Archimedes Tech SPAC Partners III Co. beneficial ownership disclosure: Adage Capital Management, L.P., together with Robert Atchinson and Phillip Gross, report shared voting and dispositive power over 1,800,000 Ordinary Shares, representing 5.10% of 35,262,000 Ordinary Shares outstanding as of January 26, 2026.
The shares are directly held by Adage Capital Partners, L.P. and reported by the named managers in a joint Schedule 13G filing; the cover lists CUSIP G0453R105.
Positive
None.
Negative
None.
Insights
Holding represents a mid-single-digit passive stake reported under Schedule 13G.
The filing shows 1,800,000 shares with shared voting and dispositive power held via Adage entities, equal to 5.10% of the company's 35,262,000 shares outstanding as of January 26, 2026
Future filings may show changes in ownership or voting status; any material change in voting power or ownership percentage would be reported in subsequent amendments.
Schedule 13G indicates passive investment reporting rather than active control.
The joint filing attributes shared power through Adage Capital Partners and names Messrs. Atchinson and Gross as managing members. The statement references Exhibit 99.1 (Joint Filing Agreement) and cites the outstanding share base used to compute 5.10%.
Compliance focus: the filing structure and signatures align with typical Schedule 13G practice for institutional investors; monitor for any Rule 13D amendments that would indicate active intent.
Key Figures
Shares with shared power:1,800,000 sharesPercent of class:5.10%Outstanding shares used:35,262,000 shares+1 more
4 metrics
Shares with shared power1,800,000 sharesShared voting and dispositive power reported on cover page
Percent of class5.10%Calculated using 35,262,000 shares outstanding as of <date>January 26, 2026</date>
Outstanding shares used35,262,000 sharesOutstanding share count cited from Exhibit 99.1 to Form 8-K
CUSIPG0453R105Identifier for Ordinary Shares class
"Item 2(a) and cover reference to joint filing agreement"
A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.
shared dispositive powerfinancial
"Cover page rows list Shared Dispositive Power 1,800,000.00"
beneficially ownedregulatory
"Item 4(a) references Amount beneficially owned and Row 9 of the cover page"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Archimedes Tech SPAC Partners III Co.
(Name of Issuer)
Ordinary Shares, par value $0.0001
(Title of Class of Securities)
G0453R105
(CUSIP Number)
03/31/2026
(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)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
G0453R105
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
1,800,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,800,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,800,000.00
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)
5.10 %
12
Type of Reporting Person (See Instructions)
IA, PN
SCHEDULE 13G
CUSIP Number(s):
G0453R105
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
1,800,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,800,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,800,000.00
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)
5.10 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
CUSIP Number(s):
G0453R105
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
1,800,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,800,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,800,000.00
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)
5.10 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Archimedes Tech SPAC Partners III Co.
(b)
Address of issuer's principal executive offices:
2093 Philadelphia Pike #1968, Claymont, DE 19703
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 ordinary shares, par value $0.0001 per share ("Ordinary Shares") of Archimedes Tech SPAC Partners III Co., 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, L.L.C., a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Class A 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 Class A 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:
Ordinary Shares, par value $0.0001
(e)
CUSIP Number(s):
G0453R105
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 35,262,000 Ordinary Shares outstanding as of January 26, 2026, as reported in Exhibit 99.1 to the Company's Current Report on Form 8-K filed with the Securities and Exchange Commission on January 30, 2026.
(b)
Percent of class:
5.10%
(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, L.L.C., its General Partner, By: Robert Atchinson, its Managing Member
Adage reports shared voting and dispositive power over 1,800,000 Ordinary Shares, equal to 5.10% of the class. This percentage uses an outstanding share base of 35,262,000 shares as of January 26, 2026 reported in Exhibit 99.1.
Who are the reporting persons in the ARCI Schedule 13G?
The filing is made by Adage Capital Management, L.P. and two individuals, Robert Atchinson and Phillip Gross, as managing members of affiliated Adage entities that manage the shares directly held by Adage Capital Partners, L.P.
Does this Schedule 13G indicate control of ARCI?
No explicit control claim is made; the filing reports shared voting and dispositive power over 1,800,000 shares under Schedule 13G, which is typically used for passive institutional holdings rather than active control positions.
What registry identifiers are shown for ARCI shares?
The filing lists the class as Ordinary Shares, par value $0.0001 and CUSIP G0453R105. The ownership percentage is calculated using the stated outstanding share count of 35,262,000 as of January 26, 2026.
