Foundation Base

Open Source Budget App

Create your own zero-based budget app from a working envelope planner with real rollover balances — and no bank connection to hand over.

Recommended foundation

Start with the working app that most closely matches this use case.

Details
BPProduction Ready

/finance / updated Jul 25, 2026

Budget Planner

v1.0.0

A zero-based monthly budget planner with envelopes, real rollover balances, overspend warnings, and a safe-to-spend-per-day figure.

  • Use it today.
  • Create your editable copy.
  • Customize it with AI.
RunnableAgent-readyInstall-readyDeploy-ready
Next.jsReactTypeScript+1
Anyone running a zero-based or envelope budget, Households that want budgeting without linking a bank accountBest forMITLicense
5 min setupAgent-readyApp Link path
Create My AppTry DemoDetails

Creates your editable project with setup files and AI-agent instructions.

What you can build

  • A zero-based monthly budget
  • An envelope budgeting app
  • A household budget for two people
  • A sinking-fund planner

Alternative related foundations

EXProduction Ready

/finance / updated Jul 2, 2026

Expense Tracker

v1.0.0

A fast expense logger with categories, a monthly budget, and a breakdown that shows exactly where the money went.

  • Use it today.
  • Create your editable copy.
  • Customize it with AI.
RunnableAgent-readyInstall-readyDeploy-ready
Next.jsReactTypeScript+1
private money workflows, local-first trackingBest forMITLicense
5 min setupAgent-readyApp Link path
Create My AppTry DemoDetails

Creates your editable project with setup files and AI-agent instructions.

DPProduction Ready

/finance / updated Jul 4, 2026

Debt Payoff Planner

v1.0.0

A debt snowball and avalanche calculator: list your debts, set an extra monthly payment, and compare payoff time, total interest, and payoff order side by side.

  • Use it today.
  • Create your editable copy.
  • Customize it with AI.
RunnableAgent-readyInstall-readyDeploy-ready
Next.jsReactTypeScript+1
private money workflows, local-first trackingBest forMITLicense
5 min setupAgent-readyApp Link path
Create My AppTry DemoDetails

Creates your editable project with setup files and AI-agent instructions.

SUProduction Ready

/finance / updated Jul 2, 2026

Subscription Tracker

v1.0.0

Track every recurring charge, see your true monthly burn, and catch renewals before they catch you.

  • Use it today.
  • Create your editable copy.
  • Customize it with AI.
RunnableAgent-readyInstall-readyDeploy-ready
Next.jsReactTypeScript+1
private money workflows, local-first trackingBest forMITLicense
5 min setupAgent-readyApp Link path
Create My AppTry DemoDetails

Creates your editable project with setup files and AI-agent instructions.

Pick a working app. Make it yours.

Try the shared demo, create your editable copy, customize with AI, deploy your App Link, and install your version.

1

Try Demo

Use the original Foundation Base demo.

2

Create My App

Create the editable source package.

3

Customize with AI

Open the folder in Claude Code, Codex, Cursor, or another coding agent.

4

Deploy App Link

Publish your own stable URL.

5

Install Your Version

Add your deployed App Link to your phone or desktop.

The Foundation Base demo does not update when you customize your copy. Install your own App Link after you deploy.

Demo Link

The original Foundation Base version. Good for trying the app.

Preview Link

A temporary testing link while your app is being customized.

App Link

Your stable deployed URL. Install this version if you want your changes to appear on your phone or desktop.

Questions

What happens when I click Create My App?

You download an editable source package with setup files and AI-agent instructions. Your copy is separate from the Foundation Base demo.

Does the Foundation Base demo update when I customize my copy?

No. The demo is the original shared version. Install your own deployed App Link when you want your customized app on a device.

Can I use Claude Code, Codex, Cursor, or another agent?

Yes. Foundations are designed to be opened by an AI coding agent after you download and unzip the source package.