# RuntimeError: Cannot run the event loop while another loop is running

- **ID:** `python/asyncio-loop-already-running-nested`
- **Domain:** python
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

loop.run_until_complete() was called from inside a coroutine that is already executing on the same loop, causing nested loop execution which asyncio forbids.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.8 | active | — | — |
| 3.9 | active | — | — |
| 3.10 | active | — | — |
| 3.11 | active | — | — |
| 3.12 | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   async def outer():
    # WRONG: loop.run_until_complete(inner())
    await inner()  # correct
   ```
2. **** (88% success)
   ```
   result = await asyncio.to_thread(sync_blocking_fn, arg1, arg2)
   ```

## Dead Ends

- **** — get_event_loop returns the running loop; run_until_complete still raises. (90% fail)
- **** — The loop is still running; a yield point does not allow re-entrant run_until_complete. (85% fail)