v3.25.4

Summary of Significant Accounting Policies (Details) kr in Millions	12 Months Ended
	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Nov. 07, 2025 USD ($)	Nov. 07, 2025 SEK (kr)	May 31, 2025 USD ($)
Class of Stock [Line Items]
Accumulated deficit	$ (224,284,000)	$ (200,126,000)
Cash and cash equivalents	116,729,000	119,709,000
Marketable investment securities	182,776,000	173,421,000
Allowance for credit losses	0	0
Convertible loan receivable				$ 2,100,000	kr 20.0
Convertible loan receivable, basis spread on variable rate				2.00%	2.00%
Long-lived assets, impairment charges	0	0	$ 0
Earnout payment of contingent consideration	2,500,000	0	0
Accrued bonuses	28,100,000	23,300,000
Discretionary matching contributions	$ 6,100,000	$ 5,500,000	$ 4,600,000
Stock options
Class of Stock [Line Items]
Service period	4 years
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Service period	4 years
Capsulomics
Class of Stock [Line Items]
Additional consideration payable based on achievement of certain commercial milestones						$ 2,500,000
Earnout payment of contingent consideration	$ 500,000
Contingent consideration, milestone achievement	60 days
Minimum
Class of Stock [Line Items]
Property, plant and equipment, useful life	5 years
Maximum
Class of Stock [Line Items]
Property, plant and equipment, useful life	10 years

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CASTLE BIOSCIENCES INC 10-K