chore: import upstream snapshot with attribution

examples/stories/streaming/server.py

@@ -0,0 +1,40 @@
+"""Progress, in-flight logging, and cancellation from a single long-running tool."""
+
+import anyio
+import mcp_types as types
+
+from mcp.server.mcpserver import Context, MCPServer
+from stories._hosting import run_server_from_args
+
+
+def build_server() -> MCPServer:
+    mcp = MCPServer("streaming-example")
+
+    @mcp.tool()
+    async def countdown(steps: int, ctx: Context) -> dict[str, int]:
+        """Emit one progress + one log notification per step; observes cancellation."""
+        try:
+            for i in range(1, steps + 1):
+                await ctx.report_progress(float(i), float(steps), f"step {i}/{steps}")
+                # No non-deprecated logging helper on Context yet, so send the raw
+                # notification. `related_request_id` keeps it on this request's response
+                # stream (matters over streamable HTTP).
+                await ctx.request_context.session.send_notification(
+                    types.LoggingMessageNotification(
+                        params=types.LoggingMessageNotificationParams(
+                            level="info", logger="countdown", data=f"step {i}/{steps}"
+                        )
+                    ),
+                    related_request_id=ctx.request_context.request_id,
+                )
+        except anyio.get_cancelled_exc_class():
+            # The client abandoned the call. Release resources here, then re-raise so
+            # the dispatcher unwinds the request — never swallow cancellation.
+            raise
+        return {"completed": steps, "total": steps}
+
+    return mcp
+
+
+if __name__ == "__main__":
+    run_server_from_args(build_server)