X0609 4 2026-05-18 0001816431 Quantum-Si Inc QSI 0001184421 RAKIN KEVIN false C/O QUANTUM-SI INCORPORATED 29 BUSINESS PARK DRIVE BRANFORD CT 06405 true false Class A Common Stock 1200000 I See Footnote Class A Common Stock 20512 D Stock Option (right to buy) 0.8539 2026-05-18 4 A 0 251185 0 A 2036-05-18 Class A Common Stock 251185 251185 D HighCape Partners QSI II Invest, L.P. distributed in kind these shares of the Company's Class A common stock to its limited partners on a pro rata basis, for no consideration. Consists of (i) 24,527 shares of the Company's Class A common stock held by HighCape Partners II, L.P. and (ii) 1,175,473 shares of the Company's Class A common stock held by HighCape Partners QP II, L.P. Mr. Rakin is the managing member of HighCape Capital II GP, LLC, which is the general partner of HighCape Partners II GP, L.P., which is the general partner of each of HighCape Partners II, L.P. and HighCape Partners QP II, L.P., and as a result each may be deemed to share voting and investment discretion with respect to the Class A common stock held by such entities. The shares underlying this option vest on the date of the Issuer's next regular annual stockholders meeting, subject to continued service through the applicable vesting date. /s/ Christian LaPointe, Ph.D., Attorney-in-Fact. 2026-05-20