[hyamero]

What

nosleep on now restores sleep when the charge drops to/below 20% while running on battery, not just when the window ends. On AC power a low reading is ignored, since it's charging. --battery=N (1–99) moves the threshold; --no-battery opts out and auto-offs on DURATION alone.

This is on by default: an unplugged Mac left awake in clamshell mode would otherwise drain flat waiting out its window, and the old behavior is one flag away.

Usage

nosleep on 3h                  # auto-off at 3h OR at 20% charge (while unplugged)
nosleep on 3h --battery=10     # ...with a custom threshold (1–99)
nosleep on 3h --no-battery     # time-only, the previous behavior

The threshold is only read from --battery=N, never a separate --battery N token: DURATION accepts a bare number of hours, so the two would be ambiguous — nosleep on --battery 3 means three hours at the default threshold.

Example status with the guardrail armed:

disablesleep : ON  (Mac will not sleep, even with the lid closed)
caffeinate   : running
lid watcher  : running
auto-off in  : 2h 47m (at 04:53 AM)
battery      : auto-off <= 20% (currently 63%, on battery)

Why

An unplugged Mac running lid-closed with sleep disabled could drain its battery flat instead of falling back to normal sleep. 20% restores sleep with reserve to spare, ahead of macOS's own low-battery warning (~10%) and emergency sleep (~2–3%) — a graceful sleep rather than a scramble at the bottom.

How

• The inline root-owned auto-off timer is refactored into a _guardrail subcommand. With --no-battery it just sleeps out DURATION (byte-for-byte the previous behavior). Otherwise the same root process polls pmset -g batt every 30s and, on a low-while-unplugged read, tears down caffeinate and the lid watcher (which restores brightness) before pmset -a disablesleep 0.
• Because that guardrail is now a separate process rather than an inline snippet with literal paths baked in, cmd_on hands it the resolved state dir explicitly (NOSLEEP_STATE_DIR, alongside NOSLEEP_PMSET_BIN / NOSLEEP_POLL_INTERVAL). sudo's env_reset drops XDG_STATE_HOME, so a guardrail left to re-derive its own paths would operate on a different directory and silently skip the teardown.
• The poll loop sleeps min(poll, remaining) so the timed auto-off can't land after the moment status advertised.
• Thresholds are normalized to base 10 before comparison (bash reads a leading zero as octal, which would reject 08 and quietly turn 010 into 8), and armed-ness is tracked separately from the value so that no input a user can type — 0, empty — disarms the guardrail silently.
• A Mac with no battery skips the guardrail rather than reporting it as armed, and only says so when it was asked for by name.
• is_our_timer now matches the _guardrail command line; battery_read does one pmset call and one parse, shared by the poll loop and status.
• status shows the armed threshold and current charge; state adds a battery_threshold file, cleaned up alongside the rest.