A bring-your-own-key design separates the application's interface and tools from the upstream model account. The user supplies an authorized API credential, the application sends requests under that account, and the provider bills or limits the user according to the provider relationship.
This approach can preserve model choice when bundled access ends, but it shifts setup, cost visibility, quota, and credential management to the user. Applications must protect keys, avoid exposing them to untrusted content or clients, and clearly explain which service receives each request.
ELI5
Bring your own key means connecting an application with your own private access key for another service. The application supplies the interface, but the model request uses your provider account and usually your provider bill.
For example, a coding tool may let a user paste or securely store their own model-provider key after bundled access disappears. The tool must keep that key private and show which provider will receive the code or prompt.
