Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2025	Nov. 05, 2025
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
Trading Symbol	KLRS
Entity Registrant Name	KALARIS THERAPEUTICS, INC.
Entity Central Index Key	0001754068
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		18,702,418
Security12b Title	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity File Number	001-39409
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	83-1971007
Entity Address Address Line1	400 Connell Drive, Suite 5500
Entity Address City Or Town	Berkeley Heights
Entity Address State Or Province	NJ
Entity Address Postal Zip Code	07922
City Area Code	650
Local Phone Number	249-2727
Document Quarterly Report	true
Document Transition Report	false