Initiating cobrowse session via API returns 400 Bad Request

I’m trying to kick off a cobrowse session programmatically using the Conversations API. The goal is to trigger a session from our backend service when a specific queue event happens, rather than relying on the agent clicking a button in the desktop client.

I’ve been following the docs for POST /api/v2/conversations/cobrowse/sessions. I’m constructing the JSON payload to include the participant ID and the target URL. Here’s what the request body looks like:

{
 "cobrowseParticipantId": "participant-uuid-here",
 "targetUrl": "https://example.com/page"
}

When I send this request with the appropriate Bearer token, I keep hitting a 400 Bad Request. The error response is pretty generic:

{
 "message": "Invalid request",
 "code": "bad.request"
}

I’ve double-checked the participant ID format and made sure the user is actually in an active conversation. I’m wondering if there’s a specific header I’m missing or if the targetUrl needs to be encoded in a certain way. The docs aren’t super clear on what constitutes an “invalid” request in this context. Any ideas on what might be breaking the payload?