В старых версиях windows есть ограничение 1024 символа на длину переменной окружения. Как ты делаешь действие “хочу вставить” точно?
When an application calls the CreateEnvironmentBlock function to retrieve the environment variables on a Microsoft Windows Server 2003-based or Microsoft Windows XP-based computer, the returned path environment variable is truncated to 1,024 bytes. This behavior occurs even though the maximum size of an environment variable is 2,048 bytes. This problem prevents the application from obtaining the correct environment variable.
const int bufferSize = 4096; // Set the buffer size to 4096 characters
var inputStream = new StreamReader(Console.OpenStandardInput(bufferSize));
Console.SetIn(inputStream);
string input = Console.ReadLine();