One completed command from a completion-ordered batch stream (`Exec.outputStream` / `Exec.outputStreamBytes`): the command's **input index** — its position in the `commands` sequence handed to the verb — paired with that command's own independent `Result`. The index is what keeps a result traceable to its source once items no longer arrive in input order, and it is always the position in the ORIGINAL sequence, never a counter of how many items the stream has yielded so far. The `Result` means exactly what one element of `Exec.outputAll` means: an `Error` is a genuine run failure (`ProcessError`: couldn't start, timed out, was cancelled, exhausted its `Retry` budget, …), while a non-zero exit stays `Ok` data whose `Code` you inspect.