How MonstarX works
In shortYou describe an app. An AI agent plans it as a checklist of features, then writes the code on a secure cloud computer where your app runs live in the preview as it is built. Every change to the code is saved as a version you can go back to. MonstarX Cloud gives the app its database, sign-in, email, storage and AI. You can test it in real browsers, publish it to its own address in one click, and keep improving it by chatting.
MonstarX does the work of a small software team: it plans what to build, writes the code, runs it, checks it, and puts it online. This page explains each stage in plain words, so you know what is happening while you wait — and what you can do at every point.
The journey of an app
Section titled “The journey of an app”Steps 3 to 7 repeat for every change you ask for. Here is each one in turn.
1. Describe
Section titled “1. Describe”Everything starts with a request: a sentence or two about what the app is for and what people do in it. You can add pictures, documents, a spreadsheet or a Figma design, and you can choose how MonstarX starts:
| You press | What happens first |
|---|---|
| Build it | MonstarX starts building straight away, filling any gaps with sensible choices. |
| Plan it (with Plan first on) | MonstarX asks a few questions — one at a time, each with suggested answers — and builds once you have answered. |
| Build it (with Design first on) | You first see a few finished-looking first screens and pick the look you like. |
See Describe your app and Prompting tips.
2. Plan
Section titled “2. Plan”For a new app, or a request with several features, MonstarX first writes a feature plan: a short, numbered checklist of what it will build. The plan sits at the top of the chat under Features, with a bar showing how many are built. You can add, remove, reopen or build single features yourself.
See The feature plan.
3. Build
Section titled “3. Build”An AI agent — MonstarX’s builder — works through the plan one feature at a time. For each one it reads what is there, writes and edits the app’s files, sets up the database tables it needs, and checks that the pages still work. It can also draw photos for the app while it works.
The chat shows this as it happens, folded into one plain line per stretch of work — “Created 4 files · read 2 files”, “Built 1 feature · updated the database” — with every single step one click away.
Which AI model does the work? On Auto (the default), MonstarX picks a suitable model and effort for each request and shows its choice on the reply. You can pick one yourself. See Choose a model.
The build runs on MonstarX, not in your browser. You can close the tab or lock your phone: the build carries on, and you can get a notification when it ends. Requests you send while a build runs wait in a queue and start by themselves. See Follow a build and The queue.
4. Preview
Section titled “4. Preview”Your app runs on a secure cloud computer of its own, and the Preview tab shows it live — the real app, not a picture. While the build writes files, MonstarX keeps half-written pages out of sight and shows a status card instead, so you only see the app once a page really works.
- Switch between desktop, tablet and phone widths.
- Click and type in it like any visitor.
- Point at anything with Edit or Clip to ask for a change.
A preview that nobody has used for 20 minutes goes to sleep. When you come back you first see a saved copy of the page, and the live app wakes up as soon as you move or click. See The preview.
5. Test
Section titled “5. Test”MonstarX checks every build as it goes: after a feature is built it makes sure the pages render. For a deeper check you can run Automated QA: MonstarX writes a test plan from your app, and cloud browsers click through it like real customers — signing up, booking, checking out — with a recording of every run. After big changes, MonstarX suggests a QA run and asks before it starts. See QA testing.
The Security tab scans the app for security holes, and the SEO/GEO tab checks how search engines and AI assistants see it. See Security scan and SEO and GEO.
6. Publish
Section titled “6. Publish”Until you publish, only you, the people you share the project with and anyone you give the preview’s link to can see the app. Publish builds a production copy of the app and puts it on the internet at its own address — your-app.monstarx.app — with HTTPS, served from Cloudflare’s global network. You can add a domain of your own.
Publishing takes a snapshot of the app as it is now. Keep working in the preview as much as you like: the live site changes only when you click Republish. See Publish your app.
7. Keep improving
Section titled “7. Keep improving”An app is never finished. Ask for the next feature, fix what a customer reported, or pick one of the Ideas for what’s next MonstarX suggests when everything on the plan is built — click Add on one (or Add all), then Build it. Each request goes round the same loop: plan, build, preview, test, publish.
What is a version?
Section titled “What is a version?”Every time your app’s code changes — after a build, a save in the Code tab or a restore — MonstarX saves a version: a snapshot of all of the app’s code at that moment. Chat and Plan requests change nothing, so they save no version. Open Versions at the top of the project to see them, newest first, and click Restore to go back to one. Restoring replaces the current code; your app’s data (its users, bookings, orders) is not changed.
See Versions.
What is MonstarX Cloud?
Section titled “What is MonstarX Cloud?”Every app needs more than pages: somewhere to keep data, a way for people to sign in, emails, uploads. MonstarX Cloud gives each app all of this, ready to use, with nothing to set up and no keys to paste:
| Service | What your app gets |
|---|---|
| Database | Its own database. The preview and the published app use the same data. |
| User accounts | Sign-up, sign-in and password reset for the app’s users. |
Emails from the app’s own address, like your-app@monstarx.app. | |
| File storage | Uploaded photos and documents. |
| AI | Text, answers, images and web search inside the app. |
| Maps | Maps and pins, with no key needed. |
| Secrets | Encrypted keys for services you connect, never written into the code. |
You can see and manage all of it in the Backend tab, and swap in your own accounts where you prefer — for example Supabase for the database, or your own email domain. See MonstarX Cloud.
What happens behind the scenes?
Section titled “What happens behind the scenes?”| When you… | MonstarX… |
|---|---|
| Press Build it | Creates the project and starts your request on its servers at once. |
| Wait | Reads, writes and checks the app’s files on a secure cloud computer that runs the preview. |
| Close the tab | Keeps going. The result is waiting when you come back. |
| Send another request mid-build | Puts it in the queue; it starts when the build before it is done. Chat and Plan questions are answered right away, beside the build. |
| Finish a build | Saves a version, updates the project’s picture on your Projects page, and suggests what to build next. |
| Press Publish | Builds a production copy and puts it online. |
| Connect GitHub | Saves each change to your repository as a commit, and brings back edits made there on the next sync. |
Frequently asked questions
Section titled “Frequently asked questions”Does my computer need to stay on while MonstarX builds?
No. Builds run on MonstarX's servers. You can close the tab or turn off your computer, and see the result when you come back.
Can I see the code MonstarX writes?
Yes. The Code tab shows every file, and you can edit and save them. You can also export the project or save it to GitHub.
Is the preview the same as the published app?
It is the same app, but the published app only changes when you click Republish, while the preview changes with every build. Both use the same database.
Does restoring a version delete my app's data?
No. Restoring changes the code only. Users, bookings and other data in the app stay as they are.
What does MonstarX build apps with?
A standard, modern web stack: TanStack Start, React and TypeScript, with a SQL database. Any web developer can pick it up.