| Document And Entity Information | Dec. 18, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 18, 2024 |
| Entity Registrant Name | Lexeo Therapeutics, Inc. |
| Entity Central Index Key | 0001907108 |
| Entity Emerging Growth Company | true |
| Entity File Number | 001-41855 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 85-4012572 |
| Entity Address, Address Line One | 345 Park Avenue South, Floor 6 |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10010 |
| City Area Code | 212 |
| Local Phone Number | 547-9879 |
| Entity Information, Former Legal or Registered Name | N/A |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Ex Transition Period | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share |
| Trading Symbol | LXEO |
| Security Exchange Name | NASDAQ |
