Why bring-your-own-key

BYOK matters for two reasons:

1. Cost attribution. If a user brings their own provider key, their model usage bills to them, not the operator. Essential for self-hostable or cost-sensitive products.
2. Flexibility and trust. Users (or their organizations) may require using their own accounts, their own rate limits, their own data-processing agreements with a provider.

So a mature agent supports both an operator-wide key (everyone uses it) and per-user keys (each user uses their own), with per-user taking precedence.