Herdr Sysmon

System metrics in the Herdr sidebar — a faithful port of a tmux-cpu / tmux-battery / tmux-online-status status bar into Herdr workspace tokens.

Renders in the left sidebar, per workspace:

• CPU % (100 − idle)
• Memory — active + wired pages → GB (port of ~/dotfiles/tmux/memory.sh)
• Battery — Nerd Font glyph + percentage, charging-aware
• Network — 󰖩 on / 󰖪 off (ping)
• Disk — free space on the home filesystem
• Clock — weekday, month, day, time
• Focused pane path (basename, truncated), zoom flag, prefix indicator

Built-in workspace / branch / git_status tokens are reused, so the sidebar also covers what tmux status-left showed for session name and Git context.

How it works

Herdr's startup hook is one-shot, so the plugin's startup hook detaches a long-running poll.sh poller and exits. The poller:

1. Collects every metric once per cycle (default 5s).
2. Pushes them as custom workspace metadata tokens via herdr workspace report-metadata --source sysmon.
3. Repeats across all workspaces, picking up new ones on the next cycle.

The sidebar config renders those tokens as $sys_*.

Reliability

• No set -e in the loop — a single metric or CLI failure never exits.
• Never-empty tokens — every collector falls back to --; a total command failure is coerced to a placeholder so a sidebar row never vanishes.
• Primed on first cycle — tokens exist before the sidebar first paints.
• Pidfile guard — Herdr restarts never spawn duplicate pollers.
• Graceful on socket loss — if the Herdr server is stopped, the poller retries next cycle; tokens are restored the moment a workspace reappears.

Install

Once Herdr is installed and the plugin API is available:

# from a local checkout
herdr plugin install ~/local-dev/getpipher/herdr-sysmon

# or, once published, from GitHub
herdr plugin install getpipher/herdr-sysmon

Then merge the sidebar config into your config.toml:

cat ~/local-dev/getpipher/herdr-sysmon/config/sidebar.toml.snippet >> ~/.config/herdr/config.toml
herdr server reload-config

Verify the path with prefix+s (in-app settings) if ~/.config/herdr/ is not correct on your system.

Requirements

• Herdr ≥ 0.7.0
• macOS (v0.1 uses pmset, vm_stat, df). Linux reads land in v0.2.
• jq (for parsing herdr … --json)
• A Nerd Font for the battery / wifi / clock glyphs (JetBrainsMono Nerd Font works, matching the existing Ghostty config)

Config

Env var	Default	Meaning
SYSMON_CADENCE_SEC	5	Seconds between pushes. Lower = fresher, more CPU.
HERDR_BIN_PATH	herdr	Set by the plugin runtime; override for manual runs.
HERDR_PLUGIN_STATE_DIR	<plugin>/.state	Where the pidfile + log live.

State files (in HERDR_PLUGIN_STATE_DIR or .state/):

• sysmon.pid — poller pid
• sysmon.log — per-cycle log

Operate

# start manually (foreground, for testing)
bash scripts/poll.sh --run

# spawn detached (what the startup hook does)
bash scripts/poll.sh --spawn

# stop the poller
bash scripts/poll.sh --stop

# tail the log
tail -f .state/sysmon.log

v0.1 scope

• macOS only (pmset, vm_stat, df ~). v0.2 adds Linux reads.
• $sys_path / $sys_prefix are best-effort — $sys_path reads herdr pane current (.result.pane.cwd, confirmed shape); $sys_zoom reads herdr pane layout (.result.layout.zoomed, confirmed it flips on toggle). $sys_prefix has no CLI/snapshot exposure in v0.1 (prefix-active state is not surfaced) and stays empty pending a socket subscription in v0.2. The 6 system metrics (the core requirement) are fully covered regardless.
• No supervisor beyond the startup hook. The poller is self-healing within a run (a failed metric never kills the loop), but a shell crash leaves it down until the next Herdr restart relaunches via the startup hook. A launchd KeepAlive wrapper is planned as a Phase 2 belt-and-suspenders layer for "never down" guarantees.
• No theming — v0.1 renders tokens in the sidebar's contextual style. The Catppuccin per-widget color map (maroon / teal / lavender / peach / blue / yellow from the old status bar) is v0.2 via inline fg style tables.

Uninstall

herdr plugin uninstall getpipher.herdr-sysmon
# remove the merged sidebar block from config.toml, then:
herdr server reload-config

License

MIT © 2026 RECTOR