Income taxes - Schedule of effective income tax rate reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Income Tax Expense (Benefit), Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected provision at statutory federal rate	$ (22,025)
State and local income tax - net of federal benefit	95
Foreign tax effects	0
Effect of changes in tax laws or rates enacted in the current period	0
Effect of cross-border tax laws	0
R&D credits	(3,008)
Change in valuation allowance	23,093
Stock-based compensation	1,910
Other permanent difference & true up	52
Change in unrecognized tax benefits	0
Others	4
Total tax provision	$ 121	$ 131
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Expected provision at statutory federal rate	21.00%	21.00%
State and local income tax - net of federal benefit	(0.10%)	6.40%
Foreign tax effects	0.00%
Effect of changes in tax laws or rates enacted in the current period	0.00%
Effect of cross-border tax laws	0.00%
R&D credits	2.80%
Change in valuation allowance	(22.00%)	(26.60%)
Stock-based compensation	(1.80%)	(4.20%)
Other permanent difference & true up	0.00%	(1.00%)
Change in unrecognized tax benefits	0.00%
Others	0.00%
Total Income Tax Provision	(0.10%)	(0.10%)