Claude Opus 5.5 and OpenAI GPT-6 Sol & Luna both launch today with lower costs

Ben Schoon | Sep 22 2026 - 1:20 pm PT

Anthropic and OpenAI are both launching new model updates today, with Claude Opus 5.5 and GPT-6 Sol & Luna both being announced within roughly an hour of each other.

Claude Opus 5.5 was up to bat first today, so we’ll start there.

Anthropic explains that its latest model update performs at the level of Claude Fable 5.1 on “most work” while cutting costs to run by around 40% compared to Opus 5 – which was already around half the price of Fable 5.

Opus 5.5 requires less compute to serve than Opus 5, and its pricing reflects that. Our tests show that at default settings it will cost 40% less than Opus 5 on typical workloads. Input and output tokens are $4 and $20 per million, 20% less than Opus 5. Cache reads (which make up the majority of agentic and coding work costs) are $0.20 per million tokens, 60% less than Opus 5. Opus 5.5 also generates output more than 30% faster than Opus 5.

Despite the lower compute costs, Anthropic says that Opus 5.5 is more powerful, beating out Fable 5.1 in every metric and beating OpenAI’s GPT-6 Astra in virtually every category measured as well including metrics such as agentic coding, knowledge work, and more.

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Claude Opus 5.5 is available now on “all platforms,” Anthropic says.

And that’s not all. OpenAI, roughly an hour after Claude’s announcement, launched its GPT-6 Sol & Luna models, also focused on costs.

Like Opus 5.5, OpenAI says that GPT-6 Sol and Luna are both much more affordable to run compared to their GPT-5.6 counterparts. Specifically, they’re both about 50% less expensive when measuring input and output per 1 million tokens in API use.

Both models are marginally more powerful than their predecessors, but well behind that of Astra, which remains the overall most powerful model OpenAI offers. Luna prioritizes cost over capability, while Sol strikes a balance between the two by offering more horsepower than Luna but at a more affordable cost compared to Astra.

We trained GPT‑6 Sol and Luna with similar methods as GPT‑6 Astra, bringing the advances behind Astra’s state-of-the-art performance in professional work, factuality, coding, computer use, and alignment to faster, more affordable models.

The GPT‑6 models lead across the cost–intelligence curve, combining exceptional capabilities at every tier with infrastructure that delivers them efficiently at scale. Improvements in caching and inference let us serve these models at lower cost, and we’re passing those savings directly on to users and customers by reducing API prices for Sol and Luna by 50% compared with their GPT‑5.6 promotional pricing.

OpenAI says Sol and Luna are available in ChatGPT Work and Codex starting today for Plus, Pro, Business, Enterprise, and Edu users, while Luna is available in the desktop app for Free and Go users. Neither model is available in Chat just yet.