| Document and Entity Information | Feb. 18, 2025 |
| Cover [Abstract] | |
| Amendment Flag | true |
| Entity Central Index Key | 0001759138 |
| Document Type | 8-K/A |
| Document Period End Date | Feb. 18, 2025 |
| Entity Registrant Name | CABALETTA BIO, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39103 |
| Entity Tax Identification Number | 82-1685768 |
| Entity Address, Address Line One | 2929 Arch Street |
| Entity Address, Address Line Two | Suite 600 |
| Entity Address, City or Town | Philadelphia |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19104 |
| City Area Code | (267) |
| Local Phone Number | 759-3100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.00001 per share |
| Trading Symbol | CABA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Description | Cabaletta Bio, Inc. (the “Company” or “Cabaletta”) filed a Current Report on Form 8-K on February 18, 2025 in connection with a press release announcing new and updated clinical data from the first 10 patients dosed with resecabtagene autoleucel (rese-cel, formerly referred to as CABA-201) across the RESET clinical development program (the “Original 8-K”). This Amendment No. 1 (“Amendment No. 1”) to the Original 8-K is being filed to clarify that as of the data cut-off date of January 8, 2025, in the RESET-Myositis trial, the first adult dermatomyositis patient was off all immunosuppressants and tapering steroids, to revise other similar statements, and to note that a revised copy of the corporate presentation has been posted to the Company’s website and a copy of the revised press release has been furnished herewith to reflect the same, and no changes to the other information filed with the Original Form 8-K have been made. |
