v3.26.1
Cover - shares
 6 Months Ended
Jun. 30, 2026
Aug. 13, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Entity Interactive Data Current Yes  
Amendment Flag false  
Document Period End Date Jun. 30, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Entity Registrant Name KPET Ultra Paceline Corporation  
Entity Central Index Key 0002095297  
Entity Tax Identification Number 98-1888520  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Non-accelerated Filer  
Entity File Number 001-43216  
Entity Shell Company true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Small Business true  
Entity Incorporation, State or Country Code E9  
Entity Address, Address Line One 5109 S. Broadband Lane  
Entity Address, City or Town Sioux Falls  
Entity Address, Country SD  
Entity Address, Postal Zip Code 57108  
City Area Code (605)  
Local Phone Number 308-0233  
Units, each consisting of one Class A ordinary share, $0.0001 par value, and one-sixth of one warrant    
Document Information [Line Items]    
Trading Symbol KPET.U  
Title of 12(b) Security Units, each consisting of one Class A ordinary share, $0.0001 par value, and one-sixth of one warrant  
Security Exchange Name NYSE  
Class A ordinary shares, par value $0.0001 per share    
Document Information [Line Items]    
Trading Symbol KPET  
Title of 12(b) Security Class A ordinary shares, par value $0.0001 per share  
Security Exchange Name NYSE  
Warrants, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 per share    
Document Information [Line Items]    
Trading Symbol KPET.WS  
Title of 12(b) Security Warrants, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 per share  
Security Exchange Name NYSE  
Class A Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   23,235,000
Class B Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   5,750,000