v3.26.1
Cover Page
 3 Months Ended
Mar. 31, 2026
Document Information [Line Items]  
Entity Registrant Name CYCLERION THERAPEUTICS, INC.
Document Type S-4/A
Entity Filer Category Non-accelerated Filer
Entity Small Business true
Entity Emerging Growth Company false
Entity Central Index Key 0001755237
Amendment Flag false
Entity Tax Identification Number 83-1895370
Entity Incorporation, State or Country Code MA
Entity Address, Address Line One 245 First Street, 18th Floor
Entity Address, City or Town Cambridge
Entity Address, State or Province MA
Entity Address, Postal Zip Code 02142
City Area Code 857
Local Phone Number 327-8778
Entity Primary SIC Number 2834
Business Contact [Member]  
Document Information [Line Items]  
Entity Address, Address Line One 245 First Street, 18th Floor
Entity Address, City or Town Cambridge
Entity Address, State or Province MA
Entity Address, Postal Zip Code 02142
City Area Code 857
Local Phone Number 327-8778
Contact Personnel Name Regina Graul, Ph.D.