GPT-6 Luna launch: benchmarks, pricing, and the cheap GPT-6 pin
GPT-6 Luna launched on 22 September 2026 as the cheap GPT-6 row: $0.10 input and $0.50 output per million tokens, half of GPT-5.6 Luna. Artificial Analysis scores its Coding Agent Index at 41, two points under GPT-5.6 Luna, at about 60% lower cost per task. AshnaAI catalog id is gpt-6-luna.
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What shipped on 22 September
On 22 September 2026 Microsoft added GPT-6 Luna to generally available Foundry deployments with GPT-6 Sol, in GPT-6 Astra, Sol, and Luna for production AI agents. Luna is the high-volume row. Artificial Analysis the same day said the list price is about half of GPT-5.6 Luna: $0.10 input and $0.50 output per million tokens, with the same 90% cache-read discount and 25% cache-write premium.
AshnaAI lists the catalog id `gpt-6-luna` on the same Azure Responses path as `gpt-6-astra`. The context window on that row is 1.05 million tokens. Output on the short-context sheet is $0.50 per million tokens, the same output rate as GLM-5.3-Flash and a fifth of the input rate.
Benchmarks vs GPT-5.6 Sol and Luna
Read Luna’s column as a cheaper GPT-5.6 Luna, not as a coding upgrade. Coding Agent Index moves from 43 to 41. DeepSWE v1.1 moves from 66% to 64%. SWE-Atlas-QnA moves from 49% to 44%. Terminal-Bench 4.0 in the Intelligence Index breakdown moves from 12% to 13%. Hallucination rate on AA-Omniscience falls from 93% to 77%, and accuracy stays about flat (44% versus 43%). AutomationBench-AA moves from 50% to 53%. Artificial Analysis also says Luna drops about 75 Elo on GDPval-AA v2.1 and about 45 Elo on AA-Briefcase. Intelligence Index cost per task is $0.07 versus $0.18.
The table is Artificial Analysis at max effort, dated 22 September 2026. It is an independent scoreboard, not OpenAI’s launch table. GPT-6 Astra still leads OpenAI’s own 3 September computer-use and science cells; those Astra numbers are on the GPT-6 Astra launch post.
| Benchmark | GPT-6 Sol | GPT-5.6 Sol | GPT-6 Luna | GPT-5.6 Luna |
|---|---|---|---|---|
| Coding agents | ||||
| Coding Agent Index (Codex harness) | 57 | 55 | 41 | 43 |
| Terminal-Bench 4.0 (Codex harness) | 43% | 37% | — | — |
| SWE-Atlas-QnA | 58% | 54% | 44% | 49% |
| DeepSWE v1.1 | — | — | 64% | 66% |
| Knowledge and agents | ||||
| AA-Omniscience Index | 27 | 22 | 1 | −10 |
| Hallucination rate (lower is better) | 60% | 92% | 77% | 93% |
| AutomationBench-AA | 62% | 60% | 53% | 50% |
| Terminal-Bench 4.0 (Intelligence Index breakdown) | 44% | 40% | 13% | 12% |
What the token bill looks like
Luna at $0.10 / $0.50 is the GPT-6 pin for volume. Sol is $2 / $10. Astra is $10 / $50. GPT-5.6 Luna on the Ashna sheet is $0.20 / $1.20. Cached input is 10% of uncached input. Cache writes are 1.25× uncached input. On Ashna, reasoning tokens for this family are billed at 1.5× the short-context output rate ($0.75 per million for Luna). GLM-5.3-Flash stays $0.15 / $0.50 if you want a non-OpenAI cheap coding pin.
| Rate per 1M tokens | GPT-6 Sol | GPT-6 Luna | GPT-6 Astra | GPT-5.6 Sol | GPT-5.6 Luna |
|---|---|---|---|---|---|
| Input | $2.00 | $0.10 | $10.00 | $4.00 | $0.20 |
| Cached input | $0.20 | $0.01 | $1.00 | $0.40 | $0.02 |
| Cache write | $2.50 | $0.125 | $12.50 | $5.00 | $0.25 |
| Output | $10.00 | $0.50 | $50.00 | $20.00 | $1.20 |
Long context is a separate Azure rate
Microsoft’s long-context column for Luna is $0.20 input, $0.02 cached input, $0.25 cache write, and $0.75 output. Ashna’s billed sheet stays on the short-context rates. A long prompt is still cheap next to Sol, and it is not the $0.10 / $0.50 short-context line at the provider.
| Rate per 1M tokens | GPT-6 Sol | GPT-6 Luna |
|---|---|---|
| Input | $4.00 | $0.20 |
| Cached input | $0.40 | $0.02 |
| Cache write | $5.00 | $0.25 |
| Output | $15.00 | $0.75 |
When to pin Luna instead of Sol or Flash
Pin Luna when the task is repetitive, the output is short, and a miss is cheap to rerun. Pin GPT-6 Sol when the Coding Agent Index gap or the GDPval regression shows up in the file you needed. Pin GPT-6 Astra for computer use and the science cells Astra published. Keep GLM-5.3-Flash as the other volume coding default so one lab does not own the cheap tier.
Mixed everyday work can stay on Ashna-X1. Cost ladder: Cheapest coding AI vs Claude Opus 5 and GPT-5.6 Sol.
Try gpt-6-luna now
New accounts start at app.ashna.ai/signup. Open GPT-6 Luna in AshnaAI chat. Run the same prompt on GPT-6 Sol and GLM-5.3-Flash before you leave a production job on the cheapest id.
Product API traffic uses Account → API and the AshnaAI API docs. The model id is `gpt-6-luna`.
Frequently asked questions
- What is GPT-6 Luna?
- GPT-6 Luna is the low-cost GPT-6 model Microsoft added to Foundry on 22 September 2026, next to GPT-6 Sol. The AshnaAI catalog id is gpt-6-luna. It is the volume row in the GPT-6 family, under Sol and Astra.
- How much does GPT-6 Luna cost?
- Azure Global Standard short context is $0.10 per million input tokens, $0.01 cached input, $0.125 cache write, and $0.50 per million output tokens. Long context is $0.20 input and $0.75 output. Ashna bills the short-context sheet. GPT-5.6 Luna on the same catalog is $0.20 input and $1.20 output. GPT-6 Astra is $10 and $50.
- Is GPT-6 Luna better than GPT-5.6 Luna?
- It is cheaper, and it hallucinates less on AA-Omniscience (77% versus 93%), with the index moving from −10 to 1. The Coding Agent Index slips from 43 to 41. DeepSWE v1.1 is 64% versus 66%, and SWE-Atlas-QnA is 44% versus 49%. Artificial Analysis also reports about a 75 Elo drop on GDPval-AA and about 45 Elo on AA-Briefcase. Treat it as a price cut with a small quality trade on coding and long knowledge work.
- What is the context window?
- The Ashna catalog gives gpt-6-luna the same 1.05 million token window as gpt-6-sol and gpt-6-astra. Reasoning stays on. Effort levels are low, medium, high, xhigh, and max, and the catalog default is low.
- Where do I try GPT-6 Luna?
- Open https://app.ashna.ai/chat?agent=gpt-6-luna The same id is on the OpenAI-compatible API. Compare it with https://app.ashna.ai/chat?agent=gpt-6-sol and https://app.ashna.ai/chat?agent=glm-5.3-flash before you move a production job.
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