Segment Reporting - Summary of Segment Loss Including Significant Segment Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Research and development expenses:
Other expense, net	$ (27)	$ (26)
Net loss	(44,635)	(26,693)
Operating Segment
Research and development expenses:
Other research and development expenses	14,754	8,851
General and administrative expenses	9,975	6,882
Interest income	(2,825)	(2,735)
Other expense, net	52	70
Net loss	44,635	26,693
Operating Segment | KYV-101 program
Research and development expenses:
External research and development expenses allocated by program	22,120	10,997
Operating Segment | Other Programs
Research and development expenses:
External research and development expenses allocated by program	$ 559	$ 2,628