How far a **soft stop** — a `Signal.Term`/`Signal.Int`-class request that asks a tree to exit cleanly rather than hard-killing it — reaches on *this* group, right now: the honest answer to "if I call `group.Signal(Signal.Term)` this instant, which of its members have a live target for that request?", read with `ProcessGroup.SoftStopScope()` *before* the signal is attempted. This is a capability report, not a delivery guarantee — see below. This is a **capability report, not an action**: querying it delivers no signal, posts no `WM_CLOSE`, spawns nothing, and does not mutate the group — asking never changes the answer a later `Signal` call gets. A caller (a CLI wrapping this library, an orchestrator deciding whether a soft stop is worth attempting at all) can state the real reach to its own operator instead of firing `Signal(Term)`, parsing a `ProcessError.Unsupported` back, and guessing at the scope from a hard-coded platform assumption. # It reports the *soft* tier only This describes only the graceful `Signal.Int`/`Signal.Term` soft-stop tier. The unconditional **hard** kill — `Signal.Kill`, `ProcessGroup.KillAll`, and disposing the group — always tears the whole tree down on every platform regardless of this value; that guarantee is unchanged and never `Unsupported`. # Runtime, per-group — not a fixed platform constant Unlike `KillOnParentDeathScope` (fixed per platform at build time), this is read from the group's **live membership** on every call, so the *same* build reports different scopes for different groups — most visibly on Windows, where a group with a live console-CTRL leader (a child started with `Command.WindowsCtrlSignals()`) or a live windowed member reports `OptInMembers`, while a group with neither reports `Unsupported`. "Live" is checked, not assumed: a CTRL-capable leader whose handle is still open (and so still registered) but has already exited does NOT count, because `GenerateConsoleCtrlEvent` on its now-torn-down console process group would then fail. The read is side-effect-free — it posts no `WM_CLOSE`, sends no CTRL+BREAK, and mutates nothing — but it is a capability report, not a delivery guarantee: `OptInMembers` says a live target for the soft stop exists, not that a later `Signal(Int/Term)` is certain to reach it (`GenerateConsoleCtrlEvent` can still fail for reasons this read does not probe, such as the caller having no console to share). | Mechanism | Scope | Why | |---|---|---| | Linux cgroup v2 | `WholeTree` | `Signal(Int/Term)` writes to every process in the cgroup. | | FreeBSD process reaper | `WholeTree` | `PROC_REAP_KILL` reaches every process in every subtree the group owns, with no escapee at all — not even a child that `setsid`s away: this is the strongest form of the promise on any unix. | | POSIX process group (macOS / the other BSDs / Linux without cgroup v2) | `WholeTree` | `killpg` reaches every tracked group leader and its descendants — a child that `setsid`s away escapes, the same documented weakness the kill-on-drop guarantee already has, not new to the soft stop. | | Windows Job Object | `OptInMembers` or `Unsupported` | A Job Object has no POSIX signal; a soft stop reaches only members it can *trigger* — a console-CTRL leader (opted in via `Command.WindowsCtrlSignals()`) or any live windowed member (`WM_CLOSE`). `OptInMembers` when at least one such member is live, else `Unsupported`. |