Integration Studio

Event Bus

Workspace-scoped async messaging — publish events from workflows or SDK artifacts, subscribe via triggers, inspect topic streams, and replay events.

The Event Bus is an internal pub/sub system for decoupled, async communication between workflows and SDK artifacts. Unlike webhooks (which deliver to external URLs), the event bus routes messages within your FlowOS workspace. Manage topics at Integrations → Events.

Topics

Topics are named channels. Publishers send messages to a topic; subscribers receive them. Topic names are free-form strings — use dotted notation for namespacing (incident.resolved, github.push, etl.batch.completed).

•Topics are created automatically the first time a message is published to them.
•Wildcard subscriptions: a workflow trigger set to topic incident.* fires on incident.created, incident.resolved, etc.
•Messages are retained for 72 hours by default, extendable to 30 days on Enterprise.
•Each message can be up to 1 MB.

Publishing Events

From a Workflow Node

Add an Emit Event node to your canvas:

Emit Event node config

{
  "type": "EmitEvent",
  "config": {
    "topic": "incident.resolved",
    "payload": {
      "incidentId":  "{{trigger.record.id}}",
      "number":      "{{trigger.record.number}}",
      "resolvedBy":  "{{trigger.record.assigned_to}}",
      "duration_ms": "{{vars.resolutionDurationMs}}"
    },
    "deduplicationKey": "{{trigger.record.id}}"
  }
}

From an SDK Artifact

typescript

await ctx.events.publish('incident.resolved', {
  incidentId: incident.id,
  number:     incident.number,
  resolvedBy: incident.assigned_to,
}, {
  dedup: incident.id,   // deduplicated within 5 minutes
  delay: 0,
})

Via API

POST

/api/v1/events/publish

Publish a message to a topic.

json

{
  "topic": "etl.batch.completed",
  "payload": { "batchId": "batch_01HX...", "rowCount": 50000 },
  "deduplicationKey": "batch_01HX..."
}

Subscribing via Workflow Trigger

Set a workflow's trigger type to Event Bus and configure the topic(s):

Workflow trigger config

{
  "type": "event_bus",
  "config": {
    "topics": ["incident.resolved"],
    "filter": {
      "payload.incidentId": { "exists": true }
    }
  }
}

The workflow fires once per matching message. The trigger payload contains the full event object.

Event Schema

Field	Type	Description
id	varchar(26)	ULID event ID.
topic	varchar(200)	Topic name.
payload	jsonb	Message body.
publisher_type	enum	workflow \| sdk_artifact \| api \| system
publisher_id	varchar(26)	ID of the publishing entity.
dedup_key	varchar(200)	Deduplication key. Same key within 5 min = deduplicated.
workspace_id	varchar(26)	Owning workspace.
published_at	timestamptz	When the message was published.
expires_at	timestamptz	When the message will be purged.

Event Log

The Event Log tab on the Events page shows a live stream of all published messages. Filter by topic, publisher, or time range. Click a message to see its full payload and which workflows it triggered.

GET

/api/v1/events

List published events with filters.

GET

/api/v1/events/topics

List all known topics.

Event Replay

Replay any retained event to re-trigger its subscribers:

POST

/api/v1/events/:id/replay

Replay an event to all active subscribers.

Useful when a subscriber workflow was inactive during the original event and you need to process it retroactively.

Deduplication is scoped to a 5-minute window per topic. Publishing the same dedup key twice within that window results in only one delivery to subscribers. This prevents double-processing from retries or race conditions.