v3.26.1
Cover - shares
 3 Months Ended
Mar. 31, 2026
May 11, 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 Mar. 31, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Entity Registrant Name ONEIM ACQUISITION CORP.  
Entity Central Index Key 0002088325  
Entity File Number 001-43053  
Entity Tax Identification Number 98-1883783  
Entity Incorporation, State or Country Code E9  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Shell Company true  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Address, Address Line One 11th Floor  
Entity Address, Address Line Two 390 Park Avenue  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10022  
City Area Code (646)  
Local Phone Number 222 9570  
Units, each consisting of one Class A ordinary share and one-sixth of one redeemable warrant    
Document Information [Line Items]    
Title of 12(b) Security Units, each consisting of one Class A ordinary share and one-sixth of one redeemable warrant  
Trading Symbol OIMAU  
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 OIM  
Security Exchange Name NASDAQ  
Warrants, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 per share    
Document Information [Line Items]    
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  
Trading Symbol OIMAW  
Security Exchange Name NASDAQ  
Class A Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   7,187,500
Class B Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   28,750,000