[SCHEDULE 13G] Dune Acquisition Corporation II Units SEC Filing

Rhea-AI Filing Summary

Magnetar Financial LLC, Magnetar Capital Partners LP, Supernova Management LLC and David J. Snyderman have filed a Schedule 13G disclosing a 5.91 % passive stake in Dune Acquisition Corp II (Class A ordinary shares, CUSIP G2867S109, symbol IPODU). As of the event date 30 Jun 2025, the group beneficially owned 850,000 shares out of 14.375 million outstanding, crossing the 5 % reporting threshold but remaining below the 10 % level that could trigger greater regulatory scrutiny.

The position is spread across eight Magnetar-managed funds, with Constellation Master Fund holding the largest block (229,500 shares). All voting and dispositive powers are shared; none are held solely. The filing was signed 8 Aug 2025 and states that the shares were acquired in the ordinary course of business, with no intent to change or influence control of the issuer, qualifying the group to file on a passive 13G basis rather than an activist 13D.

Positive

• Institutional validation: Magnetar’s 850,000-share position reflects confidence from a sophisticated hedge fund complex.
• Regulatory clarity: Passive 13G filing confirms no activist intent, reducing uncertainty about potential control contests.

Negative

• None.

Insights

Financial Analyst

TL;DR — Magnetar’s 5.9 % passive stake brings moderate institutional validation with limited near-term governance impact.

Magnetar’s disclosure signals that a sophisticated multi-strategy manager views the SPAC’s risk-reward profile as attractive enough to commit nearly 6 % of outstanding shares. While the stake is not activist, the participation of eight separate Magnetar funds may improve secondary-market liquidity and help the issuer maintain the minimum public float required for exchange listing. Because all voting/dispositive powers are shared and there is no control intent, the filing is unlikely to alter board composition or strategic direction. Investors may take incremental comfort from the presence of an experienced credit-and-event-driven investor, yet the position alone does not constitute a catalyst. Impact: neutral-to-slightly positive.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Dune Acquisition Corp II

(Name of Issuer)

Class A ordinary shares, par value $0.0001

(Title of Class of Securities)

G2867S109

(CUSIP Number)

06/30/2025

(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. G2867S109

1

Names of Reporting Persons

MAGNETAR FINANCIAL LLC

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 850,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 850,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

850,000.00

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)

5.91 %

12

Type of Reporting Person (See Instructions)

IA, OO

SCHEDULE 13G

CUSIP No. G2867S109

1

Names of Reporting Persons

MAGNETAR CAPITAL PARTNERS LP

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 850,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 850,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

850,000.00

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)

5.91 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. G2867S109

1

Names of Reporting Persons

SUPERNOVA MANAGEMENT LLC

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 850,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 850,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

850,000.00

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)

5.91 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. G2867S109

1

Names of Reporting Persons

DAVID J. SNYDERMAN

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 850,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 850,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

850,000.00

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)

