sell-window API

Endpoint

Parameters

Request

curl -H "X-Api-Key: YOUR_API_KEY" \
  "https://lab.flashalpha.com/v1/strategies/sell-window/SPY"

import requests

resp = requests.get(
    "https://lab.flashalpha.com/v1/strategies/sell-window/SPY",
    headers={"X-Api-Key": "YOUR_API_KEY"}
)
resp.raise_for_status()
data = resp.json()
for w in data["windows"]:
    print(w.get("expiry"), w["action"], len(w.get("candidates", [])))

const resp = await fetch(
  "https://lab.flashalpha.com/v1/strategies/sell-window/SPY",
  { headers: { "X-Api-Key": "YOUR_API_KEY" } }
);
if (!resp.ok) throw new Error(`HTTP ${resp.status}`);
const data = await resp.json();
for (const w of data.windows) console.log(w.expiry, w.action, (w.candidates ?? []).length);

{
  "symbol": "SPY",
  "session": "2026-10-16",
  "spot": 772.255,
  "quoted_at": "2026-10-16T13:35:00Z",
  "legs_indicative": false,
  "windows": [
    {
      "expiry": "2026-10-16",
      "days_to_expiry": 0,
      "action": "sell",
      "candidates": [
        {
          "structure": "short_put",
          "exit": "expiry",
          "legs": [
            {
              "side": "sell",
              "quantity": 1,
              "type": "put",
              "strike": 769,
              "delta": -0.19,
              "bid": 0.39,
              "ask": 0.4
            }
          ],
          "mid_credit": 0.395
        },
        {
          "structure": "short_strangle",
          "exit": "expiry",
          "legs": [
            {
              "side": "sell",
              "quantity": 1,
              "type": "call",
              "strike": 774,
              "delta": 0.302,
              "bid": 0.63,
              "ask": 0.64
            },
            {
              "side": "sell",
              "quantity": 1,
              "type": "put",
              "strike": 770,
              "delta": -0.264,
              "bid": 0.58,
              "ask": 0.59
            }
          ],
          "mid_credit": 1.22
        }
      ]
    }
  ],
  "endpoint_version": "2026.09.30"
}

Real response for SPY at 09:35 ET on 2026-10-16, shortened to one window and two trades. Download the full response (JSON).

On a skip day there is nothing to do, and each window carries only its expiry and action. A real response from SPY on 2026-11-05:

{
  "symbol": "SPY",
  "session": "2026-11-05",
  "windows": [
    {
      "expiry": "2026-11-05",
      "days_to_expiry": 0,
      "action": "skip"
    },
    {
      "expiry": "2026-11-12",
      "days_to_expiry": 7,
      "action": "skip"
    },
    {
      "expiry": "2026-11-18",
      "days_to_expiry": 13,
      "action": "skip"
    },
    {
      "expiry": "2026-12-04",
      "days_to_expiry": 29,
      "action": "skip"
    }
  ],
  "endpoint_version": "2026.09.30",
  "data_as_of": {
    "node": "fa4",
    "equity_feed": "2026-11-05T14:11:16.332Z",
    "equity_options_feed": "2026-11-05T14:11:16Z",
    "index_feed": "2026-11-05T14:10:58.1024266Z",
    "index_options_feed": "2026-11-04T22:00:00Z",
    "futures_feed": "2026-11-05T14:11:13.291Z",
    "futures_options_feed": "2026-11-05T14:11:13.337Z",
    "flow_feed": null,
    "oi_feed": "2026-11-04T21:00:00Z",
    "macro_feed": "2026-11-04T21:15:01Z"
  }
}

Response Fields

This endpoint has its own shape, not the strategy decision envelope.

How windows are chosen

Each window trades the listed expiry closest to its target, counted in calendar days after the session.

When a window sells, the listing is the option chain's at the moment of the answer, as the backtests chose it at entry. Otherwise it is the previous close's listing.

Structures and exits

How strikes are picked

Strikes are picked from the chain with the contract rules from our backtests: only out-of-the-money contracts with a bid above zero, a bid/ask spread of at most 20% of the mid and open interest of at least 250. Among those, the contract whose delta is closest to the candidate's target and within 0.05 of it is used; ties go to the tighter spread, then the higher open interest. A candidate whose legs cannot all be found in the chain is left out.

Errors

About

More than 5 million backtests led to this endpoint. It answers one question: is this a session to sell options? The answer is set from the previous session's close and stays fixed for the whole session. Strikes, deltas and quotes come from the chain at the moment you call.

In the backtest on SPY, QQQ and IWM from January 2018 to October 2026, following it had a maximum drawdown of $255,105 against $958,924 for the same trades sold every session, and a Sharpe ratio of 0.76 against 0.61, on about a third of the trades. See every trade in the backtest.

The session switches at the close (16:00 ET, 13:00 ET on early-close days). Before the close the answer is for the current session. After the close and on closed days it is for the next session.

Plans: Basic or higher through November 2026, Growth or higher from December 1, 2026. Backtesting: on Alpha, the historical API returns the answer for any past session with ?at=, so you can reproduce it on your own fills and sizing. A paper bot follows this endpoint every session and posts its results on our Discord.

The skip call applies to new trades, so it cannot protect positions already open when a sudden shock hits. This is data, not investment advice.

Common Use Cases

• Daily routine - call once after the open and act only on windows where action is sell
• Pick a trade - read candidates[] for ready strikes, deltas, bid/ask and mid_credit instead of building the legs by hand
• Compare expiries - see the same-day, one-week, two-week and one-month windows side by side
• Manage the exit - exit tells you whether the backtest held to expiration or took profit at 50% of the credit
• Replay a past session - call the historical endpoint with at=<session>T09:35:00 to see the strikes at the backtests' entry time
• Handle gaps - treat unavailable like a skip

Related

Related reading

• sell-window: a blueprint for selling options - how the windows work and how to follow them
• sell-window backtest - every recommended trade from 2018 to 2026, with a builder
• When not to sell options - the study that started this research

Complementary endpoints

• Historical sell-window - the same answer for a past session, with strikes at 09:35 ET
• Strategy Signals overview - the other strategy endpoints
• Yield Enhancement - rank covered calls and cash-secured puts on any symbol
• Tail Pricing - how rich or cheap the downside tail is for one expiry