stutter

A focus-aware process priority daemon.

When you switch windows, stutter automatically raises the CPU priority of the focused process and restores the previous one. This reduces input latency and makes the active window feel more responsive under load.

How it works

stutter connects to your compositor's IPC socket and listens for focus change events. On each focus change it calls setpriority(2) to set the focused process to nice -5 and resets the previously focused process back to 0. On exit, the last focused process is restored to the default priority.

Supported backends

• Hyprland
• Niri

Configuration

The configuration file is located at ~/.config/stutter/config.toml. It is automatically created with default values on the first run.

# CPU priority of the focused window (lower = higher priority, min -20)
focused_nice = -5

# CPU priority of all other windows (restored when window loses focus)
default_nice = 0

# Per-app overrides (optional)
# The key is the window class or app_id
[apps]
"kitty" = { focused_nice = -10 }
"firefox" = { focused_nice = -2 }

You can reload the configuration without restarting the daemon by sending a SIGHUP signal:

pkill -HUP stutter
# or via systemd
systemctl --user reload stutter

Requirements

• Permission to lower nice values - either run as root, or grant the binary CAP_SYS_NICE:

sudo setcap cap_sys_nice+ep /usr/bin/stutter

Installation

AUR (recommended)

yay -S stutter-daemon
# or
paru -S stutter-daemon

Pre-built binary

curl -L https://github.com/Kleshzz/stutter/releases/latest/download/stutter \
  -o /tmp/stutter
sudo install -Dm755 /tmp/stutter /usr/bin/stutter

From source

cargo install stutter-daemon
# or build manually:
cargo build --release
sudo install -Dm755 target/release/stutter /usr/bin/stutter

Setup

Grant permissions (pick one)

# Option A - capability (recommended)
sudo setcap cap_sys_nice+ep /usr/bin/stutter

# Option B - run as root (not recommended)

Autostart

systemd (recommended):

# AUR install — service is already in place:
systemctl --user enable --now stutter

# Manual install — copy service file first:
cp stutter.service ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user enable --now stutter

hyprland.conf:

exec-once = stutter

niri (config.kdl):

spawn-at-startup "stutter"

License

MIT