FunctionNode events invisible in BigQueryAgentAnalyticsPlugin in graph workflow adk 2

[wdai-chwy]

🔴 Required Information

Describe the Bug:

FunctionNodes in an ADK 2 graph Workflow are invisible to BigQueryAgentAnalyticsPlugin. A workflow made of function nodes produces BigQuery rows for the invocation and for any Agent nodes, but not a single row that identifies a function node or carries its result.

Two independent causes, both narrow:

1. NodeRunner never dispatches plugin callbacks. rg plugin_manager src/google/adk/workflow/ returns zero matches across all 29 files. Agent nodes are covered only incidentally, because _llm_agent_wrapper.py:325 calls agent.run_async(ic) and the callbacks fire from inside BaseAgent. FunctionNode._run_impl has no equivalent path, so before_agent_callback / after_agent_callback / the tool callbacks never fire for it.

2. BigQueryAgentAnalyticsPlugin.on_event_callback ignores Event.output. Function-node events carry their payload in Event.output with Event.content unset (_base_node.py:179, Event(output=validated)). Every content path in on_event_callback reads event.content or event.actions; rg 'event\.output' src/google/adk/plugins/bigquery_agent_analytics_plugin.py returns zero matches. So the one hook that does fire for function nodes discards their payload.

The net effect is that a node emits an event, the plugin receives it, and nothing is written.

Steps to Reproduce:

1. pip install google-adk==2.3.0
2. Run the script under Minimal Reproduction Code below. It needs no GCP access — _log_event is stubbed to record the event_type of each row the plugin would write.
3. Compare the recorded rows against the two nodes that ran.

Expected Behavior:

A two-node workflow should produce BigQuery rows that identify step_one and step_two and carry their outputs, comparable to the AGENT_STARTING / AGENT_COMPLETED coverage an Agent node gets.

Observed Behavior:

agent/tool callbacks fired: NONE

on_event_callback saw:
  path='repro_wf@1/step_one@1'    output=True  content=False
  path='repro_wf@1/step_two@1'    output=True  content=False

BigQuery rows the plugin would write: ['USER_MESSAGE_RECEIVED', 'INVOCATION_STARTING', 'INVOCATION_COMPLETED']

Three rows, none referencing either node. The events reach on_event_callback with correct node_info.path, so the identity information is present and simply unused.

In a real workflow the only node-derived rows are incidental STATE_DELTA entries from nodes that happen to write ctx.state — nodes that only return a value are entirely absent.

Environment Details:

• ADK Library Version: google-adk==2.3.0 (also verified against main @ 27548e39)
• Desktop OS: macOS 15 (darwin 24.6.0)
• Python Version: 3.13

Model Information:

• Are you using LiteLLM: No
• Which model is being used: N/A — the repro contains no LLM call