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proposals/3389-relation-redactions.md

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+# MSC3389: Redaction changes for events with a relation
+
+[MSC2674](https://github.com/matrix-org/matrix-doc/pull/2674) defines a
+standard shape for indicating events which relate to other events.
+
+When redacting events relating to other events, some information needs to be
+preserved for the best user experience. Given that this will require
+a room version change, it was split up into a separate MSC here.
+
+## Proposal
+
+Events with a relation may be redacted like any other event.
+
+The `m.relates_to`.`rel_type` and `m.relates_to`.`event_id` fields should
+be preserved over redactions, so that clients can still distinguish
+redacted relations from other redacted events of the same event type.
+If `m.relates_to` is not an object, or `m.relates_to` would be
+an empty object after redacting any other keys, then `m.relates_to`
+should also be removed from `content`.
+
+One example is telling redacted edits (as proposed in
+[MSC 2676](https://github.com/matrix-org/matrix-doc/pull/2676)) apart from
+from normal redacted messages, and maintain reply ordering.
+
+This modification to the redaction algorithm requires a new room version.
+However, event relationships can still be used in existing room versions, but
+the user experience may be worse if redactions are performed.