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feat(client): store serverInfo from initialization result #1565

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feat(client): store serverInfo from initialization result #1565

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db43067
use serverInfo if _client_info is DEFAULT_CLIENT_INFO
bjoaquinc Nov 3, 2025
5e62109
move functionality to after protocolVersion check
bjoaquinc Nov 3, 2025
86eae4b
add unit test asserts
bjoaquinc Nov 4, 2025
744949e
Merge branch 'main' into client-info-from-server
bjoaquinc Nov 4, 2025
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3 changes: 3 additions & 0 deletions src/mcp/client/session.py
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Original file line number Diff line number Diff line change
Expand Up @@ -170,6 +170,9 @@ async def initialize(self) -> types.InitializeResult:
if result.protocolVersion not in SUPPORTED_PROTOCOL_VERSIONS:
raise RuntimeError(f"Unsupported protocol version from the server: {result.protocolVersion}")

if self._client_info is DEFAULT_CLIENT_INFO:
self._client_info = result.serverInfo

await self.send_notification(types.ClientNotification(types.InitializedNotification()))

return result
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8 changes: 7 additions & 1 deletion tests/client/test_session.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,8 @@ async def mock_server():

# Assert that the custom client info was sent
assert received_client_info == custom_client_info
# Assert that the client info was not replaced with server info after initialization
assert session._client_info == custom_client_info


@pytest.mark.anyio
Expand All @@ -183,6 +185,7 @@ async def test_client_session_default_client_info():
server_to_client_send, server_to_client_receive = anyio.create_memory_object_stream[SessionMessage](1)

received_client_info = None
received_server_info = None

async def mock_server():
nonlocal received_client_info
Expand Down Expand Up @@ -231,10 +234,13 @@ async def mock_server():
server_to_client_receive,
):
tg.start_soon(mock_server)
await session.initialize()
result = await session.initialize()
received_server_info = result.serverInfo

# Assert that the default client info was sent
assert received_client_info == DEFAULT_CLIENT_INFO
# Assert that the default client info was replaced with server info after initialization
assert session._client_info == received_server_info


@pytest.mark.anyio
Expand Down