Incoming Webhooks

What is an incoming webhook?

A webhook is an HTTP endpoint that an external system calls to notify FlowX when an event happens. Instead of FlowX polling for updates, the third-party system sends an HTTP POST the moment something occurs — and FlowX starts a process in response. Common uses include receiving events from payment processors, CRMs, ERPs, or CI/CD pipelines.

Overview

Incoming Webhooks allow external systems to trigger FlowX processes by sending HTTP POST requests to a generated URL. Each webhook gets a unique, cryptographically secure API key for authentication — no IMAP setup, no polling, just a direct HTTP call. Use webhooks when you need to:

Receive events from third-party platforms (payment processors, CRMs, ERPs) that support outbound webhooks
Trigger processes from CI/CD pipelines or internal tools via simple HTTP calls
Replace polling-based integrations with event-driven process starts

API key authentication

Each webhook gets a unique, secure API key included in the URL

JSON payload forwarding

Webhook body and HTTP headers are forwarded to the process instance as variables

Manage Triggers UI

Activate, deactivate, and manage webhook URLs from Runtime Settings

Zero configuration

No server settings needed — create the data source, connect to a process, activate

How it works

A webhook does one of two things, depending on the Webhook Behavior you choose when you create the data source.

Start a process
Resume a waiting process

Each POST creates a new process instance.

Create an Incoming Webhook data source

In Integration Designer, create a new data source and select Incoming Webhook. Provide a name and optional description, and leave Webhook Behavior on Start a Process/Workflow. No connection settings are required.

Connect to a Message Start Event

In your process definition, add a Message Start Event node. Set the Trigger Type to Incoming Webhook and select your webhook data source.

Commit and activate

Commit the version, then go to Runtime → Manage Triggers. The webhook appears as Deactivated. Click the action menu and select Activate.

Get the webhook URL

From the trigger’s action menu, select Get URL. Copy the generated URL (includes the API key as a query parameter) and configure it in your external system.

External system sends POST request

When the external system POSTs JSON to the webhook URL, the webhook-gateway service validates the API key, publishes the event to Kafka, and the process engine starts a new process instance.

Each POST resumes an already-running instance and hands it the payload. Use this to push data into a process in flight — for example, sending updated credit data into a loan application that is parked waiting on an external system.

Create an Incoming Webhook data source

In Integration Designer, create a new data source and select Incoming Webhook. Set Webhook Behavior to Resume a Waiting Process, then set Webhook Correlation Key to the path in the incoming payload that identifies the instance to resume (for example, application.applicationId).

Connect to a Message Catch Intermediate Event

In your process definition, add a Webhook Trigger message catch event where the process should pause. Select the webhook as its Data Source, then set Process Correlation Key to the matching process variable and Process Key to where the incoming data should land.

Commit and activate

Commit the version, then activate the webhook in Runtime → Manage Triggers, exactly as for a start webhook.

Get the webhook URL

From the trigger’s action menu, select Get URL and configure that URL in your external system.

External system sends POST request

When the external system POSTs JSON, webhook-gateway validates the API key, reads the correlation value at the Webhook Correlation Key path, and publishes a message event. The process engine matches it against instances waiting on that catch event and resumes the one whose Process Correlation Key holds the same value, storing the incoming data at the Process Key.

If no waiting instance matches the correlation value, or the correlation path does not resolve in the payload, the request is rejected and nothing is resumed. See Error handling.

Creating a webhook data source

Navigate to Data Sources

Go to Integrations → Data Sources in your project.

Add a new data source

Click + and select Incoming Webhook as the data source type.

Configure basic information

Field	Required	Description
Name	Yes	A unique name for the webhook (3–50 characters, letters, numbers, `[] () . _ -`)
Description	No	Purpose or context for this webhook
Webhook Behavior	Yes	Whether each POST starts a new process or resumes a waiting one. See Webhook Behavior.
Webhook Correlation Key	Only for Resume a Waiting Process	Dotted path into the incoming payload whose value identifies which waiting process instance to resume. See Webhook Correlation Key path syntax.

Create

Click Create. The webhook data source is ready to be connected to a process.

Incoming Webhooks accept POST requests with JSON payloads (max 1 MB). No connection settings, credentials, or polling configuration is needed.

When deleting a webhook data source, deactivate it first and remove the URL from any third-party systems that use it. Deleting the webhook in FlowX does not notify external systems — they will continue sending requests that return errors.

Connecting to a Message Catch Event

A webhook can drive two kinds of message catch events:

Event placement	Webhook Behavior (API value)	What the webhook does
Message Start Event	`START_PROCESS`	Creates a new process instance on each POST
Message Catch Intermediate Event	`RESUME_PROCESS`	Resumes a process instance waiting on the catch

You choose which of the two a webhook does when you create the data source, using the Webhook Behavior setting.

