AI Voice Agent + Zendesk Sunshine Conversations: Side Convos and Switchboard

Sunshine Conversations is the most under-discussed Zendesk asset for voice teams. One REST API gives you WhatsApp, Messenger, Instagram, SMS, and Web Messenger — and Switchboard lets your voice agent pass control to a human or another bot without dropping context.

What the integration unlocks

flowchart LR
  Repo[GitHub repo] --> CI[GitHub Actions]
  CI --> Eval[Agent eval suite · PromptFoo]
  Eval -->|pass| Deploy[Deploy]
  Eval -->|fail| Block[Block PR]
  Deploy --> Prod[Production agent]
  Prod --> Trace[(LangSmith trace)]
  Trace --> Eval

A CallSphere voice agent finishes triaging a support call. The customer needs a human escalation but they prefer text. Voice agent says "I will text you the details so we have a paper trail" — and behind the scenes Sunshine Conversations opens a WhatsApp thread, posts the call summary, attaches the recording, and Switchboards control to the next available Zendesk Support agent. From the customer's perspective it is one conversation. From Zendesk's perspective it is a Ticket with full context.

How the Sunshine Conversations API exposes it

The base URL is https://api.smooch.io/v2. Key resources: POST /apps/{appId}/conversations to start a conversation, POST /apps/{appId}/conversations/{conversationId}/messages to post into it, POST /apps/{appId}/conversations/{conversationId}/passControl to invoke Switchboard and hand the conversation to another integration (Zendesk Agent Workspace, a third-party bot, or back to the customer-only state). POST /apps/{appId}/users to create or upsert the messaging user, and POST /apps/{appId}/users/{userId}/identities to link the WhatsApp/SMS identity.

Auth: server-to-server uses Basic auth with a Sunshine Conversations API key, or JWT for short-lived sessions. Sunshine Conversations is included only on Zendesk Suite Professional, Enterprise, and Enterprise Plus.

How CallSphere implements it

CallSphere runs 37 specialist agents across 6 verticals with 90+ tools. Healthcare's 14 tools (lookup_patient, create_new_patient, get_available_slots, schedule_appointment, send_intake_link...) routinely escalate to a clinic's Zendesk Support workspace via Sunshine. Real Estate OneRoof's 10 specialist agents post property cards into a WhatsApp thread mid-call so the buyer has the listings on their phone the second they hang up. The Salon GlamBook integration uses SMS Sunshine threads for booking confirmations and same-day reschedule prompts.

Explore a live demo and compare current plans to find the right fit for your business.

Build steps

1. In Zendesk Admin Center, enable Sunshine Conversations and create an Integration. Capture the App ID and API key.
2. Create a Switchboard with two participants: callsphere (your voice agent integration) and zd-agentWorkspace (Zendesk's native Agent Workspace).
3. From CallSphere, when a call requires a text follow-up, call POST /users with the customer's E.164 phone. Then POST /conversations with that user.
4. POST /messages with the structured summary (call topic, attempted resolutions, disposition).
5. Call passControl with target zd-agentWorkspace so the next Zendesk human picks it up. Sunshine fires a switchboard:passControl webhook back to CallSphere if you need to know.
6. Subscribe to message:appUser webhooks so a later customer reply re-engages CallSphere if the human marks the ticket back to bot-handled.
7. Test on a non-prod App ID first; messaging quotas vary by Zendesk plan.

Code snippet

// Hand off from CallSphere voice to Zendesk Agent Workspace via Switchboard
await fetch(
  `https://api.smooch.io/v2/apps/${appId}/conversations/${conversationId}/passControl`,
  {
    method: "POST",
    headers: {
      Authorization: `Basic ${btoa(`${keyId}:${secret}`)}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      switchboardIntegration: "zd-agentWorkspace",
      metadata: {
        callSphereCallId: turn.callId,
        callSummary: turn.summary,
        recordingUrl: recording.s3Url,
      },
    }),
  }
);

FAQ

What is the difference between Side Conversations and Sunshine? Side Conversations are internal Zendesk threads used for vendor or coworker coordination on a Ticket. Sunshine is the customer-facing messaging fabric. CallSphere uses both — Side Convos for "ping the supervisor," Sunshine for the multichannel customer thread.

Does Switchboard work with our existing Zendesk routing? Yes. Switchboard wraps Zendesk's Agent Workspace as one participant. Routing, SLAs, and views all behave normally once a human picks the conversation up.

Will the customer see "bot to human" handoff messages? Only if you publish them as messages. passControl itself is silent. Most teams send a one-line "Connecting you with a teammate" before the handoff.

How does Sunshine pricing work? It is bundled with Suite Professional and above. Per-conversation MAUs apply on Enterprise. Plan accordingly.

Explore a live demo and compare current plans to find the right fit for your business.

Sources

• Sunshine Conversations API Reference
• Zendesk: What is Sunshine Conversations
• Sunshine Conversations 2026 Guide