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Agent Platform AI models

doc/user/duo_agent_platform/model_selection.md

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  • Tier: Premium, Ultimate
  • 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. For some features, you can select a different model, which persists until you change it.

Default models

This table lists the default model for each feature in the Agent Platform.

FeatureModel
GitLab Duo Agentic ChatClaude Sonnet 4.6 Vertex
Code Review FlowClaude Sonnet 4.6 Vertex
All other agentsClaude Sonnet 4.6 Vertex

Supported models

This table lists the models you can select for features in the Agent Platform.

ModelGitLab Duo Agentic ChatCode Review FlowAll other agents
Claude Fable 5 <sup>1</sup>{{< yes >}}{{< no >}}{{< yes >}}
Claude Sonnet 4.5{{< yes >}}{{< yes >}}{{< yes >}}
Claude Sonnet 4.6{{< yes >}}{{< yes >}}{{< yes >}}
Claude Haiku 4.5{{< yes >}}{{< no >}}{{< yes >}}
Claude Opus 4.5{{< yes >}}{{< no >}}{{< yes >}}
Claude Opus 4.6{{< yes >}}{{< no >}}{{< yes >}}
Claude Opus 4.7{{< yes >}}{{< no >}}{{< yes >}}
Claude Opus 4.8{{< yes >}}{{< no >}}{{< yes >}}
Gemini 3.5 Flash{{< yes >}}{{< no >}}{{< yes >}}
GPT-5{{< yes >}}{{< no >}}{{< yes >}}
GPT-5.1{{< yes >}}{{< no >}}{{< yes >}}
GPT-5.2{{< yes >}}{{< yes >}}{{< yes >}}
GPT-5.5 <sup>1</sup>{{< yes >}}{{< no >}}{{< yes >}}
GPT-5 Codex{{< yes >}}{{< no >}}{{< yes >}}
GPT-5.2 Codex{{< yes >}}{{< no >}}{{< yes >}}
GPT-5.3 Codex{{< yes >}}{{< yes >}}{{< yes >}}
GPT-5 Mini{{< yes >}}{{< no >}}{{< yes >}}
GPT-5.4 Mini{{< yes >}}{{< no >}}{{< yes >}}
GPT-5.4 Nano{{< yes >}}{{< no >}}{{< yes >}}

Footnotes:

  1. This model is subject to limited vendor-side data retention.

Select a model for a feature

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  • Offering: GitLab.com

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{{< history >}}

  • 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.
  • Introduced model selection for GitLab Duo Agent Platform in GitLab 18.4 with a flag called duo_agent_platform_model_selection. Disabled by default.
  • Generally available in GitLab 18.5. Feature flag ai_model_switching enabled.
  • Feature flag duo_agent_platform_model_selection enabled in GitLab 18.6.
  • Feature flag ai_model_switching removed in GitLab 18.7.
  • Feature flag duo_agent_platform_model_selection removed in GitLab 18.9.
  • LLM updated to Claude Sonnet 4.6 Vertex for Code Review Flow in GitLab 19.1.
  • Separate model selection from GitLab Duo Code Review introduced for Code Review Flow in GitLab 19.1, using the Agentic Code Review setting.
  • GPT-5.2 and GPT-5.3 Codex added as selectable models for Code Review Flow in GitLab 19.1.
  • Ability to restrict GitLab Duo Agentic Chat to specific models added in GitLab 19.1.

{{< /history >}}

You can select a model to be the default 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.

Select a model for Agentic Chat

To select a model for Agentic Chat:

  1. In the top bar, select Search or go to and find your group.

  2. In the left sidebar, select Settings > GitLab Duo.

  3. Select Configure features.

  4. Go to the GitLab Duo Agentic Chat section.

  5. Select a model from the dropdown list to set as the default model.

  6. Optional. To restrict what other models users can select for Agentic Chat:

    1. Under Available models, select Configure.
    2. In the Available models: Agentic Chat dialog, select the Restrict to specific models checkbox.
    3. Select the models that you want Agentic Chat to be able to use.
    4. Select Save.

    [!note] If you do not restrict Agentic Chat to specific models, users can choose from all GitLab-managed models.

Select a model for a non-Agentic Chat feature

To select a model for a non-Agentic Chat feature:

  1. In the top bar, select Search or go to and find your group.
  2. In the left sidebar, select Settings > GitLab Duo.
  3. Select Configure features.
  4. Go to the GitLab Duo Agent Platform section.
  5. Select a model from the dropdown list to set as the default model.
  6. Optional. To apply the model to all features in the section, select Apply to all.

To specify a model for the GitLab Duo CLI, see select a model.

Selecting the right model

For many use cases, starting with a faster, more cost-effective model like Claude Haiku 4.5 or GPT-5.4 Mini can be the optimal approach. For this approach:

  1. Select Claude Haiku 4.5 or GPT-5.4 Mini.
  2. Test your use case thoroughly.
  3. Evaluate if performance meets your requirements.
  4. Upgrade only if necessary for specific capability gaps.

You can use this approach for the following:

  • Exploratory or high-volume tasks
  • Applications with strict latency requirements
  • Cost-sensitive implementations

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 indicates that you need to set a default GitLab Duo namespace.

This issue occurs when you belong to multiple GitLab Duo namespaces or work on a project locally that does not have a GitLab remote configured.

To resolve this, set a default GitLab Duo namespace.

Model selection for Agentic Chat in IDEs does not work

When selecting a model for Agentic Chat in your IDE, you might find that model selection does not work.

To resolve this:

  1. Check that the connection type for your IDE is set to WebSocket.
  2. Ask your network administrator to make sure WebSocket traffic to your GitLab instance is allowed.