why we get this content "{"role": "model", "parts": []}" in events table

[caichuanwang]

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Describe the bug
sometimes, we got this json data in filed 'content' in events table. Is this a error or result?

To Reproduce
Please share a minimal code and data to reproduce your problem.
Steps to reproduce the behavior:
It happens sporadically; I can't reproduce it.

Expected behavior
It is sporadic; once it occurs, the entire agent stops running.
The parts is empty list, and I do not know how to deal with it ? It means the running agent is finished or error?

Screenshots

Desktop (please complete the following information):

• OS: linux
• Python version(python -V): 3.12
• ADK version(pip show google-adk):1.14.0

Model Information:

• Are you using LiteLLM: Yes
• Which model is being used: gemini-2.5-flash

Additional context
Add any other context about the problem here.

[adk-bot]

Response from ADK Answering Agent (experimental, answer may be inaccurate)

TLDR: The {"role": "model", "parts": []} content is a valid, though empty, response from the model. Your agent is likely crashing because your code is trying to access an element from the empty parts list without checking if the list is empty first. You should add a check to your event handling logic to ensure parts is not empty before accessing its elements.

---

Hello! Thank you for reaching out.

This is a great question. The behavior you're observing, where you receive {"role": "model", "parts": []} in the events table, is not an error but a valid, albeit empty, response from the model. This can occur for several reasons, such as the model's safety filters being triggered or the model having no output for a particular turn in the conversation.

The reason your agent stops running is likely due to an IndexError in your code. Many event processing examples involve directly accessing the first part of the content, like event.content.parts[0]. If the parts list is empty, this will cause a crash.

To fix this, you should make your event handling code more robust by checking if the parts list is populated before trying to access its elements.

Here is an example of how you can safely handle the event content:

# Assuming 'event' is an object you've retrieved
if event.content and event.content.parts:
    # Now it's safe to access elements from the parts list
    # For example, to get the text from the first part:
    text = event.content.parts[0].text
    print(f"Received text: {text}")
else:
    # Handle the case where the model returned an empty response
    print("Received an event with empty parts. Skipping.")

By adding this check, your agent will be able to handle these empty responses gracefully without crashing.

For more details on working with events in the ADK, you can refer to the official documentation on events. [1]

[1] https://google.github.io/adk-docs/events/