Three quick steps. The split forms as you go.
Add 2–4 founders. Names show up everywhere downstream. You can rename them anytime.
These are the strongest predictors of co-founder breakups. They feed warnings, not the score.
Based on research-backed value-contribution criteria: commitment/opportunity cost, founder experience and scarcity, product/technical value, go-to-market value, fundraising value, and idea/leadership role. Founder Fit, Governance, and Motivation answers feed warnings below - they don't move the split.
Whatever you land on, pair it with 4-year vesting, a 1-year cliff, and written dynamic terms such as buyback or forfeiture provisions. It protects all of you - including the founder who stays - if someone leaves early. Write a real founder agreement before any shares get issued.