Decision summary
- Hard coding and agents -> GPT-6 Sol
- Classification, extraction, and cheap assistant turns -> GPT-6 Luna
- Free or Go desktop trial -> GPT-6 Luna
- Hardest OpenAI flagship work -> GPT-6 Astra, not either of these
- Same tool list on the card -> still eval before you standardize
OpenAI GPT-6 tier comparison
Frontier comparisonGPT-6 Sol vs GPT-6 Luna
GPT-6 Sol and GPT-6 Luna launched together on September 22, 2026.
Featured · Updated today · Last verified: September 2026
Choose GPT-6 Sol when
Complex coding and agentic workflows that do not need Astra's price.
Choose GPT-6 Luna when
Focused, high-volume tasks and the cheapest GPT-6 API lane.
- Hard coding and agents: GPT-6 Sol
- Classification, extraction, and cheap assistant turns: GPT-6 Luna
- Free or Go desktop trial: GPT-6 Luna
Decision axes: Best for · Access and platforms · Context window · Input and output
Reasoning
Same effort ladder, none through max, default medium.
Coding
Sol is the complex-coding lane. Luna is the high-volume lane. No head-to-head score is published.
Multimodal
Text and image in, text out. No audio or video.
Speed
Fast mode is 2× Standard on both.
Enterprise
Sol is on paid ChatGPT Work and Codex. Luna is also the Free and Go desktop trial.
Curated matrix for GPT-6 Sol vs GPT-6 Luna — confirm live limits and pricing on each vendor’s official pages.
How they compare
Criterion-by-criterion notes from the catalog—not a ranking. Validate on your own gold set.
| Criterion | GPT-6 Sol | GPT-6 Luna |
|---|---|---|
| Best for | Complex coding and agentic workflows that do not need Astra's price. | Focused, high-volume tasks and the cheapest GPT-6 API lane. |
| Access and platforms | API ID gpt-6-sol. ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu. Free API tier unsupported. | API ID gpt-6-luna. Free and Go can try it in the desktop app. Paid plans also get it in ChatGPT Work and Codex. Free API tier unsupported. |
| Context window | 1,050,000 input; 128,000 max output. Knowledge cutoff April 20, 2026. | 1,050,000 input; 128,000 max output. Knowledge cutoff May 18, 2026. |
| Input and output | Text and image input; text output. Audio and video are not supported. | Text and image input; text output. Audio and video are not supported. |
| Reasoning control | none, low, medium (default), high, xhigh, and max. Chat Completions function calling only at effort none. | Same effort ladder as Sol, default medium. Same Chat Completions limit at effort none. |
| Coding and agents | Responses API tools include computer use, code interpreter, hosted shell, MCP, and apply patch. | The same Responses API tool list is documented. That does not mean Luna matches Sol on hard repos. |
| Cost posture | $2 / $0.20 cached / $2.50 cache write / $10 output per 1M. Above 272K input, 2× input and cache and 1.5× output for the full request. | $0.10 / $0.01 cached / $0.125 cache write / $0.50 output per 1M. Same 272K long-context multipliers. |
| Operational risk | No official quality delta versus Luna is published. Prove Sol is necessary on your eval before paying the higher rate. | Using Luna as the default for Astra-class work because the tool list looks the same. |
Key insights
Concrete technical or product signals.
- The price gap is 20× on input ($2 vs $0.10) and 20× on output ($10 vs $0.50) at standard short-context rates.
- Knowledge cutoffs differ: Sol is April 20, 2026; Luna is May 18, 2026.
- OpenAI's announcement says both list prices are 50% below GPT-5.6 promotional pricing. Compare the live cards, not the slogan, when you budget.
Use cases
Where this shines in production.
- Routing inside the GPT-6 family
- Cutting volume traffic off Sol
- Deciding whether Free/Go Luna is enough to trial
Limitations & trade-offs
What to watch for.
- No published Sol-versus-Luna benchmark. Missing scores are not a tie and not a win.
- Not a substitute for the Astra comparison when you need the flagship.
- Fast mode is 2× on both; it does not close the capability question.
Watch-outs
Who should pass, and what to validate before rollout.
- Do not send Astra-class repos to Luna because the tools look the same.
- Do not pay Sol rates for extraction and classification that Luna already clears.
- Do not expect a free API tier on either ID.
Final recommendation
What to do after reading the table.
Route complex work to Sol and volume to Luna. Do not infer a winner from missing scores.
FAQ
Is GPT-6 Sol better than GPT-6 Luna?
Route complex work to Sol and volume to Luna. Do not infer a winner from missing scores.
Which is better for coding: GPT-6 Sol or GPT-6 Luna?
GPT-6 Sol: Responses API tools include computer use, code interpreter, hosted shell, MCP, and apply patch. GPT-6 Luna: The same Responses API tool list is documented. That does not mean Luna matches Sol on hard repos. The catalog does not declare a winner on coding and agents.
Which is cheaper: GPT-6 Sol or GPT-6 Luna?
Listed unit prices: GPT-6 Sol $2 / $0.20 cached / $2.50 cache write / $10 output per 1M. Above 272K input, 2× input and cache and 1.5× output for the full request; GPT-6 Luna $0.10 / $0.01 cached / $0.125 cache write / $0.50 output per 1M. Same 272K long-context multipliers. A lower listed unit price is not the same as a lower total workload cost—tokens, session minutes, caching, introductory rates, and add-on modes can reverse the ranking. Confirm live rates on each vendor’s official page.
Can I use both GPT-6 Sol and GPT-6 Luna?
Yes. Many teams keep both and route by constraint. Use GPT-6 Sol for Complex coding and agentic workflows that do not need Astra's price, and GPT-6 Luna for Focused, high-volume tasks and the cheapest GPT-6 API lane. Confirm vendor terms before mixing them in one production workflow.