fix: preserve root task input across clarification turns

src/google/adk/flows/llm_flows/context/_contents.py

@@ -335,6 +335,21 @@ def _build_task_input_user_content(
           parts.append(types.Part(text=_SINGLE_TURN_NUDGE))
         return types.Content(role='user', parts=parts)
 
+  if '@' in isolation_scope and '/' not in isolation_scope:
+    invocation_id = isolation_scope.rpartition('@')[2]
+    for event in all_events:
+      if (
+          event.invocation_id == invocation_id
+          and event.author == 'user'
+          and event.content
+          and event.content.parts
+          and not any(p.function_response for p in event.content.parts)
+      ):
+        parts = list(event.content.parts)
+        if is_single_turn:
+          parts.append(types.Part(text=_SINGLE_TURN_NUDGE))
+        return types.Content(role='user', parts=parts)
+
   # Fallback: workflow-node task with no originating FC.  Use the
   # node_input that the wrapper stamped onto ``ic.user_content``.
   if user_content and user_content.parts:

src/google/adk/workflow/_dynamic_node_scheduler.py

@@ -348,7 +348,10 @@ async def _execute_step(
         override_isolation_scope is None
         and getattr(node, 'mode', None) == AgentMode.TASK
     ):
-      override_isolation_scope = node_path
+      if not curr_parent_path:
+        override_isolation_scope = f'{target_node_name}@{ctx.invocation_id}'
+      else:
+        override_isolation_scope = node_path
 
     # Rehydration chronological sequence barrier setup for the parent path
     if self._enable_replay and curr_parent_path:

tests/unittests/a2a/integration/test_client_server_v1.py

@@ -37,6 +37,7 @@
 
 from .client import create_a2a_client
 from .client import create_client
+from .server import agent_card
 from .server import create_server_app_v1
 
 
@@ -847,3 +848,91 @@ def _status_update(text: str, state: int) -> pb.StreamResponse:
   # the latest status is applied to the running task.
   final_task, _ = results[2]
   assert final_task.status.state == pb.TASK_STATE_COMPLETED
+
+
+@pytest.mark.asyncio
+async def test_a2a_task_clarification_and_resumption():
+  """Tests that root task input preservation works across the A2A boundary.
+
+  When a RemoteA2aAgent operates in mode="task", it acts as a sub-agent on the
+  client, but runs as a root agent on the server. The server-side Runner must
+  successfully associate the clarification turn with the paused task's scope
+  and reconstruct the strictly-alternating task history correctly.
+  """
+  from google.adk.agents.llm_agent import LlmAgent
+  from tests.unittests import testing_utils
+
+  model = testing_utils.MockModel.create(
+      responses=[
+          "What is your specific question?",
+          "Task completed.",
+      ]
+  )
+  server_agent = LlmAgent(name="my_task", model=model, mode="task")
+
+  from google.adk.runners import Runner
+  from google.adk.a2a.executor.a2a_agent_executor import A2aAgentExecutor
+  from google.adk.a2a import _compat
+  from starlette.applications import Starlette
+  from a2a.server.tasks import InMemoryTaskStore as TaskStore
+
+  server_runner = Runner(
+      app_name="ServerApp",
+      agent=server_agent,
+      session_service=InMemorySessionService(),
+  )
+  executor = A2aAgentExecutor(runner=server_runner)
+  app = Starlette()
+  _compat.attach_a2a_routes_to_app(
+      app,
+      agent_card=agent_card,
+      agent_executor=executor,
+      task_store=TaskStore(),
+  )
+
+  async with app.router.lifespan_context(app):
+    client_agent = create_client(app, streaming=False, mode="task")
+
+    session_service = InMemorySessionService()
+    await session_service.create_session(
+        app_name="ClientApp", user_id="test_user", session_id="test_session"
+    )
+    client_runner = Runner(
+        app_name="ClientApp",
+        agent=client_agent,
+        session_service=session_service,
+    )
+
+    # Turn 1: Initial task request
+    new_message = types.Content(
+        parts=[types.Part(text="Do a task")], role="user"
+    )
+    async for _ in client_runner.run_async(
+        user_id="test_user", session_id="test_session", new_message=new_message
+    ):
+      pass
+
+    # Turn 2: Clarification response
+    new_message2 = types.Content(
+        parts=[types.Part(text="Here is the clarification")], role="user"
+    )
+    async for _ in client_runner.run_async(
+        user_id="test_user", session_id="test_session", new_message=new_message2
+    ):
+      pass
+
+  # Verify server-side model requests to ensure correct history reconstruction
+  assert len(model.requests) == 2
+
+  req1 = model.requests[0]
+  parts1 = [p.text for c in req1.contents if c.role == "user" for p in c.parts]
+  assert "Do a task" in parts1[0]
+  # Check strict alternation on Turn 1
+  assert [c.role for c in req1.contents] == ["user"]
+
+  req2 = model.requests[1]
+  parts2 = [p.text for c in req2.contents if c.role == "user" for p in c.parts]
+  assert "Do a task" in parts2[0]
+  assert "Here is the clarification" in parts2[1]
+  # Check strict alternation on Turn 2
+  assert [c.role for c in req2.contents] == ["user", "model", "user"]

tests/unittests/flows/llm_flows/context/test_contents.py

@@ -2347,6 +2347,46 @@ def test_task_input_user_content_preserves_non_ascii():
   assert "\\u" not in text
 
