OpenAI and Anthropic Launch Rival Models Hours Apart, Cutting Prices Sharply

OpenAI added two new models to its GPT-6 Astra family on September 22, 2026: GPT-6 Sol and GPT-6 Luna. The announcement came just 90 minutes after Anthropic unveiled its own new flagship model, Claude Opus 5.5, the same day. The back-to-back launches highlighted how intense price and performance competition among large language model providers has become, with CNBC and other outlets describing it as a direct price war.

GPT-6 Sol costs $2 per million input tokens and $10 per million output tokens, a 50% cut in both directions from GPT-5.6 Sol. GPT-6 Luna is priced at $0.10 input and $0.50 output per million tokens, down 50% and 58% respectively, with discounts reaching 90% through prompt caching. An OpenAI spokesperson confirmed the pricing is permanent, not a promotional offer. Sol is aimed at complex coding tasks, while Luna targets high-volume work such as summarization and information extraction; OpenAI said Sol cuts factual errors roughly in half compared with its predecessor. Both models rolled out through the OpenAI API, ChatGPT and Codex, and Microsoft added them to Azure AI Foundry the same day.

On the Anthropic side, the company described Claude Opus 5.5 as delivering 40% lower cost than Opus 5 for typical workloads while matching Claude Fable 5.1-level performance; VentureBeat reported the model beats Fable 5.1 on key agentic benchmarks and offers up to 60% cheaper pricing in some comparisons. Pricing was set at $4 per million input tokens and $20 per million output tokens, down from $5 and $25 for Opus 5, with cached-read pricing dropping to $0.20 and cache writes to $5. Anthropic said Opus 5.5 marks a major step up from Opus 5 in agentic coding, knowledge work and computer use, with output generation 30% faster. The company also published a system card the same day detailing added cybersecurity and biosecurity safeguards, which some outlets linked to recent AI-assisted hacking incidents.

GPT-6 Astra, OpenAI's flagship model introduced in July 2026, sits above Sol and Luna, which are positioned as its more affordable tiers. On price, Sol lands in the same range as Anthropic's Claude Sonnet 5, while the open-weight Xiaomi MiMo-V2.6-Pro undercuts both but requires self-hosting — underscoring the pricing pressure coming from Chinese open-source models. Notably, both launches arrived weeks after OpenAI, Anthropic and more than 100 other companies jointly called for action against uncontrolled AI systems, suggesting competitive pressure has not slowed despite that shared safety messaging.

With both companies shipping cheaper, more capable models within hours of each other, developers and enterprise customers now have more low-cost options to choose from. GPT-6 Luna is available to free and Go users in the ChatGPT desktop app, while Sol and Codex access remain limited to Plus, Pro, Business and Enterprise customers. Industry observers note the twin releases can also be read as a response to pricing pressure from Chinese open-source models like DeepSeek, Qwen and Kimi.