Company: GIGGU
Filing Date: 2025-11-12
Form Type: S-4
Source: 0001193125-25-277896
Chunk: 1

Company: GigCapital7 Corp.
Filing Date: 2025-11-12
Form: S-4
Chunk 1
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(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐ If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, or a smaller reporting company, or emerging growth company. See the definitions of “large accelerated filer”, “accelerated filer”, “smaller reporting company”, and “emerging growth company” in Rule 12b-2of the Exchange Act.

| Large accelerated filer |     | ☐ |     | Accelerated filer         |     | ☐ |
| Non-accelerated filer   |     | ☒ |     | Smaller reporting company |     | ☒ |
|                         |     |   |     | Emerging growth company   |     | ☒ |

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐ If applicable, place an ☒ in the box to designate the appropriate rule provision relied upon in conducting this transaction: Exchange Act Rule 13e-4(i)(Cross-Border Issuer Tender Offer) ☐ Exchange Act Rule 14d-1(d)(Cross-Border Third-Party Tender Offer) ☐

| * | Prior to the consummation of the Business Combination described herein, the Registrant intends to effect a deregistration under Section 206 of the Companies Act (as revised) of the Cayman Islands and a domestication under Section 388 of the Delaware General Corporation Law, pursuant to which the Registrant’s jurisdiction of incorporation will be changed from the Cayman Islands to the State of Delaware. All securities being registered will be issued by GigCapital7 Corp. (after its domestication as a corporation incorporated in the State of Delaware), the continuing entity following the Domestication, which will be renamed “Hadron Energy, Inc.” effective immediately following the consummation of the Business Combination. |

The Registrant and Co-Registranthereby amend this registration statement on such date or dates as may be necessary to