Logitech Host Switch

Switch both your Logitech mouse and keyboard to another host by holding the Forward Button for 400ms. Short taps preserve normal browser-forward behavior.

Built for multi-host setups (Linux/Mac/Windows) where you want one-button switching from Linux. Uses Solaar for key diversion and raw HID++ for fast, reliable host switching.

How It Works

Hold Forward Button (>=400ms)
  -> switch_host.py sends raw HID++ change-host commands
  -> both keyboard and mouse switch to the target host

Tap Forward Button (<400ms)
  -> switch_host.py emits XF86Forward keypress via evdev
  -> normal browser-forward behavior preserved

Two Solaar rules intercept the Forward Button press and release events, calling switch_host.py for each. The script measures hold duration using monotonic timestamps.

Host switching bypasses Solaar's CLI entirely — HID++ commands are written directly to the Unifying receiver's hidraw device for speed and reliability.

A companion redivert_watch.py daemon runs in the background to fix a Solaar bug where key diversion is lost after a host-switch reconnect.

Requirements

• Solaar (with GUI or daemon running)
• Python 3 with PyYAML (sudo apt install python3-yaml)
• python3-evdev (sudo apt install python3-evdev) — for Forward key passthrough on short taps

Quick Start

git clone https://github.com/YOUR_USER/logitech-host-switch.git
cd logitech-host-switch

# 1. Edit config.yaml with your device settings (see Configuration below)
nano config.yaml

# 2. Divert the Forward Button in Solaar GUI:
#    Select your mouse -> Key/Button Diversion -> enable Forward Button

# 3. Run the installer
./install.sh

# 4. Restart Solaar
killall solaar; nohup solaar >/dev/null 2>&1 &

Configuration

All device-specific settings live in config.yaml. Edit this file before running install.sh.

Finding Your Device Settings

Run solaar show to find:

Config Field	How to Find
receiver_hidraw	First "Device path" line in solaar show output
mouse.name	Device name shown by Solaar (e.g., "MX Master 3 Wireless Mouse")
mouse.dev_number	Number before the device name (e.g., "2: MX Master 3" -> 2)
mouse.change_host_feature_index	Feature list index for CHANGE_HOST (e.g., feature 10)
keyboard.name	Keyboard device name
keyboard.dev_number	Number before the keyboard name
keyboard.change_host_feature_index	Feature list index for CHANGE_HOST on keyboard
target_host_index	0 = Host 1, 1 = Host 2, 2 = Host 3
hold_threshold	Seconds to hold before triggering (default 0.4)

Example solaar show Output

Unifying Receiver
  Device path  : /dev/hidraw0        <-- receiver_hidraw
  1: MX Keys Keyboard                <-- keyboard dev_number=1
    9: CHANGE HOST  {1814}           <-- keyboard change_host_feature_index=9
  2: MX Master 3 Wireless Mouse      <-- mouse dev_number=2
    10: CHANGE HOST  {1814}          <-- mouse change_host_feature_index=10

Files

File	Purpose
config.yaml	Device-specific settings
switch_host.py	Hold detection + raw HID++ host switch
redivert_watch.py	Daemon that re-applies Forward Button diversion after reconnect
rules.yaml	Solaar rule definitions (symlinked by installer)
config_loader.py	Shared config file loader
logitech-redivert.service	systemd user service template
install.sh	Installer (symlinks rules, installs service)

Manual Setup (Without install.sh)

1. Divert the Forward Button

In Solaar GUI: select your mouse -> Key/Button Diversion -> enable Forward Button.

2. Install Rules

Edit rules.yaml — replace __INSTALL_DIR__ with the full path to this directory, then symlink:

ln -sf /path/to/logitech-host-switch/rules.yaml ~/.config/solaar/rules.yaml

3. Start the Redivert Watcher

# One-off
python3 /path/to/redivert_watch.py &

# Or install the systemd service manually
cp logitech-redivert.service ~/.config/systemd/user/
# Edit the service file: replace __INSTALL_DIR__ with actual path
systemctl --user daemon-reload
systemctl --user enable --now logitech-redivert

4. Restart Solaar

killall solaar; nohup solaar >/dev/null 2>&1 &

Testing

# Dry-run hold test (>=400ms)
cd /path/to/logitech-host-switch
python3 switch_host.py pressed && sleep 0.5 && python3 switch_host.py released --dry-run

# Dry-run tap test (<400ms)
python3 switch_host.py pressed && sleep 0.1 && python3 switch_host.py released --dry-run

# Check redivert service
systemctl --user status logitech-redivert
journalctl --user -u logitech-redivert -f

# Check switch log
cat /tmp/.solaar-switch.log

Troubleshooting

• Nothing happens on hold: Check Forward Button is diverted — solaar show YOUR_MOUSE | grep Diversion
• Only keyboard switches (not mouse): Verify receiver_hidraw, dev_number, and change_host_feature_index in config.yaml match solaar show output
• Forward key doesn't work on short tap: Ensure python3-evdev is installed and your user can write to /dev/uinput
• Permission denied on hidraw: Solaar's udev rules should grant access. Check: ls -la /dev/hidraw*
• Redivert watcher not running: systemctl --user status logitech-redivert
• Switch works once then stops: The redivert watcher should fix this automatically. Check its logs.

Rollback

Un-divert the Forward Button in Solaar GUI to restore default behavior. The rules become inert when the button isn't diverted.

# Disable the service
systemctl --user disable --now logitech-redivert

# Remove the rules symlink
rm ~/.config/solaar/rules.yaml

Why Raw HID++ Instead of solaar config?

The solaar config change-host CLI command goes through D-Bus to the running Solaar GUI. For the device that triggered the Solaar rule (the mouse), this path silently fails — the command reports success but the HID++ write doesn't reach the device. Writing directly to the receiver's hidraw device bypasses this entirely and is both faster and more reliable.