LLM API Integration

A model API is an external dependency whose outputs may vary even when inputs look similar. Integration code translates domain inputs into messages or content blocks and translates responses into application objects or user-facing content. It also manages streaming, conversation state, usage and errors. A provider abstraction can reduce duplicated code, but different models still have different tool schemas, context behavior and supported modalities. The integration boundary is where these differences become explicit contracts instead of hidden assumptions spread across business logic.

The practitioner defines the application's required response shape, failure states and maximum waiting time before selecting an API. Client code centralizes credential handling and provider adaptation, while domain code validates facts and permissions. Contract tests exercise supported inputs, truncated outputs, quota errors and unavailable dependencies. Logging captures identifiers and timing with appropriate redaction. A practical deliverable is an adapter whose documented behavior tells callers whether they received a complete result, a retryable failure or an answer requiring human review.

A common interface does not make models interchangeable in quality or semantics. Retries can increase cost and repeat side effects; streaming text can be shown before later validation rejects the full answer. Silent provider fallbacks may change behavior users depend on. Good integration tests therefore inspect application outcomes as well as network success, and release decisions include representative model evaluations rather than relying only on mocked API responses.