Answer nine questions. Ship the smallest app that tests your riskiest assumption.
This is a template for starting apps with an AI coding agent (Cursor, Claude Code, Codex, whatever you use). Instead of writing a PRD, you fill in a Lean Canvas through a short interview with your agent. The agent then builds only what tests your riskiest belief, and the canvas stays the source of truth as you learn.
A PRD is pages of detail about features nobody has validated. It made sense when engineering was the bottleneck and specs had to survive a handoff. Your agent is not that bottleneck. It can figure out the technical details on its own; what it can't know is whether anyone wants the app, will open it twice, or will pay at the paywall. That part is yours, and it fits on one page.
A Lean Canvas (Ash Maurya's one-page adaptation of the Business Model Canvas) captures exactly that part: who it's for, what problem it solves, why you, how it makes money, and the one belief that kills the whole thing if you're wrong. You build to test that belief. Everything else waits.
- Click "Use this template" above (or clone the repo).
- Open the folder in your AI IDE or agent.
- Say: "Read AGENTS.md and start."
Your agent interviews you, one question at a time, about customers, problem, pricing, and channels. Then it fills in CANVAS.md, names your riskiest assumption, proposes the smallest v0.1 that tests it, suggests a stack (override it with a sentence), and builds.
No CLI, no phases, no setup. The state of CANVAS.md is the state of the project: empty means interview, filled means build.
Four files.
| File | What it is |
|---|---|
CANVAS.md |
The Lean Canvas. Single source of truth. Every feature must trace back to a box here. |
AGENTS.md |
Instructions your agent follows: interview rules, build rules, house rules. |
LOG.md |
The agent's memory: stack, decisions, experiment results. |
README.md |
This file. Your agent replaces it with your app's readme once v0.1 runs. |
believe (canvas) -> build (smallest test) -> measure (the one metric) -> learn -> update canvas
The canvas is versioned. When an experiment invalidates a box, you edit the box and log the change. A dead assumption is progress; it saves you months of building the wrong thing.
The canvas prompts are tuned for mobile apps, because that's where the business questions get skipped the most:
- Channels asks for the App Store keywords you can realistically rank for.
- Key metrics asks for D1/D7/D30 retention, not downloads.
- Revenue asks where the paywall goes and what the top three competitors charge.
- The house rules ban polling (batteries) and require main to stay TestFlight-able.
Building for web? Everything still works; skip the mobile hints.
The short version (full list in AGENTS.md):
- No backwards compatibility before launch. There are no users to break. Change the code, delete the old path.
- No polling where push or reactive mechanisms exist.
- No premature architecture: no microservices, feature flags, or design systems at v0.1.
- Boring, hosted, free-tier stack by default. The stack is not the product.
- The key metric gets instrumented before feature two.
Where's the tech design doc? There isn't one. Your agent proposes a stack during the interview and records it in LOG.md. Override it with a sentence.
Can I fill in the canvas by hand? Yes. Your agent switches to build mode once the boxes are filled.
What if I already have an app? Fill in the canvas for what exists, be honest about which boxes are guesses, and let the riskiest assumption drive the next release.
Isn't this just for startups? The canvas comes from the startup world, but "who is this for, why would they care, what kills it" applies to any app you'd like people to actually use.
- Lean Canvas by Ash Maurya, adapted from the Business Model Canvas (CC BY-SA 3.0).
- The interview style borrows from The Mom Test by Rob Fitzpatrick: ask about their life, not your idea.
- Prior art: KhazP/vibe-coding-prompt-template, a PRD-driven workflow. This template is the business-first, four-file version of the same instinct.
MIT