Document and Entity Information	12 Months Ended
	Dec. 31, 2024
Document and Entity Information [Abstract]
Document Type	S-4
Entity Registrant Name	ALUMIS INC.
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Central Index Key	0001847367
Amendment Flag	false