S Spellbook

AI contract review, drafting, and negotiation for lawyers, inside Microsoft Word.

Spellbook builds almost entirely on foundation models — it tried fine-tuning early and abandoned it, betting instead on the harness around the models and on surviving Microsoft Word's formatting spec. Its review surface alone orchestrates roughly 15 Claude agent configurations, matched by subtask complexity, and model selection is decided by grading candidates against a larger oracle model with criteria vetted by legal experts. Engineering runs the same pattern internally on Claude Code: a large model writes and reviews the plan, a cheaper one executes it.

spellbook.legal