LINE Channel Setup

OpenCrust supports the LINE Messaging API for both 1-on-1 chats and group/room conversations.

Prerequisites

A LINE Official Account. Create one at the LINE Business ID portal.
A Channel in the LINE Developers Console.
Channel Access Token (long-lived) and Channel Secret.

Configuration

Add the line channel to your ~/.opencrust/config.yml:

channels:
  line:
    type: line
    enabled: true
    channel_access_token: "YOUR_CHANNEL_ACCESS_TOKEN"
    channel_secret: "YOUR_CHANNEL_SECRET"

You can also use environment variables instead of hardcoding credentials:

Setting	Environment variable
`channel_access_token`	`LINE_CHANNEL_ACCESS_TOKEN`
`channel_secret`	`LINE_CHANNEL_SECRET`

Access Control

DM policy (`dm_policy`)

Controls who can send the bot direct messages.

Value	Behaviour
`open`	Anyone can message the bot (no auth required).
`pairing`	New users must enter a 6-digit pairing code (default).
`allowlist`	Only LINE user IDs listed under `allowlist` are accepted.

channels:
  line:
    type: line
    enabled: true
    channel_access_token: "YOUR_CHANNEL_ACCESS_TOKEN"
    channel_secret: "YOUR_CHANNEL_SECRET"
    dm_policy: pairing        # open | pairing | allowlist
    allowlist:
      - "Uxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"   # LINE user ID

Group policy (`group_policy`)

Controls how the bot behaves in LINE groups and rooms.

Value	Behaviour
`open`	Respond to every message in the group (default).
`mention`	Respond only when the bot is @mentioned in the group.
`disabled`	Ignore all group/room messages.

channels:
  line:
    type: line
    enabled: true
    channel_access_token: "YOUR_CHANNEL_ACCESS_TOKEN"
    channel_secret: "YOUR_CHANNEL_SECRET"
    group_policy: mention     # open | mention | disabled

Note: Mention detection uses message.mention.mentionees from the LINE webhook payload. The bot's own user ID is resolved automatically from GET /v2/bot/info at startup — no manual configuration required.

Webhook Setup

In the LINE Developers Console, go to Messaging API settings.
Set the Webhook URL to: https://your-domain.com/webhooks/line
Enable Use webhook.
(Optional) Disable Auto-response messages and Greeting messages in the LINE Official Account manager to avoid duplicate responses.

Features

Reply vs Push API

OpenCrust uses a "Reply-first" strategy:

Reply API: Used for immediate responses to user messages. This is free and does not count against your messaging limit.
Push API: Used as a fallback if the reply token expires or for proactive messages (like scheduled tasks). Note that Push messages may count toward your monthly free limit depending on your LINE plan.

Groups and Rooms

The agent works in LINE groups and rooms.

Session isolation: Each group/room has its own conversation session, shared by all members.
Mention detection: With group_policy: mention, the bot responds only when directly @mentioned. The bot user ID is fetched from the LINE API automatically on startup.

When voice.auto_reply_voice is enabled in your config, the bot synthesizes TTS audio and attempts to deliver it as a voice message. LINE requires an externally accessible CDN URL for audio delivery; if unavailable the bot falls back to a text response.

Security

All incoming requests are verified using the X-Line-Signature header (HMAC-SHA256) to ensure they originate from the LINE platform.

Diagnostics

Use the opencrust doctor command to verify your LINE configuration:

opencrust doctor

It will check if the access token is valid and if the webhook endpoint is reachable.

OpenCrust Documentation