0DTE Gamma Regime Today — Positive or Negative Gamma, and Why It Matters By 10 AM

What a gamma regime actually is

A gamma regime is a statement about the aggregate direction of dealer hedging flow for a given underlying over a given expiration window. It has two possible values on the 0DTE endpoint:

• Positive gamma — dealers are net long gamma from 0DTE contracts. They must sell rallies and buy dips to stay delta-neutral. Their hedging dampens moves. Ranges compress.
• Negative gamma — dealers are net short gamma. They must buy rallies and sell dips, amplifying moves. Ranges expand.

The regime classification comes from the sign of net 0DTE GEX relative to the 0DTE gamma flip level. If spot is above the flip, regime is positive; if below, negative. "Undetermined" happens when the chain has too few strikes with meaningful OI — usually a quiet session or thinly-traded symbol.

The convention attributes calls as short-dealer positions and puts as long-dealer positions, matching the assumption that retail is the dominant buyer of both. The regime label is the sign of the spot-adjusted sum.

Why the 0DTE flip is different from the full-chain flip

Most GEX dashboards show a single gamma flip level computed across the entire options chain — every expiration from today through LEAPS. That number is useful as a macro-structural anchor, but it can be misleading intraday. 0DTE contracts dominate same-day hedging flows because their gamma is 3-10× larger than equivalent weekly contracts at the same strike. The full-chain flip can be 20-30 points away from the 0DTE-specific flip, and it is the 0DTE flip that matters for today's range.

The FlashAlpha 0DTE endpoint returns the 0DTE-specific flip at regime.gamma_flip. The full-chain flip is available separately at the /v1/exposure/gex/{symbol} endpoint's gamma_flip field. Read both. Day traders use the 0DTE flip; swing traders use the full-chain flip. A morning session where they disagree substantially is a setup to watch — a test of one often leads to a test of the other.

How regimes behave intraday

Regimes are not static for the session. The 0DTE flip moves as OI re-balances and gamma rolls off with time. Three patterns are common:

Stable regime day

Spot stays 20+ points away from the flip all session. Regime is one sign from open to close. The opening hour's range is a good estimate of the closing hour's range — positive gamma days produce compressing ranges, negative gamma days produce expanding ranges. These are the easiest setups to trade because the structural backdrop does not change.

Flip-crossing day

Spot opens on one side of the flip, drifts through it mid-session, and closes on the other side. The regime flips with it. This is the setup where 0DTE traders get wrecked — a credit spread placed at 10:00 AM in a positive-gamma regime is still open at 2:00 PM in a negative-gamma regime, and dealer hedging is now amplifying rather than dampening the move that is threatening the short strike. Watch for the cross, not just the level.

Flip-drift day

Spot stays roughly constant; the flip drifts toward spot as 0DTE gamma decays and OI redistributes. The regime can flip without price moving materially. This is rare but happens on low-volume Fridays and around holiday sessions. The signal is a compressing distance between spot and flip — usually visible by 1:00 PM if it is going to happen.

Positive gamma day — what actually happens

When the 0DTE regime is positive, three things tend to be true:

1. Ranges compress. The ATM straddle at open implies a 1σ range for the day; by midday, realised range is often 30-50% of that implied move. The rest comes out as late-session decay, not a late breakout.
2. Dips get bought, rallies get sold. Not by discretionary traders — by dealer hedging flow, which is mechanical. This is the source of the "invisible bid" and "invisible offer" patterns that day-traders notice without being able to locate their origin.
3. Pin risk builds as the session progresses. The 0-100 pin score rises through the day in positive-gamma regimes because the same hedging flow that dampens moves also biases price toward the highest-OI strike.

For detailed strategy mapping on positive regime days, see the 0DTE strategies guide.

Negative gamma day — what actually happens

Negative regime inverts the three patterns:

1. Ranges expand. Realised range can exceed the opening ATM straddle's implied move. The "expected move" published at 9:30 AM is a floor, not a ceiling.
2. Dips get sold, rallies get bought. Dealer hedging amplifies direction. A weak open gets weaker through lunch; a strong open adds through the afternoon.
3. Pin risk stays low or decays. Attraction to a magnet strike is weaker because the hedging flow is not biased toward mean-reversion.

The practical implication for short-premium trades is direct: negative-regime days are not the environment for iron condors or credit spreads targeting a pin. Dealer flow is not on your side. Either trade the amplification directly (long vol, long delta in the direction the regime is pushing) or sit out.

Reading the regime from the API

One call returns the regime label, the 0DTE gamma flip, and the 0DTE share of total GEX:

import requests

r = requests.get(
    "https://lab.flashalpha.com/v1/exposure/zero-dte/SPY",
    headers={"X-Api-Key": "YOUR_API_KEY"}
)
d = r.json()

regime = d["regime"]
print(f"Label:        {regime['label']}")
print(f"0DTE flip:    ${regime['gamma_flip']:.2f}")
print(f"Spot vs flip: {regime['spot_vs_flip']}")
print(f"Distance:     {regime['spot_to_flip_pct']:.2f}%")
print(f"0DTE share:   {d['exposures']['pct_of_total_gex']:.0f}% of chain")

The exposures.pct_of_total_gex field is the lever for deciding whether today's 0DTE regime matters. When it is above 50%, 0DTE hedging dominates intraday flow and the 0DTE regime is the relevant read. Below 30%, the full-chain GEX picture is more important — 0DTE contributes but does not drive.

Combining regime with pin score

The cleanest 0DTE reads come from combining the regime with the 0-100 pin score. Four combinations recur:

These four reads cover most of the session types traders encounter. They are the skeleton; the pin score numbers and hedging estimates are the meat.

Why regime reads replace chart patterns

Most retail 0DTE education teaches chart patterns. Breakouts, flags, support-resistance levels drawn by eye. These patterns are not wrong — they are downstream effects of dealer hedging flow, and sometimes they fire. But they are lossy compressions of the structural signal. The regime and flip level tell you directly which direction the hedging force is pushing; the chart tells you whether price has gotten there yet.

A breakout in a positive-gamma regime fails more often than it succeeds — dealer hedging is actively selling the rally. A breakout in a negative-gamma regime runs. Same chart pattern, opposite outcomes. The difference is not visible on the price chart at all; it is in the options book. Read the book.

For the full theory of how gamma exposure creates intraday levels, see 0DTE Gamma Exposure & Pin Risk. For the SPXW index specifics, see the SPXW 0DTE guide. For the SPY playbook, see SPY Complete 0DTE Playbook.

The short answer

0DTE regime is the sign of dealer gamma for today's expiry — positive dampens moves, negative amplifies them. The 0DTE gamma flip can be 10-40 points off the full-chain flip and it is the number that matters for today's range. Read it live alongside the pin score; those two numbers explain most of what happens intraday in same-day expiration products.