Add a v6 event format with correct depth limits (#2114)

* Add a v6 event format with correct `depth` limits

* Changelog

* numbers are hard

data/api/server-server/definitions/components/pdu_base.yaml

@@ -41,13 +41,6 @@ properties:
     type: object
     description: The content of the event.
     example: {"key": "value"}
-  depth:
-    type: integer
-    description: |-
-      The maximum depth of the `prev_events`, plus one. Must be less than the
-      maximum value for an integer (2^63 - 1). If the room's depth is already at
-      the limit, the depth must be set to the limit.
-    example: 12
   hashes:
     $ref: "event_hash.yaml"
   signatures:

data/api/server-server/definitions/pdu_v1.yaml

@@ -28,6 +28,13 @@ allOf:
         type: string
         description: For redaction events, the ID of the event being redacted.
         example: "$def456:matrix.org"
+      depth:
+        type: integer
+        description: |-
+          The maximum depth of the `prev_events`, plus one. Must be less than the
+          maximum value for an integer (2^63 - 1). If the room's depth is already at
+          the limit, the depth must be set to the limit.
+        example: 12
       auth_events:
         type: array
         description: |-

data/api/server-server/definitions/pdu_v11.yaml

@@ -17,6 +17,16 @@ description: A persistent data unit (event) for room version 11 and beyond.
 example:
   $ref: "../examples/pdu_v11.json"
 allOf:
-  # v11 is the v4 event, but without redacts.
+  # v11 is the v6 event, but without redacts.
   - $ref: "components/pdu_base.yaml"
-  - $ref: "components/auth_events_prev_events_v4.yaml"
+  - $ref: "components/auth_events_prev_events_v4.yaml"
+  - type: object
+    properties:
+      # v6 enforces Canonical JSON and therefore needs a depth limit change
+      depth:
+        type: integer
+        description: |-
+          The maximum depth of the `prev_events`, plus one. Must be less than the
+          maximum value for an integer (2^53 - 1). If the room's depth is already at
+          the limit, the depth must be set to the limit.
+        example: 12

data/api/server-server/definitions/pdu_v3.yaml

@@ -24,6 +24,13 @@ allOf:
         type: string
         description: For redaction events, the ID of the event being redacted.
         example: "$def/456+oldevent"
+      depth:
+        type: integer
+        description: |-
+          The maximum depth of the `prev_events`, plus one. Must be less than the
+          maximum value for an integer (2^63 - 1). If the room's depth is already at
+          the limit, the depth must be set to the limit.
+        example: 12
       auth_events:
         type: array
         items:

data/api/server-server/definitions/pdu_v4.yaml

@@ -26,3 +26,10 @@ allOf:
         type: string
         description: For redaction events, the ID of the event being redacted.
         example: "$def_456-oldevent"
+      depth:
+        type: integer
+        description: |-
+          The maximum depth of the `prev_events`, plus one. Must be less than the
+          maximum value for an integer (2^63 - 1). If the room's depth is already at
+          the limit, the depth must be set to the limit.
+        example: 12

data/api/server-server/definitions/pdu_v6.yaml

@@ -0,0 +1,36 @@
+# Copyright 2025 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+type: object
+title: Persistent Data Unit
+description: |-
+  A persistent data unit (event) for room versions 4, 5, 6, 7, 8, 9 and 10.
+example:
+  $ref: "../examples/pdu_v4.json"
+allOf:
+  - $ref: "components/pdu_base.yaml"
+  - $ref: "components/auth_events_prev_events_v4.yaml"
+  - type: object
+    properties:
+      redacts:
+        type: string
+        description: For redaction events, the ID of the event being redacted.
+        example: "$def_456-oldevent"
+      # v6 enforces Canonical JSON and therefore needs a depth limit change
+      depth:
+        type: integer
+        description: |-
+          The maximum depth of the `prev_events`, plus one. Must be less than the
+          maximum value for an integer (2^53 - 1). If the room's depth is already at
+          the limit, the depth must be set to the limit.
+        example: 12