Documentation

The local-development immediate-halt wiring, as three injection points so its logic is exercised without a real terminal. It exists only to give an interactive session a "quit now" key: when the server is attached to a TTY, closing standard input (Ctrl-D) forces an immediate process exit, aborting any in-progress drain -- the same hard-stop a second Ctrl-C gives, but on the dev's deliberate signal.

It is inert outside an interactive terminal: in production standard input is a non-TTY or closed, haltOnInteractive returns False, and no watcher is installed, so the signal-driven graceful lifecycle is completely untouched. The TTY guard is what enforces that zero-production-impact contract (see withInteractiveHalt).

The real local-dev halt: armed only when standard input is a terminal (hIsTerminalDevice), fired by end-of-input on standard input (Ctrl-D), and halting via exitImmediately -- an immediate _exit that bypasses the graceful drain, mirroring a second Ctrl-C. The exit status (130) is the conventional "terminated from the terminal" code.

Run an action with the local-dev immediate-halt watcher armed __only when interactive__. If haltOnInteractive is True, a watcher runs alongside the action for exactly its lifetime (withAsync, so it is torn down when the action returns or is cancelled -- it never lingers); the watcher blocks on awaitHaltSignal and, when that returns, runs halt. If False -- the production case -- the action runs alone, with no watcher and no extra thread, so nothing about the graceful lifecycle changes.