v3.26.1
Cover - shares
 6 Months Ended
Jun. 30, 2026
Jul. 29, 2026
Entity Addresses [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2026  
Document Transition Report false  
Entity File Number 001-43105  
Entity Registrant Name SpyGlass Pharma, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 83-3044245  
Entity Address, Address Line One 15326 Alton Parkway  
Entity Address, City or Town Irvine  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 92618  
City Area Code 949  
Local Phone Number 284-6904  
Title of 12(b) Security Common Stock, par value $0.00001 per share  
Trading Symbol SGP  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   33,447,979
Central Index Key 0001778922  
Amendment Flag false  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
Former Address    
Entity Addresses [Line Items]    
Entity Address, Address Line One 27061 Aliso Creek Rd  
Entity Address, Address Line Two Suite 100  
Entity Address, City or Town Aliso Viejo  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 92656