Webhook Behavior

On the webhook data source’s Settings tab, Webhook Behavior offers two options:

Option	What it does	Attach the webhook to
Start a Process/Workflow	Creates a new process or workflow instance on each POST, with the webhook payload as its input.	A Message Start Event node
Resume a Waiting Process	Resumes a process instance already waiting on a catch event, using a correlation key.	A Message Catch Intermediate Event node

Webhook data source Settings tab with Resume a Waiting Process selected and a correlation key set

Selecting Resume a Waiting Process enables Webhook Correlation Key in the Process Connection panel and marks it required. It is the dotted path into the incoming payload whose value identifies the instance to resume, and it is defined once on the data source rather than per node. Under Start a Process/Workflow the field is greyed out, and saving a value there is rejected.

Webhook Behavior is immutable after the first save. Once the webhook data source has been saved, the setting is locked in the Designer and the API rejects a change to it. To switch a webhook between starting and resuming, create a new webhook data source.

On a Message Start Event

Open your process definition

Open the process in the Process Designer.

Add a Message Start Event node

Drag a Message Start Event from the Start Events section of the node palette onto the canvas.

Configure the Process Trigger

In the node configuration panel, under Process Trigger:

Set Trigger Type to Incoming Webhook
In Select Webhook, choose your webhook data source from the dropdown

Save the node

Click Save to persist the configuration.

Message Start Event configured with Incoming Webhook trigger

On a Message Catch Intermediate Event

Use a webhook on an intermediate catch event to resume a process instance that is waiting for an external signal — for example, a callback from a third-party document scanner, a downstream system confirming an enqueued job, or a manual operator action delivered over HTTP.

Add a Webhook Trigger intermediate catch event

From the node palette, drag a Webhook Trigger message catch event onto the canvas at the point where the process should pause.

Select the webhook data source

In the node configuration panel, set the Data Source dropdown to the webhook that drives this catch event. The Webhook Correlation Key field appears as read-only and shows the correlation key defined on the webhook itself — included here so you can see how incoming requests are matched.

Set the Process Correlation Key

Set Process Correlation Key to a business or process variable from the data model (for example, applicationId, orderId). At runtime this value is matched against the incoming payload to identify which waiting process instance to resume.

Set the Process Key

Set Process Key to the data-model path where the incoming webhook data should be stored when the catch fires. The value stored there is the same { dateTime, payload, headers } envelope described in Webhook payload, not the bare POST body — read the request body from payload underneath it.

Save the node

Click Save to persist the configuration.

The same webhook data source can drive multiple intermediate catch events as long as the Process Correlation Key disambiguates which instance to resume. Without a valid correlation match, the inbound request is rejected.

Webhook Correlation Key path syntax

The Webhook Correlation Key points into the incoming webhook payload. It uses dotted-path notation and supports array indices in square brackets, so deeply nested provider payloads can be addressed directly.

Path pattern	Resolves to
`application.applicationId`	`payload.application.applicationId`
`entry[0].changes[0].value.messages[0].text.body`	The first inbound text-message body in a Meta WhatsApp webhook payload
`data.orders[2].id`	The `id` of the third element of the `orders` array

Array index syntax (field[N]) is supported in correlation keys, so the canonical Meta WhatsApp resume path works as-is. Paths like entry[0]... resolve directly and no longer need to be flattened in the producer before posting.

If the path does not resolve in an incoming request (missing field, index out of bounds, null leaf), the request is rejected and the waiting process instance is not resumed.

Managing webhooks at runtime

Activating a webhook

For a webhook to appear in Manage Triggers:

The webhook data source must be created
The webhook must be connected to a node that can carry a webhook trigger — a Message Start Event or a Message Catch Intermediate Event
The version must be committed

Navigate to Runtime → Manage Triggers to view and control webhooks:

Column	Description
State	`Active` or `Deactivated`
Trigger Type	`Webhook`
Event Name	The webhook data source name
Location	Project and branch information

Use the action menu (three-dot icon) to:

Activate — Start accepting webhook requests
Deactivate — Stop accepting requests. The API key and URL are preserved, so you can reactivate later without reconfiguring external systems.
Get URL — View and copy the webhook URL with API key

A single webhook can trigger multiple processes — add the same webhook data source to Message Start Event nodes in different process definitions. Each incoming request starts all connected processes.

