Adage discloses 7.83% passive stake in Dynamix Corp III (DNMX)

Rhea-AI Filing Summary

Adage Capital Management and its principals reported a significant passive stake in Dynamix Corp III. They beneficially own 1,575,000 Class A ordinary shares, representing 7.83% of the company’s outstanding Class A stock as of early December 2025.

The shares are held through Adage Capital Partners, with voting and investment power shared among Adage Capital Management, Robert Atchinson, and Phillip Gross. They state the position was acquired and is held in the ordinary course of business, not to change or influence control of Dynamix Corp III.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Dynamix Corp III

(Name of Issuer)

Class A Ordinary Shares, par value $0.0001 per share

(Title of Class of Securities)

G2949T109

(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. G2949T109

1

Names of Reporting Persons

Adage Capital Management, L.P.

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,575,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,575,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,575,000.00

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)

7.83 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP No. G2949T109

1

Names of Reporting Persons

Robert Atchinson

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 0.00
6	Shared Voting Power 1,575,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,575,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,575,000.00

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)

7.83 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP No. G2949T109

1

Names of Reporting Persons

Phillip Gross

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 0.00
6	Shared Voting Power 1,575,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,575,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,575,000.00

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)

7.83 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Dynamix Corp III
(b)	Address of issuer's principal executive offices: 1980 Post Oak Blvd., Suite 100, PMB 6373, Houston, TX, 77056
Item 2.
(a)	Name of person filing: This statement is filed by: (i) Adage Capital Management, L.P., a Delaware limited partnership ("ACM"), as the investment manager of Adage Capital Partners, L.P., a Delaware limited partnership ("ACP"), with respect to the Class A ordinary shares, par value $0.0001 per share ("Ordinary Shares") of Dynamix Corporation III, a Cayman Islands exempted company (the "Company") directly held by ACP; (ii) Robert Atchinson ("Mr. Atchinson"), as (1) managing member of Adage Capital Advisors, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACA"), managing member of Adage Capital Partners GP, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACPGP"), general partner of ACP and (2) managing member of Adage Capital Partners LLC, a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Ordinary Shares directly held by ACP; and (iii) Phillip Gross ("Mr. Gross"), as (1) managing member of ACA, managing member of ACPGP and (2) managing member of ACPLLC, general partner of ACM, with respect to the Ordinary Shares directly held by ACP. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party. The filing of this statement should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein.
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons is 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116.
(c)	Citizenship: ACM is a limited partnership organized under the laws of the State of Delaware. Messrs. Gross and Atchinson are citizens of the United States.
(d)	Title of class of securities: Class A Ordinary Shares, par value $0.0001 per share
(e)	CUSIP No.: G2949T109
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: The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 20,125,000 Ordinary Shares outstanding as of December 8, 2025, as reported in the Company's Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2025 filed with the Securities and Exchange Commission on December 10, 2025.
(b)	Percent of class: 7.83%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. See Item 2(a).
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:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

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.

Adage Capital Management, L.P.

Signature:	/s/ Robert Atchinson
Name/Title:	By: Adage Capital Partners LLC, its General Partner, By: Robert Atchinson, its Managing Member
Date:	02/12/2026

Robert Atchinson

Signature:	/s/ Robert Atchinson
Name/Title:	Robert Atchinson, individually
Date:	02/12/2026

Phillip Gross

Signature:	/s/ Phillip Gross
Name/Title:	Phillip Gross, individually
Date:	02/12/2026

Exhibit Information

Exhibit 99.1: Joint Filing Agreement

FAQ

What stake does Adage Capital Management hold in Dynamix Corp III (DNMX)?

Adage Capital Management and its principals report beneficial ownership of 1,575,000 Class A ordinary shares of Dynamix Corp III, equal to 7.83% of the outstanding Class A shares, based on 20,125,000 shares outstanding as of early December 2025.

Is Adage’s Dynamix Corp III (DNMX) position passive or activist?

The position is reported as passive. The investors certify the Dynamix Corp III shares were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control, consistent with a Schedule 13G rather than an activist Schedule 13D filing.

Who are the reporting persons in the Dynamix Corp III (DNMX) Schedule 13G?

The reporting persons are Adage Capital Management, L.P., and individuals Robert Atchinson and Phillip Gross. Adage acts as investment manager to Adage Capital Partners, while Atchinson and Gross are managing members of related general partner entities that share voting and dispositive power over the reported shares.

How many Dynamix Corp III (DNMX) shares does each reporting person control?

Each reporting person—Adage Capital Management, Robert Atchinson, and Phillip Gross—reports beneficial ownership of 1,575,000 Class A ordinary shares. They have shared voting and shared dispositive power over these shares, with no sole voting or sole dispositive power reported by any individual filer.

What ownership percentage in Dynamix Corp III (DNMX) triggers this Schedule 13G?

The filing reflects beneficial ownership of 7.83% of Dynamix Corp III’s Class A ordinary shares. This exceeds the 5% threshold that requires institutional and other large shareholders to publicly report their holdings on Schedule 13D or 13G under U.S. securities regulations.

On what share count is Adage’s 7.83% Dynamix Corp III (DNMX) stake based?

The 7.83% ownership figure is calculated using 20,125,000 Dynamix Corp III Class A ordinary shares outstanding as of December 8, 2025, as disclosed in the company’s Quarterly Report on Form 10-Q for the period ended September 30, 2025, filed on December 10, 2025.