diff --git a/api/client-server/v2_alpha/sync.yaml b/api/client-server/v2_alpha/sync.yaml
index 1b83d1d9d..7d60d6392 100644
--- a/api/client-server/v2_alpha/sync.yaml
+++ b/api/client-server/v2_alpha/sync.yaml
@@ -74,82 +74,92 @@ paths:
               rooms:
                 type: object
                 description: |-
-                  The updates to rooms, grouped according to the filter. By
-                  default there is a single ``default`` group.
-                additionalProperties:
-                    joined:
-                      type: array
-                      description: |-
-                        A list of room ids that the user is a member of that
-                        have updates.
-                      items:
-                        type: string.
-                    invited:
-                      type: array
-                      description: |-
-                        A list of room ids that the user has been invited to.
-                        The entries in the room_map will have an
-                        ``invite_state`` key. But will lack the ``ephemeral``
-                        key, the ``timeline`` key and the ``state`` key.
-                      items:
-                        type: string.
-                    archived:
-                      type: array
-                      description: |-
-                        A list of room ids that the user has left or been
-                        banned from. The entries in the room_map will have a
-                        ``state`` key and a ``timeline`` key. But will lack the
-                        ``ephemeral`` key.
-                      items:
-                        type: string.
-              room_map:
-                description: |-
-                  Map from room id to the updates for that room. The room ids
-                  are referenced from the ``rooms`` key.
-                type: object
-                additionalProperties:
-                  type: object
-                  properties:
-                    event_map:
+                  Updates to rooms.
+                properties:
+                  joined:
+                    type: object
+                    additionalProperties:
+                      type: object
+                      properties:
+                        event_map:
+                          type: object
+                          description: |-
+                            A map from event ID to events for this room. The
+                            events are referenced from the ``timeline`` and
+                            ``state`` keys for this room.
+                          additionalProperties:
+                            description: An event object.
+                            type: object
+                        state:
+                          description: |-
+                            The state updates for the room.
+                          allOf:
+                            - $ref: "definitions/room_event_batch.json"
+                        timeline:
+                          description: |-
+                            The timeline of messages and state changes in the
+                            room.
+                          allOf:
+                            - $ref: "definitions/timeline_batch.json"
+                        ephemeral:
+                          description: |-
+                            The ephemeral events in the room that aren't
+                            recorded in the timeline or state of the room.
+                            e.g. typing.
+                          allOf:
+                            - $ref: "definitions/event_batch.json"
+                  invited:
+                    type: object
+                    description: |-
+                      The rooms that the user has been invited to.
+                    additionalProperties:
                       type: object
-                      description: |-
-                        A map from event ID to events for this room. The events
-                        are referenced from the ``timeline`` and ``state`` keys
-                        for this room.
-                      additionalProperties:
-                        description: An event object.
-                        type: object
-                    state:
-                      description: |-
-                        The state updates for the room.
-                      allOf:
-                        - $ref: "definitions/room_event_batch.json"
-                    timeline:
-                      description: |-
-                        The timeline of messages and state changes in the room.
-                      allOf:
-                        - $ref: "definitions/timeline_batch.json"
-                    ephemeral:
-                      description: |-
-                        The ephemeral events in the room that aren't recorded
-                        in the timeline or state of the room. E.g. typing.
-                      allOf:
-                        - $ref: "definitions/event_batch.json"
-                    invite_state:
-                      description: |-
-                        The state of a room that the user has been invited to.
-                        These state events may only have the `sender``,
-                        ``type``, ``state_key`` and ``content`` keys present.
-                        These events do not replace any state that the client
-                        already has for the room, for example if the client has
-                        archived the room. Instead the client should keep two
-                        separate copies of the state: the one from the
-                        ``invite_state`` and one from the archived ``state``.
-                        If the client joins the room then the current state
-                        will be given as a delta against the archived ``state``
-                        not the ``invite_state``.
-                      allOf:
-                        - $ref: "definitions/event_batch.json"
+                      properties:
+                        invite_state:
+                          description: |-
+                            The state of a room that the user has been invited
+                            to. These state events may only have the `sender``,
+                            ``type``, ``state_key`` and ``content`` keys
+                            present. These events do not replace any state that
+                            the client already has for the room, for example if
+                            the client has archived the room. Instead the
+                            client should keep two separate copies of the
+                            state: the one from the ``invite_state`` and one
+                            from the archived ``state``. If the client joins
+                            the room then the current state will be given as a
+                            delta against the archived ``state`` not the
+                            ``invite_state``.
+                          allOf:
+                            - $ref: "definitions/event_batch.json"
+                  archived:
+                    type: object
+                    description: |-
+                      The rooms that the user has left or been banned from. The
+                      entries in the room_map will lack an ``ephemeral`` key.
+                    additionalProperties:
+                      type: object
+                      properties:
+                        event_map:
+                          type: object
+                          description: |-
+                            A map from event ID to events for this room. The
+                            events are referenced from the ``timeline`` and
+                            ``state`` keys for this room.
