OpenAI cuts GPT-6 Sol and Luna prices 50%

OpenAI released GPT-6 Sol and GPT-6 Luna on 22 September 2026, cutting their API prices 50% against the GPT-5.6 models they replace. Sol falls from $4 to $2 per million input tokens and $20 to $10 for output. Luna falls from $0.20 to $0.10 for input and $1.20 to $0.50 for output. Cached input — for reused context — is $0.20 for Sol and $0.01 for Luna.

The models carry the API ids gpt-6-sol and gpt-6-luna. Both roll out the same day to ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu users. Luna additionally reaches the ChatGPT desktop app for Free and Go users. GitHub added both to Copilot the same day: Sol for Pro+, Max, Business and Enterprise; Luna for every paid tier including plain Pro. OpenAI says Sol makes about half as many mistakes as GPT-5.6 Sol on its internal factuality evaluation, approaching Astra-level reliability. On OpenAI's own benchmark tables, Sol at maximum effort scores 68.8% on DeepSWE 1.1 — near Claude Fable 5's 69.9% — at roughly 80% lower cost per task, and 60.5% on OSWorld 2.0, level with Claude Opus 5's 60.3%, also at about 80% lower cost. On AutomationBench 1.0.6, a 47-tool business-workflow test, Sol at maximum effort scores 33.2% at $0.27 per task, which OpenAI says beats Claude Opus 5's 26.9% at 11 times the cost.

OpenAI's comparison charts benchmark Sol and Luna against Claude Opus 5 and Claude Fable 5.1 — not Claude Opus 5.5, which Anthropic released roughly 90 minutes before OpenAI's own announcement, at $4 input / $20 output, itself a 20% per-token cut on Opus 5. VentureBeat noted there is no same-harness result yet comparing Sol directly against the newer Anthropic model. xAI's Grok 4.7, priced at $2/$6, had already launched the day before, holding its price steady from Grok 4.6 while improving benchmark scores through a larger base model.

GPT-6 Astra, the flagship launched 3 September, keeps its $10/$50 pricing unchanged. Anthropic says Claude Sonnet 5.5 and Haiku 5.5 follow in the coming weeks with similar cost claims. OpenAI told VentureBeat the Sol and Luna cuts are permanent, not a limited-time promotion.