Insider Thomas Anthony Shea reports 16.3% OneStream (OS) ownership stake

Rhea-AI Filing Summary

Thomas Anthony Shea filed an amended Schedule 13G reporting significant ownership in OneStream, Inc. Class A common stock. He beneficially owns 18,173,259 shares on an as-converted basis, representing 16.3% of the class.

Shea has sole voting and dispositive power over 5,897,454 shares and shared voting and dispositive power over 12,275,805 shares held through family trusts and related entities. The stake includes Class D common stock that is convertible into Class A common stock, as well as options exercisable within 60 days of December 31, 2025.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

ONESTREAM, INC.

(Name of Issuer)

Class A Common Stock, par value $0.0001 per share

(Title of Class of Securities)

68278B107

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 68278B107

1

Names of Reporting Persons

Thomas Anthony Shea

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 5,897,454.00
6	Shared Voting Power 12,275,805.00
7	Sole Dispositive Power 5,897,454.00
8	Shared Dispositive Power 12,275,805.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

18,173,259.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

16.3 %

12

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person: Items 5, 7, and 9 consist of (i) 325,232 shares of Class D common stock, par value $0.0001 per share ("Class D Common Stock"), held by TSICU Corp., of which Mr. Shea is the sole owner and maintains control, issuable upon redemption or exchange of Common Units of OneStream Software LLC ("Common Units"), together with the cancellation of an equal number of shares of Class C common stock, par value $0.0001 per share ("Class C Common Stock"); (ii) 3,894,049 shares of Class D Common Stock held of record by Mr. Shea; (iii) 57,617 shares of Class A common stock, par value $0.0001 per share ("Class A Common Stock") held of record by Mr. Shea; and (iv) 1,620,556 shares of Class A Common Stock subject to options that are vested and exercisable within 60 days of December 31, 2025. Items 6, 8, and 9 consist of (i) 7,525,803 shares of Class D Common Stock held by the Shea Family Trust dated December 25, 2019, of which Mr. Shea's spouse serves as co-trustee; and (ii) 4,750,002 shares of Class D Common Stock held by the Thomas A. Shea 2020 Annuity Trust dated December 23, 2020, of which Mr. Shea's spouse serves as trustee. Items 5, 6, 7, 8, and 9 assume conversion of Class D Common Stock beneficially owned by Mr. Shea, including those shares issuable upon redemption or exchange of Common Units, into Class A Common Stock. Each share of Class D Common Stock is convertible at any time at the option of the holder into one share of Class A Common Stock. In addition, each share of Class D Common Stock will convert automatically 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), provided that, with respect to Mr. Shea and his permitted transferees, conversion would be deferred for nine months following any such event, and (iii) the first trading day following the seventh anniversary of the Issuer's initial public offering. Item 11 is based on the quotient obtained by dividing (a) the aggregate amount beneficially owned by Mr. Shea as set forth in Item 9 by (b) the sum of (i) 93,318,973 shares of Class A Common Stock outstanding as of December 31, 2025, as reported by the Issuer to the Reporting Person; (ii) 325,232 shares of Class D Common Stock issuable upon redemption or exchange of the Common Units; (iii) 16,169,854 shares of Class D Common Stock beneficially owned by Mr. Shea; and (iv) 1,620,556 shares of Class A Common Stock subject to options that are vested and exercisable within 60 days of December 31, 2025. The aggregate number of shares of Class D Common Stock beneficially owned by Mr. Shea, including those issuable upon redemption or exchange of Common Units, as set forth in clauses (ii) and (iii) of this footnote are treated as converted into Class A Common Stock only for the purpose of computing the percentage ownership of Mr. Shea.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: ONESTREAM, INC.
(b)	Address of issuer's principal executive offices: 191 N. Chester Street, Birmingham, MI, 48009.
Item 2.
(a)	Name of person filing: This statement is filed by Thomas Anthony Shea, also referred to herein as the "Reporting Person."
(b)	Address or principal business office or, if none, residence: c/o OneStream, Inc. 191 N. Chester Street Birmingham, Michigan 48009
(c)	Citizenship: See response to Item 4 on the cover page.
(d)	Title of class of securities: Class A Common Stock, par value $0.0001 per share
(e)	CUSIP No.: 68278B107
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: See response to Item 9 on the cover page hereto.
(b)	Percent of class: See response to Item 11 on the cover page hereto
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See response to Item 5 on the cover page hereto.
	(ii) Shared power to vote or to direct the vote: See response to Item 6 on the cover page hereto.
	(iii) Sole power to dispose or to direct the disposition of: See response to Item 7 on the cover page hereto.
	(iv) Shared power to dispose or to direct the disposition of: See response to Item 8 on the cover page hereto.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.	Certifications:
	Not Applicable

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Thomas Anthony Shea

Signature:	/s/ Thomas Anthony Shea
Name/Title:	Thomas Anthony Shea
Date:	02/13/2026

FAQ

What ownership stake in OneStream (OS) does Thomas Anthony Shea report?

Thomas Anthony Shea reports beneficial ownership of 18,173,259 OneStream shares, representing 16.3% of the Class A common stock on an as-converted basis. This reflects both direct holdings and indirect interests through entities and stock options.

How many OneStream shares does Thomas Anthony Shea control solely?

Thomas Anthony Shea has sole voting and dispositive power over 5,897,454 OneStream shares. These include Class D common stock, Class A common stock held in his name, and stock options that are vested and exercisable within 60 days of December 31, 2025.

How many OneStream shares does Thomas Anthony Shea hold with shared control?

Shea reports shared voting and dispositive power over 12,275,805 shares. These are primarily Class D common stock held by the Shea Family Trust and the Thomas A. Shea 2020 Annuity Trust, where his spouse serves as trustee or co-trustee.

What is the structure of Thomas Anthony Shea’s Class D holdings in OneStream (OS)?

Shea’s Class D holdings include shares held by TSICU Corp., the Shea Family Trust, and the Thomas A. Shea 2020 Annuity Trust. Each Class D share is convertible into one Class A share, with automatic conversion triggered by certain transfers, events, or time-based conditions.

How is the 16.3% ownership percentage for Thomas Anthony Shea calculated?

The 16.3% is calculated by dividing Shea’s 18,173,259 beneficially owned shares by a base that includes 93,318,973 Class A shares outstanding, certain Class D shares (including those issuable upon unit redemptions), and 1,620,556 vested, exercisable Class A options.

What types of OneStream securities are included in Thomas Anthony Shea’s beneficial ownership?

His beneficial ownership includes Class A common stock, Class D common stock convertible into Class A, shares issuable upon redemption or exchange of Common Units, and 1,620,556 Class A options that are vested and exercisable within 60 days of December 31, 2025.