X0508 4 2025-10-16 0001816431 Quantum-Si Inc QSI 0001076352 ROTHBERG JONATHAN M C/O QUANTUM-SI INCORPORATED 29 BUSINESS PARK DRIVE BRANFORD CT 06405 true true true Class A Common Stock 2025-10-16 4 S 0 26095 3.07 D 1904866 I By NVR TR, LLC Class A Common Stock 1930960 I By JNR TR, LLC Class A Common Stock 1930960 I By GBR TR, LLC Class A Common Stock 1930960 I By EJR TR, LLC Class A Common Stock 1250000 I By JAR TR, LLC Class A Common Stock 2568443 D Class A Common Stock 1917067 I By 23rd Century Capital LLC Class A Common Stock 273422 I By Bonnie E Gould Rothberg MD Class B Common Stock 17943750 I By 4C Holdings I, LLC Class B Common Stock 1993750 I By 4C Holdings V, LLC This sale was effected in connection with estate planning pursuant to a 10b5-1 trading plan established by Dr. Rothberg on September 13, 2024. Represents the weighted average sales price per share. The shares sold at prices ranging from $3.07 to $3.09 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Includes additional shares of Class A common stock previously held by 2012 JMR Trust Common, LLC that were distributed for estate planning purposes to NVR TR, LLC, JNR TR, LLC, GBR TR, LLC and EJR TR, LLC. Dr. Rothberg is the sole manager of 4C Holdings I, LLC, 4C Holdings V, LLC, 2012 JMR Trust Common, LLC, NVR TR, LLC, JNR TR, LLC, GBR TR, LLC, EJR TR, LLC and JAR TR, LLC and. Dr. Rothberg is the spouse of Bonnie E. Gould Rothberg MD and Dr. Rothberg's son is the manager of 23rd Century Capital LLC. Dr. Rothberg disclaims beneficial ownership of the shares held by his spouse and 23rd Century Capital LLC. /s/ Jonathan M. Rothberg, Ph.D. 2025-10-17