Gavelrush: a live online auction for a charity's auction week
Lots with photos and countdowns, bids at a set increment, late bids that extend the close, outbid emails, and pay-by-card links.
Agent specs
- Agent
- Claude Code, Opus 5.5 Medium
- Time
- 22 min
- Cost
- $6.56*
Agents work faster and more accurately on Elements.
* Cost at API rates, September 2026.
Run it yourself
Paste this prompt into your AI agent. You get the finished app on your own machine, ready to change however you like.
Install elements: curl -fsSL 'https://install.elements.dev?os=darwin' | sh && export PATH=~/elements/bin:$PATH Create an Elements app from the elementscode/demo-gavelrush scaffold: cd ~/elements/projects elements create gavelrush -scaffold=elementscode/demo-gavelrush cd gavelrush Start the app.
How it's built
Gavelrush needed bids that land for everyone at once, a close time that moves when a late bid comes in, outbid and winner emails, photo uploads and card payments. Each of those is a part of Elements, so the agent spent its 22 minutes on the auction itself.
What Elements gave the app
- Live lots and bids. Lots, bids and watchlists are LiveTables. A bid lands on every open lot card, countdown and the admin's total raised the moment it is placed, and each lot page hears only its own bid history.
- Bidding as a function call. The lot page places a bid through an
@rpcserver function that locks the lot, checks the increment, extends the close by two minutes when a bid comes in late, and queues the outbid email, all in one transaction. - Jobs and email. A one-line cron schedule closes lots every minute, records each winner and queues the winner's email with a link to pay. The outbid email checks at send time that the bidder is still behind.
- Card payments. The winner pays through Stripe for the amount on the lot, and the payment is recorded once whether the return page or Stripe's webhook arrives first. Without a Stripe key, a test checkout inside the app records payments through the same function, and in production the app registers its own webhook on the first checkout.
- Photos in the database. The admin uploads lot photos straight through a server call, and the app serves each one at an address browsers keep for a year.
- Data from SQL files. Migrations define the auction and seed one admin, four bidders and twelve lots with photos, bids and watchlists, one closing in minutes.
What the project server gave the agent
The project server runs alongside the agent and answers as soon as a file is saved: it type-checks the templates, TypeScript and SQL, applies migrations and reruns the tests, so every question came back right away and the agent kept building.
What shipped
The app type-checks with zero errors and all 28 tests pass. Every page works on desktop and phone. A real sandbox payment went through Stripe end to end.
The code
Build it from scratch
To watch your agent build this app from an empty project, use the prompt we used instead. It takes longer than starting from the finished app above.
Install elements: curl -fsSL 'https://install.elements.dev?os=darwin' | sh && export PATH=~/elements/bin:$PATH Create an Elements app: cd ~/elements/projects elements create gavelrush cd gavelrush Start the app, then build this: Build a live auction site named gavelrush for a charity's online auction week. BIDDER - Sign up, log in. - Browse lots with photos, description, current bid, and a countdown to close. - Place a bid at least the minimum increment above the current bid. - A bid in the last two minutes extends that lot's close by two minutes. - Watch lots, and get an email when outbid. - The winner of each lot gets an email when it closes, with a link to pay by card. ADMIN - Create lots: photos, description, starting bid, increment, close time. - Results: each lot's winner, amount and payment status, and the total raised. Payments by Stripe. Seed one admin, four bidders, and twelve lots with photos, bids, and close times spread over the next few days, with one closing in minutes. Show the seeded logins on the sign-in page. Bids, countdowns and the total raised update in real time.
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