Anthropic

Anthropic's API enforces rigid "user" → "assistant" → "user" message patterns with only a single system prompt at the beginning, making it difficult to build dynamic applications that need to inject new information mid-conversation or switch context.

Developers must manually handle tool use infinite loops (where models repeatedly call the same tool) by implementing iteration counts, and catch truncated output by checking `stop_reason == "max_tokens"`. Without proper handling, production deployments fail silently.

Integrating Anthropic API calls into automated testing and CI/CD pipelines is problematic because API keys are often restricted or unavailable in test environments, requiring developers to use workarounds like test mocking tools to maintain test coverage.

Anthropic's prompt caching has a 5-minute time-to-live, meaning low-traffic endpoints may not see consistent cache hits. Even minor whitespace changes invalidate cached prefixes, requiring exact matching across calls.