The Provider Protocol Pattern

When your code is tightly coupled to one LLM provider, swapping is painful and testing requires live API calls. Python's Protocol fixes both.

class LLMProvider(Protocol):
    def complete(self, messages: list[dict]) -> str: ...

Any class with a matching complete method satisfies this — no inheritance needed. Your service only sees the Protocol, never the concrete class.

Why care? Swap providers by changing one line at the call site. Test without hitting any API. The cohort uses this same pattern to support OpenAI and Groq side by side — once you've got the Protocol, adding a third provider is a 30-line file.

Task

The LLMProvider Protocol is defined. Implement:

• ClaudeProvider — wraps the Anthropic SDK
• MockProvider — returns a fixed string and records every call in self.calls