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This guide walks you through setting up and using cubic’s AI code reviewer for the first time. By the end, you’ll know how to install the app, trigger reviews, interact with AI comments, and set up custom agents.

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1. Install the cubic GitHub App

1

Sign up

Go to cubic.dev/sign-up and sign in with your GitHub account.
2

Authorize GitHub and start your free trial

Authorize cubic to access the repositories you want to review. You’ll get 14 days free, no credit card required.

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Share with your team

Copy and paste this message into Slack after you install cubic: 
We've just enabled cubic on our repositories: https://cubic.dev

cubic is the top-ranked AI code reviewer on Code Review Bench.

What to expect:

- cubic will automatically review new PRs on GitHub and leave comments when it finds issues
- You can reply to cubic's comments to ask questions and give feedback so it learns over time
- When cubic flags an issue on GitHub, it can generate a prompt you can paste into your coding agent to help fix it
- If you want a faster inner loop, install the cubic CLI to run lightweight reviews locally: https://docs.cubic.dev/ide/cli-review

Learn more about the benchmark: https://www.cubic.dev/blog/cubic-is-the-best-ai-code-reviewer-on-martian-s-benchmark

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2. Trigger your first review

To get your first AI review, you have two options: Option 1: Open a new pull request cubic automatically reviews new pull requests within a few minutes. 
git checkout -b feature/my-feature
# Make some changes
git add .
git commit -m "Add new feature"
git push origin feature/my-feature
Open the PR on GitHub, and cubic will automatically start the review. Option 2: Tag cubic in an existing PR For existing pull requests, add a comment tagging @cubic-dev-ai to trigger a review. cubic will start within a few minutes. What you’ll see:
  • A comment from @cubic-dev-ai with the PR summary
  • Inline comments on specific code changes pointing out bugs and improvements
  • Actionable suggestions with explanations

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3. Interact with cubic

You can reply to cubic, provide feedback, and request changes.
1

Ask follow-up questions

Reply to any AI comment to ask for clarification:
@cubic-dev-ai Can you explain why this is a concern?
The AI will respond with more context.
2

Provide feedback

Help cubic learn by reacting to comments:
  • Thumbs up if the suggestion is helpful
  • Thumbs down if it’s not relevant
cubic remembers your feedback and improves over time.
3

Request fixes

Ask cubic to generate a fix:
@cubic-dev-ai Can you fix this?
If background agents are enabled, cubic can automatically apply the fix.
You can also ask cubic to explain code directly in PR comments, for example @cubic-dev-ai explain this function.

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4. Use cubic in your editor

Once the GitHub review flow is working, add cubic to your coding agent so you can fix PR issues without leaving the editor and optionally add local reviews later.

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5. Set up your first custom agent

Custom agents are review rules that enforce team-specific standards. Let’s create a simple one.
1

Navigate to custom agents

  1. Go to cubic.dev/dashboard
  2. Select your repository
  3. Click Custom Agents in the sidebar
2

Create a rule

Click New Rule and define it using natural language:Example rule:
All API endpoints must include error handling with try-catch blocks
You can also use code patterns:
Avoid using `any` type in TypeScript function parameters
3

Test the rule

Open a new PR that violates the rule. cubic will flag it:
// This will trigger the rule
function apiCall(data: any) {
  return fetch('/api', { body: data })
}
cubic will comment: “This function parameter uses any type, which violates the custom agent.”
For more advanced rule configurations, see Custom review rules.

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6. Use background agents

Background agents automatically fix issues without manual intervention.
1

Enable background agents

In your repository settings on cubic.dev, enable Background Agents.
2

Trigger a fix

When cubic identifies an issue, you can request a fix by clicking the Fix with cubic button in the GitHub comment, or by tagging cubic:
@cubic Please fix this
Use any supported cubic tag in the current comment when you want cubic to edit code:
  • @cubic Please fix this
  • @cubic-dev-ai Please fix this
  • @cubic open a fix PR
Replying inside an existing cubic thread without a fresh cubic tag is treated as discussion, not permission to push changes.
By default, cubic pushes commits to your PR branch. If you want a separate PR instead, include “open a fix PR.”cubic will:
  1. Generate the fix
  2. Push commits to your PR branch by default, or open a fix PR when requested
  3. Update the comment with the result
3

Review the fix

Check the new commit to verify the changes. You can always:
  • Request modifications
  • Revert the commit if needed
  • Provide feedback for future fixes

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7. Explore PR summaries

cubic automatically generates PR descriptions based on your code changes. When you create a PR, cubic will:
  1. Analyze the diff
  2. Generate a summary including:
    • What changed
    • Why it changed
    • Potential impacts
  3. Post it as the first comment
You can also request a summary update: 
@cubic-dev-ai update the PR summary

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What’s next?

Now that you’ve experienced the basics, explore more features:
Have questions? Check out the FAQ section or contact support.