A stop order on an option comes in two flavors, and the difference is the whole game when the tape is moving fast.

Stop-market: guaranteed exit, uncertain price

A stop-market becomes a market order the instant your stop price trades. It gets you out, but at whatever the market offers, which in a fast, wide 0DTE option can be meaningfully worse than your trigger (slippage). You're trading price certainty for exit certainty.

Stop-limit: guaranteed price, uncertain exit

A stop-limit becomes a limit order at your chosen price. You won't sell below your limit, but if the option gaps straight through it (very possible on 0DTE), the limit never fills and you're still holding a losing position that keeps falling. You protected the price and lost the protection.

On 0DTE, the risk isn't a few cents of slippage — it's a stop-limit that never fills while the option craters. Protection means getting out.

Which to use

For a fast-moving same-day option where the point of the stop is capital protection, a stop-market is usually the safer choice: a little slippage is a cheap price for actually exiting. A stop-limit makes more sense on calmer, more liquid positions where a bad fill is the bigger worry than a missed one. The failure mode to fear on 0DTE is the un-filled stop-limit. NoVo's exits lean toward guaranteed protection for exactly this reason — a stop that doesn't fire isn't a stop.