SPX dealer gamma — Monday, September 21, 2026
dealer positioning for the session, reconstructed from the 0DTE options tape
These are the CLOSING levels for 2026-09-21, read at 15:45 ET, before the expiring contracts' last minutes. Where the SPX dealer book stands right now — the current zero-gamma flip, call resistance and put support — is on /now, free, at least fifteen minutes behind the tape.
SPX opened at 7,694.21 and closed at 7,764.87, up 0.92% on the session (range 7,690.07–7,778.41). The close sat 49.8 points above the zero-gamma flip at 7,715.1, on the positive-gamma side of the volume book. Call resistance 7,775, put support 7,690. 0DTE ATM IV opened at 4.9%.
Price crossed the flip 3 times, first at 09:31 ET. The tape spent 99% of the day above VWAP.
| Open → Close | 7,694.21 → 7,764.87 (+0.92%) |
| Session range | 7,690.07 – 7,778.41 |
| VWAP at the close | 7,744.83 |
| Zero-gamma flip | 7,715.1 |
| Call resistance | 7,775 |
| Put support | 7,690 |
| 0DTE ATM IV at the open | 4.9% |
| Regime at the close | positive gamma |
| Close vs flip | +49.8 |
| Net-gamma percentile | 50 |
The tape: complete, 390 of 390 minutes, 23,400 seconds with a print · 0 dropped packets · no engine restart · published 16:13:14 ET. Every session's receipt.
End of day: Cboe: SPX put/call 0.81 on 16.3M contracts, index put/call 0.80 · OCC: 0.0M contracts cleared.
This day in its week: the week's numbers · its calendar.
Minutes that moved the tape
| Minute | What | Tag | 5 min, pt | 15 min, pt |
|---|---|---|---|---|
10:21 | book moved 4.1σ · skew (no headline) | flow | +8.6 | +10.0 |
12:07 | book moved 3.3σ · measured gamma (no headline) | flow | +6.2 | +7.1 |
14:22 | book moved 3.8σ · measured gamma (no headline) | flow | +3.9 | +3.8 |
A minute is marked by the tape itself: a one-minute move of the index at least four times the trailing half-hour's usual change, or three with the dealer book moving in the same minute. Where two public news desks carried an item inside three minutes of it, the row says so with our own label and never the headline's text; where nothing did, it says so too. Calendar events the tape reacted to are in the list above. Moves are the index in points from the minute before to 5 and 15 minutes on; measurements, not forecasts.
What changed since 2026-09-18
| Level | 2026-09-21 | Change |
|---|---|---|
| Zero-gamma flip | 7,715.1 | up 85.0 |
| Call resistance | 7,775 | up 125 |
| Put support | 7,690 | up 75 |
Changes compare each session's closing level with the preceding trading session; they are measurements, not forecasts.
Sessions like this one, by the same closing measurements: the screener.
Open this session in the terminal → Share session
The terminal replays the full session minute by minute: dealer gamma, vanna and charm by strike, the flip and the walls as they moved, the day's large orders on the candles they printed in, and IV against realised vol in the READOUTS drawer. Every historical session is free and needs no account. New to these terms? Start with what GEX is. Measured across the whole archive: how often these levels hold, why a hold rate alone says little and how far SPX travels before the close.
Measurements are model output derived from public trade and quote data; they are approximations and can be wrong. Nothing here is investment advice — see the Terms.