OneStream (NYSE: OS) director reports 7,956-share sale under 10b5-1 plan

Rhea-AI Filing Summary

OneStream, Inc. director Jonathan D. Mariner reported open-market sales of the company’s Class A Common Stock under a pre-arranged Rule 10b5-1 trading plan adopted on February 28, 2025. On January 6, 2026, he sold 2,415 shares at a weighted average price of $22.66, followed by a sale of 5,541 shares at a weighted average price of $23.59.

After these transactions, Mariner reported owning 7,130 shares of Class A Common Stock directly, and the reported holdings include unvested restricted stock units. Both transactions were coded as routine sales, and there were no derivative security transactions reported.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

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

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

MARINER JONATHAN D

(Last) (First) (Middle)

C/O ONESTREAM, INC.

191 N. CHESTER STREET

(Street)

BIRMINGHAM MI 48009

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
OneStream, Inc. [ OS ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
01/06/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	01/06/2026		S(1)		2,415	D	$22.66(2)	12,671(3)	D
Class A Common Stock	01/06/2026		S(1)		5,541	D	$23.59(4)	7,130(3)	D

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on February 28, 2025.

2. Represents the weighted average share price of an aggregate total of 2,415 shares sold in the price range of $22.375 to $23.275, inclusive, by the Reporting Person. The Reporting Person undertakes to provide upon request by the staff of the Securities and Exchange Commission, the issuer or any security holder of the issuer, full information regarding the number of shares sold at each separate price within the range set forth in this footnote in this Form 4.

3. The shares reported include unvested restricted stock units.

4. Represents the weighted average share price of an aggregate total of 5,541 shares sold in the price range of $23.555 to $23.635, inclusive, by the Reporting Person. The Reporting Person undertakes to provide upon request by the staff of the Securities and Exchange Commission, the issuer or any security holder of the issuer, full information regarding the number of shares sold at each separate price within the range set forth in this footnote in this Form 4.

	/s/ Holly Koczot, attorney-in-fact	01/08/2026
	** Signature of Reporting Person	Date
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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FAQ

Who reported the insider stock transactions at OneStream (OS)?

The transactions were reported by Jonathan D. Mariner, a director of OneStream, Inc., in a Form 4 filed under SEC Section 16 rules.

How many OneStream (OS) shares did the director sell in this Form 4?

Jonathan D. Mariner reported selling 2,415 shares of Class A Common Stock at a weighted average price of $22.66 and 5,541 shares at a weighted average price of $23.59 on January 6, 2026.

What trading plan governed the OneStream (OS) director’s stock sales?

The sales were effected pursuant to a Rule 10b5-1 trading plan that the reporting person adopted on February 28, 2025, as disclosed in the footnotes.

How many OneStream (OS) shares does the director hold after these sales?

Following the reported transactions, Jonathan D. Mariner reported 7,130 shares of OneStream Class A Common Stock held directly.

What do the weighted average prices in the OneStream (OS) Form 4 mean?

The filing states that $22.66 and $23.59 represent weighted average prices for sales of 2,415 and 5,541 shares within specified price ranges. Detailed per-trade prices are available on request from the reporting person.

Do the director’s reported OneStream (OS) holdings include restricted stock units?

Yes. A footnote explains that the shares reported include unvested restricted stock units as part of the director’s beneficial ownership.