GPT-5 models not appearing in Model Configuration dropdown

Summary

GPT-5, GPT-5 Mini, and GPT-5 Codex models are not visible in the Model Configuration dropdown under Admin Area > GitLab Duo > Model Configuration > Code Suggestions, despite documentation indicating these models should be available.

Environment

• GitLab Version: 18.5.1 (Self-Managed)
• GitLab Edition: Enterprise Edition
• Configuration Type: GitLab-managed models (not self-hosted)
• Location: Admin Area > GitLab Duo > Model Configuration > AI-native features tab

Expected Behavior

According to the GitLab documentation on supported models, GPT-5 should be available in the dropdown

Actual Behavior

When navigating to:

1. Admin Area > GitLab Duo > Model Configuration
2. AI-native features tab
3. Code Suggestions > Code Generation (or Code Completion)
4. Model dropdown

Only Claude and other models are visible. GPT models are not visible

Steps to Reproduce

1. Navigate to Admin Area (left sidebar, bottom)
2. Select "GitLab Duo"
3. Click "Model Configuration"
4. Go to "AI-native features" tab
5. Expand "Code Suggestions" section
6. Click the "Model" dropdown for "Code Generation" or "Code Completion"
7. Observe available models

Impact

Unable to select or test GPT-5 models for Code Suggestions features despite documentation indicating availability, limiting model selection options for enterprise customers.