Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Sep. 30, 2025
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 95,708	$ 95,672
Less accumulated depreciation and amortization	(31,291)	(28,951)
Total property and equipment, net	64,417	66,721	$ 64,417
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment, gross	69,533	66,487
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment, gross	668	668
Research Equipment
Property Plant And Equipment [Line Items]
Total property and equipment, gross	18,380	17,576
Computers and Software
Property Plant And Equipment [Line Items]
Total property and equipment, gross	388	373
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 6,739	$ 10,568