google · ftnext · Aug 12, 2026 · Aug 12, 2026
diff --git a/src/google/adk/agents/base_agent.py b/src/google/adk/agents/base_agent.py
@@ -176,6 +176,11 @@ class MyAgent(BaseAgent):
       will be appended to event history as an additional agent response.
   """
 
+  async def _get_transfer_description(self, ctx: InvocationContext) -> str:
+    """Returns the description used to select this transfer target."""
+    del ctx
+    return self.description
+
   def _load_agent_state(
       self,
       ctx: InvocationContext,

diff --git a/src/google/adk/agents/remote_a2a_agent.py b/src/google/adk/agents/remote_a2a_agent.py
@@ -37,6 +37,7 @@
 from google.adk.platform import uuid as platform_uuid
 from google.genai import types as genai_types
 import httpx
+from typing_extensions import override
 
 from ..a2a import _compat
 
@@ -503,6 +504,31 @@ async def _validate_agent_card(self, agent_card: AgentCard) -> None:
 
     self._validate_card_rpc_targets(agent_card)
 
+  @override
+  async def _get_transfer_description(self, ctx: InvocationContext) -> str:
+    """Returns local or agent-card metadata for transfer selection."""
+    if self.description:
+      return self.description
+
+    if self._agent_card:
+      return self._agent_card.description or ""
+
+    agent_card = await self._resolve_agent_card(ctx)
+    await self._validate_agent_card(agent_card)
+
+    # Public cards are shared across invocations, matching the existing client
+    # cache. Authenticated cards remain invocation-scoped because their metadata
+    # may vary by session.
+    per_invocation_card = bool(
+        self._config.card_request_interceptors
+        and self._agent_card_source
+        and self._agent_card_source.startswith(("http://", "https://"))
+    )
+    if not per_invocation_card:
+      self._agent_card = agent_card
+
+    return agent_card.description or ""
+
   def _validate_card_rpc_targets(self, agent_card: AgentCard) -> None:
     """Constrains where a card fetched over the network may aim RPC traffic.
 
@@ -594,9 +620,11 @@ async def _ensure_resolved(
         # Validate agent card
         await self._validate_agent_card(self._agent_card)
 
-        # Update description if empty
-        if not self.description and self._agent_card.description:
-          self.description = self._agent_card.description
+      # A public card may already have been resolved for transfer selection.
+      # Preserve the existing behavior of adopting its description when the
+      # remote agent itself is initialized.
+      if not self.description and self._agent_card.description:
+        self.description = self._agent_card.description
 
       # Initialize A2A client
       if not self._a2a_client:

diff --git a/src/google/adk/flows/llm_flows/agent_transfer.py b/src/google/adk/flows/llm_flows/agent_transfer.py
@@ -16,6 +16,8 @@
 
 from __future__ import annotations
 
+import asyncio
+import logging
 import typing
 from typing import AsyncGenerator
 from typing import Sequence
@@ -35,6 +37,9 @@
   from ...agents.llm_agent import LlmAgent
 
 
+logger = logging.getLogger('google_adk.' + __name__)
+
+
 class _AgentTransferLlmRequestProcessor(BaseLlmRequestProcessor):
   """Agent transfer request processor."""
 
@@ -54,11 +59,16 @@ async def run_async(
         agent_names=[agent.name for agent in transfer_targets]
     )
 
+    transfer_target_infos = await asyncio.gather(*[
+        _build_transfer_target_info(target, invocation_context)
+        for target in transfer_targets
+    ])
+
     llm_request.append_instructions([
         _build_transfer_instructions(
             transfer_to_agent_tool.name,
             agent,
-            transfer_targets,
+            transfer_target_infos,
         )
     ])
 
