spec lazy_load_members and include_redundant_members

api/client-server/definitions/room_event_filter.yaml

@@ -32,4 +32,24 @@ properties:
     type: boolean
     description: If ``true``, includes only events with a url key in their content. If
       ``false``, excludes those events.
+  lazy_load_members:
+    type: boolean
+    description: If ``true``, the only ``m.room.member`` events returned in the ``state``
+      section of the ``/sync`` response are those which are definitely necessary for a
+      client to display the ``sender`` of the timeline events in that response.  If
+      ``false``, ``m.room.member`` events are not filtered.  By default, servers should
+      suppress duplicate redundant lazy-loaded ``m.room.member`` events from being sent to a
+      given client across multiple calls to ``/sync``, given that most clients cache
+      membership events (see include_redundant_members to change this behaviour).
+  include_redundant_members:
+    type: boolean
+    description: If ``true``, the ``state`` section of the ``/sync`` response will
+      always contain the ``m.room.member`` events required to display the ``sender``
+      of the timeline events in that response, assuming ``lazy_load_members`` is enabled.
+      This means that redundant duplicate member events may be returned across multiple
+      calls to ``/sync``. This is useful for naive clients who never track membership data.
+      If ``false``, duplicate ``m.room.member`` events may be suppressed by the server
+      across multiple calls to ``/sync``.  If ``lazy_load_members`` is ``false`` this field
+      is ignored.
+
 type: object

api/client-server/sync.yaml

@@ -133,6 +133,12 @@ paths:
                             ``timeline`` (or all state up to the start of the
                             ``timeline``, if ``since`` is not given, or
                             ``full_state`` is true).
+
+                            N.B. state updates for ``m.room.member`` events will
+                            be incomplete if ``lazy_load_members`` is enabled in
+                            the ``/sync`` filter, and only return the member events
+                            required to display the senders of the timeline events
+                            in this response.
                           allOf:
                             - $ref: "definitions/event_batch.yaml"
                         timeline: