OpenAI Launches GPT-5.6, Sol Leads Charge

Last updated: August 2026

OpenAI officially released its GPT-5.6 model family for general availability on July 9, 2026. This launch, following a limited preview, introduces three models: Sol, the new flagship; Terra, a balanced option for daily use; and Luna, the most cost-efficient variant.

GPT-5.6 Sol establishes a new standard for AI intelligence and efficiency. It achieves state-of-the-art results in coding, knowledge work, cybersecurity, and scientific applications, outperforming previous and competing frontier models with fewer tokens and lower estimated costs. This translates to superior performance per dollar.

Efficiency and Performance Redefined

The models deliver more intelligence per token and stronger performance per dollar. The 'ultra' setting, for instance, coordinates multiple agents across parallel workstreams, accelerating complex tasks.

On the Agents’ Last Exam, an evaluation spanning 55 professional workflows, GPT-5.6 Sol achieved a score of 53.6, surpassing Claude Fable 5 by 13.1 points. Even at medium reasoning, it beat Fable 5 by 11.4 points at roughly one-quarter the estimated cost. This large language model efficiency extends to Terra and Luna, which outperform Fable 5 at about one-sixteenth the cost.

GPT-5.6 Sol also excels in coding, setting a new state-of-the-art score of 80 on the Artificial Analysis Coding Agent Index. This is 2.8 points above Fable 5, accomplished with less than half the output tokens, under half the time, and at approximately one-third less cost. OpenAI GPT-5.6 Sol performance is further bolstered by new features like Programmatic Tool Calling in the Responses API, streamlining tool-heavy tasks with fewer tokens and model round trips.

Beyond efficiency, GPT-5.6 demonstrates a significant leap in design judgment. It can create tasteful, functional interfaces from high-level directions and refine rendered results, not just generate code.

End-to-End Knowledge Work and Safeguards

For professional tasks, GPT-5.6 processes messy context from various documents and platforms like Slack and Microsoft 365, converting it into expert-level artifacts. GPT-5.6 Sol achieved new state-of-the-art results on BrowseComp at 92.2% and OSWorld 2.0 at 62.6%.

The model family also enhances presentations, documents, and spreadsheets, producing more polished and accurate outputs. It can infer and apply design systems consistently, crucial for repeatable knowledge work.

OpenAI emphasizes robust safeguards with GPT-5.6, designed to be resilient against misuse without limiting legitimate applications. The models underwent extensive evaluation, combining human red teaming with large-scale automated testing, prior to general availability.

GPT-5.6 Sol in August 2026: Rollout and Updates

Since the July 9 launch, OpenAI has continued to expand GPT-5.6 deployment. The week of August 6, 2026, GPT-5.6 Luna began rolling out as the default for all Free and Go ChatGPT users, the largest expansion of the model family's reach to date. Sol remains the flagship for premium and enterprise use cases, while Terra and Luna handle balanced and high-volume workloads respectively. All three models share a 1,050,000-token context window; enterprise subscribers can access a 1.5 million token context on the highest tier.

ChatGPT Work, an agentic system built directly on GPT-5.6, launched to handle multi-hour, multi-step projects autonomously across connected team files and apps. The model's tool-call refusal rate has dropped below 4%, a significant improvement from approximately 12% on GPT-5.5. On August 11, OpenAI added real-time monitoring of Astra's chain of thought to detect and interrupt risky or misaligned actions before completion.

StartupHub.ai tracks OpenAI across 13,000+ startups and rates it at 84 out of 100 overall, placing it at the top of the AI platform category by our composite scoring.

Frequently Asked Questions

What is GPT-5.6 Sol?

GPT-5.6 Sol is OpenAI's flagship model in the GPT-5.6 family, designed for ambitious agentic and knowledge work. It scored 53.6 on the Agents' Last Exam and 80 on the Artificial Analysis Coding Agent Index, setting state-of-the-art results on both at lower cost than competing models. It is available via the API and on ChatGPT Plus, Pro, and Enterprise tiers.

What is the difference between GPT-5.6 Sol, Terra, and Luna?

Sol is the flagship, optimized for complex reasoning, long-horizon agentic tasks, and maximum performance. Terra is the balanced mid-tier for professional everyday work. Luna is the fast, cost-efficient model for high-volume tasks. As of August 2026, Luna is the default for Free and Go ChatGPT users. All three share a 1,050,000-token context window.

When was GPT-5.6 released?

OpenAI released GPT-5.6 on July 9, 2026, with general availability across Sol, Terra, and Luna variants. GPT-5.6 Luna began rolling out as the free-tier default in the week of August 6, 2026.

How does GPT-5.6 Sol compare to Claude Fable 5?

On the Agents' Last Exam, GPT-5.6 Sol scored 53.6 against Claude Fable 5's score, a margin of 13.1 points. On the Artificial Analysis Coding Agent Index, Sol scored 80, which is 2.8 points above Fable 5, achieved with less than half the output tokens, under half the time, and at approximately one-third less cost.