BUG: AG-UI-ADK middle ware. `ValueError: Both invocation_id and new_message are None` when message_batch is None

[minhquan23102000]

---

Environment

• Package: ag_ui_adk
• ADK: google.adk
• Python: 3.12

---

Bug Description

runner.run_async() raises ValueError when both invocation_id and new_message are None. This occurs intermittently when there's no message_batch and no user messages to process.

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Error Log

Background execution error: Both invocation_id and new_message are None.

Traceback (most recent call last):
  File "...\ag_ui_adk\adk_agent.py", line 1232, in _run_adk_in_background
    async for adk_event in runner.run_async(**run_kwargs):
  File "...\google\adk\runners.py", line 443, in run_async
    async for event in agen:
  File "...\google\adk\runners.py", line 382, in _run_with_trace
    raise ValueError('Both invocation_id and new_message are None.')
ValueError: Both invocation_id and new_message are None.

---

Root Cause

In adk_agent.py → _run_adk_in_background:

# Line 1080
user_message = await self._convert_latest_message(input, unseen_messages) if message_batch else None

# Line 1186-1188 (else branch)
else:
    new_message = user_message  # Can be None

# Line 1225-1232
run_kwargs = {
    "user_id": user_id,
    "session_id": input.thread_id,
    "new_message": new_message,  # None
    "run_config": run_config
    # invocation_id is NOT included
}
async for adk_event in runner.run_async(**run_kwargs):  # Raises error

Condition:

1. message_batch = None → user_message = None
2. active_tool_results = None or empty
3. Falls to else branch → new_message = None
4. invocation_id not in run_kwargs
5. ADK receives both as None → raises error

---

Suggested Fix

Add validation before calling runner.run_async():

# Before line 1225
if new_message is None:
    logger.warning(
        f"No new_message to process for thread {input.thread_id}, skipping ADK execution"
    )
    await event_queue.put(None)  # Signal completion
    return

---

Affected File

ag_ui_adk/adk_agent.py ~ line 1225

---

[minhquan23102000]

FYI: @brandonmcconnell

[contextablemark]

Also reported in #712 (see screenshot in comments)

[xomanova]

I think this might also be the same issue in #734 and the comments in #712
In my case it was likely caused by thinking events from google adk llm
As a workaround I added a wrapper around TextMessageContentEvent to deal with delta=='' situations which were valid events.

class SafeTextMessageContentEvent(TextMessageContentEvent):
    def __init__(self, **data):
        if data.get('delta', '') == '':
            data['delta'] = '\u200B'  # Pass validation with invisible char
            super().__init__(**data)
            self._is_empty_delta = True
        else:
            super().__init__(**data)
            self._is_empty_delta = False

ag_ui_adk.event_translator.TextMessageContentEvent = SafeTextMessageContentEvent

So combined_text being empty here fails validation

ag-ui/integrations/adk-middleware/python/src/ag_ui_adk/event_translator.py

Line 350 in d10ebc0

delta=combined_text,

Potential fix

if not combined_text:
  return # No text events without text :)

[contextablemark]

Should be addressed by the merging of #745