# Admin Models Auto Model Fix

## Summary
Fixed two issues with the admin models page related to the auto model setting for hobby/free plan users:

1. **Added missing UI**: Created the UI elements for setting the auto model for hobby/free plan users
2. **Fixed model selection logic**: Ensured that paid plan users can select their own models without the auto model setting interfering

## Changes Made

### 1. Frontend - admin.html
**File**: `/home/engine/project/chat/public/admin.html`

Added a new card section for configuring the auto model for hobby/free plan users:
- Form: `auto-model-form`
- Select dropdown: `auto-model-select`
- Status display: `auto-model-status`

The UI explains that this setting only affects hobby/free plan users, while paid plan users can select their own models.

### 2. Backend - server.js
**File**: `/home/engine/project/chat/server.js`

Modified the `resolvePlanModel()` function to fix the model selection logic:

**Previous Behavior**:
- For paid plans, if configured models existed, it would always return the first configured model, ignoring user selections

**New Behavior**:
- **For hobby/free plan users**: 
  - Uses the admin-configured `freePlanModel` setting when no specific model is requested
  - Still allows them to explicitly request specific models if they have a valid tier
  
- **For paid plan users**:
  - Always respects the user's model selection
  - If user requests a model (even without a tier), uses it
  - Only falls back to first configured model if user doesn't request anything or requests 'auto'

## Test Results

Created comprehensive tests (`test_model_resolution.js`) that verify:

✓ Hobby users get the auto model when no specific request  
✓ Hobby users get the auto model when requesting 'auto'  
✓ Hobby users can explicitly request other models  
✓ Paid users always get their requested model  
✓ Paid users can request models without tiers  
✓ Paid users get first configured model when no request  
✓ Paid users get first configured model when requesting 'auto'  

All 8 test cases pass.

## Technical Details

### Model Resolution Flow

1. **Explicit model with tier (not 'auto')**: Return requested model immediately
2. **Hobby/Free plan**:
   - Check admin's `freePlanModel` setting
   - Fall back to first configured model
   - Fall back to default model
3. **Paid plan**:
   - If specific model requested (not 'auto'), use it
   - Otherwise use first configured model
   - Fall back to default model

### API Integration

The feature integrates with existing API endpoints:
- **GET** `/api/admin/plan-settings` - Retrieves current settings including `freePlanModel`
- **POST** `/api/admin/plan-settings` - Saves the `freePlanModel` setting

### JavaScript Integration

The admin.js file already had all the necessary handlers:
- `populateAutoModelOptions()` - Populates the dropdown with available models
- Form submission handler at lines 1515-1532
- Proper element references at lines 38-40

## User Impact

### For Admins
- New UI section in Admin Panel → Build models page
- Can configure which model hobby/free users automatically use
- Clear indication that paid users can choose their own models

### For Hobby/Free Plan Users
- Automatically assigned the admin-configured model
- Can still explicitly select other models if available

### For Paid Plan Users
- Full control over model selection
- Their choices are always respected
- Auto model setting does not affect them
