fix: Fixes thought handling in contents.py and refactors its unit tests

Before this change, other agent's reply with thought will still be inserted in the outgoing LlmRequest due to the wrong `else` statement for calling all other type of part. This commit also refactors test_contents.py to be behavior-oriented tests, instead of implementation-oriented, and add more test cases to cover expected scenarios. The tests are divided into the following files with different focus: - test_contents.py: covers the basic logic of event filter; - test_contents_branch.py: covers the behavior related to branch, which takes effect when ParallelAgent is used. - test_contents_other_agent.py: covers the retelling behavior to include other agents' reply as context for the current agent. - test_contents_function.py: covers the function_call/function_response rearrangement logic mainly for `LongRunningFunctionTool`. PiperOrigin-RevId: 802759821

Author: Jacksunwei

src/google/adk/agents/remote_a2a_agent.py

@@ -63,8 +63,8 @@
 from ..a2a.logs.log_utils import build_a2a_response_log
 from ..agents.invocation_context import InvocationContext
 from ..events.event import Event
-from ..flows.llm_flows.contents import _convert_foreign_event
 from ..flows.llm_flows.contents import _is_other_agent_reply
+from ..flows.llm_flows.contents import _present_other_agent_message
 from ..flows.llm_flows.functions import find_matching_function_call
 from .base_agent import BaseAgent
 
@@ -338,7 +338,7 @@ def _construct_message_parts_from_session(
  context_id = None
  for event in reversed(ctx.session.events):
  if _is_other_agent_reply(self.name, event):
- event = _convert_foreign_event(event)
+ event = _present_other_agent_message(event)
  elif event.author == self.name:
  # stop on content generated by current a2a agent given it should already
  # be in remote session

src/google/adk/flows/llm_flows/contents.py

@@ -16,7 +16,6 @@
 
 import copy
 from typing import AsyncGenerator
-from typing import Generator
 from typing import Optional
 
 from google.genai import types
@@ -203,6 +202,25 @@ def _rearrange_events_for_latest_function_response(
  return result_events
 
 
+def _contains_empty_content(event: Event) -> bool:
+ """Check if an event should be skipped due to missing or empty content.
+
+ This can happen to the evnets that only changed session state.
+
+ Args:
+ event: The event to check.
+
+ Returns:
+ True if the event should be skipped, False otherwise.
+ """
+ return (
+ not event.content
+ or not event.content.role
+ or not event.content.parts
+ or event.content.parts[0].text == ''
+ )
+
+
 def _get_contents(
  current_branch: Optional[str], events: list[Event], agent_name: str = ''
 ) -> list[types.Content]:
@@ -222,16 +240,7 @@ def _get_contents(
  # Parse the events, leaving the contents and the function calls and
  # responses from the current agent.
  for event in events:
- if (
- not event.content
- or not event.content.role
- or not event.content.parts
- or event.content.parts[0].text == ''
- ):
- # Skip events without content, or generated neither by user nor by model
- # or has empty text.
- # E.g. events purely for mutating session states.
-
+ if _contains_empty_content(event):
  continue
  if not _is_event_belongs_to_branch(current_branch, event):
  # Skip events not belong to current branch.
@@ -242,11 +251,12 @@ def _get_contents(
  if _is_request_confirmation_event(event):
  # Skip request confirmation events.
  continue
- filtered_events.append(
- _convert_foreign_event(event)
- if _is_other_agent_reply(agent_name, event)
- else event
- )
+
+ if _is_other_agent_reply(agent_name, event):
+ if converted_event := _present_other_agent_message(event):
+ filtered_events.append(converted_event)
+ else:
+ filtered_events.append(event)
 
  # Rearrange events for proper function call/response pairing
  result_events = _rearrange_events_for_latest_function_response(
@@ -305,19 +315,18 @@ def _is_other_agent_reply(current_agent_name: str, event: Event) -> bool:
  )
 
 
-def _convert_foreign_event(event: Event) -> Event:
- """Converts an event authored by another agent as a user-content event.
+def _present_other_agent_message(event: Event) -> Optional[Event]:
+ """Presents another agent's message as user context for the current agent.
 
- This is to provide another agent's output as context to the current agent, so
- that current agent can continue to respond, such as summarizing previous
- agent's reply, etc.
+ Reformats the event with role='user' and adds '[agent_name] said:' prefix
+ to provide context without confusion about authorship.
 
  Args:
- event: The event to convert.
+ event: The event from another agent to present as context.
 
  Returns:
- The converted event.
-
+ Event reformatted as user-role context with agent attribution, or None
+ if no meaningful content remains after filtering.
  """
  if not event.content or not event.content.parts:
  return event
@@ -326,8 +335,10 @@ def _convert_foreign_event(event: Event) -> Event:
  content.role = 'user'
  content.parts = [types.Part(text='For context:')]
  for part in event.content.parts:
- # Exclude thoughts from the context.
- if part.text and not part.thought:
+ if part.thought:
+ # Exclude thoughts from the context.
+ continue
+ elif part.text:
  content.parts.append(
  types.Part(text=f'[{event.author}] said: {part.text}')
  )
@@ -354,6 +365,10 @@ def _convert_foreign_event(event: Event) -> Event:
  else:
  content.parts.append(part)
 
+ # If no meaningful parts were added (only "For context:" remains), return None
+ if len(content.parts) == 1:
+ return None
+
  return Event(
  timestamp=event.timestamp,
  author='user',
@@ -429,7 +444,11 @@ def _merge_function_response_events(
 def _is_event_belongs_to_branch(
  invocation_branch: Optional[str], event: Event
 ) -> bool:
- """Event belongs to a branch, when event.branch is prefix of the invocation branch."""
+ """Check if an event belongs to the current branch.
+
+ This is for event context segration between agents. E.g. agent A shouldn't
+ see output of agent B.
+ """
  if not invocation_branch or not event.branch:
  return True
  return invocation_branch.startswith(event.branch)

src/google/adk/flows/llm_flows/functions.py

@@ -65,7 +65,15 @@ def populate_client_function_call_id(model_response_event: Event) -> None:
  function_call.id = generate_client_function_call_id()
 
 
-def remove_client_function_call_id(content: types.Content) -> None:
+def remove_client_function_call_id(content: Optional[types.Content]) -> None:
+ """Removes ADK-generated function call IDs from content before sending to LLM.
+
+ Strips client-side function call/response IDs that start with 'adk-' prefix
+ to avoid sending internal tracking IDs to the model.
+
+ Args:
+ content: Content containing function calls/responses to clean.
+ """
  if content and content.parts:
  for part in content.parts:
  if (

tests/unittests/agents/test_remote_a2a_agent.py

@@ -515,7 +515,7 @@ def test_construct_message_parts_from_session_success(self):
  self.mock_session.events = [mock_event]
 
  with patch(
- "google.adk.agents.remote_a2a_agent._convert_foreign_event"
+ "google.adk.agents.remote_a2a_agent._present_other_agent_message"
  ) as mock_convert:
  mock_convert.return_value = mock_event
 
@@ -937,7 +937,7 @@ async def test_full_workflow_with_direct_agent_card(self):
 
  # Mock dependencies
  with patch(
- "google.adk.agents.remote_a2a_agent._convert_foreign_event"
+ "google.adk.agents.remote_a2a_agent._present_other_agent_message"
  ) as mock_convert:
  mock_convert.return_value = mock_event