Scenario 1
You know the product category but not whether the market is real
Start at the vertical branch that matches your product (SaaS, AI Startup, Marketplace, Mobile App, Chrome Extension, B2B, or API). Each vertical pillar assumes the canonical validation framework but adds the failure modes that category founders hit most often — chicken-and-egg for marketplaces, defensibility for AI, buying committees for B2B, distribution cost for mobile apps. Read the vertical pillar first; the framework will fall into place once you have seen the category-specific version. The Customer Discovery branch is the second stop regardless of vertical — the conversations that produce validation evidence are not vertical-specific.