Description

Mattermost inline buttons (interactive message actions) return 404 when clicked. The gateway does not register the /mattermost/interactions/default endpoint, even though the inlineButtons capability is enabled and interactions.callbackBaseUrl is configured.

Config

{
  "channels": {
    "mattermost": {
      "capabilities": ["inlineButtons"],
      "interactions": {
        "callbackBaseUrl": "http://100.64.0.9:39247",
        "allowedSourceIps": ["100.64.0.22"]
      }
    }
  }
}

Steps to Reproduce

1. Enable inlineButtons in Mattermost channel capabilities
2. Configure interactions.callbackBaseUrl pointing to the gateway
3. Send a message with buttons via the message tool
4. User clicks a button
5. Mattermost POSTs to http://<gateway>/mattermost/interactions/default
6. Gateway returns 404

Mattermost Server Log

{"msg":"DoPostActionWithCookie POST request, through DoActionRequest","url":"http://100.64.0.9:39247/mattermost/interactions/default"}
{"msg":"Action integration error.","err_where":"DoActionRequest","http_code":400,"error":"DoActionRequest: Action integration error., status=404"}

Verification

• curl -s -X POST http://100.64.0.9:39247/mattermost/interactions/default returns Not Found
• The route is not listed in gateway logs (only /api/channels/mattermost/command is registered)
• Mattermost CAN reach the gateway (confirmed with AllowedUntrustedInternalConnections and direct curl)
• This previously worked on March 9 (gateway log shows successful interaction: action=testok10)
• Broke sometime after, possibly after a gateway update/restart

Environment

• OpenClaw: v2026.3.13
• Mattermost: latest (HDD NAS Docker)
• Gateway bind: tailnet (100.64.0.9)
• macOS arm64