Segment Reporting - Segment Loss, Including Significant Segment Expenses (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
License revenue		$ 0	$ 10,844
Research and development expense	[1]	14,034	138,086
Provision for income taxes		0	2,000
Net loss and comprehensive loss		(17,867)	(153,942)
Net loss and comprehensive loss		(17,867)	(153,942)
Reportable Segment
Segment Reporting Information [Line Items]
License revenue		0	10,844
Personnel costs		1,214	31,022
Milestone and license fees		6,400	84,710
Professional and other fees		2,216	11,609
Other expense (income)		676	(690)
Provision for income taxes		0	2,000
Net loss and comprehensive loss			(153,942)	$ (17,867)
Net loss and comprehensive loss		(17,867)	(153,942)
Reportable Segment | CR-001 external research and development costs
Segment Reporting Information [Line Items]
Research and development expense		6,610	25,547
Reportable Segment | CR-002 external research and development costs
Segment Reporting Information [Line Items]
Research and development expense		751	8,636
Reportable Segment | Discovery external research and development costs
Segment Reporting Information [Line Items]
Research and development expense		$ 0	$ 1,952

[1] Includes related party amount of $23,653 for the twelve months ended months ended December 31, 2025 and $13,185 for the period from September 19, 2024 (inception) through December 31, 2024.