How to make cloud to pick up my Dockerfile?

Support Help
1

I pushed an environment.json


{
 "build": {
 "dockerfile": "Dockerfile",
 "context": ".."
},
"install": "bash .cursor/cloud-agent-install.sh",
"start": "bash .cursor/cloud-agent-start.sh",
"terminals": [
 {
  "name": "Convex",
  "command": "pnpm exec convex dev"
 },
 {
  "name": "App",
  "command": "pnpm dev",
  "ports": [
    3000
   ]
  }
 ]
}

cloud detects environment. but I only have 1 button - start agent setup. And when I click it - the agent is able to set up the env, but it does not do anything with Docker at all. I want to use node24 image, but agent detects it is 22 and then goes circles installing v24 via nvm instead of using the Docker image. How it should work? I dont understand how to use docker setup at all. Please help

5

Hey, thanks for the request. Two different environment setup modes got mixed up here, and that’s why it’s confusing.

There are two mutually exclusive options:

  1. Interactive snapshot
    This is the Set up agent or Start agent setup button. Cursor starts a base Ubuntu image with Node 22, then the agent installs dependencies interactively, which is why it uses nvm to get to 24. After that it offers to save a snapshot. This mode completely ignores build.dockerfile, so it looks like nothing happens with Docker.

  2. Dockerfile mode
    For this one, you don’t need to click Set up agent. Just commit .cursor/environment.json with your build block plus .cursor/Dockerfile, then start a normal cloud agent on this repo and branch. The image will be built from the Dockerfile automatically.

What to double check in your config:

  • File location. Paths in build are resolved relative to .cursor. So "dockerfile": "Dockerfile" means .cursor/Dockerfile, the file must physically be there. "context": ".." points to the repo root, that’s fine.
  • Your Dockerfile must install git and ideally sudo. Cloud Agent runs git clone inside the container, and a custom image without git fails with a clone error. Add something like RUN apt-get update && apt-get install -y git sudo.
  • Don’t COPY the project into the image. Cursor will fetch the right commit itself.
  • If you previously saved a snapshot for this repo in Dashboard > Environments, it overrides the Dockerfile and keeps restoring. Delete the saved environment to force a fresh Dockerfile build.

More details on both modes: Cloud Environment Setup | Cursor Docs

Let me know how it goes after deleting the snapshot and confirming git is installed in the image.