Custom Docker image for Cloud Agent Environment doesn't work at all

[laniakealandscape (Sasha)]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

When I trying to use custom Dockerfile in Cloud Agent Setup it does not work.
When I press “Use Custom Dockerfile” button in Cloud Agent Setup UI whole setup window closing and nothing else happen.
If I try to use something like

{
  "build": {
    "dockerfile": "./Dockerfile.nix",
    "context": ".."
  },
  "terminals": []
}

Cursor still using default ubuntu image

Steps to Reproduce

• Cmd + Shift + P; Cursor: Start Cloud Agent Setup
• Press “Use Custom Dockerfile”

• Put in environment.json something like

{
  "build": {
    "dockerfile": "./Dockerfile.nix",
    "context": ".."
  },
  "terminals": []
}

• Build environment
• On validation step type in terminal whoami

Expected Behavior

1. Something but not just closing setup window
2. Username from my Dockerfile, but not ubuntu

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.0.77 (Universal)
VSCode Version: 1.99.3
Commit: ba90f2f88e4911312761abab9492c42442117cf0
Date: 2025-11-13T23:10:43.113Z
Electron: 37.7.0
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Darwin arm64 25.2.0

Additional Information

As a feedback I can say that whole custom cloud agent environment setup is buggy and incomplete

Does this stop you from using Cursor

No - Cursor works, but with this issue

[deanrie]

Hey, thanks for the report. The Cloud Agent custom Dockerfile currently has limited debugging capabilities, and the team is working on improvements.

A community member found a workaround that might help:

• Place both environment.json and Dockerfile in the .cursor/ directory
• Install sudo in your Dockerfile
• Grant execute permissions to scripts in bin/ (for example, bundle, rails, setup, etc.)

The thread with the solution is here.

The team knows the current UX needs improvement. Please try the workaround and let us know if it helps.