OpenAI's GPT-6.1 Sol promises near-Astra intelligence at one-fifth of Astra's token prices. Here is how the GPT-6 lineup (Astra, Sol, Luna) fits together, how the prices compare with Claude Opus 5.5 and Sonnet 5.5, and what cheaper near-frontier models mean for businesses running AI agents.
On September 29, 2026, OpenAI released GPT-6.1 Sol, an upgrade to the GPT-6 Sol model it had shipped one week earlier. OpenAI's pitch is in the post below: "near-Astra intelligence for a fifth of the price." Astra is OpenAI's top GPT-6 model. In the API, GPT-6.1 Sol costs $2 per million input tokens and $10 per million output tokens, against $10 and $50 for GPT-6 Astra, according to OpenAI's API pricing page.
gpt-6.1-sol.GPT-6.1 Sol: near-Astra intelligence for a fifth of the price.
— OpenAI (@OpenAI) September 29, 2026
It’s the most cost-efficient model for its performance available today.
Post credit: video and post by OpenAI (@OpenAI) on X, published September 29, 2026 (3.1 million views and 21,000 likes when we wrote this). View the post on X. All rights to the video belong to its creator; we embed it with X's standard embed and add our own commentary.
OpenAI's GPT-6 family now comes in three tiers, named like the sky: a star, a sun, and a moon. Astra arrived first, on September 3, 2026, according to The Next Web. OpenAI's model page calls it "our most capable model for the most demanding work."
On September 22, the @ChatGPT account announced GPT-6 Sol and GPT-6 Luna, rolling out in ChatGPT Work and Codex for paid plans. OpenAI says the two models bring much of Astra's strength into faster, cheaper models for work at scale. One week later, GPT-6.1 Sol replaced Sol as the recommended mid-tier model.
| Model | Released | What OpenAI positions it for |
|---|---|---|
| GPT-6 Astra | September 3, 2026 | The hardest work: complex reasoning, coding, computer use, research |
| GPT-6 Sol | September 22, 2026 | Professional work, coding, and automation at lower cost |
| GPT-6.1 Sol | September 29, 2026 | "Near-Astra performance for complex work at a lower cost" |
| GPT-6 Luna | September 22, 2026 | "Focused, high-volume tasks" |
All three tiers list a context window of about 1.05 million tokens and up to 128,000 output tokens on OpenAI's model pages.
Here are the standard API prices per million tokens, from OpenAI's pricing page and Anthropic's pricing page, as of October 6, 2026:
| Model | Input | Cached input | Output |
|---|---|---|---|
| GPT-6 Astra | $10.00 | $1.00 | $50.00 |
| GPT-6.1 Sol | $2.00 | $0.10 | $10.00 |
| GPT-6 Sol | $2.00 | $0.20 | $10.00 |
| GPT-6 Luna | $0.10 | $0.01 | $0.50 |
| Claude Opus 5.5 | $4.00 | $0.20 | $20.00 |
| Claude Sonnet 5.5 | $2.00 | $0.20 | $10.00 |
Two details are easy to miss. First, GPT-6.1 Sol costs the same as GPT-6 Sol for fresh input and output. The upgrade is in quality, plus cached input at half the old price. Second, GPT-6.1 Sol lists at the same headline price as Claude Sonnet 5.5 and at half the price of Claude Opus 5.5. Both providers offer a 50% discount for batch jobs, and long prompts can cost more. Different tokenizers also mean the same text can produce a different number of tokens on each model, so compare cost per finished task, not just the price list.
According to OpenAI's launch post:
These are vendor-run benchmarks, picked by the company selling the model. Independent results and your own tests on your own tasks matter more. OpenAI's system card addendum also says GPT-6.1 Sol gets the same safeguards as Astra.
The post reached about 3.1 million views. The message is easy to repeat: the same quality for less money. That reaches far beyond developers. It also landed in the middle of a tight race. Anthropic's Claude Opus 5.5 arrived the same week as GPT-6 Sol, and OpenAI's launch named Opus 5.5 in its comparisons. And "a fifth of the price" fits the price drops many people have watched over the past two years: each new mid-tier model reaches a level that used to cost far more.
AI agents use many more tokens than a chat. One task can mean reading a long instruction file, calling tools, checking results, and trying again. Most of that is input, and much of it repeats, which is why the cheaper cached input matters. Here is a rough example for one agent task with 200,000 input tokens (150,000 of them cached) and 20,000 output tokens, at list prices and ignoring cache-write fees:
| Model | Rough cost per task | 1,000 tasks a month |
|---|---|---|
| GPT-6 Astra | $1.65 | $1,650 |
| Claude Opus 5.5 | $0.63 | $630 |
| Claude Sonnet 5.5 | $0.33 | $330 |
| GPT-6.1 Sol | $0.32 | $315 |
| GPT-6 Luna | $0.02 | $17 |
This is arithmetic, not a forecast. Real costs depend on how many tokens each model uses and how many retries a task needs. But it shows the shift in practice:
If you don't write code against the OpenAI API, you won't use GPT-6.1 Sol directly. You will feel it through the tools you already pay for, which can now run stronger models for the same money. If you have a ChatGPT Plus or Business plan, you can try it in ChatGPT Work and Codex today.
Three honest takeaways:
For background, read AI agents vs agentic AI and how to automate business processes.
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GPT-6.1 Sol is OpenAI's mid-tier GPT-6 model, released September 29, 2026. OpenAI says it delivers near GPT-6 Astra performance on coding, computer use, and professional work at one-fifth of Astra's standard API token prices.
On OpenAI's API pricing page, GPT-6.1 Sol costs $2 per million input tokens, $0.10 per million cached input tokens, and $10 per million output tokens. GPT-6 Astra costs $10, $1, and $50.
Astra is the most capable and most expensive tier. Sol is the mid tier for most professional and agent work. Luna is the cheapest tier, built for focused, high-volume tasks.
At list prices, GPT-6.1 Sol and Claude Sonnet 5.5 both cost $2 input and $10 output per million tokens, and Claude Opus 5.5 costs $4 and $20. OpenAI claims GPT-6.1 Sol beats Opus 5.5 on AutomationBench at about a third of the cost, but that is a vendor benchmark.
In ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users, and in the OpenAI API as gpt-6.1-sol.
Not directly. Most small businesses benefit through the AI tools and agents they use, which can now run stronger models for less. The bigger challenge is setting up agents with the right access and approvals, which services like Dooza handle.
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Anthropic's Claude Opus 5.5 is the first model in the Claude 5.5 family. It performs at roughly the level of Claude Fable 5.1 on most work, costs 40% less to run than Opus 5, and generates output more than 30% faster. Here is what changed, how to choose between Opus 5.5, Fable 5.1 and Sonnet 5.5, and what it means for businesses running AI agents.
Anthropic's Claude Sonnet 5.5 is the second model in the Claude 5.5 family. It keeps Sonnet 5's token prices, runs more than 30% faster, and Anthropic says it costs up to 30% less per task because it needs fewer tokens. Here is how it compares with Opus 5.5, where it fits best, and what it means for small businesses.
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