---
id: "2026-09-22-gpt-6-sol-luna"
url: "https://postcutoff.com/e/2026-09-22-gpt-6-sol-luna/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2026-09-22"
date_precision: day
category: model-release
importance: 4
confidence: high
status: [Confirmed]
sources: 11
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-09-22-gpt-6-sol-luna/

# OpenAI launches GPT-6 Sol and GPT-6 Luna at half the price of GPT-5.6

On Sept 22, 2026, 19 days after Astra, OpenAI released GPT-6 Sol (complex tasks, coding) and GPT-6 Luna (high-volume clerical tasks), trained with Astra's methods and priced 50% below their GPT-5.6 predecessors ($2/$10 and $0.10/$0.50 per 1M tokens); OpenAI says Sol makes about half as many factual mistakes as GPT-5.6 Sol, reaching "Astra-level reliability at much lower cost".

## Key facts
- Released Sept 22, 2026 in ChatGPT Work, Codex and the API
- Plus, Pro, Business, Enterprise and Edu get both models; Free and Go users get GPT-6 Luna in the desktop app
- GPT-6 Sol API: $2 input / $10 output per 1M tokens, cached input $0.20 (OpenAI compared against $4/$20 for GPT-5.6 Sol)
- GPT-6 Luna API: $0.10 input / $0.50 output per 1M tokens, cached input $0.01 (vs $0.20/$1.20 for GPT-5.6 Luna)
- Price cut attributed to caching and inference improvements
- Sol: about half the factual mistakes of GPT-5.6 Sol on OpenAI's internal factuality eval
- Agents' Last Exam: Sol 56.4% (~95% of Astra's top score)
- DeepSWE v1.1: Sol 68.8%, Luna 66.6%; OSWorld 2.0 Offline: Sol 60.5%, Luna 58.1%
- AutomationBench 1.0.6: Sol 33.2% (extra-high effort)
- Codex CLI 0.156.1 (Sept 23) added Sol and Luna to its model picker; Codex 0.157.0 (Sept 25) added Amazon Bedrock support for them
- 'Better prompt caching for GPT-6' (Sept 22): the GPT-6 family launched with a new caching system with higher default hit rates; cache discounts apply to eligible shared prefixes reused within a 30-minute window; new Prompt Caching Dashboard and a cache-miss diagnostics tool

## What happened

OpenAI extended the GPT-6 generation with two cheaper models. **GPT-6 Sol** targets complex work such as coding; **GPT-6 Luna** targets
"high-volume tasks with a clear goal, like summarizing documents, extracting information, or answering quick questions". Both were trained
with similar methods to GPT-6 Astra. OpenAI: "GPT-6 Astra introduced a new generation of intelligence; these models extend its benefits by
making that intelligence more efficient and accessible." OpenAI also claims both beat Anthropic's Fable and Opus models on its comparisons.

## Why it matters

Frontier-level reliability dropped in price by half within three weeks of the flagship launch, and a GPT-6-class model (Luna) reached free
users. This continues the 2026 pattern of rapid price compression across OpenAI's tiers (see the July 30 GPT-5.6 price cut).

Caveat: OpenAI's comparison uses $4/$20 for GPT-5.6 Sol, whereas launch-time third-party sources listed GPT-5.6 Sol at $5/$30; the
developer-community post refers to "GPT-5.6 promotional pricing". Context window not confirmed in sources read.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): 145 days after its cutoff
- Claude Opus 5.5 (training cutoff June 2026): 84 days after its cutoff
- Gemini 4 Hydrogen (training cutoff March 2026): 175 days after its cutoff
- Grok 4.7 (training cutoff May 2026): 114 days after its cutoff

## Sources

1. [Introducing GPT-6 Sol and Luna (OpenAI)](https://openai.com/index/introducing-gpt-6-sol-and-luna/) (openai.com, official)
2. [OpenAI Developer Community announcement](https://community.openai.com/t/announcing-gpt-6-sol-and-gpt-6-luna-in-the-api-codex-and-chatgpt/1399925) (community.openai.com, official)
3. [OpenAI on X: 'Please welcome GPT-6 Sol and GPT-6 Luna'](https://x.com/OpenAI/status/2102460975790137662) (x.com, official)
4. [Sam Altman on X: Sol and Luna at half the price](https://x.com/sama/status/2102464672519815512) (x.com, official)
5. [OpenAI: Better prompt caching for GPT-6](https://openai.com/index/better-prompt-caching-for-gpt-6/) (openai.com, official)
6. [TechCrunch: OpenAI launches GPT-6 Sol and Luna](https://techcrunch.com/2026/09/22/openai-launches-gpt-6-sol-and-luna/) (techcrunch.com, press)
7. [The New Stack: OpenAI releases GPT-6 Sol and Luna and cuts token prices in half](https://thenewstack.io/openai-gpt-6-sol-luna-release/) (thenewstack.io, press)
8. [Vellum: GPT-6 Sol and Luna benchmarks explained](https://www.vellum.ai/blog/gpt-6-sol-and-luna-benchmarks-explained) (vellum.ai, press)
9. [ZDNet: OpenAI launches GPT-6 Sol and Luna](https://www.zdnet.com/innovation/openai-gpt-6-sol-luna-release/) (zdnet.com, press)
10. [The Deep View: OpenAI's cheaper GPT-6 models change the math](https://www.thedeepview.com/articles/openai-s-cheaper-gpt-6-models-change-the-math) (thedeepview.com, press)
11. [Releasebot: OpenAI release notes (Codex versions)](https://releasebot.io/updates/openai) (releasebot.io, discussion)

## Changes

- 2026-09-30: Added OpenAI's GPT-6 prompt-caching post
- 2026-09-29: Added ZDNet and Deep View links
- 2026-09-29: Added post link(s)
- 2026-09-29 (filed): Created

## Related

- 2026-09-03: [OpenAI releases GPT-6 Astra, its first GPT-6 model](https://postcutoff.com/e/2026-09-03-gpt-6-astra/index.md)
- 2026-07-30: [OpenAI cuts GPT-5.6 Luna price 80% and Terra 20%](https://postcutoff.com/e/2026-07-30-gpt-5-6-price-cut/index.md)
- 2026-07-09: [OpenAI broadly releases GPT-5.6 after government-gated preview](https://postcutoff.com/e/2026-07-09-gpt-5-6-sol-terra-luna/index.md)
- People: [Sam Altman](https://postcutoff.com/person/sam-altman/)
- Archived: 3 posts and 2 videos, listed in https://postcutoff.com/e/2026-09-22-gpt-6-sol-luna/index.json