"""Call a tool whose SSE stream the server closes mid-flight; the call still completes. HTTP-only — no SSE on stdio.""" import anyio from mcp_types import TextContent from mcp.client import Client from stories._harness import Target, run_client async def main(target: Target, *, mode: str = "auto") -> None: async with Client(target, mode=mode) as client: messages: list[str | None] = [] async def on_progress(progress: float, total: float | None, message: str | None) -> None: messages.append(message) with anyio.fail_after(10): result = await client.call_tool("long_operation", {}, progress_callback=on_progress) # The result arrived — the client transport survived the server-initiated close, # reconnected with Last-Event-ID, and received the replayed response. assert not result.is_error, result assert isinstance(result.content[0], TextContent) assert result.content[0].text == "resumed" # "after-close" was emitted while no SSE stream was open; receiving it proves the # event store buffered it and the reconnect replayed it. assert messages == ["before-close", "after-close"], messages if __name__ == "__main__": run_client(main)