On Samsung phones, the headset button belongs to Bixby or Google — not Muse
A user set Muse as the default assistant on a Samsung phone, but the Bluetooth headset button still offers only Bixby or Google, and button-remapper apps do not fix it. The cause is Samsung's assistant routing, which reserves the headset button for its own assistants. The workarounds are Muse's own voice trigger or a home-screen widget, plus keeping Bixby disabled so it stops intercepting.