chore: Add a new endpoint to fetch the base agent graph in DOT format

Co-authored-by: Yifan Wang <wanyif@google.com>
PiperOrigin-RevId: 893730378

Author: wyf7107

src/google/adk/cli/adk_web_server.py

@@ -1906,6 +1906,37 @@ async def event_generator():
           media_type="text/event-stream",
       )
 
+    @app.get(
+        "/dev/{app_name}/graph",
+        response_model_exclude_none=True,
+        tags=[TAG_DEBUG],
+    )
+    async def get_app_graph_dot(
+        app_name: str, dark_mode: bool = False
+    ) -> GetEventGraphResult | dict:
+      """Returns the base agent graph in DOT format without any highlights.
+
+      This endpoint allows the frontend to fetch the graph structure once
+      and compute highlights client-side for better performance.
+
+      Args:
+        app_name: The name of the agent/app
+        dark_mode: Whether to use dark theme background color
+      """
+      agent_or_app = self.agent_loader.load_agent(app_name)
+      root_agent = self._get_root_agent(agent_or_app)
+
+      # Get graph with NO highlights (empty list) and specified theme
+      dot_graph = await agent_graph.get_agent_graph(
+          root_agent, [], dark_mode=dark_mode
+      )
+
+      if dot_graph and isinstance(dot_graph, graphviz.Digraph):
+        return GetEventGraphResult(dot_src=dot_graph.source)
+      else:
+        return {}
+
+    # TODO: This endpoint can be removed once we update adk web to stop consuming it
     @app.get(
         "/apps/{app_name}/users/{user_id}/sessions/{session_id}/events/{event_id}/graph",
         response_model_exclude_none=True,

src/google/adk/cli/agent_graph.py

@@ -282,9 +282,12 @@ def draw_edge(from_name, to_name):
       draw_edge(agent.name, get_node_name(tool))
 
 
-async def get_agent_graph(root_agent, highlights_pairs, image=False):
+async def get_agent_graph(
+    root_agent, highlights_pairs, image=False, dark_mode=True
+):
+  bg_color = '#333537' if dark_mode else '#ffffff'
   graph = graphviz.Digraph(
-      graph_attr={'rankdir': 'LR', 'bgcolor': '#333537'}, strict=True
+      graph_attr={'rankdir': 'LR', 'bgcolor': bg_color}, strict=True
   )
   await build_graph(graph, root_agent, highlights_pairs)
   if image: