Cabaletta Bio, Inc. Quarterly report [Sections 13 or 15(d)]

Quarterly report [Sections 13 or 15(d)]

Common Stock - Additional Information (Details)

Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 23, 2019	Oct. 31, 2019	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Jan. 01, 2025	May 31, 2024	Jan. 01, 2024	Jun. 01, 2023	Jan. 01, 2023	Jan. 01, 2022	Dec. 31, 2020	Oct. 30, 2019	Jan. 31, 2019
Class Of Stock [Line Items]
Common stock, authorized shares			150,000,000		150,000,000
Non-voting common stock, Terms of conversion		Each share of the Company’s non-voting common stock may be converted at any time into one share of common stock at the option of its holder by providing 61 days written notice to the Company
Common stock issuance				$ 5,746
Weighted average grant-date fair value of stock options granted			$ 1.45	$ 19.72
Unrecognized compensation cost related to unvested stock-based awards			$ 49,872
Unrecognized compensation cost, period for recognition			2 years 8 months 12 days
Payment of offering costs related to issuance of common stock			$ 0	$ 5,746
Issuance of common stock, net of issuance costs				$ 147
Shares remaining available for issuance			573,972
At-The-Market Offering Sales Agreement
Class Of Stock [Line Items]
Common stock issuance, Shares				258,070	1,225,000	4,760,899
Payment of offering costs related to issuance of common stock				$ 5,746	$ 5,129	$ 91,740
Payments for Commissions					$ 105
Issuance of common stock, net of issuance costs				$ 147		2,352
At-The-Market Offering Sales Agreement \| Maximum
Class Of Stock [Line Items]
Common stock issuance			$ 200,000			$ 100,000
2018 Plan \| Employee Stock Option
Class Of Stock [Line Items]
Share-based compensation unvested number of shares													0
Number of options granted			1,959,411
2018 Plan \| Maximum \| Employee Stock Option
Class Of Stock [Line Items]
Share-based compensation, vesting period			4 years
2018 Plan \| Minimum \| Employee Stock Option
Class Of Stock [Line Items]
Share-based compensation, vesting period			3 years
2019 Plan
Class Of Stock [Line Items]
Shares reserved for issuance	2,342,288						2,029,724
Increase in share reserved percentage	4.00%
2019 Plan \| Employee Stock Option
Class Of Stock [Line Items]
Number of options granted			2,869,050
2019 ESPP
Class Of Stock [Line Items]
Common stock issuance, Shares			314,259
Shares reserved for issuance	234,229								0		0	0
2019 ESPP \| Minimum
Class Of Stock [Line Items]
Shares reserved for issuance															234,229
Increase in share reserved percentage	1.00%
Payroll deduction percentage of eligible compensation			15.00%
Employee stock purchase plan maximum annual rights to purchase common stock			$ 25
Percentage of shares to be purchased			85.00%
Voting Common Stock
Class Of Stock [Line Items]
Common stock, authorized shares			143,590,481		143,590,481									143,590,481
Common stock, par value			$ 0.00001		$ 0.00001
Voting Common Stock \| 2019 Plan
Class Of Stock [Line Items]
Shares reserved for issuance										3,000,000
Non-voting Common Stock
Class Of Stock [Line Items]
Common stock, authorized shares			6,409,519		6,409,519			1,444,295						6,409,519