[v1.x] fix: handle non-UTF-8 bytes in stdio server stdin (#2303)

src/mcp/server/stdio.py

@@ -44,7 +44,7 @@ async def stdio_server(
     # python is platform-dependent (Windows is particularly problematic), so we
     # re-wrap the underlying binary stream to ensure UTF-8.
     if not stdin:
-        stdin = anyio.wrap_file(TextIOWrapper(sys.stdin.buffer, encoding="utf-8"))
+        stdin = anyio.wrap_file(TextIOWrapper(sys.stdin.buffer, encoding="utf-8", errors="replace"))
     if not stdout:
         stdout = anyio.wrap_file(TextIOWrapper(sys.stdout.buffer, encoding="utf-8"))
 
@@ -63,7 +63,7 @@ async def stdio_server(
                 async for line in stdin:
                     try:
                         message = types.JSONRPCMessage.model_validate_json(line)
-                    except Exception as exc:  # pragma: no cover
+                    except Exception as exc:
                         await read_stream_writer.send(exc)
                         continue