SPX dealer gamma — Thursday, September 17, 2026
dealer positioning for the session, reconstructed from the 0DTE options tape
These are the CLOSING levels for 2026-09-17. 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 7,640.62 and closed at 7,637.80, down 0.04% on the session (range 7,612.54–7,646.25). The close sat 33.4 points below the zero-gamma flip at 7,671.2 — dealer hedging in vol-amplifying territory. Call resistance 7,645, put support 7,650. 0DTE ATM IV opened at 4.4%.
Price crossed the flip once, first at 09:44 ET. The tape spent 82% of the day above VWAP. The expected-hold band 7,554.2–7,670.5 contained the entire session.
| Open → Close | 7,640.62 → 7,637.80 (-0.04%) |
| Session range | 7,612.54 – 7,646.25 |
| VWAP at the close | 7,632.24 |
| Zero-gamma flip | 7,671.2 |
| Call resistance | 7,645 |
| Put support | 7,650 |
| Expected-hold band | 7,554.2 – 7,670.5 |
| 0DTE ATM IV at the open | 4.4% |
| Regime at the close | negative gamma |
| Close vs flip | -33.4 |
| Net-gamma percentile | 92 |
The tape: complete, 390 of 390 minutes, 23,400 seconds with a print · 0 dropped packets · 25 engine restarts at 10:25, 10:28, 10:28, 10:28, 10:28, 10:29, 10:30, 10:31, 10:32, 10:33, 10:34, 10:35, 10:36, 10:39, 10:40, 10:41, 10:42, 11:19, 11:24, 11:29, 11:33, 11:38, 11:41, 11:41, 14:01 ET, replayed from the tape · published 10:35:33 ET. Every session's receipt.
End of day: Cboe: SPX put/call 1.15 on 13.7M contracts, index put/call 1.07 · OCC: 0.0M contracts cleared.
This day in its week: the week's numbers · its calendar.
Events this day
08:30Housing starts · pre-open
Housing starts actual 1275K prior 1309K08:30Philly Fed Manufacturing Index · pre-open
US releases, Fed events, Treasury auctions and mega-cap earnings from the market calendar; each links to its source, and every kind has its own archive page (FOMC days, CPI days, and so on). Times are ET. The line under an in-session event is the day's own book fifteen minutes on: spot, the zero-gamma flip, the net gamma of the ladder, the walls; measurements, not forecasts.
Minutes that moved the tape
| Minute | What | Tag | 5 min, pt | 15 min, pt |
|---|---|---|---|---|
12:55 | geopolitical headline (flash at 2 desks 12:55:59) | geopolitics | +2.1 | -1.0 |
15:50 | book moved 3.3σ · measured gamma, ATM IV, straddle (no headline) | flow | +3.3 |
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 2026-09-16
| Level | 2026-09-17 | Change |
|---|---|---|
| Zero-gamma flip | 7,671.2 | up 97.3 |
| Call resistance | 7,645 | up 90 |
| Put support | 7,650 | up 100 |
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 hold levels as they moved, IV and realised vol side by side. 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 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.