Share-based compensation - Options - Fair Value Assumptions (Details) - Share Options - $ / shares	3 Months Ended		12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024	Apr. 30, 2025	Mar. 31, 2025	Apr. 30, 2024	Mar. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate (%)	4.24%	4.05%	4.54%	4.21%
Expected volatility range (%)	83.92%	82.15%	55.32%	55.11%
Fair market value per ordinary share as at grant dates (in dollars per share)					$ 2.45	$ 4.05	$ 6.60	$ 7.50