PRDs capture intent. Test suites verify assertions. But between those two, there's no artifact that tracks what the product promises to do — grounded in code, confirmed by humans. That's the PBC layer.
When an outsourcing engagement wraps up, product knowledge walks out the door. A living product contract keeps it in the codebase — not in someone's head.
AI can now extract product logic from your codebase. Stewie builds a living product contract your whole team can read — no code, no stale docs, no waiting on engineers.
PMs confirm behaviors. BAs clarify domain logic. QA knows what to protect. New hires onboard in hours. Vendor teams skip the reverse-engineering phase. Here's how each role contributes to a living product contract.
Strategic leaders shouldn't need three meetings to verify whether a product decision was implemented correctly. A living product contract gives you a direct line to what's running in production.
Your coding agent ships correct-looking code that breaks product promises. The problem isn't capability — it's a missing context layer that AGENTS.md and memory banks were never designed to provide.
Shipping fast with AI coding tools is genuinely good. The problem isn't the speed — it's what gets left behind. Product reasoning doesn't survive the vibe.
A Product Behavior Contract (PBC) is a living, code-grounded spec that describes how your product actually behaves — not how you think it does.
Product knowledge lives in heads, not docs. Here's why that gap compounds — and what a Product Behavior Contract does about it.