chat/docs/slash-commands.mdx

Unified chat abstraction for Slack, Teams, Google Chat, and Discord

---
title: Slash Commands
description: Handle slash command invocations and respond with messages or modals.
type: guide
prerequisites:
  - /docs/getting-started
related:
  - /docs/modals
  - /adapters/official/slack
  - /adapters/official/discord
---

Slash commands let users invoke your bot with `/command` syntax. Register handlers with `onSlashCommand` to respond.

Slash commands are supported on [Slack](/adapters/official/slack) and [Discord](/adapters/official/discord).

## Handle a specific command

```typescript title="lib/bot.ts" lineNumbers
bot.onSlashCommand("/status", async (event) => {
  await event.channel.post("All systems operational!");
});
```

## Handle multiple commands

```typescript title="lib/bot.ts" lineNumbers
bot.onSlashCommand(["/help", "/info"], async (event) => {
  await event.channel.post(`You invoked ${event.command}`);
});
```

## Catch-all handler

Register a handler without a command to catch all slash commands:

```typescript title="lib/bot.ts" lineNumbers
bot.onSlashCommand(async (event) => {
  console.log(`Command: ${event.command}, Args: ${event.text}`);
});
```

## SlashCommandEvent

The `event` object passed to slash command handlers:

| Property | Type | Description |
|----------|------|-------------|
| `command` | `string` | The command name (e.g., `/status`) |
| `text` | `string` | Arguments after the command |
| `user` | `Author` | The user who invoked the command |
| `channel` | `Channel` | The channel where the command was invoked |
| `adapter` | `Adapter` | The platform adapter |
| `triggerId` | `string` (optional) | Platform trigger ID for opening modals |
| `openModal` | `(modal) => Promise<{ viewId: string } \| undefined>` | Open a modal dialog |
| `raw` | `unknown` | Platform-specific payload |

## Respond to a command

Use `event.channel` to post messages:

```typescript title="lib/bot.ts" lineNumbers
bot.onSlashCommand("/greet", async (event) => {
  // Public message to the channel
  await event.channel.post(`Hello, ${event.user.fullName}!`);

  // Ephemeral message (only visible to the user)
  await event.channel.postEphemeral(
    event.user,
    "This message is just for you!",
    { fallbackToDM: false }
  );
});
```

## Open a modal

Use `event.openModal()` to open a [modal](/docs/modals) in response to a slash command:

```tsx title="lib/bot.tsx" lineNumbers
import { Modal, TextInput, Select, SelectOption } from "chat";

bot.onSlashCommand("/feedback", async (event) => {
  const result = await event.openModal(
    <Modal callbackId="feedback_form" title="Send Feedback" submitLabel="Send">
      <TextInput id="message" label="Your Feedback" multiline />
      <Select id="category" label="Category">
        <SelectOption label="Bug" value="bug" />
        <SelectOption label="Feature" value="feature" />
      </Select>
    </Modal>
  );

  if (!result) {
    await event.channel.post("Couldn't open the feedback form. Please try again.");
  }
});
```

<Callout type="info">
When a modal is opened from a slash command, the submit handler receives `relatedChannel` instead of `relatedThread`. Use this to post back to the channel where the command was invoked.
</Callout>

```typescript title="lib/bot.ts" lineNumbers
bot.onModalSubmit("feedback_form", async (event) => {
  const { message, category } = event.values;

  // Post to the channel where the slash command was invoked
  if (event.relatedChannel) {
    await event.relatedChannel.post(`Feedback received! Category: ${category}`);
  }
});
```

## Discord

Discord slash commands are received via [HTTP Interactions](/adapters/official/discord#http-interactions-vs-gateway) — no Gateway connection is needed. The adapter automatically sends a deferred response to Discord, then resolves it when your handler calls `event.channel.post()`.

### Subcommands

Discord supports subcommand groups and subcommands. The adapter flattens these into the `event.command` path:

| Discord command | `event.command` | `event.text` |
|-----------------|-----------------|--------------|
| `/status` | `/status` | `""` |
| `/project create --name="Acme"` | `/project create` | `Acme` |
| `/project issue list --status="open"` | `/project issue list` | `open` |

For full option details (names, types), use `event.raw` to access the original Discord interaction payload.

### Registering commands with Discord

You need to register slash commands with the [Discord API](https://discord.com/developers/docs/interactions/application-commands) before they appear in the client. The Chat SDK handles incoming commands but does not register them for you.