OpenAI released GPT-6 Sol and Luna on Tuesday, essentially more affordable versions of GPT-6 Astra that come closer to Astra on alignment than GPT-5.6 Sol did, but still fall short of the flagship model. 

Most notably, the AI company slashed token prices, making the new GPT-6 models significantly cheaper to use. Beyond token prices, though, OpenAI says better caching can also help developers push costs down even more.

Per OpenAI: “Improvements in caching and inference let us serve these models at lower cost,” with API prices for Sol and Luna down 50% compared to their GPT-5.6 counterparts (58% lower for Luna output tokens).

What improvements? Namely, higher cache-hit rates by default, the ability to preserve earlier context even when reasoning effort and tool availability change, and new tools to monitor and diagnose caching performance. 

Prompt caching isn’t, of course, novel to the new GPT-6 models themselves. But the upgraded Sol and Luna come with improvements designed to keep more previously processed context reusable as the agent moves forward on a task. 

“We’ve improved prompt caching for GPT‑6 to deliver higher cache hit rates by default, helping agents reuse more context, respond faster, and benefit from discounts of 90% on cached input-token reads.”

6 pricing; what’s new is how often the cache gets hit. By using cached context to reuse work it’s already done, the model doesn’t have to process the same context again from scratch for every single call, thereby reducing latency — and token costs.

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