Build, debug, and optimize Claude API / Anthropic SDK apps with prompt caching.
TRIGGER when: code imports `anthropic` or `@anthropic-ai/sdk`; user asks about the
Claude API, Anthropic SDK, tool use, streaming, or prompt caching; user adds or
tunes a Claude feature (caching, thinking, tool use, batch, files, citations).
SKIP: file imports `openai` or other provider SDKs; provider-neutral code; general
programming questions with no Anthropic SDK usage.
