BALANCE SHEET COMPONENTS - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (1,202)	$ (1,171)
Property and equipment, net	379	410
Depreciable Property, Plant and Equipment
Property, Plant and Equipment [Line Items]
Total in service	1,581	1,581
Research and development equipment
Property, Plant and Equipment [Line Items]
Total in service	1,291	1,291
Office and computer equipment
Property, Plant and Equipment [Line Items]
Total in service	84	84
Autos
Property, Plant and Equipment [Line Items]
Total in service	54	54
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total in service	47	47
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total in service	$ 105	$ 105