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GPT-5.6 Sol: The Flagship Model in the GPT-5.6 Family

GPT‑5.6 Sol is OpenAI’s highest‑capability model in the GPT‑5.6 family, designed for complex, multi‑step professional work such as agentic coding, security review, and large‑document analysis. It sits above Terra (balanced) and Luna (fast, affordable) in the GPT‑5.6 tiering.

What "Sol" Means in GPT‑5.6

OpenAI adopted an astronomical naming convention for the GPT-5.6 family to clearly distinguish each model's relative size, compute power, and cost efficiency:

Sol (The Sun): The largest, most capable, and most computationally intensive model. It is built for complex reasoning, long-horizon problem-solving, and advanced multi-agent tasks.
Terra (The Earth): The mid-tier option, designed to balance high capability with lower costs for everyday knowledge work.
Luna (The Moon): The smallest, fastest, and most affordable model in the family.

Core Capabilities of GPT‑5.6 Sol

Relative to earlier GPT models, Sol emphasizes:

Advanced Reasoning and Planning

GPT-5.6 Sol represents a paradigm shift in how models handle extended, multi-step problem solving. Rather than simply executing the first available solution, Sol focuses on orienting itself within unfamiliar environments.

The model introduces scalable compute options, allowing users to dial up the AI's processing time. The "Max" and "Ultra" modes allow the model to spend significantly more time thinking before responding.

Coding and Software Engineering

Sol operates as a persistent, high-level software engineer rather than a simple code-completion tool, especially when integrated into environments like OpenAI's Codex and the new ChatGPT Work platform. It can trace bugs through massive, unfamiliar production codebases and carry out large projects end-to-end.

Science and Technical Domains

The model’s advanced reasoning directly translates to improved capabilities in rigorous STEM fields, supported by a massive 1-million-token context window. Due to this long context, Sol can ingest and synthesize massive amounts of scientific literature, biological datasets, and complex mathematical proofs in a single prompt.

Cybersecurity and Safety

The model is exceptionally good at vulnerability research, patch development, and defensive testing. However, it is explicitly restricted from completing autonomous, end-to-end offensive cyberattacks against hardened targets.

Document and Presentation Quality

Beyond technical execution, GPT-5.6 Sol is heavily optimized for enterprise productivity and polished knowledge work.

Unlike previous models that struggled to force content into rigid existing templates, Sol exhibits strong design judgment. It can autonomously choose superior visual directions and formatting structures for slide decks and reports.

How GPT‑5.6 Sol Differs from GPT‑5.5 and Earlier

In practical terms, Sol is:

More autonomous: can coordinate sub‑agents and run longer, more complex plans without constant human prompting.
Stronger on hard reasoning: noticeably better on tough coding, math, and multi‑step scientific problems.
Safer but more controlled: deployed with stricter usage policies and monitoring, especially for high‑risk domains.

How GPT-5.6 Sol Compares to Other Models?

Model	Release date	Input / output price (per 1M tokens)	Context window	Max output tokens	Tool use & agents
GPT‑5.6 Sol	July 9, 2026	$5 / $30	1M	128K	Full agent stack (tool calling, code execution, browser, computer use)
GPT‑5.6 Terra	July 9, 2026	$2.50 / $15	1M	128K	Full agent stack (same capabilities as Sol, slightly lower reliability on hardest tasks)
GPT‑5.6 Luna	July 9, 2026	$1 / $6	1M	128K	Full agent stack, optimized for latency and throughput (some very hard tasks may degrade more than Sol/Terra)
GPT‑5.5	April 23, 2026	$5 / $30	1M	128K	Full agent stack, but weaker on complex multi‑step tool use and long‑horizon planning vs 5.6
Claude Opus 4.8	May 28, 2026	$5 / $25	1M	128K	Mature tool use (function calling, code execution, browser, computer use) via Claude Code / SDKs

Questions and Answers

What are the primary use cases for GPT-5.6 Sol?

GPT-5.6 Sol is expertly optimized for high-value knowledge work requiring deep, persistent analysis. It is ideal for end-to-end software development in environments like Codex, complex scientific discovery, enterprise decision support, and advanced security workflows such as vulnerability detection and long-horizon cybersecurity investigations.

What are the Max and Ultra modes of GPT-5.6 Sol?

The Max setting grants Sol extended compute time to deeply explore alternatives and refine complex answers. Ultra mode goes further by coordinating four AI sub-agents in parallel by default, empowering them to simultaneously execute different parts of massive, multi-step workflows.

What is the knowledge cutoff of GPT-5.6 Sol?

GPT-5.6 Sol’s foundational training data features a strict knowledge cutoff of February 2026. However, its capabilities certainly do not end there. For any events or developments occurring after this date, Sol seamlessly utilizes advanced web browsing tools to retrieve real-time information.

How do I decide between Sol, Terra, and Luna?

Choose Sol for highly complex coding, deep reasoning, and autonomous multi-agent workflows. Opt for Terra as your balanced, cost-effective default for everyday professional tasks. Finally, select Luna for lightweight, repetitive requests where maximum speed and lowest overall cost are your top priorities.

What safety and compliance considerations apply to Sol?

OpenAI treats Sol, Terra, and Luna as High capability in cybersecurity and biological/chemical risk under its Preparedness Framework, but not at the Critical threshold. Safeguards are designed to make prohibited offensive activity more difficult, uncertain, and detectable. Human review remains essential for production risk decisions; Sol should not be the sole authority on security posture.