While the cash market is shut, Trader watches the S&P 500 perp and the Nasdaq 100 perp. It sends a push the first time one of them is half a percent from its price at the cash close. The threshold is not arbitrary, and the way it repeats is deliberate.
Why half a percent
A threshold needs a benchmark. The natural one for an index is the expected move, the range options are pricing for a session. On 2 October 2026 SPY’s expected daily move was 0.46%. Half a percent is about that size. So the alert fires when the perp has moved roughly as far as the options market had priced for a whole day.
A much smaller threshold would fire on thin-book drift most weekends. People stop reading an alert that fires most weekends. A much larger one would stay silent through moves that already change where SPY sits on its map. An alert that never fires covers that second failure.
How it steps
The push fires at the first half percent and at each further half percent. A perp that keeps going sends a second push at one percent and a third at the next step. Each step is a new fact: the move has grown by another expected-move-sized unit.
Once per direction
Each step fires once per direction. A perp hovering near the line can cross it many times in an hour. One push covers that. If the perp later falls half a percent below the close, that is a different direction and it gets its own push. Why alerts need a cooldown makes the general argument: an alert that repeats on the same condition trains you to ignore it.
What the push says
It says an index perp is half a percent, or a multiple of it, from its own print at the last regular cash close. It names the perp and the direction. That is a measured fact about a market on another venue.
What it does not say
It does not say where SPY opens. It carries no advice. It says nothing about IWM, which has no perp to watch. And it does not know why the perp moved. The push is the prompt to go and look: at the seven mega-cap perps, at Friday’s flip and walls, and at the news.
What to do when it arrives
Apply the move to Friday’s SPY close and place the implied level on Friday’s map. Check which side of the gamma flip it lands on and how near a wall it sits. A weekend move across the gamma flip covers that reading. Then check whether the move holds. The push is sent once, and the perp keeps trading.