New to charm exposure? Vanna & Charm Guide covers time-decay effects on dealer positioning.

Works with CME index futures. Pass ES=F or NQ=F and URL-encode the = as %3D - e.g. /v1/exposure/chex/ES%3DF. Options-on-futures are priced with Black-76 using the CME multiplier ($50/pt ES, $20/pt NQ); CME index futures are Growth-tier. See the futures hub.

Endpoint

GET /v1/exposure/chex/{symbol}

Auth required (X-Api-Key) Rate Limited: Yes Basic+

Parameters

Name	In	Required	Default	Description
`symbol`	path	yes	-	Underlying symbol
`expiration`	query	no	`all`	Filter by expiry date `yyyy-MM-dd`, or `0dte` for same-day only

curl -H "X-Api-Key: YOUR_API_KEY" \
  "https://lab.flashalpha.com/v1/exposure/chex/SPY"

import requests

resp = requests.get(
    "https://lab.flashalpha.com/v1/exposure/chex/SPY",
    headers={"X-Api-Key": "YOUR_API_KEY"}
)
data = resp.json()
print(f"Net CHEX: ${data['net_chex']:,.0f}")

const resp = await fetch(
  "https://lab.flashalpha.com/v1/exposure/chex/SPY",
  { headers: { "X-Api-Key": "YOUR_API_KEY" } }
);
const data = await resp.json();
console.log(`Net CHEX: $${data.net_chex.toLocaleString()}`);

API Key

Response

{
  "symbol": "SPY",
  "underlying_price": 597.505,
  "as_of": "2026-02-28T16:30:45Z",
  "net_chex": 850000000,
  "chex_interpretation": "Positive charm  -  time decay benefits dealers",
  "strikes": [
    {
      "strike": 575.0,
      "call_chex": 950000,
      "put_chex": 620000,
      "net_chex": 1570000
    }
  ]
}

Key Response Fields

Field	Type	Description
`symbol`	string	Underlying symbol
`underlying_price`	number	Current price of underlying
`as_of`	string	ISO 8601 timestamp
`net_chex`	number	Aggregate net charm exposure in dollars
`chex_interpretation`	string	Plain-English directional interpretation of charm exposure
`strikes`	array	Per-strike breakdown
`strikes[].strike`	number	Strike price
`strikes[].call_chex`	number	Call charm exposure at this strike
`strikes[].put_chex`	number	Put charm exposure at this strike
`strikes[].net_chex`	number	Net (call + put) charm exposure

What Is Charm Exposure?

Charm exposure (CHEX) measures how dealer delta shifts purely due to the passage of time (dDelta/dTime). As options age, their delta drifts - calls slowly gain delta and puts lose it. This forces dealers to continuously rebalance. The effect intensifies near expiration, making charm particularly useful for predicting end-of-day flows and weekly OpEx rebalancing. Positive CHEX means time decay is pushing dealers to buy shares, providing support. Negative CHEX means dealers are selling, adding pressure.

Common Use Cases

Predict the close from net_chex - positive means time decay pushes dealers to buy into the close, negative means they sell; set your end-of-day bias from the sign
Trade weekly OpEx - large net_chex ahead of Friday expiration signals strong charm-driven rebalancing flows to position around
Confirm with the interpretation field - use chex_interpretation for a plain-English read of which way charm flows are tilting before acting
Locate charm-heavy strikes - scan strikes[].net_chex to see which levels dealer time-decay hedging will pull price toward into expiry
Anticipate the open - overnight charm-driven delta drift shapes next-day opening flows; read net_chex after the close to gauge gap pressure
Time it against gamma - combine net_chex with GEX to judge whether the close drifts toward or away from key levels, and size accordingly

Complementary endpoints

Vanna Exposure (VEX) - the vol-sensitivity counterpart to charm's time decay
Gamma Exposure (GEX) - hedging acceleration that pairs with charm's end-of-day drift
Delta Exposure (DEX) - the directional tilt that charm rebalances as time passes
Dealer Premium - the premium dealers carry as charm flows rebalance into expiry

Charm Exposure (CHEX) API