As of November 6, 2026, 3 holders' latest Schedule 13D or 13G filings report owning 5% or more of ACP Holdings Acquisition Corp. The largest reported stake is Adage Capital Management, L.P.'s, at 8.2%. 3 filings are on record since August 12, 2026 (Schedule 13G, August 12, 2026).
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Key facts
- · Reporting person: Polar Asset Management Partners Inc. · Sole voting: 1,605,150 · Shared voting: 0 · Sole dispositive: 1,605,150 · Shared dispositive: 0 · SCHEDULE 13G, 2026-08-14
- · Reporting person: Magnetar Financial LLC · Sole voting: 0 · Shared voting: 1,600,000 · Sole dispositive: 0 · Shared dispositive: 1,600,000 · SCHEDULE 13G, 2026-08-13
- · Reporting person: Adage Capital Management, L.P. · Sole voting: 0 · Shared voting: 1,800,000 · Sole dispositive: 0 · Shared dispositive: 1,800,000 · SCHEDULE 13G, 2026-08-12
ACP Holdings Acquisition Corp. has 3 Schedule 13D or 13G filings on record since 2026-08-12. 3 holders' latest filing reports 5% or more of class a ordinary shares, $0.0001 par value per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| Adage Capital Management, L.P. | 8.2% | 1,800,000 | SCHEDULE 13G, 2026-08-12 | 2026-06-30 |
| Polar Asset Management Partners Inc. | 7.3% | 1,605,150 | SCHEDULE 13G, 2026-08-14 | 2026-06-30 |
| Magnetar Financial LLC | 7.29% | 1,600,000 | SCHEDULE 13G, 2026-08-13 | 2026-06-30 |
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More on ACP Holdings Acquisition Corp. and the records around it.
Companies that share a holder
- Polar Asset Management Partners Inc. also filed stake reports on 69 other companies: Aeon Acquisition I Corp. (Aug 2026), Bitcoin Depot Inc. (Aug 2026), Aperture AC (Aug 2026)
- MAGNETAR FINANCIAL LLC also filed stake reports on 97 other companies: Blue Acquisition Corp. (Sep 2026), CENTURION ACQUISITION CORP. (Sep 2026), Churchill Capital Corp IX (Sep 2026)
- Adage Capital Management, L.P. also filed stake reports on 136 other companies: AmperCap Acquisition Company (Aug 2026), Aura Biosciences, Inc. (Aug 2026), Bleichroeder Acquisition Corp. II (Aug 2026)
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What the Full Report on ACP Holdings Acquisition Corp. covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Adage Capital Management, L.P. | 0 | 1,800,000 | 0 | 1,800,000 | SCHEDULE 13G, 2026-08-12 |
| Robert Atchinson | 0 | 1,800,000 | 0 | 1,800,000 | SCHEDULE 13G, 2026-08-12 |
| Phillip Gross | 0 | 1,800,000 | 0 | 1,800,000 | SCHEDULE 13G, 2026-08-12 |
| Polar Asset Management Partners Inc. | 1,605,150 | 0 | 1,605,150 | 0 | SCHEDULE 13G, 2026-08-14 |
| Magnetar Financial LLC | 0 | 1,600,000 | 0 | 1,600,000 | SCHEDULE 13G, 2026-08-13 |
| Magnetar Capital Partners LP | 0 | 1,600,000 | 0 | 1,600,000 | SCHEDULE 13G, 2026-08-13 |
| Supernova Management LLC | 0 | 1,600,000 | 0 | 1,600,000 | SCHEDULE 13G, 2026-08-13 |
| David J. Snyderman | 0 | 1,600,000 | 0 | 1,600,000 | SCHEDULE 13G, 2026-08-13 |
The latest filing identifies ACP Holdings Acquisition Corp. by CUSIP G0113G101 and gives its principal executive office as 3131 Eastside Street, Houston, TX 77098 (SCHEDULE 13G, 2026-08-14).
What the percentages are based on
As of June 30, 2026, each of the Reporting Persons were deemed to be the beneficial owner constituting approximately 7.29% of the total number of shares outstanding (based upon the information provided by the Issuer in the Form 10-Q filed on 05/14/2026 there were approximately 21,946,600 Shares outstanding).Magnetar Financial LLC, SCHEDULE 13G, 2026-08-13
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2026-08-12 | Adage Capital Management, L.P. | 8.2% | SCHEDULE 13G |
| 2026-08-13 | Magnetar Financial LLC | 7.29% | SCHEDULE 13G |
| 2026-08-14 | Polar Asset Management Partners Inc. | 7.3% | SCHEDULE 13G |
Questions about who owns ACP Holdings Acquisition Corp.
Who owns ACP Holdings Acquisition Corp.?
On this page, 3 holders' latest ownership filings report 5% or more of ACP Holdings Acquisition Corp.: Adage Capital Management, L.P. (8.2%, Schedule 13G, filed 2026-08-12), Polar Asset Management Partners Inc. (7.3%, Schedule 13G, filed 2026-08-14) and Magnetar Financial LLC (7.29%, Schedule 13G, filed 2026-08-13).
Who are the largest shareholders of ACP Holdings Acquisition Corp.?
By the share each holder's latest filing reports, the largest holders of ACP Holdings Acquisition Corp. on this page are Adage Capital Management, L.P. (8.2%), Polar Asset Management Partners Inc. (7.3%) and Magnetar Financial LLC (7.29%).
When did Adage Capital Management, L.P. buy into ACP Holdings Acquisition Corp.?
The filings give report dates, not purchase dates. The earliest filing from Adage Capital Management, L.P. on this page is the Schedule 13G, filed 2026-08-12, reporting 8.2%.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 3 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Also on the record for ACP Holdings Acquisition Corp.
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| April 7, 2026 | IPO filing, Form 424B4 | $10 a share | IPO filings | Source |
| March 30, 2026 | IPO filing, Form S-1/A | — | IPO filings | Source |
| March 20, 2026 | IPO filing, Form S-1/A | — | IPO filings | Source |
| March 6, 2026 | IPO filing, Form S-1 | — | IPO filings | Source |
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.