v3.26.3
Nature of the Business and Basis of Presentation (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 08, 2026
Sep. 30, 2026
USD ($)
$ / shares
shares
Sep. 30, 2026
USD ($)
$ / shares
shares
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
shares
Nature of Business          
Common stock, shares issued | shares   45,541,358 45,541,358   1,244,400
Net loss   $ (46,400) $ (77,295) $ (21,948)  
Accumulated deficit   (113,025) (113,025)   $ (35,730)
Cash and cash equivalents   $ 456,221 456,221   $ 154,135
Fairmount          
Nature of Business          
Aggregate purchase price     75,000    
Venrock          
Nature of Business          
Aggregate purchase price     $ 60,000    
Cyclerion          
Nature of Business          
Stock conversion terms In accordance with an exchange ratio determined in accordance with the terms of the Merger Agreement (the “Exchange Ratio”), at the effective time of the First Merger (the “First Effective Time”), (i) each then-outstanding share of common stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana common stock") (including shares of Pre-Merger Korsana common stock issued in connection with the Pre-Closing Financing (as defined below)) automatically converted into the right to receive a number of shares of common stock, no par value per share, of Cyclerion (the "Cyclerion common stock") equal to the Exchange Ratio, (ii) each then-outstanding share of Series Seed Preferred Stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana Series Seed Preferred Stock") was converted into the right to receive a number of shares of Series B Non-Voting Convertible Preferred Stock, no par value, of Cyclerion (the "Series B Preferred Stock"), equal to the Exchange Ratio divided by 1,000, (iii) each-then-outstanding share of Series A Preferred Stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana Series A Preferred Stock") automatically converted into the right to receive to a number of shares of Cyclerion common stock equal to the Exchange Ratio; provided, that to the extent the shares of Cyclerion common stock otherwise issuable to any holder would exceed such holder's beneficial ownership limitation (initially set at a percentage of up to 9.99% of the outstanding Cyclerion common stock), such holder received, in lieu of the excess shares, pre-funded warrants to purchase an equal number of shares of Cyclerion common stock, subject to adjustment as set forth in the form of the pre-funded warrant, (iv) each then-outstanding option to purchase Pre-Merger Korsana common stock was assumed by Cyclerion and was converted into an option to purchase shares of Cyclerion common stock, adjusted for the Exchange Ratio, (v) each then-outstanding warrant to purchase Pre-Merger Korsana common stock was assumed by Cyclerion and was converted into a warrant to purchase shares of Cyclerion common stock, subject to adjustment as set forth in the Merger Agreement, (vi) each then-outstanding share of Pre-Merger Korsana restricted stock was assumed by Cyclerion, subject to adjustment as set forth in the Merger Agreement, and (vii) each then-outstanding pre-funded warrant to purchase shares of Pre-Merger Korsana common stock was converted into a pre-funded warrant to purchase shares of Cyclerion common stock, subject to adjustment as set forth in the Merger Agreement and the form of pre-funded warrant.        
Reverse stock split     1-for-7 reverse stock split    
Cyclerion | Common Stock          
Nature of Business          
Stock conversion ratio 0.0002074        
Cyclerion | Common Stock | Series B Preferred Stock          
Nature of Business          
Stock conversion ratio 0.0000002074        
Pre-Merger Korsana          
Nature of Business          
Common stock, shares issued | shares   140,516,578 140,516,578    
Common stock share purchase price | $ / shares   $ 2.3648 $ 2.3648    
Aggregate purchase price     $ 380,000    
Pre-Merger Korsana | Pre-Funded Warrants          
Nature of Business          
Warrants purchase for common stock | shares   20,171,961 20,171,961    
Exercise price per share | $ / shares   $ 2.3647 $ 2.3647    
Pre-funded warrants outstanding | shares   4,183,665 4,183,665    
Pre-Merger Korsana | Common Stock          
Nature of Business          
Common stock shares issued | shares   29,143,142 29,143,142