children, regardless of room membership. Will not fetch information over federation about remote rooms that the server is not participating in.
2026-08-27 22:34:55 +00:00 · 2025-10-24 15:32:16 -05:00
parent 9d81bb703c
commit f1695ac20e
6 changed files with 475 additions and 21 deletions
@@ -1115,3 +1115,76 @@ Example response:
  ]
 }
 ```
+
+# Admin Space Hierarchy Endpoint
+
+This API allows an admin to fetch the space/room hierarchy for a given space, 
+returning details about that room and any children the room may have, paginating
+over the space tree in a depth-first manner to locate child rooms. This is
+functionally similar to the [CS Hierarchy](https://spec.matrix.org/v1.16/client-server-api/#get_matrixclientv1roomsroomidhierarchy) endpoint but does not check for
+room membership when returning room summaries.
+
+The endpoint does not query other servers over federation about remote rooms
+that the server has not joined. This is a deliberate trade-off: while this
+means it will leave some holes in the hierarchy that we could otherwise
+sometimes fill in, it significantly improves the endpoint's response time and
+the admin endpoint is designed for managing rooms local to the homeserver
+anyway.
+
+**Parameters**
+
+The following query parameters are available:
+
+* `from` - An optional pagination token, provided when there are more rooms to 
+    return than the limit. 
+* `limit` - Maximum amount of rooms to return. Must be a non-negative integer,
+   defaults to `50`.
+* `max_depth` - The maximum depth in the tree to explore, must be a non-negative
+   integer. 0 would correspond to just the root room, 1 would include just the
+   root room's children, etc.  If not provided will recurse into the space tree without limit.
+
+Request:
+
+```http
+GET /_synapse/admin/v1/rooms/<room_id>/hierarchy
+```
+
+Response:
+
+```json
+{
+  "rooms":
+      [
+        { "children_state": [
+            {
+              "content": {
+                "via": ["local_test_server"]
+              },
+              "origin_server_ts": 1500,
+              "sender": "@user:test",
+              "state_key": "!QrMkkqBSwYRIFNFCso:test",
+              "type": "m.space.child"
+            }
+        ],
+        "name": "space room",
+        "guest_can_join": false,
+        "join_rule": "public",
+        "num_joined_members": 1,
+        "room_id": "!sPOpNyMHbZAoAOsOFL:test",
+        "room_type": "m.space",
+        "world_readable": false
+      },
+
+      {
+        "children_state": [],
+        "guest_can_join": true,
+        "join_rule": "invite",
+        "name": "nefarious",
+        "num_joined_members": 1,
+        "room_id": "!QrMkkqBSwYRIFNFCso:test",
+        "topic": "being bad",
+        "world_readable": false}
+    ],
+  "next_batch": "KUYmRbeSpAoaAIgOKGgyaCEn"
+}
+```