Amendment to New Listing Registration (Form 8-A12B/A)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-A /A

AMENDMENT NO. 1

to

FORM 8-A

FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES

PURSUANT TO SECTION 12(b) OR 12(g) OF

THE SECURITIES EXCHANGE ACT OF 1934

GigCapital8 Corp.

(Exact Name of Registrant as Specified in Its Charter)

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

If this form relates to the registration of a class of securities pursuant to Section 12(b) of the Exchange Act and is effective pursuant to General Instruction A.(c) or (e), please check the following box. ☒

If this form relates to the registration of a class of securities pursuant to Section 12(g) of the Exchange Act and is effective pursuant to General Instruction A.(d) or (e), please check the following box. ☐

If this form relates to the registration of a class of securities concurrently with a Regulation A offering check the following box. ☐

Securities Act registration statement or Regulation A offering statement file number to which this form relates:

333-289479

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

None

(Title of Class)

Explanatory Note

This Amendment No. 1 on Form 8-A/A amends and restates in its entirety the information set forth in the Registration Statement on Form 8-A previously filed by GigCapital8 Corp. (the "Registrant") with the Securities and Exchange Commission on October 3, 2025.

Item 1. Description of Registrant's Securities to be Registered.

The securities to be registered hereby of the Registrant are the Class A ordinary shares, par value $0.0001 per share of the Registrant (the "Ordinary Shares"), the public units, where each unit consists of one Ordinary Share and one right to purchase one-fifth of one Ordinary Share (the "Units"), and the public rights to purchase one-fifth of one Ordinary Share (the "Rights"). The description of the Ordinary Shares, the Units and the Rights set forth under the heading "Description of Securities" in the prospectus forming part of the Registrant's Registration Statement on Form S-1 (File No. 333-289479), originally filed with the SEC on August 11, 2025, as thereafter amended and supplemented from time to time (the "Registration Statement"), is incorporated by reference herein. Any form of prospectus or prospectus supplement to the Registration Statement that includes such descriptions and that is subsequently filed is hereby also incorporated by reference herein.

Item 2. Exhibits.

Pursuant to the Instructions as to Exhibits for Form 8-A, no exhibits are required to be filed, because no other securities of the Registrant are registered on The Nasdaq Stock Market LLC, and the securities registered hereby are not being registered pursuant to Section 12(g) of the Securities Exchange Act of 1934, as amended.

SIGNATURE

Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the Registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereto duly authorized.

Date: October 6, 2025