Quick answer (updated 7 November 2026): OpenAI’s GPT-6 models come in several tiers. GPT-6 Astra is the most powerful (launched 3–4 September 2026); in ChatGPT it appears as GPT-6 Pro on Pro, Business and Enterprise plans. GPT-6.1 Sol (29 September) is the balanced everyday model and replaced GPT-6 Sol at the same price. GPT-6 Luna (22 September) is the fast, low-cost model that powers ChatGPT’s Free and Go plans. GPT-6.1 Terra is the least clear — reports disagree on whether it has been officially released. In the API, prices per million tokens are reported as Astra $10/$50, Sol $2/$10 and Luna $0.10/$0.50 (input/output).
OpenAI’s new naming confuses a lot of people: there is no single “GPT-6” anymore, and what you get depends on your ChatGPT plan. This guide explains each model in plain language and helps you pick the right one.
GPT-6 models at a glance
| Model | Released | Role | API price (input / output, per 1M tokens) | In ChatGPT |
|---|---|---|---|---|
| GPT-6 Astra | 3–4 Sep 2026 | Top tier: hardest reasoning, research, complex coding | $10 / $50 | As “GPT-6 Pro” on Pro, Business, Enterprise (staged rollout) |
| GPT-6.1 Sol | 29 Sep 2026 (replaced GPT-6 Sol, 22 Sep) | Balanced everyday model | $2 / $10 | Main chat model on Plus (as reported) |
| GPT-6 Luna | 22 Sep 2026 | Fast, low-cost model | $0.10 / $0.50 | Free and Go plans |
| GPT-6.1 Terra | Disputed | Unclear; one report places it in ChatGPT Work and Codex | Not confirmed | Not confirmed |
Prices are from API pricing trackers and may change; check OpenAI’s official pricing page before building on them.
GPT-6 Astra: the most powerful
Astra is OpenAI’s top model in the GPT-6 family. In the API (gpt-6-astra) it is reported to support a context window of about 1.05 million tokens and up to 128,000 output tokens. In ChatGPT it is offered as GPT-6 Pro on Pro, Business and Enterprise plans, rolled out in stages — so not every eligible account may see it yet.
Use it for: long research reports, complex code changes, difficult maths and analysis where accuracy matters more than speed or cost.
Note: reports say a planned GPT-6.1 Astra release was cancelled or paused in late September 2026 after internal safety testing; no public GPT-6.1 Astra exists.
GPT-6.1 Sol: the everyday all-rounder
Sol is the middle model. GPT-6 Sol launched on 22 September and was replaced a week later by GPT-6.1 Sol at the same API price. Reports say it is the main chat model on ChatGPT Plus.
Use it for: writing, studying, coding help, summaries — most daily tasks.
GPT-6 Luna: fast and cheap
Luna is the budget model and powers ChatGPT Free and Go. At a reported $0.10/$0.50 per million tokens in the API, it is the cheapest option for developers building high-volume apps.
Use it for: quick answers, simple drafts, classification and chatbots where speed and cost matter most.
GPT-6.1 Terra: what we know
Terra is the model with the most conflicting information. One source says it reached ChatGPT Work and Codex for Plus, Pro, Enterprise and Edu users on 26 October 2026; another says no official release has been confirmed; and no GPT-6.1 Luna is confirmed either. We will update this section when OpenAI’s own pages are clear.
Which GPT-6 model do you get in ChatGPT?
| ChatGPT plan (India price, as reported) | Main model (as reported) |
|---|---|
| Free (₹0) | GPT-6 Luna |
| Go (₹399/month) | GPT-6 Luna, higher limits |
| Plus (₹1,999/month) | GPT-6.1 Sol in chat; reports conflict on Astra access (some say only in Work/Codex) |
| Pro / Business / Enterprise | GPT-6 Pro (Astra), staged rollout |
Chat context limits are much smaller than the API’s: one guide reports about 27K tokens on Free, 54K on Go/Plus/Business and 128K on Pro (up to 400K in reasoning mode) — third-party figures, not official. Full plan prices: ChatGPT price in India.
Which GPT-6 model should you use?
| You want… | Choose |
|---|---|
| Free everyday help | ChatGPT Free (Luna) |
| More usage on a budget | ChatGPT Go (Luna, higher limits) |
| Better answers for daily work | ChatGPT Plus (Sol) |
| The hardest research and coding | Pro (GPT-6 Pro / Astra) |
| Cheapest API for an app | GPT-6 Luna |
| Best quality-to-cost API | GPT-6.1 Sol |
GPT-6 vs Gemini 4 vs Claude
Google’s Gemini 4 Argon and Carbon and Anthropic’s Claude models compete directly with GPT-6. Our model-vs-model pages compare specifics: GPT-6 Astra vs GPT-6.1 Sol, GPT-6.1 Terra vs GPT-6 Luna, Gemini 4 Argon vs GPT-6.1 Sol and Claude Sonnet 5.5 vs GPT-6.1 Sol. For the bigger picture, see the best AI chatbots of 2026.
Common mistakes
- Expecting the top model on a free plan: Free and Go use Luna, not Astra.
- Paying for Pro for simple tasks: Sol on Plus handles most daily work.
- Comparing API context with ChatGPT context: chat limits are much smaller than API limits.
- Trusting every “GPT-6.1” headline: several 6.1 models are unconfirmed or cancelled.
Frequently Asked Questions
What is GPT-6 Astra?
OpenAI’s most powerful GPT-6 model, launched in early September 2026. In ChatGPT it appears as GPT-6 Pro on Pro, Business and Enterprise plans.
Which GPT-6 model is in ChatGPT Free?
GPT-6 Luna, according to reports. ChatGPT Go also uses Luna with higher limits.
What is the difference between GPT-6 Sol and GPT-6.1 Sol?
GPT-6.1 Sol replaced GPT-6 Sol on 29 September 2026 as an updated version at the same API price.
Is GPT-6.1 Terra released?
Reports conflict. One says it reached ChatGPT Work and Codex in October 2026; others say no official release is confirmed.
How much does the GPT-6 API cost?
Reported prices per million input/output tokens: Astra $10/$50, Sol $2/$10, Luna $0.10/$0.50.
Is there a GPT-6.1 Astra?
Reports say its release was cancelled or paused in late September 2026; no public model exists.
Conclusion
Think of GPT-6 as three tiers: Luna (fast and cheap), Sol (everyday) and Astra (maximum power). Most people get the best value from ChatGPT Plus with Sol; developers should start with Sol or Luna and move to Astra only for tasks that need it.
How we researched this
We compiled release dates, plan availability and API prices from Wikipedia, OpenAI developer documentation mirrors and AI industry trackers published up to November 2026. Sources disagree on GPT-6.1 Terra, on Astra access for Plus, and on ChatGPT context limits; we flag each. We could not open OpenAI’s official pages directly, so confirm details there before relying on them.
Sources
- Wikipedia – GPT-6
- OpenAI Developers – Using GPT-6
- Lindy – GPT-6 explained: Astra, Sol, Luna and costs
- BenchLM – GPT-6 models compared
- APIMaster – GPT-6.1 models release status
- DataStudios – GPT-6 Astra, GPT-6 Pro access and pricing
- Developers Digest – ChatGPT Free vs Go vs Plus after GPT-6
- DataStudios – ChatGPT context window by plan
