fix(web): restore build_graph_image endpoint

Author: MukundaKatta

src/google/adk/cli/adk_web_server.py

@@ -37,6 +37,7 @@
 from fastapi import Response
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import RedirectResponse
+from fastapi.responses import Response
 from fastapi.responses import StreamingResponse
 from fastapi.staticfiles import StaticFiles
 from fastapi.websockets import WebSocket
@@ -1033,6 +1034,24 @@ async def get_trace_dict(event_id: str) -> Any:
 
     if web_assets_dir:
 
+      @app.get("/dev/build_graph_image/{app_name}")
+      async def get_app_graph_image(
+          app_name: str, dark_mode: bool = False
+      ) -> Response:
+        agent_or_app = self.agent_loader.load_agent(app_name)
+        root_agent = self._get_root_agent(agent_or_app)
+
+        graph_image = await agent_graph.get_agent_graph(
+            root_agent, [], image=True, dark_mode=dark_mode
+        )
+
+        if isinstance(graph_image, bytes):
+          return Response(content=graph_image, media_type="image/png")
+
+        raise HTTPException(
+            status_code=500, detail="Failed to render app graph image"
+        )
+
       @app.get("/dev/build_graph/{app_name}")
       async def get_app_info(app_name: str) -> Any:
         runner = await self.get_runner_async(app_name)

tests/unittests/cli/test_fast_api.py

@@ -1769,6 +1769,53 @@ def list_agents(self):
   assert "dotSrc" in response.json()
 
 
+def test_build_graph_image_returns_png_bytes():
+  """Ensure legacy graph-image endpoint still returns a PNG for the dev UI."""
+  from google.adk.cli.adk_web_server import AdkWebServer
+
+  root_agent = DummyAgent(name="dummy_agent")
+  app_agent = App(name="test_app", root_agent=root_agent)
+
+  class Loader:
+
+    def load_agent(self, app_name):
+      return app_agent
+
+    def list_agents(self):
+      return [app_agent.name]
+
+  adk_web_server = AdkWebServer(
+      agent_loader=Loader(),
+      session_service=AsyncMock(),
+      memory_service=MagicMock(),
+      artifact_service=MagicMock(),
+      credential_service=MagicMock(),
+      eval_sets_manager=MagicMock(),
+      eval_set_results_manager=MagicMock(),
+      agents_dir=".",
+  )
+
+  fast_api_app = adk_web_server.get_fast_api_app(
+      setup_observer=lambda _observer, _server: None,
+      tear_down_observer=lambda _observer, _server: None,
+  )
+
+  client = TestClient(fast_api_app)
+
+  with patch(
+      "google.adk.cli.agent_graph.get_agent_graph",
+      new=AsyncMock(return_value=b"png-bytes"),
+  ) as mock_get_agent_graph:
+    response = client.get("/dev/build_graph_image/test_app?dark_mode=true")
+
+  assert response.status_code == 200
+  assert response.content == b"png-bytes"
+  assert response.headers["content-type"] == "image/png"
+  mock_get_agent_graph.assert_awaited_once_with(
+      root_agent, [], image=True, dark_mode=True
+  )
+
+
 def test_a2a_agent_discovery(test_app_with_a2a):
   """Test that A2A agents are properly discovered and configured."""
   # This test mainly verifies that the A2A setup doesn't break the app