fix: #1594 support Azure OpenAI Realtime connection using headers

src/agents/realtime/model.py

@@ -118,6 +118,12 @@ class RealtimeModelConfig(TypedDict):
     the OpenAI Realtime model will use the default OpenAI WebSocket URL.
     """
 
+    headers: NotRequired[dict[str, str]]
+    """The headers to use when connecting. If unset, the model will use a sane default.
+    Note that, when you set this, authorization header won't be set under the hood.
+    e.g., {"api-key": "your api key here"} for Azure OpenAI Realtime WebSocket connections.
+    """
+
     initial_model_settings: NotRequired[RealtimeSessionModelSettings]
     """The initial model settings to use when connecting."""
 

src/agents/realtime/openai_realtime.py

@@ -188,15 +188,23 @@ async def connect(self, options: RealtimeModelConfig) -> None:
         else:
             self._tracing_config = "auto"
 
-        if not api_key:
-            raise UserError("API key is required but was not provided.")
-
         url = options.get("url", f"wss://api.openai.com/v1/realtime?model={self.model}")
 
-        headers = {
-            "Authorization": f"Bearer {api_key}",
-            "OpenAI-Beta": "realtime=v1",
-        }
+        headers: dict[str, str] = {}
+        if options.get("headers") is not None:
+            # For customizing request headers
+            headers.update(options["headers"])
+        else:
+            # OpenAI's Realtime API
+            if not api_key:
+                raise UserError("API key is required but was not provided.")
+
+            headers.update(
+                {
+                    "Authorization": f"Bearer {api_key}",
+                    "OpenAI-Beta": "realtime=v1",
+                }
+            )
         self._websocket = await websockets.connect(
             url,
             user_agent_header=_USER_AGENT,
@@ -490,9 +498,7 @@ async def _handle_ws_event(self, event: dict[str, Any]):
         try:
             if "previous_item_id" in event and event["previous_item_id"] is None:
                 event["previous_item_id"] = ""  # TODO (rm) remove
-            parsed: AllRealtimeServerEvents = self._server_event_type_adapter.validate_python(
-                event
-            )
+            parsed: AllRealtimeServerEvents = self._server_event_type_adapter.validate_python(event)
         except pydantic.ValidationError as e:
             logger.error(f"Failed to validate server event: {event}", exc_info=True)
             await self._emit_event(
@@ -583,11 +589,13 @@ async def _handle_ws_event(self, event: dict[str, Any]):
         ):
             await self._handle_output_item(parsed.item)
         elif parsed.type == "input_audio_buffer.timeout_triggered":
-            await self._emit_event(RealtimeModelInputAudioTimeoutTriggeredEvent(
-                item_id=parsed.item_id,
-                audio_start_ms=parsed.audio_start_ms,
-                audio_end_ms=parsed.audio_end_ms,
-            ))
+            await self._emit_event(
+                RealtimeModelInputAudioTimeoutTriggeredEvent(
+                    item_id=parsed.item_id,
+                    audio_start_ms=parsed.audio_start_ms,
+                    audio_end_ms=parsed.audio_end_ms,
+                )
+            )
 
     def _update_created_session(self, session: OpenAISessionObject) -> None:
         self._created_session = session

tests/realtime/test_openai_realtime.py

@@ -84,8 +84,45 @@ def mock_create_task_func(coro):
 
                 # Verify internal state
                 assert model._websocket == mock_websocket
-                assert model._websocket_task is not None
-                assert model.model == "gpt-4o-realtime-preview"
+        assert model._websocket_task is not None
+        assert model.model == "gpt-4o-realtime-preview"
+
+    @pytest.mark.asyncio
+    async def test_connect_with_custom_headers_overrides_defaults(self, model, mock_websocket):
+        """If custom headers are provided, use them verbatim without adding defaults."""
+        # Even when custom headers are provided, the implementation still requires api_key.
+        config = {
+            "api_key": "unused-because-headers-override",
+            "headers": {"api-key": "azure-key", "x-custom": "1"},
+            "url": "wss://custom.example.com/realtime?model=custom",
+            # Use a valid realtime model name for session.update to validate.
+            "initial_model_settings": {"model_name": "gpt-4o-realtime-preview"},
+        }
+
+        async def async_websocket(*args, **kwargs):
+            return mock_websocket
+
+        with patch("websockets.connect", side_effect=async_websocket) as mock_connect:
+            with patch("asyncio.create_task") as mock_create_task:
+                mock_task = AsyncMock()
+
+                def mock_create_task_func(coro):
+                    coro.close()
+                    return mock_task
+
+                mock_create_task.side_effect = mock_create_task_func
+
+                await model.connect(config)
+
+                # Verify WebSocket connection used the provided URL
+                called_url = mock_connect.call_args[0][0]
+                assert called_url == "wss://custom.example.com/realtime?model=custom"
+
+                # Verify headers are exactly as provided and no defaults were injected
+                headers = mock_connect.call_args.kwargs["additional_headers"]
+                assert headers == {"api-key": "azure-key", "x-custom": "1"}
+                assert "Authorization" not in headers
+                assert "OpenAI-Beta" not in headers
 
     @pytest.mark.asyncio
     async def test_connect_with_callable_api_key(self, model, mock_websocket):