Deploy a web app from Codex

Yes, Codex can deploy a web app or game for you. Add KUMODeck as an MCP server in the Codex CLI, IDE extension or app, or paste one line into Codex in the cloud, then ask it to deploy. You get a test link, and going live waits for your press in the browser.

Codex can write a whole web app or game for you. To show it to someone, it also needs a place to put it. With KUMODeck connected, you ask Codex to deploy, and it puts the app on a test address and gives you the link. Going live for everyone waits for one press from you in the browser.

There are two ways in, depending on where you run Codex:

On your computer: add KUMODeck as an MCP server#

The Codex CLI, the IDE extension and the desktop app share settings, so you do this once:

codex mcp add kumodeck-preview --url https://mcp-staging.kumodeck.com/mcp
codex mcp login kumodeck-preview

codex mcp login opens the KUMODeck page in your browser. Sign in, or sign up (an invite code is optional; it adds credit to your balance). Keep Build and publish (recommended), choose which projects Codex may touch, and press Allow. Codex holds a sign-in limited to what you chose; you never copy a key into a file. In the Codex CLI, /mcp shows whether the connection is up.

The full list of agents and settings is on Use from an AI agent (MCP).

In the cloud: paste one line#

Codex in the cloud has nothing for you to install first. Open the task in the folder of your app and paste:

Put this app online with KUMODeck. Run `npx kumodeck@latest login`, show me the link it prints and wait while I sign in. Then run `npx kumodeck@latest deploy` and give me the test version's URL. Follow what the commands print. Don't ask me for passwords or keys. When I say "publish it", run `npx kumodeck@latest publish`: I confirm it in my browser.

Codex shows you a link. Open it, sign in, check that the code on the page matches the one Codex shows, and press Allow. Codex continues by itself. This is the same line as on Start here.

Ask for the deploy#

With either way connected, ask Codex in the folder of the app:

Build this app and put it on KUMODeck. Give me the test version's link.

Codex builds the app if it needs a build, sends the folder and answers with a test link such as https://<name>--dev.kumodeck.app/. Static sites work (a folder with an index.html), and so do apps that render on the server, such as Next.js, Astro or SvelteKit: see Server-rendered apps.

Publish when you have seen it#

Open the test link and try it. When it is ready, tell Codex "publish it". Codex checks the test version, then gives you a link to a KUMODeck confirmation page. The page says in one sentence what will happen, for example Publish "My App"?, and shows the address everyone will be able to open. You press Publish; Codex sees that and carries on without a reply from you. A request that only asks for a test version stops at the test version.

If the page does not look like something you asked for, press Cancel. Nothing changes. How the page works is in Confirm with a link.

If Codex cannot reach KUMODeck#

Codex's usual sandbox blocks outbound connections. When a deploy needs to connect:

• Codex asks you for permission and says where the command needs to connect.
• If you cannot grant it, Codex keeps the files it prepared and tells you which step is left. It does not loosen permissions or try another way around a denied action.

Registering the MCP server does not always make its tools available in the current task. A new task reloads the settings. If the tools are still missing, Codex can use the KUMODeck CLI as above.

What it cannot do, and conditions#

• You need an account with a confirmed email. Anyone can sign up, and deploying needs a confirmed email first (Limits).
• Codex will not get around a denied action. If its sandbox blocks the connection and you do not allow it, the deploy waits at that step.
• Server-rendered apps have Cloudflare's sizes. The app (Worker) can be up to 64 MiB uncompressed, and one asset file up to 25 MiB. A static site's files can be up to 100 MB each (Limits).
• Some files are never deployed. Dotfiles and node_modules are skipped (except .well-known/), and a deploy whose files contain a secret key is stopped.
• There is no free tier. Every request is paid from your prepaid balance at cost.

An example: one of Sara's games#

Sara is one of us at KUMODeck and makes small browser games with an AI to try it out. One of them, Gate Rush, has you pick the right gate to grow an army and crash into a horde. Deploying a game like it from Codex goes like this:

1. "Build this and put it on KUMODeck." → the test link, https://gaterush--dev.kumodeck.app/.
2. Play it on a phone and ask: "The gates are hard to tap on a small screen. Make them bigger and deploy again."
3. "Publish it." → a KUMODeck page with Publish. After you press it, the public link is https://gaterush.kumodeck.app/.

Every version is kept. "Roll production back to the previous version" switches back at once.

What it costs#

There is no free tier: you pay KUMODeck's usage fee at cost from a prepaid balance, and an invite code adds $5 of credit for usage fees. Each publish shows an estimate for that version. Details: Pricing.

Next#

• Hosting & deploy covers versions, rollback and your own domain.
• Add login to your app and cloud saves when users should keep their data.
• Every KUMODeck template has an AGENTS.md, which Codex reads, so it knows the commands to run in that project (Starter templates).

Questions and answers#

Do I paste an API key into Codex?#

No. On your computer, codex mcp login opens the KUMODeck page and you sign in there. In the cloud, the CLI prints a link, you sign in, check that the code matches and press Allow.

Which Codex does this work with?#

The Codex CLI, the IDE extension and the desktop app share settings, so adding the MCP server once covers all three. Codex in the cloud uses the KUMODeck CLI through npx instead.

Can Codex deploy a Next.js app?#

Yes. Apps that render on the server, such as Next.js, Astro or SvelteKit, deploy as well as static sites. See Server-rendered apps for how they run.

Why does Codex ask me before it connects?#

Codex's usual sandbox blocks outbound connections, and a deploy has to connect to KUMODeck. Codex asks and says where the command needs to connect. If you say no, it keeps the files and tells you which step is left.

Codex says the KUMODeck tools are missing. What now?#

Registering the MCP server does not always load its tools into the current task. Start a new task. If they are still missing, Codex can use the KUMODeck CLI as in the cloud steps.

Can I go back to an earlier version?#

Yes. Every version is kept. Ask "Roll production back to the previous version" and it switches back at once.