From 8de0bf0c918aeab88082cb3babc38c26a53b8270 Mon Sep 17 00:00:00 2001
From: Kirill Osenkov <kirillo@microsoft.com>
Date: Tue, 9 Jun 2026 18:34:53 -0700
Subject: [PATCH] Work around
 https://github.com/modelcontextprotocol/csharp-sdk/issues/1638

---
 .../Client/StdioClientTransport.cs            | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/ModelContextProtocol.Core/Client/StdioClientTransport.cs b/src/ModelContextProtocol.Core/Client/StdioClientTransport.cs
index b0af062b1..2e44ee34f 100644
--- a/src/ModelContextProtocol.Core/Client/StdioClientTransport.cs
+++ b/src/ModelContextProtocol.Core/Client/StdioClientTransport.cs
@@ -187,14 +187,29 @@ public async Task<ITransport> ConnectAsync(CancellationToken cancellationToken =
             lock (s_consoleEncodingLock)
             {
                 Encoding originalInputEncoding = Console.InputEncoding;
+                bool encodingChanged = false;
                 try
                 {
-                    Console.InputEncoding = StreamClientSessionTransport.NoBomUtf8Encoding;
+                    try
+                    {
+                        Console.InputEncoding = StreamClientSessionTransport.NoBomUtf8Encoding;
+                        encodingChanged = true;
+                    }
+                    catch
+                    {
+                        // Host has no usable console (e.g. WPF/WinForms on .NET Framework with no
+                        // AllocConsole). The child inherits the current Console.InputEncoding;
+                        // non-ASCII stdin may be misencoded, but the connect itself proceeds.
+                    }
+
                     processStarted = process.Start();
                 }
                 finally
                 {
-                    Console.InputEncoding = originalInputEncoding;
+                    if (encodingChanged)
+                    {
+                        Console.InputEncoding = originalInputEncoding;
+                    }
                 }
             }
 #endif