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GPT-6 Sol and GPT-6.1 Sol: pricing, Luna and what changed
OpenAI released GPT-6 Sol and GPT-6 Luna on September 22, 2026, then GPT-6.1 Sol a week later on September 29, 2026. Here is how the three differ and what they cost to run.
API pricing
USD per 1M tokens, standard tier, from OpenAI's API pricing page and launch posts.
| Model | API ID | Input | Cached input | Output |
|---|---|---|---|---|
| GPT-6.1 Sol | gpt-6.1-sol | $2 | $0.10 | $10 |
| GPT-6 Sol | gpt-6-sol | $2 | $0.60 | $10 |
| GPT-6 Luna | gpt-6-luna | $0.10 | $0.01 | $0.50 |
| GPT-5.6 Sol | gpt-5.6-sol | $4 | $0.40 | $20 |
Longer prompts cost more: above OpenAI's long-context threshold GPT-6.1 Sol is $4 / $15 and Luna $0.20 / $0.75. The Batch tier halves every price.
Source: OpenAI API pricing
GPT-6 Sol vs GPT-6.1 Sol
- GPT-6 Sol came out on September 22, 2026; GPT-6.1 Sol followed on September 29, 2026.
- Same input and output price. Cached input drops from $0.60 to $0.10, which matters for agents that resend the same context.
- OpenAI reports GPT-6.1 Sol 6.4 points higher on DeepSWE v1.1, 4.8 on AutomationBench and 7 on OSWorld 2.0.
What OpenAI claims for GPT-6.1 Sol
- It matches GPT-6 Astra on DeepSWE v1.1 at roughly one-fifth of the cost.
- It scores 2.2 points above Claude Opus 5.5 on AutomationBench.
- On Terminal-Bench Science 0.1, OpenAI puts the average cost per task at $5.47, against $23.21 for Opus 5.5 and $23.80 for Astra.
- An Ultrafast version for Codex, up to 8x faster, is announced but not out yet.
Source: OpenAI: Introducing GPT-6.1 Sol
GPT-6 Sol vs GPT-5.6 Sol
- Price: $2 / $10 against $4 / $20 for GPT-5.6 Sol, so half the price.
- On DeepSWE v1.1, OpenAI reports GPT-6 Sol at 68.8%, close to Claude Fable 5 at 69.9%. On OSWorld 2.0 it scored 60.5% against 60.3% for Claude Opus 5.
- GPT-5.6 Sol is still on the API, now listed under OpenAI's cyber models.
GPT-6 Luna vs Sol
- Luna costs $0.10 / $0.50, a twentieth of Sol.
- OpenAI reports Luna at 66.6% on DeepSWE v1.1, not far behind Sol's 68.8%.
- Luna is the one Free and Go ChatGPT users get, in the desktop app. Sol needs Plus or above.
Source: OpenAI: Introducing GPT-6 Sol and Luna
Cost per coding task
List prices with our calculator's assumptions, per agent task:
| Codebase size | GPT-6.1 Sol | GPT-6 Sol | GPT-6 Luna | Sonnet 5.5 |
|---|---|---|---|---|
| Small (< 10k lines) | $0.112 | $0.130 | $0.006 | $0.115 |
| Medium (10k-100k lines) | $0.249 | $0.294 | $0.013 | $0.258 |
| Large / monorepo (> 100k lines) | $0.594 | $0.714 | $0.031 | $0.618 |
At 173 tasks a month on a medium codebase: about $43 on GPT-6.1 Sol, $45 on Claude Sonnet 5.5 and $2 on Luna.
Price Codex and other tools in the calculator All model prices
FAQ
How much does GPT-6 Sol cost?
$2 per 1M input tokens and $10 per 1M output tokens. GPT-6.1 Sol has the same price with cheaper cached input ($0.10).
Is there a GPT-6.1?
The released GPT-6.1 model is GPT-6.1 Sol. A GPT-6.1 Astra was reported as held back over safety concerns and has no public API.
Can I use GPT-6 Sol for free?
Not in ChatGPT: Sol needs Plus, Pro, Business, Enterprise or Edu. Free and Go users get GPT-6 Luna in the desktop app.
GPT-6.1 Sol or Claude Sonnet 5.5?
Same list price ($2 / $10). GPT-6.1 Sol has cheaper cached input; each vendor claims wins on its own benchmarks. Try both on your own tasks.
Independent page. Not affiliated with OpenAI. Benchmarks are OpenAI's own; we have not run our own tests.