AI & Models
OpenAI expands GPT-6 lineup with cheaper Sol and Luna models
OpenAI launched updated GPT-6 Sol and Luna models on Tuesday, cutting API prices in half versus the prior 5.6 series and claiming fewer factual and coding errors.
Earlier this month, OpenAI launched GPT-6 Astra, which it called its most powerful and capable model yet and the “world’s best model” for tasks including computer work and coding. The company is now expanding the GPT-6 generation with updated versions of its smaller Sol and Luna models. “GPT-6 Astra introduced a new generation of intelligence; these models extend its benefits by making that intelligence more efficient and accessible,” OpenAI wrote in its announcement.
The first Sol and Luna models were introduced earlier this year, representing different tiers in OpenAI’s model hierarchy: Sol is designed for complex tasks like coding, while Luna is positioned for clerical work — “high-volume tasks with a clear goal, like summarizing documents, extracting information, or answering quick questions,” per OpenAI. The 6-series models will be available at half the cost of the 5.6-series Sol and Luna, a price drop OpenAI attributes to improvements in caching and inference. The company also claims its newest models produce more factually accurate answers and have a lower error rate on coding tasks. “On our internal factuality evaluation, which is based on de-identified real-world conversations where users flagged mistakes by our models, GPT-6 Sol makes about half as many mistakes as its predecessor, reaching Astra-level reliability at much lower cost,” the announcement reads.
As is typical with its model releases, OpenAI repeatedly claimed in the announcement that GPT-6 Sol and Luna handle tasks substantially better than the top models from its primary competitor, Anthropic, naming Fable and Opus specifically. The release came just 90 minutes after Anthropic released a new version of Opus 5.5, reflecting the intense competition between the two companies. The new versions of Sol and Luna are now available in ChatGPT Work and Codex for most paid accounts, and in the ChatGPT API; Luna will also be available in the desktop app and for Free and Go users. OpenAI said it expects to roll out the models to ChatGPT — the app and website — gradually throughout the day.
Why it matters
The near-simultaneous releases from OpenAI and Anthropic underscore how compressed the AI lab release cycle has become, with both cutting prices as they compete for the same developer and enterprise customers.