Gamma flip — the price at which total dealer gamma crosses zero. Above it, hedging tends to lean against moves and the tape usually grinds. Below it, hedging goes the same way price is already going, and ranges tend to travel further. It is the one level here that is about regime rather than support or resistance.
Call wall — the strike above spot carrying the heaviest positive gamma. Often behaves like a ceiling, because hedging into it sells strength.
Put wall — the heaviest negative-gamma strike below spot. Often behaves like a floor for the same reason in reverse. When it prints at the money, that is pin risk rather than a level — the biggest concentration is simply where price already is.
We also show the open-interest walls, which answer a different question: not where hedging pressure is today, but where the largest positions sit. Those are usually further out and more structural — useful for the week, less so for the session.
Same-day expiries are excluded. An option's gamma runs away as it approaches expiry at the money, so a handful of contracts expiring in hours can outweigh the entire rest of the book — on 28 August one SPX put with 1,732 contracts of open interest carried more gamma than the other 7,696 combined, and reported the book as negative when it was positive. This board is built after the close for the next session, so contracts that have already settled do not belong in it.
Built from the listed chain from tomorrow out to 60 days. Longer-dated contracts are excluded too: they carry open interest nobody is hedging day to day. ES, NQ and RTY are converted using the live index-to-futures basis; GC and YM have no cash index to anchor to, so they use the live futures-to-ETF ratio instead. Both are read at build time, never a fixed offset.
Why these markets. Each book is built on wherever that complex's options actually trade, which is not always the obvious place — the Nasdaq's gamma sits in QQQ, not NDX, which carries sixty times less open interest. CL has no book at all: the crude ETFs track the underlying too poorly for their gamma to describe futures positioning, and a level from the wrong instrument is worse than no level.
Every other board on this site ships with a record. This one does not yet. The chain data we use is a live snapshot with no history, so there is no honest way to tell you how price behaved at yesterday's gamma flip — nobody publishes the open interest that would be needed to check. We are keeping our own copy from today onward, and once there is enough of it these levels get the same controlled test that killed our fair-value-gap work and our confluence work. Until that exists, treat this as a map of positioning, not a prediction, and judge it in public alongside us.