BALANCE SHEET COMPONENTS - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (2,242)	$ (2,419)
Total property, plant and equipment, net	407	388
Depreciable Property, Plant And Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,577	2,807
Total property, plant and equipment, net	335	388
Research and development equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,826	1,763
Office and computer equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	494	808
Autos
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	54	54
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	46	41
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	157	141
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 72	$ 0