Mattermost Gets Full Emoji Reaction Support in OpenClaw 2026.2.17

OpenClaw 2026.2.17 brings a highly requested feature for Mattermost users: full emoji reaction support. Your AI agent can now react to messages AND respond when users react to the agent's messages.

What's New

The new Mattermost reactions implementation adds:

• Outbound reactions: Use message(action=react) to add or remove emoji reactions to any message
• Inbound reaction events: Your agent gets notified when users react to its messages
• Remove flag: An explicit remove: true parameter prevents accidental reaction removals

How It Works

Reacting to a message is now as simple as:

To remove a reaction:

The implementation follows the same patterns established by Discord, Slack, and Telegram, so if you've used reactions on those platforms, the experience is consistent.

Configuration

Reaction support is controlled via the actions.reactions config at both the base channel level and per-account:

channels:
  mattermost:
    actions:
      reactions: true  # Enable globally
    accounts:
      - name: work-mm
        actions:
          reactions: false  # Disable for this specific account

Inbound Reaction Notifications

When users react to your agent's messages, the reaction events flow through the standard system event pipeline. This opens up interesting use cases:

• Feedback collection: Track positive/negative reactions to gauge response quality
• Approval workflows: Use 👍/👎 reactions as lightweight yes/no inputs
• Acknowledgment signals: Let users confirm they've read important messages

The implementation enforces the same DM/group policy rules as regular messages, so your existing access controls apply.

Technical Details

Under the hood, this PR adds:

• A new reactions.ts module with addMattermostReaction and removeMattermostReaction functions
• Bot user ID resolution with caching for efficient API calls
• WebSocket monitor extensions for reaction_added and reaction_removed events
• Proper HTTP handling for Mattermost's 204 No Content responses on reaction DELETE

Get Started

Upgrade to OpenClaw 2026.2.17 and enable Mattermost reactions in your config. If you're already running Mattermost, reactions work immediately — just make sure actions.reactions isn't explicitly disabled.

Thanks to @echo931 for contributing this feature!

GitHub PR: #18608