+                          additionalProperties:
+                            description: An event object.
+                            type: object
+                        state:
+                          description: |-
+                            The state updates for the room up to the point when
+                            the user left.
+                          allOf:
+                            - $ref: "definitions/room_event_batch.json"
+                        timeline:
+                          description: |-
+                            The timeline of messages and state changes in the
+                            room up to the point when the user left.
+                          allOf:
+                            - $ref: "definitions/timeline_batch.json"
               presence:
                 description: |-
                   The updates to the presence status of other users.
@@ -169,78 +179,79 @@ paths:
                   ]
                 },
                 "rooms": {
-                  "default": {
-                    "invited": ["!696r7674:example.com"],
-                    "archived": [],
-                    "joined": ["!726s6s6q:example.com"]
-                  }
-                },
-                "room_map": {
-                  "!726s6s6q:example.com": {
-                    "event_map": {
-                      "$66697273743031:example.com": {
-                        "sender": "@alice:example.com",
-                        "type": "m.room.member",
-                        "state_key": "@alice:example.com",
-                        "content": {"membership": "join"},
-                        "origin_server_ts": 1417731086795
-                      },
-                      "$7365636s6r6432:example.com": {
-                        "sender": "@bob:example.com",
-                        "type": "m.room.member",
-                        "state_key": "@bob:example.com",
-                        "content": {"membership": "join"},
-                        "origin_server_ts": 1417731086795
-                      },
-                      "$74686972643033:example.com": {
-                        "sender": "@alice:example.com",
-                        "type": "m.room.message",
-                        "unsigned": {"age": "124524", "txn_id": "1234"},
-                        "content": {"body": "I am a fish", "msgtype": "m.text"},
-                        "origin_server_ts": 1417731086797
-                      }
-                    },
-                    "state": {
-                      "events": [
-                        "$66697273743031:example.com",
-                        "$7365636s6r6432:example.com"
-                      ]
-                    },
-                    "timeline": {
-                      "events": [
-                        "$7365636s6r6432:example.com",
-                        "$74686972643033:example.com"
-                      ],
-                      "limited": true,
-                      "prev_batch": "t34-23535_0_0"
-                    },
-                    "ephemeral": {
-                      "events": [
-                        {
-                          "room_id": "!726s6s6q:example.com",
-                          "type": "m.typing",
-                          "content": {"user_ids": ["@alice:example.com"]}
-                        }
-                      ]
-                    }
-                  },
-                  "!696r7674:example.com": {
-                    "invite_state": {
-                      "events": [
-                        {
+                  "joined": {
+                    "!726s6s6q:example.com": {
+                      "event_map": {
+                        "$66697273743031:example.com": {
                           "sender": "@alice:example.com",
-                          "type": "m.room.name",
-                          "state_key": "",
-                          "content": {"name": "My Room Name"}
+                          "type": "m.room.member",
+                          "state_key": "@alice:example.com",
+                          "content": {"membership": "join"},
+                          "origin_server_ts": 1417731086795
                         },
-                        {
-                          "sender": "@alice:example.com",
+                        "$7365636s6r6432:example.com": {
+                          "sender": "@bob:example.com",
                           "type": "m.room.member",
                           "state_key": "@bob:example.com",
-                          "content": {"membership": "invite"}
+                          "content": {"membership": "join"},
+                          "origin_server_ts": 1417731086795
+                        },
+                        "$74686972643033:example.com": {
+                          "sender": "@alice:example.com",
+                          "type": "m.room.message",
+                          "unsigned": {"age": "124524", "txn_id": "1234"},
+                          "content": {
+                            "body": "I am a fish",
+                            "msgtype": "m.text"
+                          },
+                          "origin_server_ts": 1417731086797
                         }
-                      ]
+                      },
+                      "state": {
+                        "events": [
+                          "$66697273743031:example.com",
+                          "$7365636s6r6432:example.com"
+                        ]
+                      },
+                      "timeline": {
+                        "events": [
+                          "$7365636s6r6432:example.com",
+                          "$74686972643033:example.com"
+                        ],
+                        "limited": true,
+                        "prev_batch": "t34-23535_0_0"
+                      },
+                      "ephemeral": {
+                        "events": [
+                          {
+                            "room_id": "!726s6s6q:example.com",
+                            "type": "m.typing",
+                            "content": {"user_ids": ["@alice:example.com"]}
+                          }
+                        ]
+                      }
                     }
-                  }
+                  },
+                  "invited": {
+                    "!696r7674:example.com": {
+                      "invite_state": {
+                        "events": [
+                          {
+                            "sender": "@alice:example.com",
+                            "type": "m.room.name",
+                            "state_key": "",
+                            "content": {"name": "My Room Name"}
+                          },
+                          {
+                            "sender": "@alice:example.com",
+                            "type": "m.room.member",
+                            "state_key": "@bob:example.com",
+                            "content": {"membership": "invite"}
+                          }
+                        ]
+                      }
+                    }
+                  },
+                  "archived": {}
                 }
               }