5.91 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Dune Acquisition Corp II
(b)	Address of issuer's principal executive offices: 700 S. Rosemary Avenue Suite 204 West Palm Beach, FL, 33401
Item 2.
(a)	Name of person filing: This statement is filed on behalf of each of the following person (collectively, the "Reporting Persons"): i) Magnetar Financial LLC ("Magnetar Financial"); ii) Magnetar Capital Partners LP (Magnetar Capital Partners"); iii) Supernova Management LLC ("Supernova Management"); and iv) David J. Snyderman ("Mr. Snyderman"). This statement relates to the Shares (as defined herein) held for Magnetar Constellation Master Fund, Ltd ("Constellation Master Fund"), Magnetar Xing He Master Fund Ltd ("Xing He Master Fund"), Magnetar SC Fund Ltd ("SC Fund"), Purpose Alternative Credit Fund Ltd ("Purpose Credit Fund"), all Cayman Islands exempted companies; Magnetar Structured Credit Fund, LP ("Structured Credit Fund") a Delaware limited partnership; Magnetar Alpha Star Fund LLC ("Alpha Star Fund"), Magnetar Lake Credit Fund LLC ("Lake Credit Fund"), Magnetar Waterfront Series A LLC ("Waterfront Series A Fund), all Delaware limited liability companies; collectively (the "Magnetar Funds"). Magnetar Financial serves as the investment adviser to the Magnetar Funds, and as such, Magnetar Financial exercises voting and investment power over the Shares held for the Magnetar Funds' accounts. Magnetar Capital Partners serves as the sole member and parent holding company of Magnetar Financial. Supernova Management is the general partner of Magnetar Capital Partners. The manager of Supernova Management is Mr. Snyderman.
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each of Magnetar Financial, Magnetar Capital Partners, Supernova Management, and Mr. Snyderman is 1603 Orrington Avenue, 13th Floor, Evanston, Illinois 60201.
(c)	Citizenship: Place of Organization. i) Magnetar Financial is a Delaware limited liability company; ii) Magnetar Capital Partners is a Delaware limited partnership; iii) Supernova Management is a Delaware limited liability company; and iv) Mr. Snyderman is a citizen of the United States of America.
(d)	Title of class of securities: Class A ordinary shares, par value $0.0001
(e)	CUSIP No.: G2867S109
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: As of June 30, 2025, each of Magnetar Financial, Magnetar Capital Partners, Supernova Management and Mr. Snyderman held 850,000 Shares. The amount consists of (A) 229,500 Shares held for the account of Constellation Master Fund; (B) 119,000 Shares held for the account of Lake Credit Fund; (C) 102,000 Shares held for the account of Structured Credit Fund; (D) 187,000 Shares held for the account of Xing He Master Fund; (E) 68,000 Shares held for the account of Alpha Star Fund; (F) 34,000 Shares held for the account of Purpose Credit Fund; (G) 93,500 Shares held for the account of SC Fund; and (H) 17,000 Shares held for the account Waterfront Series A Fund. The Shares held by the Magnetar Funds represent approximately 5.91% of the total number of Shares outstanding (calculated pursuant to Rule 13d-3(d)(1)(i)) of the outstanding shares of the Issuer).
(b)	Percent of class: As of June 30, 2025, each of the Reporting Persons were deemed to be the beneficial owner constituting approximately 5.91% of the total number of shares outstanding (based upon the information provided by the Issuer in its prospectus filed with the SEC on May 8, 2025, there were approximately 14,375,000 Shares outstanding.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 850,000
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 850,000
Item 5.	Ownership of 5 Percent or Less of a Class.
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:

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.

MAGNETAR FINANCIAL LLC

Signature:	/s/ Hayley Stein
Name/Title:	Hayley Stein, Attorney-in-fact for David J. Snyderman, Manager of Supernova Management LLC
Date:	08/08/2025

MAGNETAR CAPITAL PARTNERS LP

Signature:	/s/ Hayley Stein
Name/Title:	Hayley Stein, Attorney-in-fact for David J. Snyderman, Manager of Supernova Management LLC
Date:	08/08/2025

SUPERNOVA MANAGEMENT LLC

Signature:	/s/ Hayley Stein
Name/Title:	Hayley Stein, Attorney-in-fact for David J. Snyderman, Manager of Supernova Management LLC
Date:	08/08/2025

DAVID J. SNYDERMAN

Signature:	/s/ Hayley Stein
Name/Title:	Hayley Stein, Attorney-in-fact for David J. Snyderman, Manager of Supernova Management LLC
Date:	08/08/2025

Comments accompanying signature: MAGNETAR FINANCIAL LLC BY: Magnetar Capital Partners LP, its Sole Member BY: Supernova Management LLC, its General Partner MAGNETAR CAPITAL PARTNERS LP By: Supernova Management LLC, its General Partner

Exhibit Information

99.1 Joint Filing Agreement, dated as of August 8, 2025, among the Reporting Persons. 99.2 Power of Attorney, dated as of December 22, 2022 filed by the Reporting Persons on August 8, 2025.

FAQ

How many Dune Acquisition Corp II shares does Magnetar own?

Magnetar and related entities report 850,000 Class A shares.

What percentage of Dune Acquisition Corp II (IPODU) does this represent?

The holding equals 5.91 % of the 14.375 million shares outstanding.

Does Magnetar have sole or shared voting power over the shares?

The group has shared voting and dispositive power over all 850,000 shares; none are held solely.

Is the filing activist or passive?

It is a passive Schedule 13G; the group states no intention to influence control.

When were the ownership levels measured and when was the filing signed?

Ownership is as of 30 Jun 2025; the filing was signed on 8 Aug 2025.