GPT-5.6 Has Landed: Sol, Terra and Luna

Every new model generation arrives with the same question: which one do I actually use?

OpenAI's answer, with GPT-5.6, is to stop making you choose one. The new generation ships as a family of three tiers, Sol, Terra and Luna, so you can pick the right balance of intelligence, speed and cost for each job. All three are live in Pencil today, in the same model pickers you already use. 

There are no feature gaps between them and the OpenAI models you use now, so you can swop text generation models out for OpenAI’s frontier offerings without breaking existing production setups and Workflow architectures.

Meet the Family

• GPT-5.6 Sol is OpenAI's flagship and strongest model yet, with the deepest reasoning. Best for the most complex briefs and long, multi-step work - the jobs where you want the model to think before it writes.
• GPT-5.6 Terra is the balanced tier for everyday work. It's competitive with GPT-5.5 quality at around half the cost, which makes it the natural default for the bulk of production copy.
• GPT-5.6 Luna is the fast one. Best for quick tasks and high-volume workloads, where you want to prioritse turnaround and scale.

A Naming System Worth Learning Once

GPT-5.6 also introduces a new naming logic from OpenAI. The number identifies the model generation. Sol, Terra and Luna are durable capability tiers that will carry forward into future generations and advance on their own cadence, much like Anthropic’s Haiku, Sonnet and Opus series. 

How to Choose

The shorthand: Sol for the hardest work. Terra as the everyday default. Luna for speed and scale.

In practice, that maps cleanly onto creative production. Give each task to the model that can best handle it: Use Sol for a dense, thirty-page brief and for multi-step campaign builds. Terra is the workhorse for day-to-day copywriting. Use Luna to take on the massive hundreds-of-variants runs, where every second of generation time compounds.

In Pencil Today

All three models appear wherever you can already pick an OpenAI model in Pencil: the Editor, Workflows, Agents, and beyond. Same pickers, new options. Nothing about your existing setup needs to change.

To enable them, an admin switches on OpenAI models under Settings → AI Governance. Once enabled, all three tiers are available across the workspace, inside the same governance and brand controls as everything else in Pencil.

Why This Matters

Frontier models now ship in families, not single releases, because one size never fit every task. A campaign manifesto and a thousand feed variants shouldn't cost the same or wait the same. Tiered families let you spend intelligence where it earns its keep and speed where it doesn't.

Pencil is built for exactly that. The Open Garden puts every tier from every leading lab in one place, so the choice between Sol, Terra and Luna, or Claude, or Gemini, is a dropdown, not a procurement cycle.

Frequently Asked Questions

What is GPT-5.6? GPT-5.6 is OpenAI's newest model generation. It ships as a family of three tiers, Sol, Terra and Luna, covering different balances of intelligence, speed and cost.

What do Sol, Terra and Luna mean? They're capability tiers, not separate products. The number (5.6) identifies the generation, while Sol, Terra and Luna are tiers that carry forward into future generations and advance on their own cadence.

Which GPT-5.6 model should I use? Sol for the hardest work, including complex briefs and long, multi-step tasks. Terra as the everyday default. Luna for speed and high-volume workloads.

Is GPT-5.6 available in Pencil? Yes. All three tiers are live in Pencil, in the same model pickers as existing OpenAI models, with no feature gaps between them and the models you use now.

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GPT-5.6 Sol, Terra and Luna are live in Pencil now.

Try them today: https://pro.trypencil.com/login