Parity Layer

Parity Layer is a gateway you point an existing OpenAI or Anthropic client at by changing the base URL. It accepts both formats, at /v1/chat/completions and /v1/messages, and supports streaming and tool calling.

The idea is to cut spend without guessing: it runs cheaper candidate models alongside your baseline on real prompts, compares the responses, and only starts routing to a cheaper model once your configured confidence threshold is met. Routing reverts automatically if quality drifts. How responses are scored is not documented publicly.

You bring your own provider keys for Anthropic, OpenAI, Google, xAI, Groq and Together, and Parity stores them to call upstream on your behalf. It also retains prompts and both models responses to build the comparison trail. Note that at the time of listing the site published no privacy policy or terms of service, which is worth asking about before sending production traffic or keys.