144 0002032947 XXXXXXXX LIVE 0001816431 Quantum-Si Inc 001-39486 29 BUSINESS PARK DRIVE BRANFORD CT 06405 (203) 458-7100 Vieceli John S. Officer Class A Common Stock Morgan Stanley Smith Barney LLC

1 New York Plaza 38th Floor New York NY 10004

30223 28052.99 197822663 06/22/2026 NASDAQ Class A Common Stock 06/20/2026 Restricted Stock Unit Vesting Quantum-Si Incorporated N 79589 06/20/2026 Equity compensation for services rendered Y Shares sold to cover tax withholding obligations in connection with the vesting of restricted stock units. The sale is mandated by the Issuers election to require the satisfaction of tax withholding obligations through a sell to cover transaction and does not represent a discretionary trade by the reporting person. 06/24/2026 /s/ Christian LaPointe, Ph.D., Attorney-in-Fact