v3.26.1
Non-cash stock-based compensation - Summary of assumptions Vesting Details (Detail) - EUR (€)
6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Weighted-Average fair values of stock options granted € 2,020.00 € 870
Bottom of Range [member]    
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Risk-free interest rate 2.92% 2.78%
Exercise price € 3.12 € 1.26
Expected volatility 71.30% 65.00%
Expected term (in years) 5.93 5.93
Top of Range [member]    
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Risk-free interest rate 3.24% 2.95%
Exercise price € 3.49 € 1.56
Expected volatility 71.90% 65.90%
Expected term (in years) 6.17 6.12
Stock options [member]    
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Share entitlement per option 1 1
Vesting conditions Performance & Service Performance & Service
Vesting period Graded Graded
Stock options [member] | Bottom of Range [member]    
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Underlying stock price at grant date € 2.97 € 1.26
Stock options [member] | Top of Range [member]    
Disclosure of terms and conditions of share-based payment arrangement [line items]    
Underlying stock price at grant date € 3.38 € 1.52