Swapping base_url Is Not Enough: Env Vars, Model Aliases and Client Defaults When Moving to the Aggregator

Why base_url alone is insufficient

Switching to an API aggregator often starts with changing the base_url in your client configuration. While this is necessary, it is rarely sufficient. The aggregator presents a unified interface but requires adjustments in three key areas: environment variables, model aliases, and client defaults. Overlooking these can lead to authentication failures, incorrect model routing, or unexpected retry behavior.

Update your API key environment variables

Most clients read the API key from an environment variable. The variable name often reflects the original vendor (e.g., OPENAIAPIKEY or ANTHROPICAPIKEY). When using an aggregator, you will receive a single API key that works across multiple providers. You need to ensure your code reads this key from the correct variable.

• Rename the variable: Use a generic name like AGGREGATORAPIKEY to avoid confusion. Update your .env files, CI/CD secrets, and deployment configurations accordingly.
• Remove old variables: If your code still references OPENAIAPIKEY, it may pick up a stale value or fail silently. Explicitly remove or override old variables in your environment.
• Check client defaults: Some SDKs fall back to vendor-specific variables if the primary one is missing. Consult your client's documentation to see if it reads multiple variables and adjust accordingly.

Map model slugs to aggregator aliases

Aggregators often use their own naming scheme for models. For example, a model that is gpt-4 with the original vendor might be openai/gpt-4 or gpt-4 in the aggregator's catalog. Similarly, Claude models might be prefixed with anthropic/.

• Consult the aggregator's model list: Each aggregator publishes a list of supported model identifiers. Use these exact strings in your code.
• Create a mapping layer: If your codebase uses model names in multiple places, define a mapping from your internal names to the aggregator's slugs. This centralizes changes and reduces errors.
• Handle vendor-specific parameters: Some models accept unique parameters (e.g., topk for Anthropic, logitbias for OpenAI). The aggregator may normalize these, but verify that your requests include only supported parameters for the target model.

Adjust retry and timeout defaults

Client libraries often come with default retry policies and timeouts tuned for direct vendor access. These defaults may not be optimal for an aggregator, which adds a network hop and may have different latency characteristics.

• Review retry settings: Aggregators may have their own retry logic or rate limits. Excessive retries from your client can compound load. Set retries to a reasonable number (e.g., 2–3) and implement exponential backoff.
• Set appropriate timeouts: If your old client had a short timeout for a fast vendor endpoint, it might be too aggressive for the aggregator. Increase timeouts moderately, but avoid setting them too high, which can delay failure detection.
• Disable vendor-specific features: Some clients enable features like automatic request ID logging or vendor-specific headers. These may be irrelevant or cause errors with the aggregator.

Test with a minimal request

After making these changes, run a minimal request to each model you plan to use. Verify that:

• Authentication succeeds with the new API key variable.
• The model slug is accepted and returns a response.
• Retry and timeout behavior is as expected (you can simulate failures by using an invalid model or temporarily blocking network access).

Summary

Changing base_url is only the first step. Update your environment variables to use the aggregator's API key, map model slugs to the aggregator's identifiers, and review client defaults for retries and timeouts. These adjustments ensure a smooth transition and prevent subtle failures in production.