> ## Documentation Index
> Fetch the complete documentation index at: https://dev-doc.dualmindlab.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# GET /api/settings/feature-flag/{key}

> Get feature flag status

## Authentication

**Not Required**: `[AllowAnonymous]` (Line 31)

Feature flags are public

## Path Parameters

<ParamField path="key" type="string" required>
  Feature flag key

  **Validation** (Lines 36-44):

  ```csharp theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  if (string.IsNullOrWhiteSpace(key)) {
      return BadRequest("Feature flag key is required");
  }
  ```

  **Known Keys**:

  * `public_sharing`: Enables public/unlisted thread access

  **Unknown Keys**: Default behavior not enforced by server contract (service returns false assumed)
</ParamField>

## Response

<ResponseField name="key" type="string">
  Echo of requested feature flag key (Line 50)
</ResponseField>

<ResponseField name="enabled" type="boolean">
  Feature flag status (Line 51)

  **Values**:

  * `true`: Feature enabled
  * `false`: Feature disabled or doesn't exist
</ResponseField>

<RequestExample>
  ```bash cURL theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  curl -X GET 'http://localhost:5079/api/settings/feature-flag/public_sharing'
  ```

  ```javascript JavaScript theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  const response = await fetch(
    'http://localhost:5079/api/settings/feature-flag/public_sharing'
  );
  const flag = await response.json();
  ```

  ```python Python theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  import requests
  response = requests.get(
      'http://localhost:5079/api/settings/feature-flag/public_sharing'
  )
  flag = response.json()
  ```
</RequestExample>

<ResponseExample>
  ```json 200 Success (Enabled) theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  {
    "key": "public_sharing",
    "enabled": true
  }
  ```

  ```json 200 Success (Disabled) theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  {
    "key": "public_sharing",
    "enabled": false
  }
  ```

  ```json 400 INVALID_REQUEST theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  {
    "success": false,
    "error": "Feature flag key is required",
    "code": "INVALID_REQUEST"
  }
  ```

  ```json 500 SETTINGS_ERROR theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
  {
    "success": false,
    "error": "Database query failed",
    "code": "SETTINGS_ERROR"
  }
  ```
</ResponseExample>

## Side Effects

**Database Reads** (Line 46):

```csharp theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
var enabled = await _settingsService.GetFeatureFlagAsync(key);
```

**Tables Read**:

* `system_settings` table

**Query**:

```sql theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
SELECT value FROM system_settings WHERE key = {key}
```

**No Database Writes**: Read-only endpoint

## Authorization

**Public Access**: No authentication required

**Security**: Feature flag keys/values visible to anyone

## Permissions

**Who Can Read**: Anyone (unauthenticated access allowed)

## Edge Cases

1. **Empty key**: 400 error (Lines 36-44)
2. **Whitespace-only key**: 400 error (Lines 36-44)
3. **Unknown key**: Returns `false` (service-level default, not enforced by server contract)
4. **Null key**: 400 error
5. **Case sensitivity**: Not enforced by server contract (service-dependent)

## Error Conditions

| Code              | HTTP | Cause                     | Controller Line |
| ----------------- | ---- | ------------------------- | --------------- |
| `INVALID_REQUEST` | 400  | Key null/empty/whitespace | 36-44           |
| `SETTINGS_ERROR`  | 500  | Service exception         | 54-62           |

**Exception Handling** (Lines 54-62):

```csharp theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
catch (Exception ex) {
    return StatusCode(500, new { error = ex.Message, code = "SETTINGS_ERROR" });
}
```

## Behavioral Guarantees

**Default Value**: `false` for unknown keys (service-level, not enforced by server contract)

**Idempotency**: YES (same key always returns same value until changed)

**Cache-Safe**: Can be cached (feature flags change infrequently)

## Known Feature Flags

**public\_sharing**:

* Controls thread visibility for public/unlisted threads
* Used by ThreadsController (Lines 134, 216)
* When `false`: All threads owner-only
* When `true`: Public/unlisted threads accessible anonymously

**Future Flags**: Additional flags not enforced by server contract

## Use Cases

**Frontend Configuration**:

* Check if features should be shown/hidden
* Enable/disable UI components based on flags

**Backend Decisions**:

* ThreadsController checks `public_sharing` for access control

**A/B Testing**: Feature flags can enable gradual rollouts

## Performance

**Query Complexity**: Single SELECT by primary key

**Index**: `system_settings.key` should be indexed

**Response Time**: Sub-10ms (simple key-value lookup)

**Caching**: Not documented in controller (service may cache)

## Security Implications

**Public Visibility**: Feature flag names and values exposed

* No sensitive data should be in feature flags
* Use for boolean toggles only

**No Rate Limiting**: Public endpoint, could be abused (not enforced by server contract)