v3.26.1
Cover - shares
 3 Months Ended
Mar. 31, 2026
Jul. 23, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Entity Registrant Name JAB Acquisition Corp I  
Document Period End Date Mar. 31, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0002128739  
Entity File Number 001-43341  
Amendment Flag false  
Entity Incorporation, State or Country Code E9  
Entity Tax Identification Number 98-1934496  
Entity Address, Address Line One 270 Sylvan Avenue  
Entity Address, Address Line Two Suite 2230  
Entity Address, City or Town Englewood Cliffs  
Entity Address, State or Province NJ  
Entity Address, Postal Zip Code 07632  
City Area Code 332  
Local Phone Number 203-6124  
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  
Entity Ex Transition Period false  
Entity Shell Company true  
Units, each consisting of one Class A ordinary share, one redeemable warrant and one right to receive one-fourth (1/4th) of one Class A ordinary share    
Document Information [Line Items]    
Title of 12(b) Security Units, each consisting of one Class A ordinary share, one redeemable warrant and one right to receive one-fourth (1/4th) of one Class A ordinary share  
Trading Symbol JABRU  
Security Exchange Name NASDAQ  
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 JAB  
Security Exchange Name NASDAQ  
Warrants, each warrant exercisable for one Class A ordinary share    
Document Information [Line Items]    
Title of 12(b) Security Warrants, each warrant exercisable for one Class A ordinary share  
Trading Symbol JABRW  
Security Exchange Name NASDAQ  
Rights to receive one-fourth (1/4th) of one Class A ordinary Share    
Document Information [Line Items]    
Title of 12(b) Security Rights to receive one-fourth (1/4th) of one Class A ordinary Share  
Trading Symbol JABRR  
Security Exchange Name NASDAQ  
Class A Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   18,345,000
Class B Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   9,857,143