OpenAI’s GPT-6 Sol doubles its accuracy rate – for half the cost

ZDNET’s key takeaways

• OpenAI says GPT-6 Sol makes half as many mistakes as GPT-5.6.
• GPT-6 Luna matches previous higher-tier AI performance at far lower cost.
• OpenAI’s real pitch is cheaper AI, not just smarter AI.

Today, OpenAI is announcing the release and general availability of its new mainstream models, GPT-6 Sol and GPT-6 Luna. While new AI model releases are now a constant drumbeat in the AI industry, the reliability improvements announced today stand out from a sea of statistics.

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OpenAI says that “GPT-6 Sol makes about half as many mistakes as its predecessor.” The company also says, “GPT-6 Luna also improves substantially; at higher effort levels it matches GPT-5.6 Sol at about a hundredth its cost.”

(Disclosure: Ziff Davis, ZDNET’s parent company, filed an April 2025 lawsuit against OpenAI, alleging it infringed Ziff Davis copyrights in training and operating its AI systems.)

In other words, if GPT-5.6 was making factual errors 20% of the time, GPT-6 is making them only 10% of the time, based on the same queries. GPT-6 Luna, the low-cost engine, now performs as well as its more capable tier in the previous release.