> ## Documentation Index
> Fetch the complete documentation index at: https://docs.automate.ax/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Automate.ax automations are TypeScript programs.
> Use Bun for installation and command examples.
> Use Automate.ax for the product name and automate.ax for the package, CLI, and domain.
> Treat documented public APIs as current; do not invent transitional or deprecated names.

# On reaction event

> Run an automation when a Slack reaction is added or removed.

`slack.onReactionEvent` emits both `reaction_added` and `reaction_removed` callbacks for visible messages, files, and file comments.

```ts automations/watch-slack-reactions.automation.ts theme={null}
import { automation } from "automate.ax"
import { slack } from "automate.ax/slack"

export default automation("Watch Slack reactions", () => {
  const reaction = slack.onReactionEvent()
  // Use reaction.item to update the Slack reaction's mirrored record.
})
```

The typed `event.type` distinguishes additions from removals. Use `slack.onReactionAdded` or `slack.onReactionRemoved` when only one lifecycle should activate the automation.