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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of risks (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Concentration of risks
Research and development	$ 45,377	$ 29,939	$ 24,844
Cash and cash equivalents	352,932	31,677
Cash deposit	337,291	31,677
Cash, Uninsured Amount	334,557
Non-US
Concentration of risks
Cash and cash equivalents	84,390	21,469
Research and development expense \| Supplier concentration risk \| A
Concentration of risks
Research and development		5,010	7,941
Research and development expense \| Supplier concentration risk \| B
Concentration of risks
Research and development	10,802	5,846	$ 6,926
Research and development expense \| Supplier concentration risk \| C
Concentration of risks
Research and development	4,987
Cash \| Geographic concentration risk \| UNITED STATES
Concentration of risks
Cash and cash equivalents	$ 252,901	$ 10,208
Cash and Cash Equivalents \| Credit Concentration Risk \| Single Financial Institution In United States
Concentration of risks
Concentration Risk, Percentage	70.00%