Auto-extracted specs read the code, not the decisions behind it. They quietly promote placeholders and fallbacks as if settled. Sign-off is the missing step.
AI-native teams need three layers of durable memory — behavior, decisions, execution. Execution has tooling. Most teams lack the behavior layer entirely.
As engineers take on more product ownership and AI accelerates shipping, product decisions vanish into Slack and PRs. Behavior specs hold the intent.
AI makes rebuilding cheap. But product decisions are expensive to recreate from memory. Here's how a behavior spec makes 'start fresh' a feature, not a failure.
Paste a prompt into Claude or ChatGPT, describe your product module briefly, and get a .pbc.md behavior spec you can view, edit, and commit to your repo.
CLAUDE.md and AGENTS.md tell agents how to work in your repo. They don't tell agents what your product promises. That's a different artifact — the PBC layer.
A step-by-step guide to writing a .pbc.md file for your product's most critical module. Start with plain Markdown; add structured blocks agents can read.
Shipping fast with AI agents feels productive. But the costliest mistake isn't bad code — it's building confidently when nobody wrote down what was decided.
PRDs capture intent. Tests verify assertions. Between them, there's no artifact tracking what the product promises — grounded in code, confirmed by humans.
AI agents have AGENTS.md, memory banks, harnesses, and monitors. They still lack the product context layer — what the product promises and what must hold.
When an outsourcing engagement wraps up, product knowledge walks out the door. A living behavior spec keeps it in the codebase — not in someone's head.
AI can extract product logic from your codebase. Stewie builds a living behavior spec your whole team can read — no code, no docs, no waiting on engineers.
Product owners confirm behaviors. BAs clarify logic. QA knows what to protect. New hires onboard fast. Vendors skip reverse-engineering. One shared contract.
Leaders shouldn't need three meetings to verify whether a product decision was implemented correctly. A living behavior spec is the direct line.
Your coding agent ships correct-looking code that breaks product promises. The fix isn't capability — it's the product context layer agents lack.
Your repo has workflow instructions, session context, and feature specs. None of them answer what the product promises to do. That's the PBC layer.
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 .pbc.md file opens in VS Code, renders on GitHub, reads like any Markdown doc. Drop it into pbc.stewie.sh and the same file becomes navigable UI.
After hitting the same product knowledge gap across multiple SaaS products, I built an open Markdown spec for capturing what your product promises to do.
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 behavior spec does about it.