Artifacts saved in before_agent_callback / after_agent_callback are never recorded in an event (artifact_delta dropped) #7478

import asyncio
from google.adk.agents import BaseAgent
from google.adk.agents.callback_context import CallbackContext
from google.adk.artifacts import InMemoryArtifactService
from google.adk.events import Event
from google.adk.runners import Runner
from google.adk.sessions import InMemorySessionService
from google.genai import types


async def save_report(callback_context: CallbackContext):
  await callback_context.save_artifact(
      "report.txt", types.Part.from_text(text="hello")
  )


class EchoAgent(BaseAgent):
  async def _run_async_impl(self, ctx):
    yield Event(
        author=self.name,
        invocation_id=ctx.invocation_id,
        content=types.Content(role="model", parts=[types.Part(text="done")]),
    )


async def main():
  artifacts = InMemoryArtifactService()
  runner = Runner(
      app_name="app",
      agent=EchoAgent(name="agent", before_agent_callback=save_report),
      session_service=InMemorySessionService(),
      artifact_service=artifacts,
  )
  session = await runner.session_service.create_session(
      app_name="app", user_id="u"
  )
  async for _ in runner.run_async(
      user_id="u",
      session_id=session.id,
      new_message=types.Content(role="user", parts=[types.Part(text="hi")]),
  ):
    pass
  session = await runner.session_service.get_session(
      app_name="app", user_id="u", session_id=session.id
  )
  print("artifact keys:", await artifacts.list_artifact_keys(
      app_name="app", user_id="u", session_id=session.id))
  print("artifact_delta in session events:",
        [e.actions.artifact_delta for e in session.events
         if e.actions.artifact_delta])


asyncio.run(main())