Webhook URL and API key

When you activate a webhook and select Get URL, a modal displays:

Webhook URL — The full URL including the API key as a flowxApiKey query parameter
Copy button — Copies the URL to clipboard
Reset API Key — Generates a new API key (invalidates the previous URL)

Webhook URL modal with API key and Reset button

URL format:

https://{services-host}/webhooks/incoming/{orgId}/{workspaceId}/{appId}/{resourceDefinitionId}?flowxApiKey={apiKey}

Resetting the API key creates a new webhook URL. Update the URL in all third-party systems that use it, or they will receive 401 Unauthorized errors.

Provider adapters

When a webhook is created in the Integration Designer, the Settings tab now exposes:

Provider — the dropdown offers three options. Like Webhook Behavior, the provider is a one-time selection: once saved it becomes immutable, and you create a new webhook to switch.
Dropdown label API value Signature validation
Generic (API Key Only) GENERIC None
Slack SLACK X-Slack-Signature HMAC-SHA256
Meta (WhatsApp, Messenger, Instagram, Threads) META X-Hub-Signature-256 HMAC-SHA256
Provider secret — the signing secret(s) obtained from the provider. Stored encrypted; can be rotated independently of the API key. The field is labelled per provider and only appears once a provider that needs it is selected: Signing Secret for Slack, Verify token plus App secret for Meta. Generic (API Key Only) has no secret field.

Dropdown label	API value	Signature validation
Generic (API Key Only)	`GENERIC`	None
Slack	`SLACK`	`X-Slack-Signature` HMAC-SHA256
Meta (WhatsApp, Messenger, Instagram, Threads)	`META`	`X-Hub-Signature-256` HMAC-SHA256

Provider dropdown on the webhook Settings tab, listing Generic, Slack and Meta

For SaaS-hosted secrets you can also reference a config parameter using the ${configParam.name} placeholder syntax — placeholders are resolved at registration time the same way LLM provider secrets are.

Generic provider

The default. No signature validation is performed; authentication relies on the FlowX flowxApiKey and HTTPS. Use GENERIC for systems that do not sign their webhooks, or where signature validation is handled inside the process via a business-rule action on the raw headers.

Slack provider

Performs Slack’s standard signature check on every incoming request:

Header	Purpose
`X-Slack-Signature`	HMAC-SHA256 signature of the version, timestamp, and raw body, prefixed with `v0=`.
`X-Slack-Request-Timestamp`	Unix timestamp; rejected if more than 5 minutes out of skew.

Requests that fail signature verification, that miss either header, or that arrive without a configured signing secret are rejected with 401 Unauthorized. Slack’s URL-verification handshake is handled automatically — a url_verification POST with a challenge field receives the challenge value back as JSON, before the request is forwarded to the process. No process configuration is required for the handshake. Selecting Slack adds a required Signing Secret field to the Settings tab. Find the value in your Slack app under Basic Information → App Credentials → Signing Secret. You can paste it directly or reference a config parameter.

Webhook Settings tab with the Slack provider selected, showing the Signing Secret field

Meta provider

Covers WhatsApp, Messenger, Instagram, and Threads. Meta-platform integrations share a common subscription model and signature scheme; the META adapter handles both. Meta webhooks require two secrets, configured as masked inputs in the Settings panel:

Field	Purpose	Where to find it
Verify token	Used during the GET URL-verification handshake.	Any random string you choose. Paste the same value in Meta → Webhooks → Verify token.
App secret	Verifies the `X-Hub-Signature-256` HMAC on every POST.	Meta Developer Dashboard → your App → Settings → Basic → App Secret.

Both values are stored together as a JSON-packed pair in the existing webhook secret field, encrypted at rest. Both are required; saving without either returns WEBHOOK_META_SECRETS_REQUIRED 400.

Webhook Settings tab with the Meta provider selected, showing the Verify token and App secret fields

GET URL verification. Meta sends a GET request with hub.mode=subscribe, hub.verify_token, and hub.challenge query parameters when you save the webhook in the Meta App configuration. The gateway:

Confirms hub.mode=subscribe.
Confirms hub.challenge is present.
Compares the received hub.verify_token to the configured Verify token using a constant-time check.
Echoes the hub.challenge value back as plain text on success.

A mismatch or missing parameter returns 403 Forbidden — Meta does not finalise the subscription. POST signature verification. Every POST is signed by Meta with an X-Hub-Signature-256 header (sha256=<hex>). The gateway recomputes the HMAC-SHA256 of the raw body with the configured App secret and rejects mismatches with 401 Unauthorized.

Path / provider mismatch

If a request hits the URL for one provider but the webhook registration is configured with a different provider, the gateway returns 400 Bad Request. Always use the URL shown in the Get URL modal — it carries the correct provider segment for the registration.

