Writing long-form documents — proposals, grant applications, playbooks, internal specs — has always lived in an awkward gap. Generic AI writers don't know your business, and copy-pasting context into a chat box every time is tedious. The new Document Builder closes that gap.

The latest models, ready to pick

The model dropdown now includes Claude Opus 4.8 and Claude Sonnet 4.6. Behind the scenes, the streaming route aliases these display names to the real provider ids, so you always get the newest available model without anything breaking when the underlying version rolls forward.

Pick Opus 4.8 when you want maximum reasoning depth, or Sonnet 4.6 when you want speed and lower cost for high-volume drafting.

Domain-aware writing

Previously, the builder leaned toward grant-and-proposal framing — great for funding applications, distracting for everything else. Now the system prompt is selected by document type:

• Grant and proposal documents get grant-savvy framing.
• Everything else gets a clean, neutral writer that doesn't assume a domain.

The result: a blog outline reads like a blog outline, and a partnership proposal reads like a proposal — no more grant boilerplate leaking into free writing.

A Context picker that actually works

The Context button in the top-right of the builder now reliably loads your saved context items, surfaces a clear error if something goes wrong, and gives you a Retry button instead of failing silently.

Even better, you can add context without leaving the builder:

1. Open the Context picker.
2. Choose Add context.
3. Paste text, or upload a .txt / .md file.

The new item is saved to your Context Library and auto-selected for the current document — so the model is grounded in your material from the first token.

The Prompt Library, one click away

When you add a Section or Chapter, you can now toggle Browse library to pull from a curated set of document prompts. No more staring at a blank section: pick a starting prompt, then refine.

💡 Tip

Combine a Context Library item with a Prompt Library starter — the prompt sets the shape, the context grounds the facts.

Small things that add up

• New sections and chapters self-select the moment you add them, so you can start typing immediately.
• Documents persist to a dedicated, owner-scoped table — your work is saved and scoped to you.

The Document Builder is now a genuinely useful long-form workspace: current models, the right framing per document, and your own context one paste away.

Related guides

• Variables & the Context Engine — the Context picker that grounds every document.
• Prompt examples — starters for the Prompt Library.
• Ask AI — the assistant that knows your account.

The Mass Team