GPT-5.6
OpenAI's three-tier family: Sol, Terra, and Luna. Flagship depth down to fast and affordable.
OpenAI split GPT-5.6 into three durable capability tiers. Sol is the flagship for the hardest reasoning and tool-use work. Terra is the balanced everyday model, matching the previous flagship's quality at half the cost. Luna is fast and affordable for high-volume, quick-turnaround drafting. Pick the tier that fits the document, all under one subscription.
Try these prompts
How it works
Describe your brief
Type what you need: a proposal, case study, specification, or creative copy.
Choose model and document type
Pick your writing model and document length. See the credit cost before you generate.
Draft generated in seconds
Your document is drafted and ready to review, edit, copy, or export. Iterate or switch models.
Ready to draft with GPT-5.6?
Jump into the Studio and start writing. Plans from $11/month.
One GPT-5.6 family, three tiers for every document.
GPT-5.6 is OpenAI's newest model family, split into three tiers that advance on their own cadence. Instead of a single flagship, you choose the depth the document actually needs: Sol for the hardest work, Terra for balanced everyday drafting, and Luna for fast, high-volume writing. Every tier is available on every Stensyl plan.
Sol is the flagship. It is the tier to reach for when the model must plan, use tools, revise, and stay on task across harder documents: multi-section reports, tender responses that must stay internally consistent, and analysis that leans on long context. It leads its class on long-document coherence, holding an entire brief in working memory without drifting.
Terra is the balanced everyday model, delivering the previous flagship's quality at roughly half the cost. For the bulk of professional writing, structured specifications, proposals, and design and access statements, Terra is the sensible default. Luna is the fast, affordable tier for the everyday drafts that fill a working week: project summaries, client emails, captions, and meeting notes, delivered in seconds.
Sol: flagship reasoning
Sol applies the deepest reasoning and best long-context handling in the family. Choose it for complex, multi-page documents that cross-reference several source materials, where internal consistency across the full length matters. It is the tier for planning appeals, lengthy proposals, and technical work that must not contradict itself.
Terra: balanced everyday
Terra matches the previous GPT-5.5 flagship's quality at about half the cost. It understands professional document formats and produces structured output that follows the conventions of each type. For most structured professional documents, tenders, specifications, and timelines, Terra is the balanced choice.
Luna: fast and affordable
Luna is the most economical tier, delivering drafts in seconds at the lowest cost per document. Use it for the majority of writing that is straightforward: quick summaries, emails, social captions, product listings, and meeting notes. Step up to Terra or Sol when a document needs deeper reasoning or heavy cross-referencing.
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Ready to draft with GPT-5.6?
Professional document drafting. Plans from $11/month.