Webhook payload

When an external system POSTs to the webhook URL, the following data is available in the process instance:

{
  "webhookMessage": {
    "dateTime": "2026-03-23T15:30:00Z",
    "payload": {
      "orderId": "ORD-12345",
      "status": "completed",
      "amount": 299.99
    },
    "headers": {
      "Content-Type": ["application/json"],
      "X-Custom-Header": ["value"]
    }
  }
}

Field	Type	Description
`dateTime`	string (ISO 8601)	Ingestion time at FlowX — when `webhook-gateway` received the request. If the provider includes its own event timestamp in the payload, use that for the original event time.
`payload`	object or string	The POST request body (parsed as JSON if valid, raw string otherwise)
`headers`	object	All HTTP headers from the incoming request. Each header maps to an array of values — access the first value with `webhookMessage.headers.Content-Type[0]` in process variables

webhookMessage paramValue on a process instance

headers includes values added by the FlowX ingress in addition to what the caller sent — typically X-Forwarded-For, X-Real-IP, X-Request-ID, X-Forwarded-Host, X-Forwarded-Proto. These are useful for logging and tracing but should not be confused with provider-supplied headers.

The maximum payload size is 1 MB. Requests exceeding this limit are rejected.

Authentication

Webhook authentication uses API keys:

Each webhook registration gets a unique 32-byte, base64-URL-encoded API key
The key is passed as the flowxApiKey query parameter in the webhook URL
Validation uses constant-time comparison to prevent timing attacks
Invalid or missing keys return 401 Unauthorized
Inactive webhooks return 404 Not Found

FlowX validates provider signatures only for providers with a built-in adapter. For the GENERIC provider — and for any third-party signature scheme without a dedicated adapter (Stripe-Signature, GitHub’s X-Hub-Signature-256 outside the Meta family, etc.) — signature headers are forwarded to the process in webhookMessage.headers but no validation is performed. Authentication for GENERIC registrations relies on the FlowX API key and HTTPS. The raw request body is not preserved after JSON parsing, which makes in-process HMAC verification impractical — for unsupported providers, design integrations assuming API key + HTTPS is the only authentication layer, or request a built-in adapter.

Error handling

HTTP Status	Cause	Resolution
`200 OK`	Webhook accepted and published to Kafka	—
`400 Bad Request`	Malformed payload (not valid JSON)	Verify the POST body is valid JSON
`401 Unauthorized`	Invalid or missing API key	Check the `flowxApiKey` parameter matches the active webhook URL
`404 Not Found`	Webhook registration not found or deactivated	Verify the webhook is activated in Manage Triggers
`413 Payload Too Large`	Request body exceeds 1 MB	Reduce the payload size or split into multiple requests
`500 Internal Server Error`	Processing error	Check webhook-gateway service logs

Failed webhook events appear in Runtime → Failed Triggers with details about the failure cause.

Best practices

Use HTTPS

Always use HTTPS URLs in production to protect the API key in transit

Validate payloads in your process

Add validation logic in your process to handle unexpected or malformed payloads gracefully

Monitor Failed Triggers

Regularly check the Failed Triggers section for webhook processing errors

Rotate keys periodically

Use the Reset API Key feature to rotate webhook credentials, then update the URL in external systems

Message Start Event

Configure message-based and webhook process triggers

Message Catch Intermediate Event

Pause a process until an internal message or an external webhook resumes it

Email Trigger

Start processes from incoming emails via IMAP

Integration Designer

Build integration workflows and manage data sources

Webhook Gateway setup

Deploy and configure the webhook-gateway microservice

​What is an incoming webhook?

​Overview

API key authentication

JSON payload forwarding

Manage Triggers UI

Zero configuration

​How it works

​Creating a webhook data source

​Connecting to a Message Catch Event

​Webhook Behavior

​On a Message Start Event

​On a Message Catch Intermediate Event

​Webhook Correlation Key path syntax

​Managing webhooks at runtime

​Activating a webhook

​Webhook URL and API key

​Provider adapters

​Generic provider

​Slack provider

​Meta provider

​Path / provider mismatch

​Webhook payload

​Authentication

​Error handling

​Best practices

Use HTTPS

Validate payloads in your process

Monitor Failed Triggers

Rotate keys periodically

​Related resources

Message Start Event

Message Catch Intermediate Event

Email Trigger

Integration Designer

Webhook Gateway setup

What is an incoming webhook?

Overview

How it works

Creating a webhook data source

Connecting to a Message Catch Event

Webhook Behavior

On a Message Start Event

On a Message Catch Intermediate Event

Webhook Correlation Key path syntax

Managing webhooks at runtime

Activating a webhook

Webhook URL and API key

Provider adapters

Generic provider

Slack provider

Meta provider

Path / provider mismatch

Webhook payload

Authentication

Error handling

Best practices

Related resources