Adjusted comm‑simulation sending so the payload file is written before the report is emitted.

This prevents the server from trying to read a missing or stale file and
dropping the Socket.IO connection. The “transport error” is Socket.IO’s
disconnect reason when the server closes the underlying connection; with
file‑based simulation and high concurrency,  the server can receive the
report before the client finishes writing the payload file, triggering
an exception and a disconnect.

Author: baochunli

plato/clients/strategies/base.py

@@ -218,5 +218,12 @@ async def send_report_and_payload(
         self, context: ClientContext, report: Any, payload: Any
     ) -> None:
         """Send both report metadata and payload to the server."""
+        if getattr(context, "comm_simulation", False):
+            # The server reads the simulated payload file as soon as the report arrives.
+            # Write the payload first to avoid races under high concurrency.
+            await self.send_payload(context, payload)
+            await self.send_report(context, report)
+            return
+
         await self.send_report(context, report)
         await self.send_payload(context, payload)