 
+def test_task_input_user_content_nested_scope_does_not_match_root_reconstruction():
+  """Nested workflow scopes (e.g. wf@1/node@2) must not enter root-task reconstruction."""
+  events = [
+      Event(
+          invocation_id="2",
+          author="user",
+          content=types.UserContent("unrelated user message from invocation 2"),
+      ),
+  ]
+  fallback_content = types.UserContent("node input content")
+
+  # Nested scope contains '@' and '/'
+  content = contents._build_task_input_user_content(  # pylint: disable=protected-access
+      events,
+      isolation_scope="wf@1/node@2",
+      user_content=fallback_content,
+  )
+
+  # Must fall back to user_content and not match invocation_id="2"
+  assert content is not None and content.parts
+  assert content.parts[0].text == "node input content"
+
+
+def test_task_input_user_content_root_scope_matches_invocation():
+  """Root task scopes (e.g. task@inv1) extract user content matching invocation_id."""
+  events = [
+      Event(
+          invocation_id="inv1",
+          author="user",
+          content=types.UserContent("root task prompt"),
+      ),
+  ]
+  content = contents._build_task_input_user_content(  # pylint: disable=protected-access
+      events,
+      isolation_scope="task@inv1",
+  )
+  assert content is not None and content.parts
+  assert content.parts[0].text == "root task prompt"
+
+
 @pytest.mark.asyncio
 async def test_include_contents_none_keeps_turn_across_long_running_resume():
   """A tool result posted back by the caller does not restart the turn.

