| Document and Entity Information | Aug. 14, 2024 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001681087 |
| Document Type | 8-K |
| Document Period End Date | Aug. 14, 2024 |
| Entity Registrant Name | Tectonic Therapeutic, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38537 |
| Entity Tax Identification Number | 81-0710585 |
| Entity Address, Address Line One | 490 Arsenal Way |
| Entity Address, Address Line Two | Suite 210 |
| Entity Address, City or Town | Watertown |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02472 |
| City Area Code | (339) |
| Local Phone Number | 666-3320 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.0001 par value per share |
| Trading Symbol | TECX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
