# OpenAI updates prompt caching for GPT-6 API

Shared prompt prefixes reused within a 30-minute window now qualify for input token discounts of up to 90%.

- Developers can adjust reasoning effort and tool availability mid-conversation via configuration_update without invalidating the cache.
- A diagnostics API and tool detail reasons for cache misses and the number of affected tokens.
- Explicit cache breakpoints allow applications to choose specific prompt prefixes to preserve.
- Cache prewarming prepares shared instructions and tool definitions before user requests arrive.
- A Prompt Caching Dashboard tracks hit rates and token composition over time.

## Why it matters

Developers building multi-turn agents on GPT-6 can lower API costs and latency while dynamically modifying session configurations.

## Sources

- [OpenAI: OpenAI upgrades prompt caching for GPT-6 API](https://x.com/OpenAIDevs/status/2102506476401258678)

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Summarized by dstilled on 2026-09-22. https://dstilled.ai/story/fbebe76a-79f1-4624-88e7-962c0f7e2163