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Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Feb. 28, 2025
Jun. 30, 2024
Cover [Abstract]      
Entity Registrant Name CYCLERION THERAPEUTICS, INC.    
Document Type 10-K/A    
Document Period End Date Dec. 31, 2024    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 4.8
Entity Common Stock, Shares Outstanding   2,710,096  
Entity Central Index Key 0001755237    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Amendment Flag true    
Amendment Description Cyclerion Therapeutics, Inc. (the “Company”) is filing this Amendment No. 1 (the “Amendment”) to its Annual Report on Form 10-K for the fiscal year ended December 31, 2024, which was originally filed with the Securities and Exchange Commission (the “Commission”) on March 4, 2025 (the “Original 10-K”), for the purpose of amending Item 8 of the Original 10-K to amend the Report of Independent Registered Public Accounting Firm of Ernst & Young LLP on the Company’s financial statements as of and for the years ended December 31, 2024 and 2023 (the “Original Audit Report”). The only change to the Original Audit Report is to add an additional paragraph regarding “Critical Audit Matter” which paragraph was inadvertently omitted by Ernst & Young LLP from the Original Audit Report. The information contained in this additional paragraph relates to information presented in Notes 2 and 5 to the Notes to Financial Statements contained in the Original 10-K. The Original Audit Report, as amended (the “Amended Audit Report”) appears on page F-2 of this Amendment along with the Financial Statements and Notes to the Financial Statements, which remain otherwise unchanged from those contained in the Original 10-K filing.    
Document Annual Report true    
Document Transition Report false    
Entity Tax Identification Number 83-1895370    
Entity File Number 001-38787    
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    
Title of 12(b) Security Common Stock, no par value    
Trading Symbol CYCN    
Security Exchange Name NASDAQ    
Documents Incorporated by Reference

Portions of the registrant’s definitive Proxy Statement, to be filed pursuant to Regulation 14A under the Securities Exchange Act of 1934, for its 2025 Annual Meeting of Stockholders are incorporated by reference in Part III of this Form 10-K.

    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Auditor Firm ID 42    
Auditor Name Ernst & Young LLP    
Auditor Location Boston, Massachusetts