flow_cross

Sent when a FLOW cross line fires: the order flow imbalance of SPX options near the money, summed since the open, had the calls' side cross the puts' (calls minus puts changed sign). An event, not a signal: FLOW describes pressure as it happens, and a cross is not a forecast.

POSTyour https addressX-FirmTape-Event: flow_cross

Plan LIVEPayload version 1Signed HMAC-SHA256Schema flow_cross.schema.json

This event serves

Plan: LIVE. LIVE: today's session every second, alerts, ASK, the levels API and the platform integrations, and 5 LAB credits a month. Every finished session is free in REPLAY. Pricing. Turn it on: Right-click the CVD band with FLOW on (Layers, Indicators, CVD) and pick Alert when calls and puts flow cross; a webhook address on Account, Level alerts.

When it is sent

At the first second the net since the open reaches or passes zero, read every 5 seconds from the per-second tape.
Armed again only once the net stands at least 20% of the day's largest net so far from zero, and never less than 1,000 contracts, so it does not chatter around zero.

Payload

Field	Meaning	Unit
version1	Payload version, `1`.
idstring	Event id, `evt_` and 24 hex digits. The same on every try and for every account the event goes to: drop one you have seen.
type"flow_cross"	`flow_cross`.
symbolstring	SPX, ES, NQ, RTY or a ticker.
levelobject	`kind` is `flow`; `value` is 0, the zero the net crossed.
pricenumber \| null	The price at the event. Null on a `premarket` event (see `phase`).	index points
bookvolume \| open_interest \| measured \| volume+open_interest	The book the event was read in, as the account picked it for that card: `volume`, `open_interest`, `measured` (SPX, ES, NQ), or `volume+open_interest` (levels of interest only, as on the chart). A symbol without the book picked is read in `volume`.
tsstring	When it was found, ISO 8601 in New York time.
daystring	The ET trading day.
levelsobject	The flip and the walls of the book in `book` at the event (the volume book's for `volume+open_interest`).
levels.flipnumber \| null	Flip.	index points
levels.call_wallnumber \| null	Call wall.	index points
levels.put_wallnumber \| null	Put wall.	index points
levels.put_supportdeprecatednumber \| null	The put wall under its first name. Deprecated: read `put_wall`; removed after 2026-11-30.	index points
textstring	The sentence Telegram and push show, ending in the time it fired, ET.
directionabove \| below	`above`: the calls' flow crossed above the puts'; `below`: the reverse.
threshold_pointsnumber	Sized events (`flip_move`, `level_near`, `interest_near`, `level_touch`, `interest_touch`): the size the account picked, SPX points.	index points
threshold_minutesnumber	`level_beyond`, `interest_beyond`: the one-minute closes in a row the account picked.	minutes
fromstring	ES, NQ, RTY: the index whose book moved by the basis gives the levels.
basisnumber \| null	ES, NQ, RTY: the basis at the event.	index points
levels_asofstring \| null	Symbols on a five-minute book: when that book was built.
phasepremarket	Present only when a price line fired before the bell, from 04:00 ET to the open on a trading day: `premarket`. The line was crossed on the premarket's minute prices; `price` is then null, and `levels` are the previous session's closing levels. Absent on every event in the session.
alertobject	The line that fired: `scope` (`z0` 0DTE, `nx` the next expiries, `all`), `mode`.
joinsarray	One event for several levels on one price (a wall and levels of interest): the types it stands for, e.g. `["wall_break", "interest_cross"]`.
flowobject	`net` the calls' minus the puts' order flow since the open at the firing second, in contracts of quoted size; `at` that second, ET.

Delivery


Answer	Any 2xx within 3 seconds. Redirects are not followed.
Retries	No answer, a 429 or a 5xx: tried again after 1 s and 4 s, three tries in all, the same id each time.
Switched off	After 10 failed events in a row; the account page shows why. Saving the address switches it on again.
Volume	Up to 30 events a minute per account; past that they are dropped and counted on the account page.
Test	`type: "test"`, from Send test
Log	The last delivery (time, status, tries) on the account page.

Verify every request before reading it: Webhooks: verify the signature.

flip_cross · wall_break · regime_change · wall_move · flip_move · level_near · level_beyond · level_touch · interest_new · interest_move · interest_drop · interest_cross · interest_near · interest_beyond · interest_touch · chorus_strength · price_alert · level_line · cvd_line · order · test

Request we send

POST https://your.server/firmtape
Content-Type: application/json
User-Agent: FirmTape-Webhooks/1
X-FirmTape-Event: flow_cross
X-FirmTape-Event-Id: evt_4c7d1e9a2b3f6a0d8e5c1b7a
X-FirmTape-Timestamp: 1760034725
X-FirmTape-Signature: sha256=9b1e...

Body

{
  "version": 1,
  "id": "evt_4c7d1e9a2b3f6a0d8e5c1b7a",
  "type": "flow_cross",
  "symbol": "SPX",
  "price": 6748.25,
  "book": "volume",
  "ts": "2026-11-06T10:52:46-05:00",
  "day": "2026-11-06",
  "levels": {
    "flip": 6731.08,
    "call_wall": 6750,
    "put_wall": 6700,
    "put_support": 6700
  },
  "level": {
    "kind": "flow",
    "value": 0
  },
  "direction": "above",
  "text": "SPX FLOW: calls crossed above puts (net +1,349 since the open, 0DTE), your FLOW cross line · 10:52:46 ET",
  "flow": {
    "net": 1349,
    "at": "10:52:46"
  },
  "alert": {
    "id": "al_7d8e9f0a1b2c",
    "kind": "flow",
    "scope": "z0",
    "mode": "repeat"
  }
}

Verify

NodePython

const crypto = require("node:crypto");
// rawBody: the request body as received, a Buffer or a string, before any JSON parsing
function verify(rawBody, headers, secret) {
  const t = headers["x-firmtape-timestamp"];
  const got = String(headers["x-firmtape-signature"] || "");
  if (!t || Math.abs(Date.now() / 1000 - Number(t)) > 300) return false;
  const want = "sha256=" + crypto.createHmac("sha256", secret).update(`${t}.${rawBody}`).digest("hex");
  return got.length === want.length && crypto.timingSafeEqual(Buffer.from(got), Buffer.from(want));
}

import hmac, hashlib, time

def verify(raw_body: bytes, headers, secret: str) -> bool:
    t = headers.get("X-FirmTape-Timestamp", "")
    got = headers.get("X-FirmTape-Signature", "")
    if not t or abs(time.time() - int(t)) > 300:
        return False
    want = "sha256=" + hmac.new(secret.encode(), t.encode() + b"." + raw_body, hashlib.sha256).hexdigest()
    return hmac.compare_digest(got, want)

Measurements of dealer positioning, never a forecast or a trade call. This page is built from FirmTape's public contract, the same files the OpenAPI document is built from; the tests hold them against the route code. Markdown: /docs/developers/live/events/flow_cross.md.

flow_cross

When it is sent

Payload

Delivery

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