GPT-5.6 Luna
Knows up to February 2026Missing 1,919 events
gpt-5.6-luna
$0.20 in, $1.20 out per 1M tokens
GPT-5.6 Sol
Previous flagship; replacement target for deprecated gpt-5/o3 snapshots.
Model idgpt-5.6-sol
Price$4 in, $20 out per 1M tokens
Checked29 September 2026
Knows up to February 2026
1,919events after its cutoff
85 historic, 439 major. 258 days of news.
It launched on 9 July 2026, already missing 138 of them.
How to call it
4 ways to use GPT-5.6 Sol, with the model id each provider expects.
| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| OpenAI API | gpt-5.6-sol |
https://api.openai.com/v1/responses |
developers.openai.com |
| Azure OpenAI (Microsoft Foundry) | gpt-5.6-sol |
learn.microsoft.com | |
| OpenRouter | openai/gpt-5.6-sol |
openrouter.ai | |
| Web app | chatgpt.com |
Pricing
| Input | $4 per 1M tokens |
|---|---|
| Cached input | $0.40 per 1M tokens |
| Output | $20 per 1M tokens |
As published: “per 1M tokens (USD), standard tier”. Note: prompts >272K input tokens billed 2x input / 1.5x output.
Source: developers.openai.com, checked 29 September 2026.
Specs
- Input
- Text and images
- Output
- Text
- Context window
- 1,050,000 tokens
- Max output
- 128,000 tokens
- Open weights
- No
- Licence
- Proprietary
- Training cutoff
- February 2026
- Released
- 9 July 2026
- Status
- Legacy
- Type
- Reasoning model
What stands out
What its maker marketed at launch, and what people found later, each with its source.
Named-tier family
GPT-5.6 introduced the Sol/Terra/Luna tier names (flagship/balanced/fast) replacing pro/mini/nano naming.
Max reasoning effort
Reasoning effort none/low/medium/high/xhigh/max.
Fast mode long context
Found after launch
Fast mode extended to long-context requests on Aug 5 2026.
Four assistants, one scale
GPT-5.6 Sol is added as a fifth row. Each row runs from what the model knows (graphite) through the months between its cutoff and its launch (hatched) to today (pink).
- GPT-6 Astra 271 at launch, 1,863 today
- Claude Opus 5.5 372 at launch, 1,795 today
- Gemini 4 Hydrogen 1,863 at launch, 1,889 today
- Grok 4.7 387 at launch, 1,829 today
- GPT-5.6 Sol 138 at launch, 1,919 today
Show as a table
| Model | Cutoff | Released | Missing at launch | Missing today |
|---|---|---|---|---|
| GPT-6 Astra | April 2026 | 3 September 2026 | 271 | 1,863 |
| Claude Opus 5.5 | June 2026 | 22 September 2026 | 372 | 1,795 |
| Gemini 4 Hydrogen | March 2026 | 12 November 2026 | 1,863 | 1,889 |
| Grok 4.7 | May 2026 | 21 September 2026 | 387 | 1,829 |
| GPT-5.6 Sol | February 2026 | 9 July 2026 | 138 | 1,919 |
Notes
GPT-5.6 flagship; the gpt-5.6 alias routes here. Superseded by GPT-6 Sol/Astra but still offered. OpenRouter lists $2/$10, lower than OpenAI list price $4/$20.
curl https://api.openai.com/v1/responses \
-H "Authorization: Bearer $OPENAI_API_KEY" -H "Content-Type: application/json" \
-d '{"model":"gpt-5.6-sol","input":"Hello"}'
Sources: