GitLab Duo in merge requests

GitLab Duo is designed to provide contextually relevant information during the lifecycle of a merge request.

Generate a description by summarizing code changes

When you create or edit a merge request, use GitLab Duo Merge Request Summary to create a merge request description.

1. Create a new merge request.

2. In the Description field, put your cursor where you want to insert the description.

3. On the toolbar above the text area, select Summarize code changes ( ).

   

The description is inserted where your cursor was.

Watch an overview

Provide feedback on this feature in issue 443236.

Data usage: The diff of changes between the source branch’s head and the target branch is sent to the large language model.

Use GitLab Duo to review your code

GitLab Duo can review your merge request for potential errors and provide feedback on alignment to standards.

Add GitLab Duo as a reviewer using one of:

• GitLab Duo Code Review (Classic): The classic code review functionality.
• Code Review Flow: The new flow available through the GitLab Duo Agent Platform. Offers improved context awareness and agentic capabilities.

The two options have different requirements and prerequisites. However, you request a review and interact with GitLab Duo the same way. Both options also support automatic reviews, custom instructions, and custom comments.

GitLab Duo Code Review (Classic)

When your merge request is ready to be reviewed, use GitLab Duo Code Review (Classic) to perform an initial review:

1. On the top bar, select Search or go to and find your project.
2. Select Code > Merge requests and find your merge request.
3. In a comment box, enter the quick action /assign_reviewer @GitLabDuo, or assign GitLab Duo as reviewer.

Watch an overview

Provide feedback on this feature in issue 517386.

Data usage: When you use this feature, the following data is sent to the large language model:

• Merge request title
• Merge request description
• File contents before changes applied (for context)
• Merge request diffs
• Filenames
• Custom instructions

Code Review Flow

The Code Review Flow is available through the GitLab Duo Agent Platform and uses agentic AI for enhanced review capabilities.

After you enable the flow, you can assign GitLab Duo as a reviewer.

For setup and requirements, see Code Review Flow.

Interact with GitLab Duo in reviews

You can mention @GitLabDuo in comments to interact with GitLab Duo on your merge request. You can ask follow-up questions on its review comments, or ask questions on any discussion thread in your merge request.

Interactions with GitLab Duo can help to improve the suggestions and feedback as you work to improve your merge request.

Feedback provided to GitLab Duo does not influence later reviews of other merge requests. There is a feature request to add this functionality, see issue 560116.

Automatic reviews from GitLab Duo for a project

Automatic reviews from GitLab Duo ensure that all merge requests in your project receive an initial review. After a merge request is created, GitLab Duo reviews it unless:

• It’s marked as draft. For GitLab Duo to review the merge request, mark it ready.
• It contains no changes. For GitLab Duo to review the merge request, add changes to it.

Prerequisites:

• You must have at least the Maintainer role in a project.

To enable @GitLabDuo to automatically review merge requests:

1. On the top bar, select Search or go to and find your project.
2. Select Settings > Merge requests.
3. In the GitLab Duo Code Review section, select Enable automatic reviews by GitLab Duo.
4. Select Save changes.

Automatic reviews from GitLab Duo for groups and applications

Use group or application settings to enable automatic reviews for multiple projects.

Prerequisites:

• To turn on automatic reviews for groups, have the Owner role for the group.
• To turn on automatic reviews for all projects, be an administrator.

To enable automatic reviews for groups:

1. On the top bar, select Search or go to and find your group.
2. Select Settings > General.
3. Expand the Merge requests section.
4. In the GitLab Duo Code Review section, select Enable automatic reviews by GitLab Duo.
5. Select Save changes.

To enable automatic reviews for all projects:

1. In the upper-right corner, select Admin.
2. Select Settings > General.
3. In the GitLab Duo Code Review section, select Enable automatic reviews by GitLab Duo.
4. Select Save changes.

Settings cascade from application to group to project. More specific settings override broader ones.

Customize review instructions for GitLab Duo

You can create custom MR review instructions to ensure consistent and specific code review standards in your project.

Both GitLab Duo Code Review (Classic) and Code Review Flow support custom code review instructions.

For more information, see customize review instructions for GitLab Duo

Summarize a code review

When you’ve completed your review of a merge request and are ready to submit your review, use GitLab Duo Code Review Summary to generate a summary of your comments.

1. On the top bar, select Search or go to and find your project.
2. Select Code > Merge requests and find the merge request you want to review.
3. When you are ready to submit your review, select Finish review.
4. Select Add Summary.

The summary is displayed in the comment box. You can edit and refine the summary before you submit your review.

Watch an overview

Provide feedback on this experimental feature in issue 408991.

Data usage: When you use this feature, the following data is sent to the large language model:

• Draft comment’s text

Generate a merge commit message

When preparing to merge your merge request, edit the proposed merge commit message by using GitLab Duo Merge Commit Message Generation.

1. On the top bar, select Search or go to and find your project.
2. Select Code > Merge requests and find your merge request.
3. Select the Edit commit message checkbox on the merge widget.
4. Select Generate commit message.
5. Review the commit message provided and choose Insert to add it to the commit.

Watch an overview

Data usage: When you use this feature, the following data is sent to the large language model:

• Contents of the file
• The filename

Related topics

• Control GitLab Duo availability
• All GitLab Duo features

Troubleshooting

When working with GitLab Duo in Merge Requests, you might encounter the following issues.

Response not received

If you ask GitLab Duo for a review by mentioning or replying to @GitLabDuo, and do not receive a response, this might be because you do not have the appropriate GitLab Duo add-on.

To check your GitLab Duo add-on, ask your group Owner to check the group’s GitLab Duo seat assignments.

To change your GitLab Duo add-on, contact your administrator.

Unable to assign GitLab Duo to review

If you cannot assign GitLab Duo as a reviewer, it might be because you do not have the appropriate GitLab Duo add-on.

To check your GitLab Duo add-on, ask your group Owner to check the group’s GitLab Duo seat assignments.

To change your GitLab Duo add-on, contact your administrator.

Error: GitLab Duo Code Review was not automatically added...

If you try to create a merge request with automatic reviews from GitLab Duo turned on, you might get the following error message:

GitLab Duo Code Review was not automatically added because your account requires
GitLab Duo Enterprise. Contact your administrator to upgrade your account.

Contact your administrator to ask them to purchase a GitLab Duo Enterprise seat and assign it to you.