v3.26.1
COVER PAGE - USD ($)
 12 Months Ended
Dec. 31, 2025
Mar. 17, 2026
Jun. 30, 2025
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-36812    
Entity Registrant Name Decoy Therapeutics Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 46-5087339    
Entity Address, Address Line One 2450 Holcombe Blvd    
Entity Address, Address Line Two Suite X    
Entity Address, City or Town Houston    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77021    
City Area Code 713    
Local Phone Number 913-5608    
Title of 12(b) Security Common Stock, par value $ 0.0001    
Trading Symbol DCOY    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction Flag false    
Entity Shell Company false    
Entity Public Float     $ 1,896,114
Entity Common Stock, Shares Outstanding   531,968  
Entity Central Index Key 0001615219    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Documents Incorporated by Reference [Text Block]

Portions of the proxy statement for the 2026 annual meeting of stockholders are incorporated by reference into Part III of the Annual Report to the extent described.