Append a single argument.

Append several arguments, in order.

Also cancel the run when `cancellationToken` fires.

Create a command for the given program.

Windows: run the child with `CREATE_NO_WINDOW` (no effect on Unix).

Set the working directory for the run.

Decode both captured streams with `encoding`.

Set an environment variable for the child.

Start the child's environment empty instead of inheriting the parent's.

Remove an inherited environment variable from the child.

Run the child under this Unix group id (`setgid`). Unix-only, same notes as `uid`. See `Command.Gid`.

Set the child's Unix supplementary groups, replacing the inherited set — the third leg of a privilege drop. Meaningful only alongside a `Uid`/`Gid` drop (else `ProcessError.Spawn`); Unix-only (a set value fails a Windows spawn with `ProcessError.Unsupported`). See `Command.Groups`.

Kill the run when it produces no output (stdout or stderr) for `duration` — reset by each chunk of output — independent of the total `Command.Timeout`.

Hand the child the parent process's own standard input directly (inherited, no pipe/feeder), for interactive/console programs. See `Command.InheritStdin`.

Keep the child's stdin pipe open after the source is exhausted.

Frame both captured/streamed streams' lines with `terminator` (default `LineTerminator.Lf`).

Emit structured lifecycle events to `logger` (argv/env never logged).

Merge the child's stderr into its stdout at the OS level (like a shell `2>&1`); the two streams then interleave byte-for-byte on the single stdout stream, and there is no separate stderr stream. See `Command.MergeStderr`.

Replace the success exit-code set with these codes (default `{0}`; include `0` to keep it; an empty set is a no-op that keeps the previously configured codes).

Invoke `handler` for each captured stderr line.

Invoke `handler` for each captured stdout line.

Bound the in-memory backlog of captured lines.

Launch the child (and its spawned tree) at a lower/higher CPU-scheduling priority (Windows priority class / Unix nice). Supported on both platforms; the default leaves the OS default.

Run the command up to `maxAttempts` times in total (initial run plus retries), waiting `delay` between attempts (`0`/`1` both mean a single run).

Explicitly disable retrying for this command, overriding any inherited `Retry` policy (e.g. from a `CliClient.WithDefaults` template). The command always runs exactly once.

Detach the child into a new session (`setsid()`). Unix-only: a set request fails a Windows spawn with `ProcessError.Unsupported`. Containment is preserved. See `Command.Setsid`.

Set how the child's standard error is connected.

Decode captured stderr with `encoding`.

Frame captured/streamed stderr lines with `terminator` (default `LineTerminator.Lf`).

Copy raw captured stderr bytes to `sink`.

Feed the child's standard input from `source`.

Set how the child's standard output is connected.

Decode captured stdout with `encoding`.

Frame captured/streamed stdout lines with `terminator` (default `LineTerminator.Lf`).

Copy raw captured stdout bytes to `sink`.

Opt in to a bounded/backpressure channel for the streaming verbs (default stays unbounded).

Kill the run after `duration`.

Terminate gracefully on timeout, force-killing only after `grace`.

Run the child under this Unix user id (`setuid`). Unix-only: a set uid fails a Windows spawn with `ProcessError.Unsupported`; dropping needs privilege (else `ProcessError.Spawn`). See `Command.Uid`.

Set the child's Unix file-mode creation mask (`umask(2)`). Unix-only: a set mask fails a Windows spawn with `ProcessError.Unsupported`. The default leaves the inherited umask untouched.

Inside a pipeline, allow this stage to exit non-zero without failing the pipeline.

Run the child under this Unix user and group id (the privilege-drop pair). See `Command.User`.

Windows: spawn the child as its own console process group so `ProcessGroup.Signal(Signal.Int/Term)` can deliver a best-effort CTRL+BREAK (no effect on Unix). See `Command.WindowsCtrlSignals`.