Redeemable Convertible Preferred Stock - Schedule of Temporary Equity (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)	0			122,231,454
Temporary equity, shares issued (in shares)	0			122,231,454
Temporary equity, shares outstanding (in shares)	0	122,231,454	122,231,454	122,231,454	122,231,454	122,231,454	122,231,454	122,231,454
Carrying Value	$ 0	$ 768,566	$ 768,566	$ 768,566	$ 768,566	$ 768,566	$ 768,566	$ 768,566
Liquidation Value	$ 0			$ 951,917
Series A
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				4,082,965
Temporary equity, shares issued (in shares)				4,082,965
Temporary equity, shares outstanding (in shares)				4,082,965
Carrying Value				$ 2,041
Liquidation Value				$ 2,041
Series B-1
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				1,954,846
Temporary equity, shares issued (in shares)				1,954,846
Temporary equity, shares outstanding (in shares)				1,954,846
Carrying Value				$ 6,940
Liquidation Value				$ 6,940
Series B-2
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				2,848,263
Temporary equity, shares issued (in shares)				2,848,263
Temporary equity, shares outstanding (in shares)				2,848,263
Carrying Value				$ 10,111
Liquidation Value				$ 10,111
Series C
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				11,343,434
Temporary equity, shares issued (in shares)				11,343,434
Temporary equity, shares outstanding (in shares)				11,343,434
Carrying Value				$ 104,378
Liquidation Value				$ 193,167
Series D
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				7,151,873
Temporary equity, shares issued (in shares)				7,151,873
Temporary equity, shares outstanding (in shares)				7,151,873
Carrying Value				$ 110,756
Liquidation Value				$ 110,854
Series E
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				12,040,980
Temporary equity, shares issued (in shares)				12,040,980
Temporary equity, shares outstanding (in shares)				12,040,980
Carrying Value				$ 304,197
Liquidation Value				$ 305,018
Series F
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				61,344,029
Temporary equity, shares issued (in shares)				61,344,029
Temporary equity, shares outstanding (in shares)				61,344,029
Carrying Value				$ 168,957
Liquidation Value				$ 262,295
Series F-1
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)				21,465,064
Temporary equity, shares issued (in shares)				21,465,064
Temporary equity, shares outstanding (in shares)				21,465,064
Carrying Value				$ 61,186
Liquidation Value				$ 61,491