fix: Prevent agent_graph.py throwing when workflow agent is root agent

Jacksunwei · copybara-github · commit 4b1c218cbe69 · 2025-06-05T12:15:14.000-07:00
Partial fix for google#1170 TODOs: - UI rendering still has issue to match the event with the correct agent. - graph building needs further fix when there is a workflow agent in the tree. PiperOrigin-RevId: 767711701
diff --git a/src/google/adk/cli/agent_graph.py b/src/google/adk/cli/agent_graph.py
@@ -145,7 +145,7 @@ def should_build_agent_cluster(tool_or_agent: Union[BaseAgent, BaseTool]):
       return False
 
   def build_cluster(child: graphviz.Digraph, agent: BaseAgent, name: str):
-    if isinstance(agent, LoopAgent):
+    if isinstance(agent, LoopAgent) and parent_agent:
       # Draw the edge from the parent agent to the first sub-agent
       draw_edge(parent_agent.name, agent.sub_agents[0].name)
       length = len(agent.sub_agents)
@@ -162,7 +162,7 @@ def build_cluster(child: graphviz.Digraph, agent: BaseAgent, name: str):
             ].name,
         )
         currLength += 1
-    elif isinstance(agent, SequentialAgent):
+    elif isinstance(agent, SequentialAgent) and parent_agent:
       # Draw the edge from the parent agent to the first sub-agent
       draw_edge(parent_agent.name, agent.sub_agents[0].name)
       length = len(agent.sub_agents)
@@ -179,7 +179,7 @@ def build_cluster(child: graphviz.Digraph, agent: BaseAgent, name: str):
         ) if currLength != length - 1 else None
         currLength += 1
 
-    elif isinstance(agent, ParallelAgent):
+    elif isinstance(agent, ParallelAgent) and parent_agent:
       # Draw the edge from the parent agent to every sub-agent
       for sub_agent in agent.sub_agents:
         build_graph(child, sub_agent, highlight_pairs)
