v3.26.1
Cover - USD ($)
12 Months Ended
Dec. 31, 2025
May 29, 2026
Jun. 30, 2025
Document Type 10-K    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2025    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2025    
Current Fiscal Year End Date --12-31    
Entity File Number 001-42138    
Entity Registrant Name Flag Ship Acquisition Corporation    
Entity Central Index Key 0001850059    
Entity Tax Identification Number 00-0000000    
Entity Incorporation, State or Country Code E9    
Entity Address, Address Line One 26 Broadway    
Entity Address, Address Line Two Suite 934    
Entity Address, City or Town New York    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 10004    
City Area Code (646)    
Local Phone Number 362-0256    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status No    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Elected Not To Use the Extended Transition Period false    
Entity Shell Company true    
Entity Public Float     $ 71,967,000
Entity Common Stock, Shares Outstanding   5,025,517  
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Auditor Name MaloneBailey, LLP    
Auditor Location Houston, Texas    
Auditor Firm ID 206    
Units, each consisting of one Ordinary Share, $0.001 par value, and one right      
Title of 12(b) Security Units, each consisting of one Ordinary Share, $0.001 par value, and one right    
Trading Symbol FSHPU    
Security Exchange Name NASDAQ    
Ordinary Shares, $0.001 par value      
Title of 12(b) Security Ordinary Shares, $0.001 par value    
Trading Symbol FSHP    
Security Exchange Name NASDAQ    
Rights to receive one-tenth (1/10      
Title of 12(b) Security Rights to receive one-tenth (1/10th) of one Ordinary Share    
Trading Symbol FSHPR    
Security Exchange Name NASDAQ