tmux bell-action vs monitor-activity for silent background job alerts

Recommended Configuration for Silent Alerts

To achieve silent, non-intrusive notifications for background jobs, avoid using bell-action to switch windows. Instead, combine monitor-activity with a silence timer and rely on the terminal emulator's visual bell for explicit alerts.

1. Handling the System Bell (Visual Alerts)

The bell-action option controls focus (which window becomes active), not the visual or audible nature of the alert. If the OS sound is muted, bell-action will not create a visual flash; that behavior is governed by your terminal emulator's "Visual Bell" setting and the visual-bell option in tmux.

To trigger a silent visual alert without switching windows, use these settings:

set-option -g bell-action none
set-option -g visual-bell on

2. Managing Background Activity Noise

The monitor-activity option is a coarse tool. It cannot be configured to ignore specific strings (like \n) or filter by output size; any write to the pane will trigger the activity flag. To reduce clutter from frequent background output, use activity-silence to group bursts of output into a single notification.

Example configuration for low-noise activity monitoring:

set-option -g monitor-activity on
set-option -g activity-silence 10s

Comparison Summary

Feature	Trigger	Notification Type	Granularity
bell-action	printf '\a'	Window switch / Terminal Bell	Explicit (Manual)
monitor-activity	Any stdout/stderr	Status bar highlight	Coarse (Any output)

Verification Steps

1. Test Visual Bell: Run printf '\a' in a pane. If no flash occurs despite visual-bell on, check your terminal emulator settings (e.g., iTerm2 > Profiles > Terminal > "Allow visual bell").
2. Test Activity Silence: Enable monitor-activity and run a loop that prints every second. Verify that the status bar does not flicker constantly if activity-silence is set to a higher value than the loop interval.

Diagnostic Detail Needed: Please specify your tmux version (tmux -V), as bell-handling options have evolved across versions and may affect option availability.