OpenDeepWiki Mermaid Diagram Generation: Required AI Models and Configuration

OpenDeepWiki relies exclusively on the ContentModel configuration setting—defaulting to gpt-5.2—to generate Mermaid diagram syntax during the document content generation phase.

OpenDeepWiki, maintained by the AIDotNet organization, is an open-source documentation generator that automates the creation of technical wiki content, including architecture and flow diagrams. Understanding which AI models power the OpenDeepWiki Mermaid diagram generation pipeline is essential for optimizing response quality, controlling API costs, and configuring self-hosted instances.

Which AI Model Powers OpenDeepWiki Mermaid Diagram Generation?

OpenDeepWiki creates Mermaid diagrams as part of the document-content generation step. The AI model responsible for producing the diagram syntax is the content-generation model defined in WikiGeneratorOptions.ContentModel.

In src/OpenDeepWiki/Services/Wiki/WikiGeneratorOptions.cs, the ContentModel property specifies which model handles all content generation tasks, including the required architecture and flow Mermaid diagrams:

// src/OpenDeepWiki/Services/Wiki/WikiGeneratorOptions.cs
public class WikiGeneratorOptions
{
    /// <summary>
    /// The AI model to use for document content generation.
    /// Default: gpt-5.2 (better quality for content generation).
    /// This model also produces the Mermaid diagram definitions.
    /// </summary>
    public string ContentModel { get; set; } = "gpt-5.2";
}

Configuring the Content Model for OpenDeepWiki Mermaid Diagram Generation

You can override the default gpt-5.2 model via appsettings.json, environment variables, or the admin UI. The configuration applies to all content generation, including Mermaid diagrams.

Using appsettings.json

Add the WikiGenerator section to your configuration file:

{
  "WikiGenerator": {
    "ContentModel": "gpt-4o-mini",
    "CatalogModel": "gpt-4o-mini"
  }
}

Using Environment Variables

Set the WIKI_CONTENT_MODEL variable before starting the service:

export WIKI_CONTENT_MODEL=gpt-4o-mini
dotnet run --project src/OpenDeepWiki/OpenDeepWiki.csproj

The mapping from environment variables to configuration options is handled in src/OpenDeepWiki/Services/Admin/SystemSettingDefaults.cs.

Other AI Models in the OpenDeepWiki Pipeline

OpenDeepWiki defines additional model settings that are not required for basic Mermaid diagram creation:

Model setting	Purpose	Required for Mermaid?
CatalogModel	Generates the repository catalog (folder and page structure).	No
ContentModel	Generates page content and Mermaid diagrams.	Yes
TranslationModel	Translates generated pages to additional languages.	Only if you need translated diagrams

If you run OpenDeepWiki in a multilingual setup, the ContentModel generates the diagram once. The TranslationModel then translates the surrounding text, leaving the Mermaid syntax unchanged (node IDs and labels remain as-is).

Source Code Implementation Details

The diagram generation logic resides in src/OpenDeepWiki/Services/Wiki/WikiGenerator.cs. This service calls the model defined in ContentModel via the ExecuteAgentWithRetryAsync method (around lines 24-30) when executing the content-generation prompt that produces Mermaid syntax.

Environment variable mapping is implemented in src/OpenDeepWiki/Services/Admin/SystemSettingDefaults.cs, ensuring that WIKI_CONTENT_MODEL properly overrides the default gpt-5.2 value in WikiGeneratorOptions.

Summary

• OpenDeepWiki uses the ContentModel configuration setting for all Mermaid diagram generation tasks.
• The default model is gpt-5.2, defined in src/OpenDeepWiki/Services/Wiki/WikiGeneratorOptions.cs.
• Configure the model via appsettings.json, the WIKI_CONTENT_MODEL environment variable, or the admin UI.
• CatalogModel and TranslationModel are not required for basic Mermaid diagram generation.

Frequently Asked Questions

What is the default AI model for OpenDeepWiki Mermaid diagram generation?

The default model is gpt-5.2, as specified in the ContentModel property of WikiGeneratorOptions.cs. This model handles all document content generation tasks, including the creation of Mermaid diagram syntax for architecture and flow charts.

Can I use a different model for Mermaid diagrams than for other content?

No. OpenDeepWiki uses a single ContentModel setting for all content generation, including Mermaid diagrams. You cannot specify a separate model exclusively for diagram generation without modifying the source code in WikiGenerator.cs where the ExecuteAgentWithRetryAsync method is called.

Do I need to configure a separate model for translating Mermaid diagrams?

No. The TranslationModel only translates the surrounding text content. Mermaid diagrams are generated once by the ContentModel and remain unchanged during translation, as the node IDs and syntax structure are preserved as-is. You only need the translation model if you require the surrounding documentation text in multiple languages.

How do I override the default model using environment variables?

Set the WIKI_CONTENT_MODEL environment variable before starting the service. This variable is mapped to WikiGeneratorOptions.ContentModel via SystemSettingDefaults.cs, overriding the default gpt-5.2 value. For example: export WIKI_CONTENT_MODEL=gpt-4o-mini.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}