The first time I held a synthetic S&P index perp over a weekend, I spent Saturday morning staring at a price that had no right to exist. The underlying cash market had been closed since Friday afternoon, futures were closed too, and yet there was a live mark on my screen ticking up and down, funding accruing every hour, my position quietly gaining and losing money against a number that no real venue was actually printing. That is the whole strange thing about these contracts in one sentence. You are trading a 24/7 instrument on top of an asset that sleeps, and the exchange has to invent a price for the hours when the truth is unavailable.
Once you get how that invented price is made, most of the weird behavior stops being weird. So let me walk through what actually happens under the hood, because the mechanics are not obvious from the ticker and they are exactly the parts that cost people money.
What the oracle does when the underlying is asleep
A perpetual needs a reference price to mark positions and to trigger liquidations. For a crypto pair like BTC that reference comes from an index of spot exchanges that never close, so the oracle always has fresh truth to point at. For a synthetic equity-index or gold perp, the exchange is usually pulling from some combination of the cash index, listed futures, and in some cases its own order book. The problem is that all three of the honest sources go dark on nights, weekends, and holidays.
Different venues handle the gap in different ways, and you should know which one you are on. Some freeze the oracle at the last real print, so the mark just sits flat until the market reopens. Some fall back to a related futures contract that trades longer hours, which helps but is not the same instrument. And some let the perp float freely on its own order book during the closed window, which means the mark is whatever the traders in that thin weekend book decide it is. That last kind is the one that surprises people. You think you are tracking the index, but for a big chunk of the week you are tracking a small self-referential crowd betting on where the index will open.
Gold is the friendlier case here because the metals market runs close to around the clock through the week, with only a short daily break and the weekend off. Equity indexes are harsher. A US index perp is priced against a real market that is open for roughly a third of the day and shut entirely on weekends, so the majority of the calendar is oracle-fabricated in one way or another.
Why funding gets strange around opens and weekends
Funding is the payment that keeps a perp tethered to its underlying. When the perp trades above the index, longs pay shorts, and that cost is supposed to pull the price back down. It works cleanly when the index is live. It gets messy when there is no live index to pull toward.
Think about a weekend where the crowd is convinced the market will gap up on the open. They buy the perp all through Saturday and Sunday. The perp drifts well above Friday's close, funding goes sharply positive, and longs are now paying every hour for the privilege of holding a directional bet against a frozen reference. If they are right and the market gaps up on Monday, fine. If they are wrong, or if the gap is smaller than priced in, they have paid two days of elevated funding and then eat the mean reversion on top. I have watched funding on a stock index perp run several times its normal rate across a long holiday weekend purely on positioning, with nothing underneath it but sentiment.
The session open itself is its own event. In the minutes around the real market reopening, the oracle switches from its fallback back to live truth, the basis snaps to reality, and funding can whip hard in the other direction as the perp price and the now-live index reconcile. If your liquidation level is anywhere near that reconciliation, the open is the single most dangerous moment in the week for you.
The basis and liquidity quirks worth checking
Basis is just the gap between the perp price and the spot index. On crypto pairs it is usually small and mean-reverting. On synthetic equity and metals perps it does something you need to expect. During closed hours the basis can widen a lot and stay wide, because there is no arbitrage path to close it. You cannot buy the real index cheaply on a Sunday and sell the rich perp against it, so the gap just persists until the underlying reopens and reality reasserts. A wide weekend basis is not a free trade. It is the market pricing an expected move you also cannot hedge.
Liquidity follows the same clock. Order books on these contracts are deepest when the underlying is live and thinnest overnight and on weekends, which is precisely when retail is most tempted to swing them. Thin books mean wide spreads, worse slippage, and liquidations that cascade further than they would in daylight. A stop that looks reasonable against Tuesday-afternoon depth can get run through a mile past your intended exit at 3am on a Sunday.
A checklist before you hold one of these
Here is roughly the sequence I run before putting real size into a synthetic index or metals perp, especially anything I plan to carry across a closed session.
- Read the venue's own docs on how the oracle behaves when the underlying is closed. Frozen, futures-fallback, or free-floating are three very different animals and they change every decision below.
- Pull the funding history and look specifically at weekends and holidays, not the weekday average. That is where the real carry cost of holding lives.
- Check the basis right now against the last real index print. If it is already wide going into a weekend, someone has an opinion, and you are paying to disagree with it.
- Note the exact reopen time of the actual underlying and treat the window around it as high risk. Do not have a tight liquidation level sitting near where the mark will snap to truth.
- Size for weekend liquidity, not weekday liquidity. Assume the book you can actually exit into is a fraction of what you see during the cash session.
The honest use case for these contracts is getting cross-asset exposure at hours when nothing else is open, or expressing a view you genuinely want to carry 24/7. That is a real thing and I use them for it. What burns people is treating a synthetic index perp as if it were the index. It is a derivative of a derivative of an asset that is closed most of the time, wrapped in an oracle that has to guess for a big share of the week, and the funding you pay is largely the price of everyone else's guessing. Hold that picture in your head and most of the surprises turn back into things you saw coming.