tests/unittests/workflow/test_task_api_e2e.py

@@ -29,7 +29,6 @@
 from __future__ import annotations
 
 from typing import Any
-from typing import AsyncGenerator
 
 from google.adk.agents.context import Context
 from google.adk.agents.llm_agent import LlmAgent
@@ -939,3 +938,199 @@ async def driver(ctx):
       p.text or "" for c in beta_request.contents or [] for p in c.parts or []
   )
   assert "ALPHA_SECRET_CONVERSATION" not in rendered_beta_context
+
+
+@pytest.mark.asyncio
+async def test_root_task_survives_clarification(
+    request: pytest.FixtureRequest,
+):
+  model = testing_utils.MockModel.create(
+      responses=["What is your specific question?", "Got it."]
+  )
+  agent = LlmAgent(name="my_task", model=model, mode="task")
+  app = App(name=request.function.__name__, root_agent=agent)
+  runner = testing_utils.InMemoryRunner(app=app)
+
+  await runner.run_async("Do a task")
+  await runner.run_async("Here is the clarification")
+
+  assert len(model.requests) == 2
+  req = model.requests[1]
+  parts = [p.text for c in req.contents if c.role == "user" for p in c.parts]
+  # Exactly two user-role text parts: original task + clarification answer.
+  # len(parts) == 2 guards against duplicated answers (regression for #7384).
+  assert len(parts) == 2
+  assert "Do a task" in parts[0]
+  assert "Here is the clarification" in parts[1]
+
+
+@pytest.mark.asyncio
+async def test_two_sequential_root_tasks_clarification_no_cross_contamination(
+    request: pytest.FixtureRequest,
+):
+  """Four-turn regression for #7384: second root task clarification isolation.
+
+  Turn 1: Task A (root task) returns a clarification question.
+  Turn 2: User answers "Clarification for A" — Task A resumes and finishes.
+  Turn 3: Task B (a new root task in the same session) is invoked with
+          "Do task B" — Task B returns its own clarification question.
+  Turn 4: User answers "Clarification for B" — Task B resumes and finishes.
+          The test verifies both of Task B's LLM requests (calls 3 & 4) only
+          contain Task B's inputs and do not leak Task A's clarification answer.
+  """
+  model_a = testing_utils.MockModel.create(
+      responses=[
+          # Turn 1: Task A asks a clarification question.
+          "What details do you need for A?",
+          # Turn 2: Task A receives the answer and finishes.
+          _finish_part({"result": "Task A done"}),
+      ]
+  )
+  model_b = testing_utils.MockModel.create(
+      responses=[
+          # Turn 3 (call 3): Task B asks its own clarification question.
+          "What details do you need for B?",
+          # Turn 4 (call 4): Task B receives the answer and finishes.
+          _finish_part({"result": "Task B done"}),
+      ]
+  )
+  agent_a = LlmAgent(name="task_a", model=model_a, mode="task")
+  agent_b = LlmAgent(name="task_b", model=model_b, mode="task")
+
+  from google.adk.runners import Runner
+  from google.adk.sessions.in_memory_session_service import InMemorySessionService
+
+  # Both runners share the same app_name so they can look up the shared session.
+  app_name = request.function.__name__
+  session_service = InMemorySessionService()
+  session = await session_service.create_session(
+      app_name=app_name,
+      user_id="u",
+  )
+
+  app_a = App(name=app_name, root_agent=agent_a)
+  runner_a = Runner(app=app_a, session_service=session_service)
+
+  app_b = App(name=app_name, root_agent=agent_b)
+  runner_b = Runner(app=app_b, session_service=session_service)
+
+  # Turn 1: Task A is invoked and asks a clarification question.
+  async for _ in runner_a.run_async(
+      user_id="u",
+      session_id=session.id,
+      new_message=testing_utils.get_user_content("Do task A"),
+  ):
+    pass
+
+  # Turn 2: User answers Task A's clarification question; Task A finishes.
+  async for _ in runner_a.run_async(
+      user_id="u",
+      session_id=session.id,
+      new_message=testing_utils.get_user_content("Clarification for A"),
+  ):
+    pass
+
+  # Task A made 2 LLM calls.
+  assert len(model_a.requests) == 2
+
+  # Turn 3 (call 3): Task B is invoked fresh in the same session and asks
+  # its own clarification question.
+  async for _ in runner_b.run_async(
+      user_id="u",
+      session_id=session.id,
+      new_message=testing_utils.get_user_content("Do task B"),
+  ):
+    pass
+
+  # Turn 4 (call 4): User answers Task B's clarification question; Task B finishes.
+  async for _ in runner_b.run_async(
+      user_id="u",
+      session_id=session.id,
+      new_message=testing_utils.get_user_content("Clarification for B"),
+  ):
+    pass
+
+  # Task B made 2 LLM calls.
+  assert (
+      len(model_b.requests) == 2
+  ), f"Task B should have been called twice; got {len(model_b.requests)}"
+
+  # Verify call 3 (Turn 3): Task B's first request should contain only "Do task B".
+  req3 = model_b.requests[0]
+  b_user_parts_turn3 = [
+      p.text
+      for c in req3.contents
+      if c.role == "user"
+      for p in c.parts
+      if p.text
+  ]
+  assert len(b_user_parts_turn3) == 1, (
+      "Expected exactly 1 user-role text part for Task B on Turn 3 (its own"
+      f" prompt), got {len(b_user_parts_turn3)}: {b_user_parts_turn3}"
+  )
+  assert "Do task B" in b_user_parts_turn3[0], (
+      "Task B's prompt not found in its first request; got:"
+      f" {b_user_parts_turn3}"
+  )
+  assert (
+      "Clarification for A" not in b_user_parts_turn3[0]
+  ), "Task A's clarification answer must not appear in Task B's context"
+
+  # Verify call 4 (Turn 4): Task B's resumption request should contain its own
+  # original prompt and its clarification answer, but never Task A's answer.
+  req4 = model_b.requests[1]
+  b_user_parts_turn4 = [
+      p.text
+      for c in req4.contents
+      if c.role == "user"
+      for p in c.parts
+      if p.text
+  ]
+  assert len(b_user_parts_turn4) == 2, (
+      "Expected exactly 2 user-role text parts for Task B on Turn 4 "
+      "(original task + clarification answer), "
+      f"got {len(b_user_parts_turn4)}: {b_user_parts_turn4}"
+  )
+  assert "Do task B" in b_user_parts_turn4[0], (
+      "Task B's prompt not found in its resumption request; got:"
+      f" {b_user_parts_turn4}"
+  )
+  assert "Clarification for B" in b_user_parts_turn4[1], (
+      "Task B's clarification answer not found in its resumption request; got:"
+      f" {b_user_parts_turn4}"
+  )
+  assert (
+      "Clarification for A" not in b_user_parts_turn4[0]
+  ), "Task A's clarification answer must not appear in Task B's prompt"
+  assert "Clarification for A" not in b_user_parts_turn4[1], (
+      "Task A's clarification answer must not appear in Task B's resumption"
+      " context"
+  )
+
+
+@pytest.mark.asyncio
+async def test_separate_root_tasks_same_session_get_separate_scopes(
+    request: pytest.FixtureRequest,
+):
+  model = testing_utils.MockModel.create(
+      responses=[
+          _finish_part({"result": "Done A"}),
+          _finish_part({"result": "Done B"}),
+      ]
+  )
+  agent = LlmAgent(name="my_task", model=model, mode="task")
+  app = App(name=request.function.__name__, root_agent=agent)
+  runner = testing_utils.InMemoryRunner(app=app)
+
+  await runner.run_async("Run A")
+  await runner.run_async("Run B")
+
+  events = runner.session.events
+  task_events = [e for e in events if e.author == "my_task" and e.output]
+  assert len(task_events) == 2
+  # scopes should be different
+  scope_a = task_events[0].isolation_scope
+  scope_b = task_events[1].isolation_scope
+  assert scope_a != scope_b
+  assert scope_a is not None
+  assert scope_b is not None