Zero gamma

Also called Gamma flip, zero GEX level, gamma flip point

The price at which total dealer gamma exposure would change sign, found where the gamma profile crosses zero.

Zero gamma is the price where total dealer gamma exposure would cross from positive to negative. Above it, dealers' hedging tends to damp moves; below it, their hedging tends to stretch them. Price crossing zero gamma is a change in how the market may move, not a support or resistance line in the usual sense.

How Theta Vantage finds it

From the gamma profile: total GEX is recomputed at 201 prices around spot (10% either side by default), holding implied volatility, time, and open interest fixed, and zero gamma is where that curve crosses zero, refined to a fraction of a cent. With more than one crossing, it's the one nearest spot. With none in range, the search widens once; with still none, there is no zero gamma and the whole range sits in one regime.

Not the same as every "gamma flip"

Some tools compute a gamma flip by adding up GEX strike by strike at today's price and finding where the running total crosses zero. That doesn't recompute gamma at other prices, so it can land somewhere else. Theta Vantage uses the profile. It keeps "gamma flip" as another name for the level, not a different calculation.

On the chart

Zero gamma is the dashed amber rule, the only amber on any chart, on the price chart, exposure by strike, and the key-levels strip, with its distance from spot.