Genesys Web Messaging Open API: Sending Quick Replies via C# SDK

I’m building a custom bot connector in C# that needs to send structured messages back to the guest. Specifically, I want to send a card with quick reply buttons using the Open Messaging API format. I’ve read the docs on /api/v2/conversations/messages, but the examples are mostly for plain text or simple attachments.

Here is the JSON payload I’m constructing in my C# code:

{
 "to": { 
 "id": "conv-123-xyz",
 "type": "conversation"
 },
 "from": {
 "id": "bot-user-id",
 "type": "user"
 },
 "type": "text",
 "text": "Please select an option:",
 "quickReplies": [
 {
 "label": "Sales",
 "value": "sales_option"
 },
 {
 "label": "Support",
 "value": "support_option"
 }
 ]
}

I’m sending this via the SDK method PlatformClient.Conversations.Messages.PostConversationMessageAsync. The request returns a 201 Created status code, which suggests it succeeded. However, the guest never sees the buttons. They just see the text “Please select an option:” as a plain message bubble.

I’ve checked the conversation history in the admin UI and the message appears there as text only. The quickReplies field is missing from the stored message object. I tried changing the type to application/vnd.genesis.open.messaging+json but that threw a 400 Bad Request saying the type is not supported for this channel.

Is there a specific wrapper object I need for the Open API format? Or does the Web Messaging channel ignore the quickReplies property in the payload entirely? I’ve been staring at this for two days and I can’t find a C# example that actually works for interactive elements.