Table of Contents As filed with the U.S. Securities and Exchange Commission on January 21, 2026 Registration No. 333-291869 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT No. 1 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 GigCapital9 Corp. (Exact name of registrant as specified in its charter) Cayman Islands 6770 98-1894186 (State or other jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) (I.R.S. ...

As filed with the U.S. Securities and Exchange Commission on December 1, 2025. Registration No. 333-[ ] UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 GigCapital9 Corp. Table of Contents (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) Cayman Islands 6770 98-1894186 (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Identificati ...