Daily News · 2 min read

OpenAI AI Updates: September 23, 2026

openai gpt-6 model-release pricing codex prompt-caching

1. GPT-6 Sol and Luna Halve Token Prices Without Moving the Intelligence Needle Much

OpenAI. Sol drops from $4/$20 to $2/$10 per million input/output tokens, and Luna from $0.20/$1.20 to $0.10/$0.50, a 50 percent cut against the GPT-5.6 generation. OpenAI attributes the reduction to caching and inference improvements passed through to users. Independent readings find performance roughly at predecessor level rather than meaningfully above it, which makes this a price move aimed at Anthropic’s costlier tiers more than a capability release. Terra, previously the cheapest model in the lineup, is gone. Source

2. Sol Is the Coding Model, Luna Is the Bulk Processor

OpenAI. OpenAI frames Sol for recurring complex tasks such as building features, reviewing code, debugging, and analyzing data, and Luna for high-volume well-defined work like document summarization, extraction, and short answers. Both carry up to 1M tokens of context. On OSWorld 2.0 the company claims GPT-6 delivers results similar to Claude Opus 5 at roughly 80 percent lower cost, though Astra still leads that category. API model IDs are gpt-6-sol and gpt-6-luna. Source

3. Prompt Caching Now Discounts Cached Input 90 Percent and Survives Config Changes

OpenAI. GPT-6 prompt caching offers a 90 percent discount on cached input tokens, and the more consequential change for agent builders is that reasoning effort and tool availability can now be altered without invalidating the cache. OpenAI also shipped a prompt caching dashboard and diagnostics tooling to let developers see where cache hits are being lost. Source

4. Both Models Landed in Codex and ChatGPT Work First, Not Regular Chat

OpenAI. At launch Sol and Luna are available in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu subscribers. Free and Go users get Luna through the desktop app. Neither model is initially available in regular chat, with ChatGPT access rolling out gradually. Codex CLI 0.156.0 shipped the same day and 0.156.1 followed on September 23. Source