Slow the producer down instead of dropping anything: the pump stops draining the OS pipe until the consumer catches up, so the child itself observably blocks writing to a full stdout/stderr pipe. Bounds memory losslessly, at the cost of the child's timing — opt in only when you intend to pace a trusted producer against your consumer (see the deadlock note in [Streaming](../../docs/streaming.md) before using it: a `Command.Timeout` kills the *child* but does not by itself free a writer parked here if you abandon reading — dispose the `RunningProcess` to release it).

"Head" semantics: keep what is already queued and drop the newest incoming item. Lossy but bounded; sets `RunningProcess.DroppedStreamLineCount`.

Ring-buffer / "tail" semantics: drop the oldest queued item to make room for the newest. Lossy but bounded; sets `RunningProcess.DroppedStreamLineCount`.

Fail-loud ceiling: once the cap is reached, fault the stream with `ProcessError.OutputTooLarge` (observed by the consumer as the streaming enumerator throwing, the same fault path a throwing per-line handler already uses).