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proposals/3417-call-room-type.md

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+# MSC3417 Call room room type
+
+[MSC3401](https://github.com/matrix-org/matrix-doc/pull/3401) defines how native
+Matrix group calls can work. It allows for immersive voice/video/call rooms.
+[MSC1772](https://github.com/matrix-org/matrix-doc/pull/1772) is a proposal for
+Matrix spaces. A part of this proposal is a way to specify a room type.
+
+We should use the `type` field in the `m.room.create` state event to inform
+clients about the fact a room is a call room.
+
+## Proposal
+
+This MSC proposes that when creating a call room the `type` field in the
+`m.room.create` state event should be set to `m.call`. This way clients can
+clearly distinguish between regular chat rooms and call rooms.
+
+In the case of the `m.intent` field in MSC3401's `m.call` state event getting out of
+sync with the the `type` field in the `m.room.create` state event, the
+information from the `m.room.create` state event is used instead.
+
+### Example
+
+```HTTP
+POST /_matrix/client/r0/createRoom
+{
+    "preset": "private_chat",
+    "name": "The Grand Duke Pub",
+    "topic": "All about happy hour",
+    "creation_content": {
+        "m.federate": false,
+        "type": "m.call",
+    }
+}
+```
+
+## Potential issues
+
+The `m.intent` field in the `m.call` state event could get out of sync with the
+value of `type` in the `m.room.create` state event.
+
+## Alternatives
+
+### Using the `m.call` state event
+
+Clients could look for the `m.call` state event and its `m.intent` field though
+this feels weird as the room type feels like the place where we should put this.
+It also is mutable which isn't ideal (see next section).
+
+### Using the `m.room.type` state event
+
+[MSC1840](https://github.com/matrix-org/matrix-doc/pull/1840) proposes a
+different way to give rooms types. While we could use the `m.room.type` state
+event, it is mutable which we'd like to avoid in the case of call rooms. Clients
+supporting call rooms will present the chat in those rooms as secondary or not
+present it at all, so it is beneficial for this to be immutable so that the chat
+history isn't "lost" when changing the room type.
+
+## Additional notes
+
+[MSC3088](https://github.com/matrix-org/matrix-doc/pull/3088) proposes a way for
+room subtyping, this could be used in the future for things such as stage rooms,
+though that isn't the focus of this MSC.
+
+## Unstable prefix
+
+|Stable  |Unstable                 |
+|--------|-------------------------|
+|`m.call`|`org.matrix.msc3417.call`|