The 0DTE Problem

Why static Open Interest is no longer enough, and why tools that rely on it are missing more than half of modern flow.

A quick reminder: what OI captures

Open Interest is the total number of option contracts that exist at a given strike, published once per day by the exchanges after the close. If you missed the details, the Open Interest guide covers it.

The key property: OI only reflects positions that survived the close.A position opened at 10am and closed at 3pm contributes zero to the OI that gets published tonight. It’s as if it never existed, from the OI’s perspective.

What changed

For most of options market history, this wasn’t a problem. The overwhelming majority of options volume was in contracts with days, weeks, or months until expiration. Daily OI snapshots captured the positioning accurately because most positions stayed open overnight.

Then, starting around 2022, the CBOE expanded SPX options to list daily expirations. What were once three expirations per week (M/W/F) became five. Traders discovered that 0DTE options — contracts expiring that same trading day — offered a leveraged way to express short-term views without overnight risk.

Volume exploded. By 2024, 0DTE contracts made up roughly 45% of SPX options volume. In 2026 that number is over 50% on most trading days, and on high-volatility sessions can exceed 60%. More than half of the options flow in the most liquid market on earth now lives entirely inside a single trading session.

Why 0DTE flow is invisible to traditional GEX tools

Here’s a concrete example. Imagine it’s 10:30am on a Tuesday. The overnight Open Interest said the SPX Call Wall was at 5800. Every traditional GEX tool opens the day showing Call Wall at 5800.

At 10:35am, a large fund buys 30,000 contracts of 5850 calls expiring today. Dealers on the other side of those trades are now short 30,000 calls that expire in 5.5 hours. They’re going to have to aggressively hedge every move price makes for the rest of the session, concentrated near 5850.

By all structural measures, 5850 just became a far more important level than 5800 for today’s price action.

What do traditional GEX tools show? Nothing changed.Call Wall still at 5800. The 5850 strike shows minimal gamma because yesterday’s OI there was small. The dashboard looks identical to how it did at market open.

At 3:45pm, the fund closes the position. It’s gone. Tonight’s OI print shows a small net change at 5850 — maybe 100 contracts. All day, the real structural level was 5850, but any tool that depended on OI never saw it.

This is not a minor edge case. It is the dominant flow pattern in today’s market. Multiply this one example by dozens of large 0DTE trades per day across multiple strikes in multiple expirations and you understand why static-OI tools are telling you a story that has nothing to do with what’s driving price today.

The two approaches to fixing this

Serious options researchers recognized this problem years ago. Two approaches emerged:

Why we read the order flow directly

Both approaches are legitimate. They make different tradeoffs. We built GammaFlux around a live directional order-flow engine — reading live options order flow at every strike, buy/sell-aware and volume-adjusted — because that’s where the 0DTE positioning is actually being set.

• bolt
  It reads the source, not the shadow.Order flow at the strike is where dealer positioning is actually created. A futures-volume proxy only sees the hedge after it lands, and can’t tell you which strike drove it.
• radar
  It’s directional, not just a magnitude. Classifying each trade as buyer- or seller-initiated is far better than assuming 50/50, and it tells you where gamma is being added or removed strike by strike — not merely that hedging happened.
• shield
  It pins the level, not just the activity. Because the flow is read per strike, it places the magnets and the Flow Flip on specific levels — exactly the 0DTE concentration that never shows up in standing OI.

What this means for you as a trader

If you’re still using a static-OI tool in 2026, you’re looking at a map of yesterday’s battlefield while the war has already moved. The information isn’t wrong, exactly — positions held overnight still matter — but it’s missing the half of the market that actually moves price intraday.

Static OI tools tell you where the slow-moving money sits. That’s useful context, but not enough to trade on by itself.

GammaFlux gives you both: the overnight OI baseline AND an estimate of how that positioning is shifting during the session as new flow arrives. When the model says a level is migrating, price is usually about to follow.

This doesn’t mean GammaFlux predicts the market — no tool does — but it gives you a structural read on where dealer hedging pressure is concentrating right now, not where it was concentrated at yesterday’s close.