GPT-5.6: OpenAI's Sol, Terra and Luna Tiers
Key facts · verified Oct 13, 2026
GPT-5.6 is an OpenAI model released on 9 Jul 2026. Its API price is $4 per million input tokens and $20 per million output tokens (Sol $4 / $20 (promotional) · Terra $2 / $12 · Luna $0.20 / $1.20 per 1M tokens). Its context window is 1.05M tokens. It is not yet ranked on LMArena's text leaderboard. Source: developers.openai.com.
GPT-5.6 is an OpenAI model family in three tiers, Sol, Terra and Luna, with a 1.05M-token context window. OpenAI's model list names GPT-6 Astra, GPT-6.1 Sol and GPT-6 Luna as its flagship models and lists GPT-5.6 under "More models". OpenAI lists Sol at $4 per million input tokens and $20 per million output tokens (promotional, through at least November 21, 2026), Terra at not published and Luna at not published.
$4 / $20 per million tokens
1.05M tokens
Not rated
Not ranked
Key Features
What is GPT-5.6?
GPT-5.6 is an OpenAI model documented in three tiers - Sol, Terra and Luna. OpenAI's model documentation lists text and image input with multilingual support, a shared 1.05 million token context window across all three tiers, a 128,000 token maximum output, and a knowledge cutoff of 16 February 2026. No dated launch announcement for GPT-5.6 appears on OpenAI's pages, so no release date is given.
The Sol, Terra, and Luna Tiers
Per OpenAI's published pricing, Sol is the most expensive at $4 input and $20 output per million tokens, a promotional price OpenAI say is available at least through 21 November 2026 (a 20% input and 33% output reduction); Terra is $2 and $12; Luna is $0.20 and $1.20 - a 20x spread in input price between Sol and Luna. All three share the same 1.05M token context window and 128k maximum output.
Pricing and Access
API pricing is tiered: Sol at $4/$20 (promotional; cached input $0.40, and prompts over 272K input tokens are billed at 2x input and 1.5x output), Terra at $2/$12, and Luna at $0.20/$1.20 per million input/output tokens. Consumer access is through ChatGPT's plans (Free, Go, Plus, Pro, Business, Enterprise); prices on OpenAI's consumer plans page are regional.
Weights and Knowledge Cutoff
OpenAI does not publish weights for GPT-5.6. Its documented knowledge cutoff is 16 February 2026.
Ranking and Price Against Other Models
On LMArena's text leaderboard GPT-5.6 Sol has 1485 Elo (rank 22, xhigh effort), Claude Opus 5 1492 Elo (rank 14, high effort), Gemini 3.1 Pro 1487 Elo (rank 20) and Grok 4.5 1465 Elo (rank 53). Published API prices per million input / output tokens: GPT-5.6 Sol $4 / $20 (OpenAI's promotional price), Gemini 3.1 Pro $2 / $12, Claude Opus 5 $5 / $25.
Key Takeaways
- Three tiers - Sol, Terra, Luna - as named by OpenAI
- Shared 1.05M token context window, 128k max output across all tiers
- Sol $4/$20 (promotional, through at least 21 November 2026), Terra $2/$12, Luna $0.20/$1.20 per million tokens - a 20x input spread
- LMArena, Sol: 1485 Elo (rank 22, xhigh effort)
- Knowledge cutoff 16 February 2026, per OpenAI's own documentation
- No dated launch announcement was found on any OpenAI page
Official Resources
Full Specifications
$4 / $20 per million tokens | |
|---|---|
| Identity | |
| Developer | OpenAI |
| Released | Jul 2026 |
| Status | GA |
| Licence | Proprietary |
| Self-hostable | No |
| Cost | |
| Blended $/1M tokensinput × 0.75 + output × 0.25 | $8.000 / 1M tokens |
| Input price | $4.000 / 1M tokens |
| Output price | $20.000 / 1M tokens |
| Cached input | $0.40 / 1M tokens |
| Batch discount | 50% off input/output (Batch API) |
| Free tier | Not offered |
| Capacity | |
| Context window | 1.05M tokens |
| Max output | 128k tokens |
| Long-context surcharge | 2x input / 1.5x output above 272k input tokens |
| Capability | |
| Vision in | Yes |
| Audio in | No |
| Function calling | Yes |
| Structured output | Yes |
| Extended reasoning | Yes |
| Web search | Yes |
| Code execution | Yes |
| Access | |
| API | Yes |
| Chat app | Yes |
| Cloud marketplaces | Microsoft Foundry (Azure) |
| Fine-tuning | No |