---
id: R16
family: GR-VAL
level: extended
profiles: [storage-api, editor-client]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-val/r16
specification: FlowDrop Workflow Specification 1.0
licence: CC BY 4.0
---

# R16 — No edge targets a trigger node's event input

*GR-VAL (Part I) · level: extended · profiles: storage-api, editor-client · added in 1.0*

A trigger's event comes from whatever started the run, never from another node. An edge into the port would replace the event with a value from inside the workflow, because a delivered edge value outranks initial data (DATA-6).

## The rule

> **Normative.** This is the rule.
>
> 1. An edge whose target is the `event` input port (SCH-47) of a node whose node type is a trigger node type MUST be refused with `R16_EDGE_EVENT_INPUT` at `edge.{index}`.
>
> 2. An authoring surface MUST NOT produce such an edge.


## What it means

The `event` port is exposed so that a value from outside can reach it, not so that it
can be wired. An edge into it would win over the event (DATA-6) and quietly turn a
trigger into an ordinary step. The validator refuses it, and an authoring surface does not
produce the connection in the first place.

## Example

```json title="An edge into a trigger node's event input" verdict="refused"
{
  "id": "e3",
  "source": "n2",
  "sourceHandle": "n2-output-result",
  "target": "on_update",
  "targetHandle": "on_update-input-event"
}
```

```json title="The error" verdict="refused"
{ "code": "R16_EDGE_EVENT_INPUT", "locator": "edge.2" }
```

## Why

Recorded under [OPEN-21](https://flowdrop.io/spec/rulings/open-21), [OPEN-25](https://flowdrop.io/spec/rulings/open-25).

## Related rules

- Names: SCH-47, DATA-6, EDGE-1
- Referenced by: SCH-47

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.