fallback behaviour

docs/features/workspace/models.md

@@ -25,6 +25,7 @@ Both actions lead to the same Model Builder interface, where you can configure t
 - **Avatar Photo**: Upload a custom image to represent your model in the chat interface.
 - **Model Name & ID**: The display name and unique identifier for your custom preset (e.g., "Python Tutor" or "Meeting Summarizer").
 - **Base Model**: The actual model beneath the hood that powers the agent. You can choose *any* model connected to Open WebUI. You can create a custom preset for `gpt-4o` just as easily as `llama3`.
+  - **Fallback Behavior**: If the configured Base Model is unavailable and the `ENABLE_CUSTOM_MODEL_FALLBACK` environment variable is set to `True`, the system will automatically fall back to the first configured default model (set in Admin Panel > Settings > Models > Default Models). This ensures mission-critical custom models remain functional even if their specific base model is removed or temporarily unavailable.
 - **Description**: A short summary of what the model does.
 - **Tags**: Add tags to organize models in the selector dropdown.
 - **Visibility & Groups**:

docs/getting-started/env-configuration.mdx

@@ -206,6 +206,12 @@ If you are running larger instances, you WILL NEED to set this to a higher value
 
 :::
 
+#### `ENABLE_CUSTOM_MODEL_FALLBACK`
+
+- Type: `bool`
+- Default: `False`
+- Description: Controls whether custom models should fall back to a default model if their assigned base model is missing. When set to `True`, if a custom model's base model is not found, the system will use the first model from the configured `DEFAULT_MODELS` list instead of returning an error.
+
 #### `MODELS_CACHE_TTL`
 
 - Type: `int`