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CancellationToken

Add System.Threading.CancellationToken as a parameter of your command handler method. It is not parsed from the command line and does not appear in --help. The source generator injects the token the runtime uses for cooperative cancellation.

public static async Task<int> Sync(
    string source,
    CancellationToken cancellationToken)
{
    await CopyTreeAsync(source, cancellationToken);
    return 0;
}
// myapp sync --source ./data   (CancellationToken is not a CLI option)

You can also add it on an [AsParameters] type as a primary constructor parameter or init property:

public record RunArgs(string Source, int Port, CancellationToken Ct);

public static async Task<int> Run([AsParameters] RunArgs args)
{
    await Task.Delay(1, args.Ct);
    return 0;
}
Tip

Keep CLI-bound members first in declaration order. All [Argument] positionals must precede flags, and CancellationToken must not appear between a flag and a later positional. Put the token last on the DTO.

The token is cancelled when the user presses Ctrl+C (and on Windows, the console break signal). The process keeps running after cancel unless your handler exits. Argh only forwards cancellation to your code.

The same console token is linked with IHostApplicationLifetime.ApplicationStopping, so the parameter also cancels when the host is shutting down.

Injected CancellationToken members are set to default. There is no host or console token in that API, so the value is non-cancellable.