EXHIBIT 32.1

CERTIFICATION PURSUANT TO 

18 U.S.C. SECTION 1350, 

AS ADOPTED PURSUANT TO 

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

The undersigned hereby certifies, in his capacity as an officer of Horizon Space Acquisition I Corp. (the “Company”), for the purposes of 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of his knowledge:

(1)	The Quarterly Report of the Company on Form 10-Q for the quarter ended June 30, 2026 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)	The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: August 13, 2026	By:	/s/ Mingyu (Michael) Li
		Mingyu (Michael) Li
		Chief Executive Officer and Chief Financial Officer
		(Principal Executive Officer, Principal Financial and Accounting Officer)