Keep Remote Mac Sessions Alive Between Logins

Published November 11, 2026 • Figment editorial team

You kick off a two-hour build on your remote Mac, close your laptop to board a flight, and land to find the build died at the fifteen‑minute mark. Two things killed it: the terminal that your remote-desktop client opened sent a hangup signal when the connection dropped, and the Mac idled into sleep because nothing was holding a power assertion. Fix both and builds, test runs, and long data jobs will outlast every disconnect.

Direct recommendation. On Figment, the $29 virtual Intel macOS host is the practical persistent build target for Intel-compatible toolchains, including supported Xcode 26-or-earlier workflows. Access is through the browser console, so when you close the tab the guest keeps running — your tmux session, your caffeinate process, and whatever it is wrapping. Pick the M-series tier from $95/month when you need Apple silicon execution (ARM-only binaries, Xcode 27, or visionOS); exact chip, RAM and disk are confirmed in the quote. Request a configuration.

The tmux behaviour below is from the tmux(1) manual; LaunchAgent behaviour is from Apple's Creating launchd Jobs. Xcode/Intel limits come from Apple's porting notes at developer.apple.com.

Why processes die when you disconnect

When a remote-desktop client closes, the login session's windowing stack tears down any terminal windows it owned. Processes started in those terminals are attached to a pseudo-terminal (pty). When the pty closes, the kernel delivers SIGHUP to the foreground process group, which terminates unless the process explicitly ignores it.

A second failure mode is idle sleep on physical Macs. macOS parks the system when no user activity is detected, so the network stack suspends and background jobs stall. The $29 virtual Intel macOS host has no hardware sleep path, but its desktop session can still blank its own screen saver, and you still want tmux there so a closed browser tab does not take the shell with it. On a physical M-series Mac both problems apply, so you want tmux and caffeinate.

tmux: a named session that outlives the connection

tmux runs a server process that owns sessions independently of any client. Install once if not present:

brew install tmux

Start a named session before starting any long job:

tmux new-session -s build

Inside the session, run your build normally. To detach without killing it:

C-b d          # detach — session and its processes keep running

After reconnecting, re-attach:

tmux attach-session -t build

tmux cheat sheet

Task	Command
New named session	`tmux new-session -s build`
Detach, keep running	`C-b d`
List sessions	`tmux ls`
Re-attach by name	`tmux attach-session -t build`
Re-attach to most recent	`tmux attach`
Kill a finished session	`tmux kill-session -t build`
Rename	`tmux rename-session -t old new`
New window inside session	`C-b c`
Split pane left/right	`C-b %`
Split pane top/bottom	`C-b "`
Peek without attaching	`tmux capture-pane -t build -p \| tail -20`

Use a naming convention so tmux ls is self-explanatory after a weekend away: job type plus a short date, e.g. release-20261110, tests-integration, data-etl.

caffeinate: keep physical Macs awake

caffeinate ships with macOS and takes an IOKit power-management assertion — the same mechanism Xcode uses when it shows "Preventing Sleep." No install required. It matters on physical hardware (Figment M-series, your own Mac Mini, a leased host); on the Intel VM it is harmless but mostly a no‑op because the guest has no real power manager.

Wrap a single job (the assertion is released when the command exits):

caffeinate -i make all 2>&1 | tee build.log

Hold one umbrella assertion for multiple jobs:

caffeinate -i &
echo "caffeinate PID: $!"

-i prevents idle sleep while letting the display dim. Add -d only if something needs the display on; -s prevents system sleep but only on AC power and so is relevant on Mac mini and Mac Studio hardware, not laptops on battery.

Auto-start caffeinate with a LaunchAgent

A LaunchAgent in ~/Library/LaunchAgents/ starts automatically when your user session opens and restarts the program if it ever exits. Put this at ~/Library/LaunchAgents/com.figment.caffeinate.plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
  "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.figment.caffeinate</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/bin/caffeinate</string>
        <string>-i</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>KeepAlive</key>
    <true/>
</dict>
</plist>

Set permissions and load without rebooting:

chmod 600 ~/Library/LaunchAgents/com.figment.caffeinate.plist
launchctl load  ~/Library/LaunchAgents/com.figment.caffeinate.plist
launchctl list | grep caffeinate     # a PID in the first column means it is running

To stop it (for example, a laptop you want to let sleep):

launchctl unload ~/Library/LaunchAgents/com.figment.caffeinate.plist

Label, ProgramArguments, RunAtLoad and KeepAlive are the keys Apple documents for this pattern; man launchd.plist on the host lists every other key you may want (StandardOutPath, WorkingDirectory, EnvironmentVariables, and so on).

Energy Saver settings as a backstop on physical Macs

On a physical Figment M-series host or any other dedicated Mac, add a system-level backstop:

System Settings → Energy Saver (desktop) or Battery (portable).
Set Turn display off after to Never for a build host.
Enable Prevent automatic sleeping when the display is off if present.
On Mac mini / Mac Studio, enable Start up automatically after a power failure so the host comes back from a power event ready to resume LaunchAgents.

These settings persist across reboots and pair cleanly with the LaunchAgent above.

Monitoring without staying attached

Once the job is running in tmux and caffeinate is live, you rarely want an open remote-desktop session to it. Three light-weight ways to check progress:

Write the build to a log inside the session, then detach:

# inside tmux
make all 2>&1 | tee ~/builds/release.log
# C-b d

Peek at the live pane without attaching:

tmux capture-pane -t build -p | tail -40

Tail the log file from any shell on the host:

tail -f ~/builds/release.log

On the $29 virtual Intel macOS host, "any shell on the host" means a second terminal window inside the browser console; inbound public SSH is not part of that plan. On an M-series plan, confirm the exact access method (browser console, VNC, or other) in the quote before you build tooling around it.

Which Figment plan fits this task

$29 virtual Intel macOS — persistent tmux host for Intel-compatible builds, scripts, scrapers, data jobs, and supported Xcode 26-or-earlier work. Browser-console access; no Apple silicon, no GPU acceleration, no audio.
M-series from $95/month — physical Apple silicon for ARM-only execution, Xcode 27 and visionOS. Exact chip, RAM and disk are confirmed per quote; physical plans collect requests until supply is confirmed.
Managed Build Mac $249/month — one M-series Mac with CI setup, backups, monitoring and 30 minutes of monthly support included. Use when you want someone else to wire up the signing keychain, runner registration and log retention.

Start at /mac-hosting or request a configuration and state your toolchain, target architecture, and whether you need the box to survive browser or network disconnects for hours or days at a time.