Sec Form 3 Filing - Hohenstein Ken @ OneStream, Inc. - 2025-05-01

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Hohenstein Ken 2. Issuer Name and Ticker or Trading Symbol OneStream, Inc. [ OS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Revenue Officer (Last) (First) (Middle) C/O ONESTREAM, INC., 191 N. CHESTER STREET 3. Date of Earliest Transaction (MM/DD/YY) 05/01/2025 (Street) BIRMINGHAM, MI48009 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class A Common Stock 1,009,443 ( 1 ) ( 2 ) D Class A Common Stock 790,279 ( 3 ) I Hohenstein Purple Elephant 2019 Irrevocable Grantor Trust ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (right to buy) $ 10.65 ( 5 ) 03/05/2033 Class A Common Stock 298,508 D Stock Option (right to buy) $ 14.51 ( 6 ) 03/10/2034 Class A Common Stock 460,322 D Stock Option (right to buy) $ 20 ( 7 ) 07/22/2034 Class A Common Stock 159,806 D Stock Option (right to buy) $ 10.65 ( 8 ) 12/04/2031 Class A Common Stock 189,210 D Common Units $ 0 ( 9 ) ( 9 ) Class D Common Stock ( 10 ) 464,002 I CaitRyan LLC ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Hohenstein Ken C/O ONESTREAM, INC. 191 N. CHESTER STREET BIRMINGHAM, MI48009 Chief Revenue Officer Signatures /s/ Holly Koczot, as Attorney-in-Fact 05/06/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares reported include unvested restricted stock units. ( 2 )A portion of the shares reported were acquired upon the conversion, at the holder's election, of Class D Common Stock held by the holder on a 1:1 basis. ( 3 )The shares reported were acquired upon the conversion, at the holder's election, of Class D Common Stock held by the holder on a 1:1 basis. ( 4 )The Reporting Person may be deemed to have voting and dispositive power over the shares held by CaitRyan LLC and the Hohenstein Purple Elephant 2019 Irrevocable Grantor Trust. ( 5 )One-fourth of the shares subject to the option vested on February 15, 2024, and 1/48th of the shares subject to the option shall vest each month thereafter, subject to the Reporting Person continuing to be a service provider through the applicable vesting date. ( 6 )One-fourth of the shares subject to the option vested on February 15, 2025, and 1/48th of the shares subject to the option shall vest each month thereafter, subject to the Reporting Person continuing to be a service provider through the applicable vesting date. ( 7 )One-sixteenth of the shares subject to the option vested on October 23, 2024, and one-sixteenth of the shares subject to the option shall vest every three months thereafter, subject to the Reporting Person continuing to be a service provider through the applicable vesting date. ( 8 )One-fourth of the shares subject to the option vested on February 15, 2023, and 1/48th of the shares subject to the option shall vest each month thereafter, subject to the Reporting Person continuing to be a service provider through the applicable vesting date. ( 9 )The Common Units may be redeemed by the holder for shares of Class D Common Stock on a 1:1 basis, and an equal number of the holder's shares of Class C Common Stock (which have no economic rights) will be cancelled in connection with the redemption. The Common Units have no expiration date. ( 10 )The Class D Common Stock is convertible at any time, at the holder's election, into Class A Common Stock on a 1:1 basis. Each outstanding share of Class D Common Stock will automatically convert into one share of Class A common stock upon the earlier of (i) any transfer, whether or not for value, except for certain transfers exempted by the Issuer's amended and restated certificate of incorporation, (ii) death or incapacity (if the holder is a natural person), and (iii) the first trading day following the seventh anniversary of the Issuer's initial public offering.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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