Segment Disclosure - Summary of Net Loss Related To Segment Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Collaboration revenue	$ 7,500	$ 0	$ 0
Direct external research and development costs	300,938	210,394	167,512
Personnel-related expenses	89,703	68,340	47,739
stock-based compensation	53,707	50,717	32,372
Other research and development costs	12,519	11,232	9,560
Other general and administrative costs	26,794	20,657	14,376
Interest income	(26,828)	(41,943)	(27,620)
Other segment items	(332)	(3,025)	(4,041)
Net loss	(345,910)	(234,330)	(182,393)
Azetukalner
Segment Reporting Information [Line Items]
Direct external research and development costs	165,950	106,806	89,303
Pain programs (XEN1701, XEN1120)
Segment Reporting Information [Line Items]
Direct external research and development costs	7,510	4,795	0
Pre-clinical, discovery and other programs
Segment Reporting Information [Line Items]
Direct external research and development costs	$ 24,387	$ 16,751	$ 20,704