GitLab Duo AI models

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• Tier: Premium, Ultimate
• Add-on: GitLab Duo Core, Pro or Enterprise
• Offering: GitLab.com, GitLab Self-Managed, GitLab Dedicated

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Every GitLab Duo feature uses a default model. GitLab might update default models to optimize performance. You can select a different model for a feature, which persists until you change it.

Default models

The following table lists the default model for each GitLab Duo feature.

Feature	Model
Code Suggestions
Code Generation	Claude Sonnet 4 Vertex
Code Completion	Codestral 25.08 Fireworks
GitLab Duo Chat
General Chat	Claude Sonnet 4.5 Vertex
Code Explanation	Claude Sonnet 4
Test Generation	Claude Sonnet 4.5 Vertex
Refactor Code	Claude Sonnet 4.5 Vertex
Fix Code	Claude Sonnet 4.5 Vertex
Root Cause Analysis	Claude Sonnet 4 Vertex
GitLab Duo for merge requests
Merge Commit Message Generation	Claude Sonnet 4 Vertex
Merge Request Summary	Claude Sonnet 4 Vertex
Code Review Summary	Claude Sonnet 4 Vertex
Code Review	Claude Sonnet 4.6 Vertex
Other GitLab Duo features
Vulnerability Explanation	Claude Sonnet 4.5 Vertex
Vulnerability Resolution	Claude Sonnet 4.5
Discussion Summary	Claude Sonnet 4.5 Vertex
GitLab Duo for CLI	Claude Haiku 4.5

Supported models

The following tables list the models you can select for each feature.

Code Suggestions

Model	Code Generation	Code Completion
Claude Sonnet 4	{{< yes >}}	{{< yes >}}
Claude Sonnet 4 Vertex	{{< yes >}}	{{< yes >}}
Claude Sonnet 4 Bedrock	{{< yes >}}	{{< yes >}}
Claude Sonnet 4.5	{{< yes >}}	{{< yes >}}
Codestral 25.01 Fireworks	{{< no >}}	{{< yes >}}
Codestral 25.08 Fireworks	{{< no >}}	{{< yes >}}
Codestral 25.08 Vertex	{{< no >}}	{{< yes >}}
Gemini 2.5 Flash Vertex	{{< yes >}}	{{< no >}}

GitLab Duo Non-Agentic Chat

Model	General Chat	Code Explanation	Test Generation	Refactor Code	Fix Code	Root Cause Analysis
Claude Haiku 4.5	{{< yes >}}	{{< no >}}			{{< no >}}
Claude Sonnet 3	{{< no >}}			{{< no >}}		{{< yes >}}
Claude Sonnet 4	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4 Vertex	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4.5	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4.5 Vertex	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}

GitLab Duo for merge requests

Model	Merge Commit Message Generation	Merge Request Summary	Code Review Summary	Code Review
Claude Sonnet 4	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4 Vertex	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4.5	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}

Other GitLab Duo features

Model	Vulnerability Explanation	Vulnerability Resolution	GitLab Duo for CLI	Discussion Summary
Claude Haiku 3	{{< yes >}}	{{< no >}}	{{< yes >}}	{{< no >}}
Claude Haiku 4.5	{{< no >}}		{{< yes >}}	{{< no >}}
Claude Sonnet 4		{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4 Vertex	{{< yes >}}		{{< yes >}}	{{< yes >}}
Claude Sonnet 4.5	{{< yes >}}	{{< yes >}}	{{< yes >}}	{{< yes >}}
Claude Sonnet 4.5 Vertex	{{< yes >}}			{{< yes >}}

Select a model for a feature

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• Offering: GitLab.com

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• Introduced for top-level groups in GitLab 18.1 with a flag named ai_model_switching. Disabled by default.
• Changed to beta in GitLab 18.4.
• Enabled in GitLab 18.4.
• Generally available in GitLab 18.5. Feature flag ai_model_switching enabled.
• Feature flag ai_model_switching removed in GitLab 18.7.

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You can select a model for a feature in a top-level group. The model that you select applies to that feature for all child groups and projects.

Prerequisites:

• You have the Owner role for the group.
• The group that you select models for is a top-level group.
• In GitLab 18.3 or later, if you belong to multiple GitLab Duo namespaces, you must assign a default namespace.

To select a model for a feature:

1. In the top bar, select Search or go to and find your group.
2. Select Settings > GitLab Duo.
3. Select Configure features.
4. For the feature you want to configure, select a model from the dropdown list.
5. Optional. To apply the model to all features in the section, select Apply to all.

Troubleshooting

When selecting models other than the default, you might encounter the following issues.

Model is not available

If you are using the default GitLab model for a GitLab Duo AI-native feature, GitLab might change the default model without notifying the user to maintain optimal performance and reliability.

If you have selected a specific model for a GitLab Duo AI-native feature, and that model is not available, there is no automatic fallback. The feature that uses this model is unavailable.

No default GitLab Duo namespace

When using a GitLab Duo feature with a selected model, you might get an error that states that you have not selected a default GitLab Duo namespace. For example, on:

• GitLab Duo Code Suggestions, you might get Error 422: I'm sorry, you have not selected a default GitLab Duo namespace. Please go to GitLab and in user Preferences - Behavior, select a default namespace for GitLab Duo.
• GitLab Duo Chat, you might get Error G3002: I'm sorry, you have not selected a default GitLab Duo namespace. Please go to GitLab and in user Preferences - Behavior, select a default namespace for GitLab Duo.

This issue occurs when you belong to multiple GitLab Duo namespaces, but have not chosen one as your default namespace.

To resolve this, set a default GitLab Duo namespace.