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What happened?

Starting from spec version 1.16, the Matrix protocol has required a new format for federated invites as a security measure. However, months after the agreed implementation deadline^[1], the Synapse homeserver still has yet to implement the new format. Its outgoing invites are now being rejected by conforming homeservers.

Practically, this means federated invites from Synapse to Continuwuity have been broken since mid-July 2026, following Continuwuity's scheduled enforcement of the new validation rules. The core functionality is now unusable between the two most deployed homeserver software implementations, making up the majority of the known public ecosystem.

This website tracks whether Synapse and other homeservers have fixed their invitation mechanisms, in terms of both sending correctly formatted invites and validating received invites. Those who do not update are more vulnerable to various security issues, and will eventually fail to send invites at all as the ecosystem upgrades.

What about other homeservers?

What can I do about this?

If you are a homeserver operator, wait for your homeserver software implementation to fix their invites and upgrade accordingly. You can also urge other homeserver operators you know to upgrade as well. Known in-progress fixes are:

• Synapse PR: element-hq/synapse#19723

If you are a user of a non-conforming homeserver and wish to invite others, you may:

• Urge your homeserver admin to upgrade their software

• Send invites only from a homeserver that conforms to MSC4311 (see table above)

• Make an invite-only room public for a brief moment for the intended invitee to join, then make the room invite-only again

• Spread the word about this issue

Related links

• MSC4311: Ensuring the create event is available on invites - The MSC resulting in the new invite format

• continuwuation/continuwuity#1971 - Continuwuity's issue tracking federated invite failure

Our 88x31 (updated daily)