Compatibility is a contract to test
Chat completions, newer response APIs, embeddings, images, audio, tool calls, structured outputs, and streaming do not all share identical semantics. List the exact endpoints and fields each application uses before assuming a base-URL change is sufficient.
Capture provider error handling, timeouts, idempotency, and retry behavior. A gateway must not multiply retries already performed by the SDK or application.
Replace shared keys with scoped identities
Issue virtual keys per environment, application, or team and map them to provider credentials held by the gateway. Do not copy plaintext provider keys into every service. Define model allowlists, rate limits, and budget ownership on the virtual identity.
Rotate one application at a time and verify that logs never expose full prompts, secrets, or provider credentials.
Run a parity suite
Replay non-sensitive fixtures through direct and gateway paths. Compare response shape, streaming chunks, tool calls, JSON validity, usage fields, headers, errors, and latency. Test provider outage and timeout behavior deliberately.
- Base URL and authentication
- Streaming and cancellation
- Tools and structured output
- Token usage and cost records
- Retries, fallbacks, and timeouts
- Rate limits and error translation
- Pass-through rollback
Enable controls in stages
Begin with pass-through plus metering. Add exact cache for approved routes, then monitor routing decisions, then enforce one well-evaluated cohort. This makes each behavior change attributable and reversible.
Frequently asked questions
Is changing the OpenAI base URL enough?
It may be enough for a basic chat call, but production migration requires testing streaming, tools, structured output, retries, errors, and usage accounting.
Should applications keep provider API keys?
Prefer scoped gateway credentials and centralized provider secrets. Keep a controlled rollback mechanism without leaving unrestricted keys broadly deployed.
Can the gateway change requested models immediately?
Start in pass-through or monitor mode. Model substitution should begin only after route-specific evaluation and approval.
Sources and further reading
FrugalAI uses primary documentation and published research where possible. Product capabilities and prices can change; verify vendor details before procurement or production changes.