Company: GIGGU
Filing Date: 2025-09-29
Form Type: 425
Source: 0001193125-25-221783
Chunk: 252

Company: GigCapital7 Corp.
Filing Date: 2025-09-29
Form: 425
Chunk 252
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. |     |                         |
| By:               |     |                         |
| Name:             |     | Dr. Avi S. Katz         |
| Title:            |     | Chief Executive Officer |

13

TRANSACTION SUPPORT AGREEMENT SPOUSAL CONSENT I [____________], spouse of [____________], have read and approve the foregoing Transaction Support Agreement (the “ Agreement”). In consideration of the terms and conditions as set forth in the Agreement, I hereby appoint my spouse as my attorney-in-factwith respect to the exercise of any rights and obligations under the Agreement, and agree to be bound by the provisions of the Agreement insofar as I may have any rights or obligations in the Agreement under the community property laws or similar laws relating to marital or community property in effect in the state of our residence as of the date of the Agreement.

| Date: ___________________                   |
| Signature of Spouse: ___________________    |
| Printed Name of Spouse: ___________________ |

14

Exhibit 99.1 Hadron Energy, an Emerging Nuclear Energy Company Advancing Innovative Light Water Micro Modular Reactors, to Go Public Via $1.2B Business Combination with GigCapital7 Corp.

| • |     | Hadron Energy, Inc. (“Hadron”) specializes in Micro Modular Reactor (MMR) development, design, and                                                                 
 research. The Hadron MMR is built on light water reactor technology, proven over decades of operating history and supported by an established licensing framework. |

| • |     | The MMR is designed to deliver a 24/7 uninterrupted supply of safe, clean, cost-efficient and rapidly                                                                                                                                                    
 deployable nuclear power well-suited for a wide range of applications. Capable of generating 10 megawatts of electricity (MWe) and 35 megawatts of thermal heat (MWth), the MMR uses a fraction of the land required by wind and solar, its reactor core 
 and containment shell is intended to be transported in standard shipping containers, and it is designed with an operationally efficient 10-year fueling cycle.                                                                                           |

| • |     | Hadron has moved quickly to address today’s accelerating energy needs across sectors, having already                            
 engaged with key potential customers in spaces such as data centers, remote geographies, industrial hubs and defense and space. |

| • |     | By providing the existing security holders of Hadron with 100 million shares of GigCapital7                                                                                
 Corp.(“GIG”) stock, the transaction values Hadron