# RuntimeError: The session is unavailable because no secret key was set.

- **ID:** `python/flask-session-not-configured`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Flask 应用未设置 SECRET_KEY，而会话功能（如 session 对象）需要密钥来签名 cookie。

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (90% success)
   ```
   import os
app.secret_key = os.environ.get('SECRET_KEY', os.urandom(24))
   ```
2. **** (85% success)
   ```
   class Config:
    SECRET_KEY = 'your-secret-key'
app.config.from_object(Config)
   ```

## Dead Ends

- **** — 虽然能运行，但密钥泄露或固定会导致安全问题，且部署时容易忘记更改。 (50% fail)
- **** — 每次重启应用密钥不同，导致用户会话失效，体验差。 (70% fail)