Three ways dealer gamma lies to you, from someone who uses it daily

Gamma levels get posted here constantly, usually as if a flip level were a price target. I use this stuff every session and I think the way it's talked about is mostly wrong, so here are the three failure modes that actually cost money.

1. The positioning is inferred, never observed.

Nobody outside a market maker's risk system knows their book. Every gamma number you have ever seen — the paid vendors', the free ones, mine — starts from open interest plus an assumption about who is long and who is short each contract. The usual assumption is that customers buy calls and buy puts and dealers take the other side. Sometimes that's badly wrong: one large institutional put-selling program flips the sign of the entire put side of the surface. When a gamma map disagrees with how the tape is behaving, the tape is right and the assumption was wrong. Treat the level as a hypothesis with a sign attached, not a measurement.

2. It's a snapshot of a book that reprices as price moves.

The flip level you screenshot pre-market is computed off a chain that assumes today's spot. Move spot 1.5% and dealer gamma redistributes, so the level you're trading toward moves while you trade toward it — and it usually moves *with* you, which is why "price rejected exactly at the flip" and "price sailed straight through the flip" are both common. Same problem with time: gamma concentrates hard into expiry, so a Thursday map and a Friday map of the same chain describe different worlds. A level with no timestamp on it is not information.

3. Open interest is not flow, and flow is what gets hedged.

Gamma from OI tells you what's sitting there. It says nothing about whether it was opened today or three weeks ago, and hedging pressure comes from the delta that has to be traded *now*. This is why 0DTE has broken a lot of gamma intuition — enormous same-day volume that never becomes open interest at all, generating real hedging flow that no OI-based map can see. If you're reading a SPY map and ignoring same-day volume you're looking at a minority of the actual hedging.

What it's genuinely good for, in my experience:

Not direction. Regime. High net positive dealer gamma near spot means hedging flow mechanically damps move — ranges hold, breakouts fail, mean reversion works, and you should be smaller and take profits earlier. Negative gamma near spot means hedging amplifies moves in whatever direction they're already going — trends extend, stops get run, and the same breakout you'd have faded works. That's the read, and that's all of it. It changes how much you trust a setup you already had and how big you go. It does not generate the setup.

The other honest use is knowing where the biggest strike concentrations sit, because that's where dealer hedging changes character, and price does behave differently around them often enough to matter. "Often enough to matter" is a much smaller claim than what usually gets made for a call wall.

If you disagree with any of this, especially if you've worked the market-making side, I'd like to hear where I'm wrong — the sign assumption in point 1 is the part I'm least confident about.