Connection Validation ​
To validate connections before they are created you can either pass a function to the is-valid-connection prop of the <Handle /> component or use the onConnect event of the <VueFlow /> component.
Another alternative is to pass a isValidConnection function to the is-valid-connection prop of the <VueFlow /> component. This function will be applied to all connections in the flow (even existing ones).
Using a handle in a custom node ​
vue
<script setup>
import { Handle, Position } from '@vue-flow/core'
</script>
<template>
<Handle type="source" :position="Position.Right" />
<Handle type="target" :position="Position.Left" />
</template>