built-in google_search tool missing grounding chunks in grounding_metadata

[Isaac-the-Man]

Describe the bug
I expected my agent that uses the built-in google_search tool to populate llm_response.grounding_metadata.grounding_chunks and llm_response.grounding_metadata.grounding_supports, but both fields returns None even though both llm_response.grounding_metadata.searchEntryPoint and llm_response.grounding_metadata.webSearchQueries are populated.

To Reproduce

agent definition:

from google.adk.agents import LlmAgent
from google.adk.tools import google_search


root_agent = LlmAgent(
    name="ic_segment_research_agent",
    description="An agent that researches related IC components for a given application using web search.",
    model="gemini-2.5-flash",
    instruction=f"""
You are an expert in IC research in the semiconductor industry.
You will be provided with a electronic component or product. Your task is to research and identify the key IC components within that application using the provided tools.

**Guidelines**:
- You *MUST* and *ONLY* use the provided google search tools to gather information.
- Identify the top IC components and their respective descriptions.
- If possible, provide the top 5 - 6 most important IC components.
- For each IC component, provide a brief description and relevant keywords.
- Relevant keywords should be terms that are commonly associated with or used to search for the IC component, such as concrete examples of IC models, technologies, or applications.
- *ONLY* output the results in the specified JSON format, avoid any additional commentary or explanation.
    """,
    tools=[google_search],
    include_contents="none",
    output_key="ic_segment_research",
)

Expected behavior
Both grounding_chunks and grounding_supports to be populated when the built-in google_search tools is used.

Screenshots

Desktop (please complete the following information):

• OS: macOS
• Python: 3.12
• ADK Version: 1.17.0

Model Information:

• tested on both gemini-2.5-flash and gemini-2.0-flash, both yields the same result.

[groovili]

I'd like to take a look at this bug