Docker Model Runner Enables Contract Testing Across Three AI API Formats Locally

Docker Model Runner exposes OpenAI-, Anthropic-, and Ollama-compatible API formats through a single local model environment, making it a practical target for testing protocol adapters without relying on remote providers. Developers can define a shared adapter interface that normalizes responses across all three formats, isolating domain code from provider-specific wire details. Contract tests can then verify properties the application actually depends on, such as non-empty responses, finish reasons, error shapes, and streaming behavior, rather than assuming API compatibility from a shared base URL alone. The approach also recommends explicitly declaring adapter capabilities, such as tool support or token usage availability, so applications can fail fast when a feature is unsupported rather than encountering silent failures mid-execution. Differences in request translation and sampling mean generated text may still vary across adapters even when all three target the same underlying model.