Net Loss Per Share Attributable to Common shareholders - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Earnings Per Share [Abstract]
Net income (loss)	$ (71,790)	$ (66,186)	$ (174,370)	$ (177,214)
Deemed dividend from Series D redeemable convertible preferred stock (see note 6)	(384,436)	0	(384,436)	0
Adjustments of redeemable convertible preferred stock to redemption value	(60,971)	(23,594)	(85,433)	(46,707)
Net loss attributable to common shareholders basic	(517,197)	(89,780)	(644,239)	(223,921)
Net loss attributable to common shareholders diluted	$ (517,197)	$ (89,780)	$ (644,239)	$ (223,921)
Net loss per share attributable to common shareholders - basic (in dollars per share)	$ (7.97)	$ (2.54)	$ (12.80)	$ (6.34)
Net loss per share attributable to common shareholders - diluted (in dollars per share)	$ (7.97)	$ (2.54)	$ (12.80)	$ (6.34)
Weighted-average shares used in computing net loss per share attributable to common shareholders - basic (in shares)	64,918,988	35,371,424	50,348,947	35,342,180
Weighted-average shares used in computing net loss per share attributable to common shareholders - diluted (in shares)	64,918,988	35,371,424	50,348,947	35,342,180