🐛(backend) fix regression in update-participant endpoint

Serialization hardening introduced a breaking change between the
frontend and backend. Adjust the Pydantic model to restore
compatibility.

Reinstate support for can_subscribe_metric, which is passed by
default from the frontend.

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to
 ### Fixed
 
 - 🔒️(backend) fix email disclosure in room invitation endpoint #1200
+- 🐛(backend) fix regression in update-participant endpoint #1204
 
 ## [1.12.0] - 2026-03-24
 

src/backend/core/api/serializers.py

@@ -303,6 +303,9 @@ class MuteParticipantSerializer(BaseParticipantsManagementSerializer):
     )
 
 
+TrackSource = Literal["SCREEN_SHARE", "SCREEN_SHARE_AUDIO", "CAMERA", "MICROPHONE"]
+
+
 class ParticipantPermission(BaseModel):
     """Mirror the LiveKit ParticipantPermission protobuf.
 
@@ -313,9 +316,7 @@ class ParticipantPermission(BaseModel):
     can_subscribe: bool | None = None
     can_publish: bool | None = None
     can_publish_data: bool | None = None
-    can_publish_sources: list[int] = Field(
-        default_factory=list
-    )  # TrackSource enum values
+    can_publish_sources: list[TrackSource] = Field(default_factory=list)
     hidden: bool | None = None
     recorder: bool | None = None
     can_update_metadata: bool | None = None
@@ -366,14 +367,6 @@ class UpdateParticipantSerializer(BaseParticipantsManagementSerializer):
                 f"Setting the following participant permissions is not allowed: "
                 f"{', '.join(suspicious_fields)}."
             )
-        if permission.can_subscribe_metrics is not None:
-            raise serializers.ValidationError(
-                {
-                    "permission": {
-                        "can_subscribe_metrics": "This permission is not implemented."
-                    }
-                }
-            )
 
         return permission
 

src/backend/core/tests/rooms/test_api_rooms_participants_management.py

@@ -130,10 +130,11 @@ def test_update_participant_success(mock_livekit_client):
             "can_publish": True,
             "can_publish_data": True,
             "can_publish_sources": [
-                1,
-                2,
-            ],  # [TrackSource.CAMERA, TrackSource.MICROPHONE]
+                "CAMERA",
+                "MICROPHONE",
+            ],
             "can_update_metadata": True,
+            "can_subscribe_metrics": True,
         },
         "name": "John Doe",
     }
@@ -155,8 +156,14 @@ def test_update_participant_success(mock_livekit_client):
         {"can_subscribe": True},
         {"can_publish": True},
         {"can_publish_data": True},
-        {"can_publish_sources": [1, 2]},
+        {
+            "can_publish_sources": [
+                "CAMERA",
+                "MICROPHONE",
+            ]
+        },
         {"can_update_metadata": True},
+        {"can_subscribe_metrics": False},
     ],
 )
 def test_update_participant_permission_fields_are_optional(
@@ -264,35 +271,6 @@ def test_update_participant_suspicious_permission_multiple(mock_suspicious):
     )
 
 
-@pytest.mark.parametrize("value", (False, True))
-def test_update_participant_unimplemented_can_subscribe_metrics(value):
-    """Test update participant raises 400 when can_subscribe_metrics is set."""
-    client = APIClient()
-    room = RoomFactory()
-    user = UserFactory()
-    UserResourceAccessFactory(
-        resource=room, user=user, role=random.choice(["administrator", "owner"])
-    )
-    client.force_authenticate(user=user)
-
-    payload = {
-        "participant_identity": str(uuid4()),
-        "permission": {
-            "can_subscribe": True,
-            "can_publish": True,
-            "can_publish_data": True,
-            "can_update_metadata": False,
-            "can_subscribe_metrics": value,
-        },
-    }
-
-    url = reverse("rooms-update-participant", kwargs={"pk": room.id})
-    response = client.post(url, payload, format="json")
-
-    assert response.status_code == status.HTTP_400_BAD_REQUEST
-    assert "can_subscribe_metrics" in str(response.data)
-
-
 def test_update_participant_forbidden_without_access():
     """Test update participant returns 403 when user lacks room privileges."""
     client = APIClient()