OS Form 4: Jonathan Mariner trims stake, still holds 33,650 shares

Rhea-AI Filing Summary

On 08/04/2025, OneStream, Inc. (OS) director Jonathan D. Mariner reported selling 6,630 Class A common shares through a Rule 10b5-1 trading plan adopted on 02/28/2025. The weighted-average sale price was $23.53 (range: $23.095-$23.79). After the transaction, he beneficially owns 33,650 shares, which include unvested restricted stock units. No derivative securities were exercised or acquired.

The sale represents a modest portion of the director’s holdings and, because it was pre-scheduled, is generally viewed as routine liquidity management rather than a directional bet. Nonetheless, any insider disposition can prompt investor scrutiny regarding short-term valuation expectations.

Insights

Financial Analyst

TL;DR: Small, pre-planned insider sale; neutral valuation signal with limited impact.

The 6,630-share disposition equates to roughly 4% of Mr. Mariner’s post-sale stake. At a $23.53 average price, proceeds are about $156k, immaterial to market cap and unlikely to alter fundamentals. The 10b5-1 structure reduces concerns about opportunistic timing, so I view the filing as informational rather than directional. Market reaction should be muted.

Corporate Governance Specialist

TL;DR: Governance-compliant 10b5-1 trade; minimal red flags.

Execution under a documented 10b5-1 plan aligns with best-practice disclosure, supporting transparency and mitigating insider-trading risk. Mariner remains a meaningful shareholder, preserving alignment with investors. Absent additional insider selling or adverse events, governance impact is neutral.

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

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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)
08/04/2025

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	08/04/2025		S(1)		6,630	D	$23.53(2)	33,650(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 6,630 shares sold in the price range of $23.095 to $23.79, 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	08/06/2025
	** 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

How many OneStream (OS) shares did Jonathan D. Mariner sell?

He sold 6,630 Class A common shares on 08/04/2025.

What was the sale price for the OS shares?

The weighted-average price was $23.53, within a $23.095-$23.79 range.

Does the director still hold OneStream stock after the sale?

Yes, he now beneficially owns 33,650 shares, including unvested RSUs.

Was the transaction conducted under a 10b5-1 plan?

Yes, the plan was adopted on 02/28/2025.

What is Jonathan D. Mariner’s role at OneStream?

He serves as a Director on the company’s board.

Were any derivative securities involved in this Form 4?

No, the filing reports only a sale of common shares; no derivatives were exercised or disposed.