v3.26.1
Stockholders' Equity - Stock reserved for issuance (Details) - shares
Jun. 30, 2026
Dec. 31, 2025
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 33,849,883 31,068,650
Employee Stock Option    
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 21,486,374 20,353,098
RSUs issued and outstanding    
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 3,263,275 2,527,377
Shares available for grant | Shares available for grant under the 2024 Equity Incentive Plan    
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 927,409 597,112
Shares available for grant | Shares available for grant under the 2024 Employee Stock Purchase Plan    
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 1,599,251 805,334
Shares available for grant | Shares available for grant under the ACELYRIN, Inc. 2023 Equity Incentive Plan    
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 6,372,372 6,585,521
Shares available for grant | Shares available for grant under the 2024 Performance Option Plan    
Stockholders' Equity (Deficit)    
Common stock reserved for future issuance 201,202 200,208