Cabaletta Bio, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Common Stock - Additional Information (Details)

Common Stock - Additional Information (Details) - USD ($)		1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 23, 2019	May 31, 2023	Dec. 31, 2022	Oct. 31, 2019	Mar. 31, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	May 31, 2024	Jan. 01, 2024	Jun. 01, 2023	Jan. 01, 2023	Jan. 01, 2022	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					$ 5,746,000	$ 93,755,000
Weighted average grant-date fair value of stock options granted							$ 15.61	$ 9.27
Unrecognized compensation cost related to unvested stock-based awards							$ 54,346,000
Unrecognized compensation cost, period for recognition							2 years 11 months 23 days
Payment of offering costs related to issuance of common stock							$ 5,746,000	$ 93,463,000
Issuance of common stock, net of issuance costs					$ 147,000	$ 6,295,000
Shares remaining available for issuance							1,999,655
At-The-Market Offering Sales Agreement
Class Of Stock [Line Items]
Common stock issuance, Shares							258,070		4,760,899
Payment of offering costs related to issuance of common stock							$ 5,746,000		$ 91,740,000
Issuance of common stock, net of issuance costs							147		2,352,000
At-The-Market Offering Sales Agreement \| Maximum
Class Of Stock [Line Items]
Common stock issuance							$ 200,000,000		$ 100,000,000
December 2022 Financing
Class Of Stock [Line Items]
Common stock issuance, Shares			126,815
Common stock price per share			$ 5.52
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										1,912,929
Increase in share reserved percentage	4.00%
2019 Plan \| Employee Stock Option
Class Of Stock [Line Items]
Number of options granted							2,848,700
2019 ESPP
Class Of Stock [Line Items]
Common stock issuance, Shares							357,368
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							$ 25,000
Percentage of shares to be purchased							85.00%
May Two Thousand Twenty Three Financing [Member]
Class Of Stock [Line Items]
Common stock issuance, Shares		8,337,500
May Two Thousand Twenty Three Financing [Member] \| Employee Stock Option
Class Of Stock [Line Items]
Additional Options To Be Purchased By Underwriters		1,087,500
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
Common stock, par value							$ 0.00001		$ 0.00001
Pre-funded Warrants \| December 2022 Financing
Class Of Stock [Line Items]
Common stock issuance, Shares			6,213,776
Common stock price per share			$ 5.51999
Decrease in exercise price of Warrents			$ 0.00001
Net proceeds from exercise of warrants			$ 32,562,000
Warrants exercised							5,589,202
Pre-funded warrants remain outstanding							624,574
Pre-funded Warrants \| May Two Thousand Twenty Three Financing [Member]
Class Of Stock [Line Items]
Decrease in exercise price of Warrents		$ 12
Net proceeds from exercise of warrants		$ 93,755
Warrants exercised		6,295