## ADDED Requirements

### Requirement: System monitors tunnel health
The system SHALL periodically check if active tunnel URLs are reachable and mark them as erroneous if not.

#### Scenario: Healthy tunnel
- **WHEN** a tunnel health check is performed on a running instance
- **THEN** the system receives an HTTP 2xx response
- **AND** the instance status remains "running"

#### Scenario: Broken tunnel
- **WHEN** a tunnel health check is performed on a running instance
- **AND** the response is not HTTP 2xx or the request fails
- **THEN** the instance is marked with tunnel_error status
- **AND** a visual error indicator is displayed in the UI

### Requirement: Users can recreate broken tunnels
The system SHALL allow users to regenerate a temporary tunnel for a running instance without restarting the instance.

#### Scenario: Recreate tunnel
- **WHEN** user clicks "Recreate Tunnel" button on an instance with a broken tunnel
- **THEN** the system stops the existing cloudflared process
- **AND** starts a new cloudflared tunnel
- **AND** updates the instance URL
- **AND** the new URL is displayed in the UI

#### Scenario: Recreate tunnel success
- **WHEN** tunnel recreation completes successfully
- **THEN** the error indicator is removed
- **AND** the instance shows as healthy

#### Scenario: Recreate tunnel failure
- **WHEN** tunnel recreation fails
- **THEN** the error indicator remains
- **AND** an error message is displayed to the user
