From 40be9d3c41dd778ee33fa6642e9cf296705a75f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gau=C2=B7Beo?= <thinhnx128@gmail.com>
Date: Sat, 7 Nov 2026 17:20:02 +0700
Subject: [PATCH] fix(stdio): flush sys.stdout before restoring fd 1 in
 stdio_server (#3821)

---
 src/mcp/server/stdio.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/mcp/server/stdio.py b/src/mcp/server/stdio.py
index de8bbae5f1..b7ac9db98a 100644
--- a/src/mcp/server/stdio.py
+++ b/src/mcp/server/stdio.py
@@ -212,6 +212,8 @@ async def stdout_writer():
             yield read_stream, write_stream
     finally:
         if restore_stdout is not None:
+            with suppress(OSError, ValueError):
+                sys.stdout.flush()
             restore_stdout()
         if restore_stdin is not None:
             restore_stdin()