Empty AIMessage in the Supervisor final response

[carlos-banuelos-dj]

Hello world! I hope you can help us.
We've been facing the issue that after calling a subagent and getting its response, the supervisor is responding with an empty message.
All agents are tool calling ReAct agents made with create_react_agent method and we are using gemini-2.0-flash-001 from ChatGoogleGenerativeAI.

Graph definition

supervisor = (
    StateGraph(MessagesState)
    .add_node(
        "supervisor",
        supervisor_agent,
        destinations=("math_agent", "web_search_agent", "news_agent", END),
    )
    .add_node("math_agent", math_agent)
    .add_node(
        "web_search_agent", google_search_node
    )
    .add_node("news_agent", factiva_search_node)  
    .add_edge(START, "supervisor")
    .add_edge("math_agent", "supervisor")
    .add_edge("web_search_agent", "supervisor")
    .add_edge("news_agent", "supervisor")
    .compile()
)

# Python modules
langchain==0.3.26
langchain-google-genai==2.1.6
langchain_google_vertexai==2.0.27
langchain-openai==0.3.25
langchain-tavily==0.2.4
langgraph-api==0.2.85
langgraph-cli==0.3.3
langgraph==0.5.3
pydantic==2.11.7
pydantic-settings==2.10.1

Output example:

Has someone faced some similar issues?

[Shkvarka]

Same issue here. Deployed to bedrock. Tried Nova Pro, Llama, Sonnet models - same result. Tried explicit system instructions to make summary for user - still empty content