Build an SMS Support Agent with Follow-Up on Telnyx Edge Compute

A lot of AI support demos stop after one reply. Customer asks a question. Model answers. Demo done. Real support usually needs a little more than that. You need message history, background processing, a way to send the reply, and sometimes a follow-up if the customer goes quiet. This example builds that flow as an SMS support agent on Telnyx Edge Compute. Code: https://github.com/team-telnyx/telnyx-code-examples/tree/main/sms-support-agent-with-followup What it does The app receives inbound SMS messages, routes each sender to a durable Agent SDK actor, calls Telnyx AI Inference, sends a reply through Telnyx Messaging, and schedules a 24-hour follow-up. The flow: Inbound SMS -> /webhooks/sms -> SupportAgent.receive() -> this.messages.add() -> this.queue("process") -> Telnyx AI Inference -> Telnyx Messaging reply -> this.schedule(24h, "followup") The important part is that the webhook does not need to wait on the LLM. It stores the message and queues the work, so the webhook can acknowledge quickly. Agent SDK primitives used The SupportAgent extends the Agent SDK Agent class from @telnyx/edge-runtime. It uses: this.messages.add() for durable conversation history this.messages.toOpenAI() to format history for the model this.queue("process") for background AI processing this.schedule(86400, "followup") for the next-day check-in this.setState() and this.getState() for sender/recipient state this.env.TELNYX for zero-credential Telnyx API access The [telnyx] binding in telnyx.toml handles API auth: [telnyx] binding = "TELNYX" Then the agent can call: await this.env.TELNYX.ai.openai.chat.createCompletion(...) await this.env.TELNYX.messages.send(...) No API key is hardcoded in the application code. The main routes POST /webhooks/sms receives Telnyx message.received webhooks POST /debug/message simulates an inbound SMS for testing GET /debug/state inspects an actor state for a sender GET /health/liveness and GET /health/readiness are health checks Try the debug route After deploying, you can simulate an inbound SMS: curl -X POST https://sms-support-agent-.telnyxcompute.com/debug/message \ -H "Content-Type: application/json" \ -d '{ "from":"+15551230000", "to":"+15559870000", "text":"How do I send an SMS?" }' Response: { "action": "queued", "from": "+15551230000", "to": "+15559870000" } For real SMS, set your Telnyx Messaging Profile webhook URL to: https://sms-support-agent-.telnyxcompute.com/webhooks/sms Then text the Telnyx number. The follow-up logic The follow-up task runs 24 hours later. It checks the last message in the durable conversation history. If the last message is still from the assistant, the customer has not replied since the AI answer, so the agent sends: Did that solve your problem? Reply yes or no, or ask for a human. If the customer already replied, it skips the nudge. That is the piece I like. The agent is not just a stateless webhook. It has memory and scheduled work. Production notes Before shipping this pattern in a real support workflow, I would add: webhook signature verification opt-out handling for SMS idempotent outbound sends rate limiting per phone number human handoff rules message retention policy monitoring for queued and scheduled tasks But as a starter pattern, this is a clean way to build an AI support agent that can answer, remember, and follow up. Resources: Code: https://github.com/team-telnyx/telnyx-code-examples/tree/main/sms-support-agent-with-followup Agent SDK docs: https://developers.telnyx.com/docs/agent-sdk Agent SDK quickstart: https://developers.telnyx.com/docs/agent-sdk/quickstart Edge Compute docs: https://developers.telnyx.com/docs/edge-compute Messaging docs: https://developers.telnyx.com/docs/messaging Telnyx AI Inference docs: https://developers.telnyx.com/docs/inference Telnyx AI skills and toolkits: https://github.com/team-telnyx/ai