v3.26.1
Document and Entity Information - shares
 3 Months Ended
Mar. 31, 2026
Jun. 05, 2026
Cover [Abstract]    
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 Seaport Therapeutics, Inc.  
Entity Central Index Key 0002042347  
Entity File Number 001-43254  
Entity Tax Identification Number 99-2235719  
Entity Incorporation, State or Country Code DE  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status No  
Entity Shell Company false  
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 101 Seaport Blvd., Floor 12  
Entity Address, City or Town Boston  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02210  
City Area Code 617  
Local Phone Number 807-4062  
Title of 12(b) Security Voting Common Stock, $0.0001 par value per share  
Trading Symbol SPTX  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   53,530,550