```python
from fastapi import FastAPI, Query
import helpers
import asyncio

app = FastAPI()


@app.get("/portfolio")
async def portfolio(symbols: str = Query(...)):
    # Split the comma‑separated list and strip whitespace
    symbol_list = [s.strip() for s in symbols.split(",") if s.strip()]
    
    # Fetch all prices concurrently using the async helper
    tasks = [helpers.afetch_price(sym) for sym in symbol_list]
    prices_list = await asyncio.gather(*tasks)
    
    # Build the result dictionary
    prices = {sym: price for sym, price in zip(symbol_list, prices_list)}
    return {"prices": prices}
```