matrix-spec/content/client-server-api/modules/room_upgrades.md
Travis Ralston f97d2944ae
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Room version 12 (#2193)
* Placeholder

* i++

* Room version 12

Template out a v12 room version

Make v12 default, per MSC4304

Update PDU checks and auth event selection per MSC4291

Describe new room_id format per MSC4291

Move v6 depth definition to a component for easier referencing

Move room_id to a component to prep for v12, per MSC4291

Create and use a new room_id component for v12+ per MSC4291

Reflect auth events selection change onto all room versions per MSC4291

The MSC asks the `description` of `auth_events` to be adjusted, however this feels like a better representation of the change.

Add `room_id` format rules and renumber per MSC4291

Reflect change to rule 1.2 per MSC4291

Insert same room_id check to v1-12 auth rules per MSC4307 and MSC4291

Deprecate `predecessor.event_id` per MSC4291

Insert auth rule to validate `additional_creators` per MSC4289

Insert rule for `users` validation of creators and renumber per MSC4289

Define "room creator(s)" per MSC4289

Spec `additional_creators` on create events per MSC4289

Spec `additional_creators` on `/upgrade` per MSC4289

The MSC doesn't mention how to handle unsupported room versions, but the Synapse implementation used for FCP ignores the field in such room versions. This feels like a good approach, and will need clarifying in the MSC too (if accepted at the spec level).

Add notes to `/upgrade` behaviour per MSC4289 and MSC4291

Describe how additional creators work during room creation per MSC4289

Fix default user power level descriptions per MSC4289

Describe tombstone power level changes per MSC4289

Warn clients about event format changes in v12 per MSC4289 and MSC4291

Flag additional room creators support for client reference per MSC4289

Remove TODO now that it's fully addressed

Copy state res into v12 as-is for modification

Apply Modification 1 to SR2.1 per MSC4297

Apply Modification 2 to SR2.1 per MSC4297

Add summary box to the top of SR2.1 for ease of developer reference

Modification 2 was split into items 2 and 3 for further ease of understanding.

Add all the changelogs

`x` is used until a real PR number can be assigned.

Some changelogs are duplicated to the Client-Server API to increase visibility of the changes to v12.

Review: Minor phrasing adjustments in changelogs

Review: Clarify that v12 isn't quite the default yet in the changelog

Review: Clarify to clients that creators are immutable

Review: Improve 'how to parse a domain' advice for legacy apps

Review: Add a bit more detail as to why a room ID might be required

Apply suggestions from code review

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

Clarify that clients can override the tombstone default

Mention creatorship UI label by finishing the Permissions section

We probably should have removed the WIP note in v1.0, but alas.

Add changelog for tombstone changes

Use assigned spec PR number in changelogs

(cherry picked from commit ec81eea7e4532fd398b8013071d6981c97117d9e)
2025-08-14 11:16:00 -06:00

3.2 KiB

Room Upgrades

From time to time, a room may need to be upgraded to a different room version for a variety of reasons. This module defines a way for rooms to upgrade to a different room version when needed.

Events

{{% event event="m.room.tombstone" %}}

Client behaviour

Clients which understand m.room.tombstone events and the predecessor field on m.room.create events should communicate to the user that the room was upgraded. One way of accomplishing this would be hiding the old room from the user's room list and showing banners linking between the old and new room - ensuring that permalinks work when referencing the old room. Another approach may be to virtually merge the rooms such that the old room's timeline seamlessly continues into the new timeline without the user having to jump between the rooms.

{{% http-api spec="client-server" api="room_upgrades" %}}

Server behaviour

When the client requests to upgrade a known room to a known version, the server:

  1. Checks that the user has permission to send m.room.tombstone events in the room.

  2. {{% changed-in v="1.4" %}} Creates a replacement room with a m.room.create event containing a predecessor field, the applicable room_version, and a type field which is copied from the predecessor room. If no type is set on the previous room, no type is specified on the new room's create event either.

{{% boxes/note %}} {{% added-in v="1.16" %}} If both the new and old room version support additional creators, the server will not transfer those additional creators automatically. They must be explicitly set during the /upgrade call. {{% /boxes/note %}}

{{% boxes/note %}} {{% added-in v="1.16" %}} When upgrading to room version 12 or later, the predecessor field MAY NOT contain an event_id. {{% /boxes/note %}}

  1. Replicates transferable state events to the new room. The exact details for what is transferred is left as an implementation detail, however the recommended state events to transfer are:

    • m.room.server_acl
    • m.room.encryption
    • m.room.name
    • m.room.avatar
    • m.room.topic
    • m.room.guest_access
    • m.room.history_visibility
    • m.room.join_rules
    • m.room.power_levels

    Membership events should not be transferred to the new room due to technical limitations of servers not being able to impersonate people from other homeservers. Additionally, servers should not transfer state events which are sensitive to who sent them, such as events outside of the Matrix namespace where clients may rely on the sender to match certain criteria.

  2. Moves any local aliases to the new room.

  3. Sends a m.room.tombstone event to the old room to indicate that it is not intended to be used any further.

  4. If possible, the power levels in the old room should also be modified to prevent sending of events and inviting new users. For example, setting events_default and invite to the greater of 50 and users_default + 1.

When a user joins the new room, the server should automatically transfer/replicate some of the user's personalized settings such as notifications, tags, etc.