v3.26.1
Cover - shares
 6 Months Ended
Jun. 30, 2026
Aug. 17, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Document Transition Report false  
Entity File Number 001-39945  
Entity Registrant Name CONSTELLATION ACQUISITION CORP I  
Entity Central Index Key 0001834032  
Entity Incorporation, State or Country Code E9  
Entity Tax Identification Number 98-1574835  
Entity Address, Address Line One 1290 Avenue of the Americas  
Entity Address, Address Line Two 10th Floor  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10104  
City Area Code (212)  
Local Phone Number 983-1602  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company true  
Class A ordinary shares, par value $0.0001 per share    
Document Information [Line Items]    
Title of 12(b) Security Class A ordinary shares, par value $0.0001 per share  
Trading Symbol CSTAF  
Security Exchange Name NONE  
Redeemable warrants, each one whole warrant exercisable for one share of Class A ordinary share at an exercise price of $11.50    
Document Information [Line Items]    
Title of 12(b) Security Redeemable warrants, each one whole warrant exercisable for one share of Class A ordinary share at an exercise price of $11.50  
Trading Symbol CSTWF  
Security Exchange Name NONE  
Units, each consisting of one Class A ordinary share and one-third of one redeemable warrant    
Document Information [Line Items]    
Title of 12(b) Security Units, each consisting of one Class A ordinary share and one-third of one redeemable warrant  
Trading Symbol CSTUF  
Security Exchange Name NONE  
Class A ordinary shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   7,646,529
Class B ordinary shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   150,000