# Zero Data Retention

Understand exactly what the ZDR response header covers and which operational metadata remains.

KosCompute API responses include:

```http
X-Zero-Data-Retention: true
```

This means the router does not retain request bodies, prompts, completion bodies, uploaded media, or generated media as request-history records.

## Operational metadata

Zero Data Retention does not mean that no operational data exists. The service can retain metadata required for security, reliability, capacity planning, and billing, including:

- server-generated request ID;
- authenticated key identifier or non-secret alias;
- endpoint and model ID;
- timestamps, latency, status, and error class;
- input, output, cached, reasoning, audio-duration, or character usage counters;
- request and response byte counts;
- coarse feature flags such as streaming or image presence.

This metadata excludes Authorization values and raw key material. It is not intended to reconstruct request content.

## Stateless APIs

The Responses endpoint rejects `store:true` and non-null `previous_response_id`. Clients must resend context needed for later turns. The ZDR header describes KosCompute's production router contract; it does not describe retention by your client, your own logs, remote image hosts, or external tools you invoke.