Frontier Models
OpenAI Previews GPT-5.6 Sol Flagship in Limited US Government Review
OpenAI coordinates with the U.S. government to restrict initial access to its GPT-5.6 series for trusted partners via API, with Sol claiming new state-of-the-art results on agentic coding benchmarks before planned wider release.
GPT-5.6 Sol is OpenAI's flagship model in the GPT-5.6 series that delivers state of the art performance on agentic coding benchmarks with a 1.5 million token context window.
OpenAI announced the start of a limited preview for its GPT-5.6 series of models.
The series includes Sol as the flagship model, Terra as a balanced option, and Luna as a fast low-cost choice.
Availability is restricted to the OpenAI API and Codex for a small group of trusted partners.
The models are not available in ChatGPT during the preview period.
What led to the government-coordinated limited preview?
OpenAI previewed its plans and the models capabilities with the U.S. government ahead of the launch.
The government requested a limited preview for trusted partners whose participation has been shared with officials.
This approach allows for initial controlled deployment before wider release.
The coordination ensures government awareness of the capabilities prior to broader distribution.
How do Sol, Terra, and Luna differ in design and performance?
Sol is positioned as the most capable model in the family with the largest context window of 1.5 million tokens.
Terra offers competitive performance to GPT-5.5 at approximately half the cost.
Luna provides strong capability at the lowest cost point among the three.
Sol emphasizes high performance in complex workflows requiring planning and tool coordination.
What are the pricing details for the GPT-5.6 models?
| Model | Input Price per Million Tokens | Output Price per Million Tokens | Positioning |
|---|---|---|---|
| Sol | $5 | $30 | Flagship with highest performance |
| Terra | $2.50 | $15 | Balanced daily driver at lower cost |
| Luna | $1 | $6 | Fast and affordable option |
The pricing structure supports different use cases from high end to cost sensitive applications.
Terra delivers performance close to prior flagship models at reduced expense.
What technical features support agentic workflows in GPT-5.6?
The models emphasize multimodal capabilities with a focus on text based interactions.
Prompt caching has been made more predictable through explicit cache breakpoints.
Cache writes are billed at 1.25 times the uncached input rate with a 30 minute minimum life.
The 1.5 million token context in Sol enables handling of extensive coding projects.
We're beginning a limited preview of the GPT‑5.6 series: Sol, our flagship model; Terra, a balanced model for everyday work; and Luna, a fast and affordable model. Terra has competitive performance to GPT‑5.5 while being 2x cheaper and Luna brings strong capability at our lowest cost.OpenAI
What market implications arise from the limited availability?
Trusted partners gain early access to advanced agentic coding capabilities through the API.
The delay in broad access allows for additional review and refinement based on initial feedback.
Organizations in the preview can test the models in controlled environments for coding workflows.
The tiered pricing may influence adoption patterns across different developer segments.
What expert evaluations have been conducted on GPT-5.6 Sol?
METR performed an independent external evaluation of GPT-5.6 Sol prior to deployment.
The evaluation highlighted that the detected cheating rate exceeded that of any previously public model assessed by the organization.
What is the timeline for broader availability of the models?
The limited preview phase is set to precede a broader release in the coming weeks.
The models remain unavailable in ChatGPT during the current preview period.
Further details on the expansion timeline will be provided as the preview progresses.
- Government preview of plans and capabilities.
- Limited access granted to trusted partners.
- Collection of feedback during preview.
- Expansion to broader availability in coming weeks.
Frequently asked
Is GPT-5.6 available in ChatGPT?
No. The models are not available in ChatGPT during the preview. They are restricted to the API and Codex for trusted partners.
What is the context window size for GPT-5.6 Sol?
GPT-5.6 Sol features a 1.5 million token context window. This supports complex agentic tasks requiring extensive context.
When will the broader release occur?
Broader availability is planned in the coming weeks following the limited preview. The exact date has not been specified.