@@ -79,6 +89,34 @@ class _AgentLike(typing.Protocol):
   description: str
 
 
+class _TransferTargetInfo:
+  """Invocation-scoped metadata used to build transfer instructions."""
+
+  def __init__(self, *, name: str, description: str) -> None:
+    self.name = name
+    self.description = description
+
+
+async def _build_transfer_target_info(
+    target_agent: BaseAgent,
+    ctx: InvocationContext,
+) -> _TransferTargetInfo:
+  """Builds transfer metadata without mutating invocation-scoped values."""
+  try:
+    description = await target_agent._get_transfer_description(ctx)
+  except Exception as e:
+    logger.warning(
+        'Failed to load transfer description for agent %s: %s',
+        target_agent.name,
+        e,
+    )
+    description = target_agent.description
+  return _TransferTargetInfo(
+      name=target_agent.name,
+      description=description,
+  )
+
+
 def _build_target_agents_info(target_agent: _AgentLike) -> str:
   return f"""
 Agent name: {target_agent.name}
@@ -134,7 +172,7 @@ def _build_transfer_instruction_body(
 def _build_transfer_instructions(
     tool_name: str,
     agent: LlmAgent,
-    target_agents: Sequence[BaseAgent],
+    target_agents: Sequence[_AgentLike],
 ) -> str:
   """Build instructions for agent transfer (agent-tree variant).
 

diff --git a/tests/unittests/agents/test_remote_a2a_agent.py b/tests/unittests/agents/test_remote_a2a_agent.py
@@ -1052,6 +1052,23 @@ async def test_ensure_resolved_with_url_source(self):
           assert agent._agent_card == agent_card
           assert agent.description == agent_card.description
 
+  @pytest.mark.asyncio
+  async def test_ensure_resolved_adopts_prefetched_card_description(self):
+    """Initializing a prefetched public card still adopts its description."""
+    agent_card = create_test_agent_card()
+    agent = RemoteA2aAgent(
+        name="test_agent", agent_card="https://example.com/agent.json"
+    )
+    agent._agent_card = agent_card
+    mock_factory = Mock()
+    mock_factory.create.return_value = Mock()
+    agent._a2a_client_factory = mock_factory
+
+    with patch.object(agent, "_ensure_httpx_client", new_callable=AsyncMock):
+      await agent._ensure_resolved(Mock())
+
+    assert agent.description == agent_card.description
+
   @pytest.mark.asyncio
   async def test_ensure_resolved_already_resolved(self):
     """Test _ensure_resolved when already resolved."""

diff --git a/tests/unittests/flows/llm_flows/test_agent_transfer_system_instructions.py b/tests/unittests/flows/llm_flows/test_agent_transfer_system_instructions.py
@@ -20,10 +20,17 @@
 """
 
 from typing import AsyncGenerator
+from unittest.mock import AsyncMock
+from unittest.mock import patch
 
+from a2a.types import AgentCard
+from google.adk.a2a import _compat
+from google.adk.a2a.agent.config import A2aRemoteAgentConfig
+from google.adk.a2a.agent.config import CardRequestInterceptor
 from google.adk.agents.base_agent import BaseAgent
 from google.adk.agents.invocation_context import InvocationContext
 from google.adk.agents.llm_agent import Agent
+from google.adk.agents.remote_a2a_agent import RemoteA2aAgent
 from google.adk.artifacts.in_memory_artifact_service import InMemoryArtifactService
 from google.adk.events.event import Event
 from google.adk.flows.llm_flows import agent_transfer
@@ -47,6 +54,16 @@ async def _run_async_impl(
     yield Event(author=self.name, invocation_id=ctx.invocation_id)
 
 
+def _make_agent_card(description: str) -> AgentCard:
+  return _compat.build_agent_card(
+      name='remote_agent',
+      description=description,
+      version='1.0',
+      url='https://example.com/rpc',
+      protocol_binding='JSONRPC',
+  )
+
+
 async def create_test_invocation_context(agent: Agent) -> InvocationContext:
   """Helper to create constructed InvocationContext."""
   session_service = InMemorySessionService()
@@ -342,3 +359,150 @@ async def test_agent_transfer_with_non_llm_peer_agent():
 
   instructions = llm_request.config.system_instruction
   assert 'non_llm_peer' in instructions
+
+
+@pytest.mark.asyncio
+async def test_agent_transfer_loads_remote_card_description_before_selection():
+  """A remote card description is available for the first transfer decision."""
+  mock_model = testing_utils.MockModel.create(responses=[])
+  remote_agent = RemoteA2aAgent(
+      name='remote_agent',
+      agent_card='https://example.com/agent-card.json',
+  )
+  main_agent = Agent(
+      name='main_agent',
+      model=mock_model,
+      sub_agents=[remote_agent],
+  )
+  invocation_context = await create_test_invocation_context(main_agent)
+  llm_request = LlmRequest()
+
+  with patch.object(
+      remote_agent,
+      '_resolve_agent_card',
+      new=AsyncMock(return_value=_make_agent_card('Handles remote research.')),
+  ):
+    async for _ in agent_transfer.request_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
+  instructions = llm_request.config.system_instruction
+  assert 'Agent description: Handles remote research.' in instructions
+
+
+@pytest.mark.asyncio
+async def test_agent_transfer_prefers_explicit_remote_description():
+  """An explicit remote description remains authoritative for transfers."""
+  mock_model = testing_utils.MockModel.create(responses=[])
+  remote_agent = RemoteA2aAgent(
+      name='remote_agent',
+      agent_card='https://example.com/agent-card.json',
+      description='Locally configured routing description.',
+  )
+  main_agent = Agent(
+      name='main_agent',
+      model=mock_model,
+      sub_agents=[remote_agent],
+  )
+  invocation_context = await create_test_invocation_context(main_agent)
+  llm_request = LlmRequest()
+
+  with patch.object(
+      remote_agent, '_resolve_agent_card', new_callable=AsyncMock
+  ) as resolve_card:
+    async for _ in agent_transfer.request_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
+  instructions = llm_request.config.system_instruction
+  assert (
+      'Agent description: Locally configured routing description.'
+      in instructions
+  )
+  resolve_card.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_agent_transfer_keeps_authenticated_descriptions_per_invocation():
+  """Authenticated card descriptions do not leak between invocations."""
+  mock_model = testing_utils.MockModel.create(responses=[])
+  remote_agent = RemoteA2aAgent(
+      name='remote_agent',
+      agent_card='https://example.com/agent-card.json',
+      config=A2aRemoteAgentConfig(
+          card_request_interceptors=[CardRequestInterceptor()]
+      ),
+  )
+  main_agent = Agent(
+      name='main_agent',
+      model=mock_model,
+      sub_agents=[remote_agent],
+  )
+  first_context = await create_test_invocation_context(main_agent)
+  second_context = await create_test_invocation_context(main_agent)
+  first_request = LlmRequest()
+  second_request = LlmRequest()
+
+  with patch.object(
+      remote_agent,
+      '_resolve_agent_card',
+      new=AsyncMock(
+          side_effect=[
+              _make_agent_card('First session description.'),
+              _make_agent_card('Second session description.'),
+          ]
+      ),
+  ):
+    async for _ in agent_transfer.request_processor.run_async(
+        first_context, first_request
+    ):
+      pass
+    async for _ in agent_transfer.request_processor.run_async(
+        second_context, second_request
+    ):
+      pass
+
+  first_instructions = first_request.config.system_instruction
+  second_instructions = second_request.config.system_instruction
+  assert 'Agent description: First session description.' in first_instructions
+  assert 'Second session description.' not in first_instructions
+  assert 'Agent description: Second session description.' in second_instructions
+  assert 'First session description.' not in second_instructions
+  assert remote_agent.description == ''
+
+
+@pytest.mark.asyncio
+async def test_agent_transfer_continues_when_remote_card_is_unavailable(caplog):
+  """An unavailable remote card does not block the parent model request."""
+  mock_model = testing_utils.MockModel.create(responses=[])
+  remote_agent = RemoteA2aAgent(
+      name='remote_agent',
+      agent_card='https://example.com/agent-card.json',
+  )
+  main_agent = Agent(
+      name='main_agent',
+      model=mock_model,
+      sub_agents=[remote_agent],
+  )
+  invocation_context = await create_test_invocation_context(main_agent)
+  llm_request = LlmRequest()
+
+  with patch.object(
+      remote_agent,
+      '_resolve_agent_card',
+      new=AsyncMock(side_effect=OSError('card service unavailable')),
+  ):
+    async for _ in agent_transfer.request_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
+  instructions = llm_request.config.system_instruction
+  assert 'Agent name: remote_agent' in instructions
+  assert 'Agent description: ' in instructions
+  assert (
+      'Failed to load transfer description for agent remote_agent'
+      in caplog.text
+  )