Company: MBVI
Filing Date: 2025-08-18
Form Type: S-1/A
Source: 0001213900-25-078000
Chunk: 353

Company: M3-Brigade Acquisition VI Corp.
Filing Date: 2025-08-18
Form: S-1/A
Chunk 353
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)the portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and (iv)any other communication that is an offer in the offering made by the undersigned registrant to the purchaser. II-3

SIGNATURES Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in New York, New York, on the 18 thday of August, 2025.

| M3-Brigade Acquisition VI Corp. |     |                      |     |                    |
| By:                             |     | /s/ Mohsin Y. Meghji |     |                    |
|                                 |     | Name:                |     | Mohsin Y. Meghji   |
|                                 |     | Title:               |     | Executive Chairman |

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

| Signature            
 /s/ Mohsin Y. Meghji |     | Title                                       
 Executive Chairman                          |     | Date            
 August 18, 2025 |
|:---------------------|:----|:--------------------------------------------|:----|:----------------|
| Mohsin Y. Meghji     |     | -Principal Executive Officer                |     |                 |
| *                    |     | Chief Financial Officer                     |     | August 18, 2025 |
| Eric Greenhaus       |     | -Principal Financial and Accounting Officer |     |                 |
| *                    |     | Director                                    |     | August 18, 2025 |
| Matthew Perkal       |     |                                             |     |                 |

| *By: |     | /s/ Mohsin Y. Meghji |
|      |     | Mohsin Y. Meghji     |
|      |     | Attorney-in-Fact     |

II-4

AUTHORIZED REPRESENTATIVE Pursuant to the requirements of Section 6(a) of the Securities Act of 1933, the undersigned has signed this registration statement, solely in its capacity as the duly authorized representative of M3 -BrigadeAcquisition VI Corp., in New York, New York, on the 18 thday of August, 202