Futures reopen on Sunday evening. The S&P 500 perp has been trading since Friday. Most weekends the two land close to each other. Sometimes they do not, and the disagreement needs reading before either number does. Three checks sort most cases.
First, check the anchors
A good share of apparent disagreement is two different start points. The perp’s move is measured from its own print at the regular cash close. A futures change is quoted from the futures market’s own reference, and futures keep trading after the cash bell on Friday. If the index moved between the cash close and the futures stop, the two figures start from different places.
Put both on the same footing before comparing them. Where was each market at the cash bell, and where is each now. Why the anchor is the perp’s own print covers the perp’s side of that.
Second, check depth
Weekend depth on a perp is thinner than weekday depth. One large order can move the price and leave it there until someone trades against it. The first minutes of a futures reopen are thin too. A disagreement at the reopen can shrink within the hour as both books fill. How far to trust a small move takes the depth question further.
Third, check the premium
A perp has a mark price and an oracle price, and the difference is the premium. If the premium is unusually wide, part of the perp’s move is the perp pulling away from its own reference. Funding leans against that stretch every hour. A perp move that arrived with a wide premium is weaker evidence than one that arrived with the premium near its usual level.
What each pattern says
Same direction and similar size: two separate crowds reached the same price, and the weekend move has a second witness. Same direction and different size: usually anchors or depth, and worth one more look in an hour. Opposite directions: slow down. One market is carrying something the other is not, such as a large order or a stale position.
The deeper market deserves more weight, and that is futures. More weight does not make it the answer. The cash open belongs to Monday’s auction, and both markets are still only prices on other venues.
What to do with the dealer map
Mark both implied levels on Friday’s SPY map. If both sit on the same side of the gamma flip, the disagreement does not change the character of the read. The open would land in the same regime either way. If the flip sits between the two levels, the markets are describing two different mornings. Note both and let the first minutes of the cash session settle it.
Trader keeps the perp read on its Perps & Futures tab and the SPY, QQQ and IWM maps beside it, so both levels can be placed against the flip and the walls in one view.