Stock-based compensation - Stock Option Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2026	Dec. 31, 2025
Number of Options
Beginning balance (in shares)	20,716,511
Granted (in shares)	6,620,200
Exercised (in shares)	(2,260,119)
Canceled/Forfeited (in shares)	(1,876,559)
Expired (in shares)	(59,622)
Ending balance (in shares)	23,140,411	20,716,511
Exercisable (in shares)	11,371,137
Weighted Average Exercise Price per Share
Beginning balance (in usd per share)	$ 3.27
Granted (in usd per share)	3.16
Exercised (in usd per share)	2.76
Canceled/Forfeited (in usd per share)	3.10
Expired (in usd per share)	7.80
Ending balance (in usd per share)	3.29	$ 3.27
Exercisable, weighted average price (in usd per share)	$ 3.44
Weighted Average Remaining Contractual Term (in years)	7 years 10 months 24 days	7 years 6 months
Exercisable, weighted average remaining contractual term (in years)	6 years 8 months 12 days
Intrinsic value, shares outstanding	$ 192,964
Intrinsic value, exercised	6,330
Exercisable, aggregate intrinsic value	$ 93,578

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.