[Core][Diffusion] Camera interaction for diffusion streaming generation (LingBot World 2 as example) (#7198)

Signed-off-by: Huang, Zeyu <11222265+fhfuih@users.noreply.github.com>

tests/entrypoints/openai_api/test_serving_video_output_stream.py

@@ -959,6 +959,76 @@ class TestStreamingVideoOutputPromptUpdate:
             },
         )
 
+    def test_composite_prompt_and_camera_interaction_forwarded(self, mocker: MockerFixture):
+        """Prompt + camera multi_modal_data is admitted and forwarded to the engine."""
+
+        async def mock_generate(*_args, **_kwargs):
+            yield OmniRequestOutput.from_diffusion(
+                request_id="req-ws",
+                images=[_fake_video_frames(2)],
+                final_output_type="image",
+                finished=False,
+            )
+            await asyncio.sleep(0.3)
+            yield OmniRequestOutput.from_diffusion(
+                request_id="req-ws",
+                images=[_fake_video_frames(2)],
+                final_output_type="image",
+                finished=True,
+            )
+
+        app, _handler, engine_client = _build_test_app(
+            mocker=mocker,
+            streaming_chunks=[(b"mp4-chunk-0", False), (b"mp4-chunk-1", True)],
+            mock_generate=mock_generate,
+        )
+
+        camera_payload = {
+            "mode": "target",
+            "data": {"translation": [0.0, 0.0, 1.0]},
+        }
+
+        with TestClient(app) as client:
+            with client.websocket_connect("/v1/realtime/video") as ws:
+                ws.send_json({"type": "session.start", "prompt": "initial scene"})
+                start = ws.receive_json()
+                assert start["type"] == "video.start"
+                request_id = start["request_id"]
+
+                assert _receive_video_chunk(ws)[1] == b"mp4-chunk-0"
+
+                ws.send_json(
+                    {
+                        "type": "session.interaction",
+                        "interaction": {
+                            "event_id": "combo-1",
+                            "event": {
+                                "prompt": "new scene",
+                                "multi_modal_data": {"camera": camera_payload},
+                            },
+                            "transition_chunks": 2,
+                        },
+                    }
+                )
+                queued = ws.receive_json()
+                assert queued["type"] == "session.interaction.queued"
+                assert queued["event_id"] == "combo-1"
+
+                assert _receive_video_chunk(ws)[1] == b"mp4-chunk-1"
+                assert ws.receive_json()["type"] == "session.done"
+
+        engine_client.submit_interaction_async.assert_awaited_once_with(
+            request_id,
+            interaction={
+                "event_id": "combo-1",
+                "event": {
+                    "prompt": "new scene",
+                    "multi_modal_data": {"camera": camera_payload},
+                },
+                "transition_chunks": 2,
+            },
+        )
+
 
 class TestStreamingVideoOutputExtraParams:
     """extra_params handling when building streaming generation inputs."""