| Cover | Nov. 04, 2024 |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 04, 2024 |
| Entity File Number | 001-42392 |
| Entity Registrant Name | Bleichroeder Acquisition Corp. I |
| Entity Central Index Key | 0002028707 |
| Entity Tax Identification Number | 98-1797826 |
| Entity Incorporation, State or Country Code | E9 |
| Entity Address, Address Line One | 1345 Avenue of the Americas |
| Entity Address, Address Line Two | Fl 47 |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10105 |
| City Area Code | 212 |
| Local Phone Number | 984-3835 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| Units, each consisting of one Class A ordinary share and one right | |
| Title of 12(b) Security | Units, each consisting of one Class A ordinary share and one right |
| Trading Symbol | BACQU |
| Class A ordinary shares, par value $0.0001 per share | |
| Title of 12(b) Security | Class A ordinary shares, par value $0.0001 per share |
| Trading Symbol | BACQ |
| Rights, each right entitling the holder to receive one-tenth (1/10) of one Class A ordinary share | |
| Title of 12(b) Security | Rights, each right entitling the holder to receive one-tenth (1/10) of one Class A ordinary share |
| Trading Symbol | BACQR |
