Decision summary
- New high-volume route -> GPT-6 Luna
- Pinned gpt-5.6-luna -> replay, then cut over
- Free or Go trial -> GPT-6 Luna in the desktop app
- Hard coding -> GPT-6 Sol or Astra, not Luna
- API free tier -> neither model supports it
OpenAI Luna successor comparison
Frontier comparisonGPT-6 Luna vs GPT-5.6 Luna
GPT-6 Luna is the September 22, 2026 high-volume GPT-6 model at $0.10 input and $0.50 output per million tokens.
Featured · Updated today · Last verified: September 2026
Choose GPT-6 Luna when
New high-volume GPT-6 traffic and the Free/Go desktop trial.
Choose GPT-5.6 Luna when
Pinned gpt-5.6-luna workloads until they are replayed on GPT-6 Luna.
- New high-volume route: GPT-6 Luna
- Pinned gpt-5.6-luna: replay, then cut over
- Free or Go trial: GPT-6 Luna in the desktop app
Decision axes: Best for · Access and platforms · Context window · Input and output
Reasoning
GPT-6 Luna documents none through max, default medium.
Coding
Both are the efficient tier. Luna is not the Sol or Astra coding lane.
Multimodal
Text and image in, text out.
Speed
GPT-6 Luna Fast mode is 2× Standard.
Enterprise
Free and Go can try GPT-6 Luna in the desktop app. That is not free API access.
Curated matrix for GPT-6 Luna vs GPT-5.6 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 Luna | GPT-5.6 Luna |
|---|---|---|
| Best for | New high-volume GPT-6 traffic and the Free/Go desktop trial. | Pinned gpt-5.6-luna workloads until they are replayed on GPT-6 Luna. |
| Access and platforms | gpt-6-luna. Free and Go in the desktop app; paid plans in ChatGPT Work and Codex. Free API tier unsupported. | gpt-5.6-luna remains in the catalog and is marked superseded by GPT-6 Luna. |
| Context window | 1,050,000 / 128K. Knowledge cutoff May 18, 2026. | Follow the live GPT-5.6 Luna card. Do not copy the GPT-6 1.05M window onto it. |
| Input and output | Text and image in; text out. | Text and image in; text out. |
| Reasoning control | none through max, default medium. | GPT-5.6 effort controls. Confirm on the current card. |
| Coding and agents | Documented as the efficient model. Tool support on the card is not a Sol or Astra quality claim. | Prior cost-sensitive GPT-5.6 tier, not a flagship coder. |
| Cost posture | $0.10 / $0.01 cached / $0.125 cache write / $0.50 output per 1M. Above 272K input: 2× input and cache, 1.5× output. | Pricing page short context: $0.20 input / $0.02 cached / $0.25 cache write / $1.20 output. Long context: $0.40 / $0.04 / $0.50 / $1.80. |
| Operational risk | Free/Go app access is not free API access. | The old ID can be the right pin if evals regress, even at the higher list price. |
Key insights
Concrete technical or product signals.
- Input list price is half ($0.10 vs $0.20). Output list price is $0.50 vs $1.20, which is lower than half.
- OpenAI's 50% promotional-pricing sentence covers Sol and Luna together. Use the pricing page when the token type matters.
- No Luna-versus-Luna benchmark is published on the GPT-6 card.
Use cases
Where this shines in production.
- Migrating gpt-5.6-luna
- Pricing high-volume GPT-6 traffic
- Trying Luna from Free or Go
Limitations & trade-offs
What to watch for.
- Not Luna vs Sol.
- Desktop Free/Go access is not an API free tier.
- Do not copy GPT-6 context limits onto the GPT-5.6 row.
Watch-outs
Who should pass, and what to validate before rollout.
- Do not assume every token type dropped by exactly 50%.
- Do not treat Free or Go app access as a free API tier.
- Do not use Luna for work that still fails unless it is on Sol or Astra.
Final recommendation
What to do after reading the table.
Use GPT-6 Luna for new high-volume work after a replay. Keep GPT-5.6 Luna where quality regresses.
FAQ
Is GPT-6 Luna better than GPT-5.6 Luna?
Use GPT-6 Luna for new high-volume work after a replay. Keep GPT-5.6 Luna where quality regresses.
Which is better for coding: GPT-6 Luna or GPT-5.6 Luna?
GPT-6 Luna: Documented as the efficient model. Tool support on the card is not a Sol or Astra quality claim. GPT-5.6 Luna: Prior cost-sensitive GPT-5.6 tier, not a flagship coder. The catalog does not declare a winner on coding and agents.
Which is cheaper: GPT-6 Luna or GPT-5.6 Luna?
Listed unit prices: GPT-6 Luna $0.10 / $0.01 cached / $0.125 cache write / $0.50 output per 1M. Above 272K input: 2× input and cache, 1.5× output; GPT-5.6 Luna Pricing page short context: $0.20 input / $0.02 cached / $0.25 cache write / $1.20 output. Long context: $0.40 / $0.04 / $0.50 / $1.80. 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 Luna and GPT-5.6 Luna?
Yes. Many teams keep both and route by constraint. Use GPT-6 Luna for New high-volume GPT-6 traffic and the Free/Go desktop trial, and GPT-5.6 Luna for Pinned gpt-5.6-luna workloads until they are replayed on GPT-6 Luna. Confirm vendor terms before mixing them in one production workflow.