144 0001063663 XXXXXXXX LIVE 0001889956 OneStream, Inc. 001-42187 191 N. Chester Street Birmingham MI 48009 1-248-650-1490 Jonathan Mariner Director Common Stock Goldman Sachs & Co. LLC 200 West Street New York NY 10282 18564 370537.44 88136155 09/03/2025 NASD Common Stock 07/27/2020 Acquired Class C common shares from Issuer; Class C common shares were converted to Class A common shares The Issuer N 18564 07/27/2020 None N Jonathan Mariner 191 N Chester St Birmingham MI 48009 Common Stock 08/04/2025 1989 47173.91 Jonathan Mariner 191 N Chester St Birmingham MI 48009 Common Stock 08/04/2025 4641 108855.58 Jonathan Mariner 191 N Chester St Birmingham MI 48009 Common Stock 07/07/2025 1989 53084.22 Jonathan Mariner 191 N Chester St Birmingham MI 48009 Common Stock 07/07/2025 4641 123179.1 The sales of shares set forth herein are made in connection with a selling plan dated 2/28/25, that is intended to comply with Rule 10b5-1(c). 09/03/2025 02/28/2025 Goldman Sachs & Co. LLC on behalf of Jonathan Mariner