# TypeError: CORSMiddleware.__init__() got an unexpected keyword argument 'allow_origins'

- **ID:** `python/starlette-cors-middleware-error`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The CORSMiddleware in Starlette uses 'allow_origins' but older versions use 'origins'.

## Version Compatibility

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

## Workarounds

1. **Check the Starlette version and use the correct parameter name.** (90% success)
   ```
   from starlette.middleware.cors import CORSMiddleware
app.add_middleware(CORSMiddleware, allow_origins=['*'])  # For newer versions
   ```
2. **Use 'origins' parameter for older Starlette versions.** (85% success)
   ```
   app.add_middleware(CORSMiddleware, origins=['*'])
   ```

## Dead Ends

- **Using both 'origins' and 'allow_origins' together.** — Only one parameter is accepted; using both causes error. (70% fail)
- **Upgrading starlette but not updating the code.** — Newer versions may have changed the parameter name. (60% fail)