v3.26.1
Document and Entity Information - shares
 6 Months Ended
Jun. 30, 2026
Jul. 30, 2026
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Entity Registrant Name Faeth Therapeutics, Inc.  
Entity Central Index Key 0001829802  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   25,840,425
Entity Shell Company false  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Title of 12(b) Security Common Stock, $0.0001 par value per share  
Trading Symbol FTH  
Security Exchange Name NASDAQ  
Entity File Number 001-39980  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 83-1863385  
Entity Address, Address Line One 701 Tillery Street  
Entity Address, Address Line Two #12 #1010  
Entity Address, City or Town Austin  
Entity Address, State or Province TX  
Entity Address, Postal Zip Code 78702  
City Area Code 512  
Local Phone Number 200-2982  
Document Quarterly Report true  
Document Transition Report false