fix(cli): serialize LiteLlm graph models safely

Author: he-yufeng

src/google/adk/cli/utils/graph_serialization.py

@@ -22,6 +22,7 @@
 logger = logging.getLogger("google_adk." + __name__)
 
 from ...agents.base_agent import BaseAgent
+from ...models.base_llm import BaseLlm
 from ...tools.base_toolset import BaseToolset
 
 # Node type mapping for cleaner lookup
@@ -227,6 +228,10 @@ def serialize_agent(agent: BaseAgent) -> dict[str, Any]:
         # Handle nested agents
         if isinstance(value, BaseAgent):
           agent_dict[field_name] = serialize_agent(value)
+        elif isinstance(value, BaseLlm):
+          agent_dict[field_name] = value.model_dump(
+              mode="python", exclude={"llm_client"}, exclude_none=True
+          )
         # Handle simple types and collections
         elif isinstance(value, (str, int, float, bool, list, dict)):
           agent_dict[field_name] = value

tests/unittests/cli/utils/test_graph_serialization.py

@@ -14,7 +14,11 @@
 
 """Tests for graph_serialization edge handling with routing maps."""
 
+import json
+
+from google.adk.agents import LlmAgent
 from google.adk.cli.utils.graph_serialization import serialize_agent
+from google.adk.models.lite_llm import LiteLlm
 from google.adk.tools.base_toolset import BaseToolset
 from google.adk.workflow import START
 from google.adk.workflow import Workflow
@@ -126,3 +130,15 @@ def __init__(self):
   assert len(result['tools']) == 1
   assert result['tools'][0]['name'] == 'MockToolset'
   assert result['tools'][0]['type'] == 'tool'
+
+
+def test_serialize_agent_with_litellm_model_is_json_safe() -> None:
+  agent = LlmAgent(
+      name='repro',
+      model=LiteLlm(model='ollama_chat/llama3'),
+  )
+
+  result = serialize_agent(agent)
+
+  assert result['model'] == {'model': 'ollama_chat/llama3'}
+  json.dumps(result)