matrix-spec-proposals/proposals/3589-v9-default-version.md

MSC3589: Room version 9 as a default

Enough time has passed to allow the public federation to upgrade their servers to support room version 9, though with some caveats (see "potential issues"). This proposal aims to make v9 the default room version.

Proposal

The specification adopts v9 as the suggested default room version, making no changes to the stability of any room versions. As of writing, v6 is currently the suggested room version.

Room version 9 is currently published here: https://spec.matrix.org/v1.2/rooms/v9/

Potential issues

Servers will be encouraged to update their config/internal defaults to use v9 instead of v6. This is considered a good problem to have.

Note that servers are not required to honour the default room version due to it being a suggestion in the specification, however they might fall behind as other servers set their defaults accordingly.

Some server implementations, like Synapse, support configurable default room versions: servers which have set this flag will not necessarily be affected by this change.

As of writing (Jan 26, 2022), some prominent server implementations are only just getting support for the room version. Namely, Dendrite released a version with support about 2 months ago and Conduit is working on including Ruma's changes which landed also about 2 months ago.

Though both Dendrite and Conduit (meaning Ruma) have not had the same amount of time as Synapse to reach maturity on v9-capable versions, both the Dendrite and Conduit communities appear to update to newer versions much more quickly. This implies, without statistics to back it up, that nearly all Dendrite servers out there will have upgraded and that a similar percentage of Conduit servers will upgrade once available.

No major issues appear to be reported to Synapse or Dendrite with respect to v9, however Conduit has reported that the auth rules for v9 might not be perfect. All of this indicates to the author that the implementation is at least sane and accomplishable, even if a bit difficult to incorporate.

For completeness, some links:

Dendrite:

• Tracking issue: https://github.com/matrix-org/dendrite/issues/2010
• Library support: https://github.com/matrix-org/gomatrixserverlib/pull/279
• Release: b4a007ecce
• Testing: https://github.com/matrix-org/complement/pull/220

Conduit:

• Tracking issue: https://gitlab.com/famedly/conduit/-/issues/161
• Library support: https://github.com/ruma/ruma/pull/771
• Release: N/A
• Testing: N/A

Alternatives

None relevant.

Security considerations

None relevant.

Unstable prefix

None relevant - servers can already choose a different default room version legally. This MSC just formalizes v9 as the default.