OpenAI API adds a 12-hour cache retention option; caches for logged-in Codex and Work users are retained permanently

The API service for OpenAI models will offer a 12-hour cache retention option, and caches for logged-in Codex and Work users will be retained permanently. On the API side, this option applies to GPT-5.6 and later models, with a default retention of 30 minutes; when 12 hours is selected, the cache write price rises from 1.25 times the input token price to 2.5 times, while the cache read price remains unchanged. OpenAI's documentation states that the 12 hours specifies the minimum lifetime corresponding to eligibility for cache-read billing; it does not guarantee that the stored KV tensors can be reused on every request, nor does it guarantee reduced latency.