## MODIFIED Requirements

### Requirement: Configuration Management
The system SHALL read configuration from config.yaml file only. The system SHALL validate configuration on startup.

#### Scenario: Load Configuration
- **WHEN** the application starts
- **THEN** the system SHALL read config.yaml file
- **AND** the system SHALL validate required configuration items
- **AND** the system SHALL fail to start if required configuration is missing
- **AND** the system SHALL NOT read or use environment variables for configuration

#### Scenario: Configuration Validation Failure
- **WHEN** config.yaml file does not exist
- **THEN** the system SHALL raise FileNotFoundError with the config file path

- **WHEN** required configuration items are missing (e.g., DashScope API key)
- **THEN** the system SHALL raise ValueError with a clear error message when the configuration is first used

## REMOVED Requirements

### Requirement: Environment Variable Configuration Override
**原因**: 简化配置管理，统一配置来源为 `config.yaml` 文件，减少配置管理的复杂性和维护成本。

**迁移**: 之前使用环境变量的用户需要将所有配置迁移到 `config.yaml` 文件中。环境变量将不再被读取或使用。