What changes
The credential boundary leaves the local host entirely.
The host now presents its own backend token and user identity. The backend decides whether to forward the call and which upstream secret to use.
Run the dry-run backend
export BACKEND_BROKER_TOKEN=demo-backend-token
python3 labs/backend-broker/server.py --config labs/backend-broker/server_config.dry-run.json
Time guide. Setup: 10–20 min if you want to compare it with the localhost broker pattern. Working through it: 20–40 min once the dry-run backend is in front of you.
Boundary
The local host no longer touches the provider credential directly; it only talks to your backend contract.
Real-world analog
Internal API gateway, backend-for-frontend, or managed-identity-backed app service.
Security companion: backend or managed identity path.