OS insider files Form 4: 141 shares sold via 10b5-1 plan, retains 33,509 shares

Rhea-AI Filing Summary

Jonathan D. Mariner, a director of OneStream, Inc. (OS), sold 141 shares of Class A common stock on 09/03/2025 under a Rule 10b5-1 trading plan. The transactions were executed at a weighted-average price of $20.07 per share within a reported price range of $20.00 to $20.16. After the sale, the reporting person beneficially owned 33,509 shares, which the filing states include unvested restricted stock units. The Form 4 indicates the sale was effected pursuant to a 10b5-1 plan adopted on February 28, 2025 and was reported by an attorney-in-fact on behalf of the reporting person.

Insights

Financial Analyst

TL;DR: A small, pre-planned insider sale under a 10b5-1 plan; ownership remains at 33,509 shares including unvested RSUs.

The Form 4 documents a sale of 141 shares at a weighted-average price of $20.07 executed under a Rule 10b5-1 plan adopted February 28, 2025. The size of the sale is modest relative to the reported post-transaction holding of 33,509 shares. Because the sale was executed under a pre-arranged plan and includes unvested restricted stock units in the remaining balance, this filing signals routine liquidity management by the director rather than a large disposition. Investors should note the explicit inclusion of unvested RSUs in beneficial ownership when assessing total stake.

Corporate Governance Expert

TL;DR: Transaction follows a documented 10b5-1 plan, which supports compliance and reduces signaling risk.

The reporting person used a Rule 10b5-1 trading plan adopted on February 28, 2025 to effect the sale, as disclosed in the Form 4. Use of an established trading plan typically mitigates concerns about opportunistic insider timing and supports procedural transparency. The filing also clarifies that remaining holdings include unvested restricted stock units, which affects the director's practical voting and economic power. This disclosure aligns with standard governance practices for orderly insider sales.

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

OMB APPROVAL

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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)
09/03/2025

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	09/03/2025		S(1)		141	D	$20.07(2)	33,509(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 141 shares sold in the price range of $20.00 to $20.16, 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.

	/s/ Holly Koczot, attorney-in-fact	09/04/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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