Magnetar group (CGCFU) discloses 1.75M-share, 6.36% stake in Cartesian Growth

Rhea-AI Filing Summary

Cartesian Growth Corp IV has a significant shareholder group led by Magnetar Financial LLC and related entities. As of June 30, 2026, these reporting persons collectively were deemed to beneficially own 1,750,000 Class A ordinary shares, representing 6.36% of the outstanding Class A shares.

The 1,750,000 shares are held across several Magnetar-managed funds, including Constellation Master Fund, Structured Credit Fund, Alpha Star Fund, Lake Credit Fund, Xing He Master Fund, Waterfront Series A Fund, and Capital Master Fund. The group reports shared voting and dispositive power over all 1,750,000 shares and no sole voting or dispositive power, based on approximately 27,500,000 Class A shares outstanding referenced from an issuer Form 8-K.

Key Figures

Beneficial ownership: 1,750,000 shares Ownership percentage: 6.36% Shares outstanding: 27,500,000 shares +4 more

7 metrics

Beneficial ownership 1,750,000 shares Class A ordinary shares beneficially owned by the reporting persons as of June 30, 2026

Ownership percentage 6.36% Portion of Cartesian Growth Corp IV Class A shares beneficially owned by the reporting persons

Shares outstanding 27,500,000 shares Approximate Class A shares outstanding based on issuer Form 8-K used for 6.36% calculation

Shared voting power 1,750,000 shares Number of shares over which the reporting persons have shared power to vote

Shared dispositive power 1,750,000 shares Number of shares over which the reporting persons have shared power to dispose

Constellation Master Fund holding 420,000 shares Portion of the 1,750,000 shares held for Magnetar Constellation Master Fund, Ltd

Structured Credit Fund holding 367,500 shares Portion of the 1,750,000 shares held for Magnetar Structured Credit Fund, LP

Key Terms

beneficial owner, shared voting power, shared dispositive power, Rule 13d-3(d)(1)(i), +2 more

6 terms

beneficial owner financial

"each of the Reporting Persons were deemed to be the beneficial owner constituting approximately 6.36%"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

shared voting power financial

"Shared Voting Power 1,750,000.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"Shared Dispositive Power 1,750,000.00"

Rule 13d-3(d)(1)(i) regulatory

"calculated pursuant to Rule 13d-3(d)(1)(i) of the outstanding shares of the Issuer"

Joint Filing Agreement regulatory

"Exhibit Information 99.1 Joint Filing Agreement, dated as of August 13, 2026"

Power of Attorney regulatory

"99.2 Power of Attorney, dated as of December 22, 2022"

A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.

FAQ

What percentage of Cartesian Growth Corp IV (CGCFU) does the Magnetar group own?

The Magnetar group is deemed to beneficially own 6.36% of Cartesian Growth Corp IV’s Class A ordinary shares, based on 1,750,000 shares out of approximately 27,500,000 shares outstanding as referenced from the issuer’s Form 8-K.

How many Cartesian Growth Corp IV (CGCFU) shares does Magnetar report owning?

The reporting persons collectively report beneficial ownership of 1,750,000 Class A ordinary shares of Cartesian Growth Corp IV as of June 30, 2026, held across multiple Magnetar-managed funds under shared voting and dispositive power arrangements.

Which Magnetar funds hold shares of Cartesian Growth Corp IV (CGCFU)?

Shares are held for seven Magnetar funds: Constellation Master Fund, Structured Credit Fund, Alpha Star Fund, Lake Credit Fund, Xing He Master Fund, Waterfront Series A Fund, and Capital Master Fund, together totaling 1,750,000 shares of Cartesian Growth Corp IV.

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

The Magnetar group reports 0 shares with sole voting power and 1,750,000 shares with shared voting power in Cartesian Growth Corp IV, indicating all reported voting authority over these shares is exercised jointly among the reporting persons.

On what date is the Magnetar ownership in Cartesian Growth Corp IV (CGCFU) measured?

The reported beneficial ownership of 1,750,000 shares, representing 6.36% of Cartesian Growth Corp IV’s Class A shares, is stated as of June 30, 2026, using outstanding share data referenced from an issuer Form 8-K filed July 8, 2026.

Who are the reporting persons in the Cartesian Growth Corp IV (CGCFU) Schedule 13G?

The reporting persons are Magnetar Financial LLC, Magnetar Capital Partners LP, Supernova Management LLC, and David J. Snyderman, who together report beneficial ownership and shared voting and dispositive power over 1,750,000 Cartesian Growth Corp IV Class A shares.

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Available on EDGAR 08/13/2026 - 06:14 AM Accepted by SEC EDGAR 08/13/2026 - 06:13 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

CARTESIAN GROWTH CORP IV

(Name of Issuer)

Class A ordinary shares, par value $0.0001

(Title of Class of Securities)

G19316101

(CUSIP Number)

06/30/2026

(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): G19316101

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 1,750,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,750,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,750,000.00

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)

6.36 %

12

Type of Reporting Person (See Instructions)

IA, OO

SCHEDULE 13G

CUSIP Number(s): G19316101

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 1,750,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,750,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,750,000.00

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)

6.36 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP Number(s): G19316101

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 1,750,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,750,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,750,000.00

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)

6.36 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP Number(s): G19316101

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 1,750,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,750,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,750,000.00

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)

6.36 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: CARTESIAN GROWTH CORP IV
(b)	Address of issuer's principal executive offices: 505 Fifth Avenue, 15th Floor New York, NY, 10017
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 Capital Master Fund Ltd ("Capital Master 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 administrative 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 Number(s): G19316101
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, 2026, each of Magnetar Financial, Magnetar Capital Partners, Supernova Management and Mr. Snyderman held 1,750,000 Shares. The amount consists of (A) 420,000 Shares held for the account of Constellation Master Fund; (B) 367,500 Shares held for the account of Structured Credit Fund; (C) 297,500 Shares held for the account of Alpha Star Fund; (D) 297,500 Shares held for the account of Lake Credit Fund; (E) 297,500 Shares held for the account of Xing He Master Fund; (F) 52,500 Shares held for the account of Waterfront Series A Fund; and (G) 17,500 Shares held for the account of Capital Master Fund. The Shares held by the Magnetar Funds represent approximately 6.36% 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, 2026, each of the Reporting Persons were deemed to be the beneficial owner constituting approximately 6.36% of the total number of shares outstanding (based upon the information provided by the Issuer in the Form 8-K filed on July 8, 2026 there were approximately 27,500,000 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: 1,750,000
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 1,750,000
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:

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:	Name:Hayley Stein, Title: Attorney-in-fact for David J. Snyderman, Administrative Manager of Supernova Management LLC
Date:	08/13/2026

MAGNETAR CAPITAL PARTNERS LP

Signature:	/s/ Hayley Stein
Name/Title:	Name:Hayley Stein, Title: Attorney-in-fact for David J. Snyderman, Administrative Manager of Supernova Management LLC
Date:	08/13/2026

SUPERNOVA MANAGEMENT LLC

Signature:	/s/ Hayley Stein
Name/Title:	Name:Hayley Stein, Title: Attorney-in-fact for David J. Snyderman, Administrative Manager of Supernova Management LLC
Date:	08/13/2026

DAVID J. SNYDERMAN

Signature:	/s/ Hayley Stein
Name/Title:	Name:Hayley Stein, Title: Attorney-in-fact for David J. Snyderman, Administrative Manager of Supernova Management LLC
Date:	08/13/2026

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 13, 2026, among the Reporting Persons. 99.2 Power of Attorney, dated as of December 22, 2022 filed by the Reporting Persons on August 13, 2026.