BALANCE SHEET COMPONENTS - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (2,201)	$ (2,419)
Property and equipment, net	380	388
Depreciable Property, Plant and Equipment
Property, Plant and Equipment [Line Items]
Total in service	2,547	2,807
Property and equipment, net	346	388
Research and development equipment
Property, Plant and Equipment [Line Items]
Total in service	1,801	1,763
Office and computer equipment
Property, Plant and Equipment [Line Items]
Total in service	494	808
Autos
Property, Plant and Equipment [Line Items]
Total in service	54	54
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total in service	46	41
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total in service	152	141
Construction in progress
Property, Plant and Equipment [Line Items]
Total in service	$ 34	$ 0