{
  "context_concepts": [
    {
      "id": "ctx_prompt_caching_what",
      "name": "What prompt caching is",
      "category": "prompt_caching",
      "description": "Prompt caching lets a client mark a prefix of a prompt (e.g. a long system prompt, a set of tool definitions, or a large shared document) as cacheable, so that repeated requests reusing that same prefix are billed and processed more cheaply and with lower latency than reprocessing it from scratch each time.",
      "how_it_works": "On a cache hit, the model does not need to reprocess the cached prefix's tokens the same way it would a fully fresh prompt — the provider serves the cached computation, and only the new (non-cached) portion of the prompt is processed at full cost/latency.",
      "source_note": "Grounded in docs/docs/platform.claude.com/docs/en/build-with-claude/prompt-caching.md, mirrored in this repo per CLAUDE.md.",
      "created_at": "2026-07-02 08:27:03",
      "cite_as": "https://subagentcontext.com/api/context-concepts/ctx_prompt_caching_what"
    },
    {
      "id": "ctx_prompt_caching_when_useful",
      "name": "When prompt caching is most useful",
      "category": "prompt_caching",
      "description": "Prompt caching pays off most when the same large prefix (system prompt, tool schema, long reference document, or few-shot examples) is reused across many requests in a short time window, such as a multi-turn agent session or a batch of requests over the same document.",
      "how_it_works": "Each cached prefix has a limited time-to-live; if requests reusing that prefix keep arriving before it expires, subsequent requests keep getting the caching benefit; if too much time passes between requests, the cache entry expires and the next request pays full cost to reprocess and re-cache it.",
      "source_note": "General usage pattern consistent with docs/docs/platform.claude.com/docs/en/build-with-claude/prompt-caching.md.",
      "created_at": "2026-07-02 08:27:03",
      "cite_as": "https://subagentcontext.com/api/context-concepts/ctx_prompt_caching_when_useful"
    }
  ]
}