Company: GIGGU
Filing Date: 2025-11-26
Form Type: 425
Source: 0001193125-25-298527
Chunk: 0

Company: GigCapital7 Corp.
Filing Date: 2025-11-26
Form: 425
Chunk 0
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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (date of earliest event reported): November 26, 2025 GigCapital7 Corp. (Exact name of Registrant as specified in its charter)

| Cayman Islands                  |     | 001-42262   |     | 98-1790710            |
| (State or other jurisdiction of 
 incorporation or organization)  |     | -Commission 
 File Number |     | -I.R.S. Employer      
 Identification Number |

1731 Embarcadero Rd., Suite 200 Palo Alto, CA 94303 (Address of principal executive offices) (650) 276-7040 (Registrant’s telephone number, including area code) Check the appropriate box below if the Form 8-Kfiling is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions ( seeGeneral Instruction A.2. below):

| ☒ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) |

| ☐ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 
 CFR 240.14a-12)                                                        |

| ☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) |

| ☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e 4(c)) |

Securities registered pursuant to Section 12(b) of the Act:

| Title of each class                                                                                                        |     | Trading 
 Symbols |     | Name of each exchange       
 on which registered         |
| Units, each consisting of one Class A ordinary share and one redeemable warrant                                            |     | GIGGU   |     | The Nasdaq Stock Market LLC |
| Class A ordinary shares, par value $0.0001 per share                                                                       |     | GIG     |     | The Nasdaq Stock Market LLC |
| Redeemable warrants, each full warrant exercisable for one Class A ordinary share at an exercise price of $11.50 per share |     | GIGGW   |     | The Nasdaq Stock Market LLC |

Indicate by check mark whether the registrant