Letterhearth is a full-stack app built with Claude Code on Elements.
Free or $8 per month subscriptions by card, a teaser on paid posts, and markdown posts the writer schedules and emails.
Run this app on your machine. Use this demo as inspiration, or as the starting point for your own app. Your agent creates a new app with this one as the scaffold, and you prompt it to add whatever features you want.
Paid subscriptions go through Stripe Checkout in subscription mode. Without a
key, payments run through the app's built-in test checkout: the paid plan
button opens an order summary with a Pay button, and paying records the
subscription through the same code a Stripe payment uses, so the paid welcome
email, the unlocked posts and the writer's live revenue all work. For real
Stripe Checkout, create a free sandbox at
dashboard.stripe.com/register and add
its secret key as STRIPE_SECRET_KEY in config/env/development.env. Test
with card 4242 4242 4242 4242, any future date and any CVC. Production
requires the key, and the app registers its own Stripe webhook on the first
checkout.
Letterhearth needed free and paid subscriptions billed monthly by card, scheduled posts that go out by email, a teaser for readers who are not paying, one-click unsubscribe, and live counts for the writer. Each of those is a part of Elements, so the agent spent its 22 minutes on the newsletter itself.
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Live counts and revenue. Subscribers are a LiveTable, so the writer's free and paid counts and monthly revenue move the moment a reader subscribes or upgrades.
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Monthly subscriptions. Subscribing, upgrading and cancelling are
@rpccalls, and paid plans go through Stripe at $8 per month. The return page and Stripe's webhook record a new subscription once. Until a Stripe key is added, a built-in test checkout takes the payment through the same code, and in production the app registers its own webhook. -
Posts on a schedule. A cron schedule checks every minute for posts whose time has come and queues one email job per reader, so a failed send retries alone. Paid posts go in full to paid readers and as a teaser to everyone else.
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One-click unsubscribe. Every email carries the headers mail clients turn into an unsubscribe button, and the app answers that button directly.
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Data from SQL files. Migrations define the newsletter and seed the writer, six posts (three paid), five free readers and three on complimentary paid plans.
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Sessions for readers and the writer. Readers are signed in when they subscribe and later by an emailed link, and every writer page shares one guard on the writer's role.
Elements is an integrated full-stack app framework and a project server. The project server checks the agent's work as it builds: it type-checks the server and browser code, analyzes the program, applies migrations and runs the tests, then reports the results to the agent. A security mistake, such as calling a server-only function from the browser, is a compile error. The agent reads the report and fixes its own mistakes before it tells you a feature is done. The same checks run on every feature you ask for next.