Income taxes - Effective Income Tax Rate Reconciliation 2024 (Details)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Expected provision at statutory federal rate	21.00%	21.00%
Stock-based compensation	(1.80%)	(4.20%)
State and local income tax - net of federal benefit	(0.10%)	6.40%
State credits		1.30%
Federal credits		3.00%
Change in valuation allowance	(22.00%)	(26.60%)
Withholding Tax		0.00%
Other permanent difference & true up	0.00%	(1.00%)
Total Income Tax Provision	(0.10%)	(0.10%)