Response Caching: Zero Cost for Identical Requests

Response caching is a feature designed to dramatically reduce response times and costs by storing and reusing identical API call results, allowing for faster and free subsequent requests. By adding the X-OpenRouter-Cache: true header, users can enable caching for various requests like chat completions, messages, and embeddings, with cached responses returning in milliseconds instead of seconds. This process involves hashing the request details into a cache key, ensuring that if an identical request is made before expiration, the cached response is served without additional provider calls or token consumption. The feature supports both streaming and non-streaming requests and includes multimodal inputs, although very large payloads are excluded. Response caching differs from prompt caching by skipping the provider entirely, delivering the full response from OpenRouter's edge cache. It is particularly beneficial in scenarios such as agent retries, test suites, and repeated context processing, where cached responses provide efficiency and cost-effectiveness. Currently available across most generation endpoints, the feature is in beta, with performance monitoring ongoing to finalize the API surface.

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