Example: Answering an incoming call

For the complete documentation index, see llms.txt.

Overview

This example answers an inbound call and connects it to Qwen Cloud with a short prompt, an English voice, and barge-in.

⬇️ Jump to the Full VoxEngine scenario.

Prerequisites

Set up an inbound entrypoint for the caller:
Create a routing rule that points the destination to this scenario.
Store your Qwen Cloud API key in Voximplant Secrets under QWEN_API_KEY.

Architecture

Usage highlights

Create a VoiceAgentAPIClient with QwenCloud.createVoiceAgentAPIClient.
The example pins model to qwen-audio-3.1-realtime-plus.
On SessionCreated, send sessionUpdate with voice, instructions, languages, and turn_detection.
On SessionUpdated, bridge audio with VoxEngine.sendMediaBetween(call, client) and ask Qwen to greet the caller.
On InputAudioBufferSpeechStarted, call clearMediaBuffer so the caller can interrupt playback.

Media bridge

QwenCloud.VoiceAgentAPIClient is not in VoxMediaUnitMap yet. sendMediaBetween matches the other realtime connectors. See Overview for the typings gap.

Turn detection and barge-in

voiceAIClient.addEventListener(
  QwenCloud.VoiceAgentAPIEvents.InputAudioBufferSpeechStarted,
  () => voiceAIClient.clearMediaBuffer()
);

Configure before you run

Set QWEN_API_KEY in Voximplant Secrets.
Change voice if you want another Qwen system voice or a cloned voice id. beth_v3.1 is an English 3.1 voice. The provider default is longanqian_v3.1.
Adjust SYSTEM_PROMPT for your brand voice and guardrails.

Try it

Suggested test prompts:

“Hello”
“What can you help me with?”
“Goodbye.”

Notes

See the VoxEngine API Reference for more details.

Full VoxEngine scenario

voxeengine-qwen-answer-incoming-call.js

require(Modules.QwenCloud);
const QWEN_MODEL = "qwen-audio-3.1-realtime-plus";
const SYSTEM_PROMPT = `
  You are Voxi, a concise phone agent for Voximplant callers.
  Voximplant is pronounced VOX-im-plant.
  Reply in English. Keep answers brief and helpful.
  If you do not know, say so and offer to connect them to a human.
`;
const SESSION_PARAMETERS = {
    session: {
        modalities: ["text", "audio"],
        voice: "beth_v3.1",
        instructions: SYSTEM_PROMPT,
        input_audio_transcription: {language: "en"},
        output_audio: {language: "en"},
        turn_detection: {type: "server_vad"},
    },
};
VoxEngine.addEventListener(AppEvents.CallAlerting, async ({call}) => {
    let voiceAIClient;
    const terminate = (event) => {
        if (event) Logger.write(JSON.stringify(event));
        voiceAIClient?.close();
        VoxEngine.terminate();
    };
    call.addEventListener(CallEvents.Disconnected, terminate);
    call.addEventListener(CallEvents.Failed, terminate);
    call.answer();
    // call.record({hd_audio: true, stereo: true});
    try {
        const providerApiKey = VoxEngine.getSecretValue("QWEN_API_KEY");
        if (!providerApiKey) throw new Error("Set QWEN_API_KEY in Voximplant Secrets");
        voiceAIClient = await QwenCloud.createVoiceAgentAPIClient({
            apiKey: providerApiKey,
            model: QWEN_MODEL,
            onWebSocketClose: terminate,
        });
        voiceAIClient.addEventListener(QwenCloud.VoiceAgentAPIEvents.SessionCreated, (event) => {
            Logger.write(`===${event.name}===>${JSON.stringify(event.data)}`);
            voiceAIClient.sessionUpdate(SESSION_PARAMETERS);
        });
        voiceAIClient.addEventListener(QwenCloud.VoiceAgentAPIEvents.SessionUpdated, (event) => {
            Logger.write(`===${event.name}===>${JSON.stringify(event.data)}`);
            VoxEngine.sendMediaBetween(call, voiceAIClient);
            voiceAIClient.conversationItemCreate({
                item: {
                    type: "message",
                    role: "user",
                    content: [{
                        type: "input_text",
                        text: "The call just connected. Greet the caller in one short sentence.",
                    }],
                },
            });
            voiceAIClient.responseCreate({});
        });
        voiceAIClient.addEventListener(QwenCloud.VoiceAgentAPIEvents.InputAudioBufferSpeechStarted, (event) => {
            Logger.write(`===${event.name}===>${JSON.stringify(event.data)}`);
            voiceAIClient.clearMediaBuffer();
        });
        [
            QwenCloud.Events.WebSocketMediaStarted,
            QwenCloud.Events.WebSocketMediaEnded,
            QwenCloud.VoiceAgentAPIEvents.ConnectorInformation,
            QwenCloud.VoiceAgentAPIEvents.ResponseCreated,
            QwenCloud.VoiceAgentAPIEvents.ResponseOutputItemAdded,
            QwenCloud.VoiceAgentAPIEvents.ResponseOutputItemDone,
            QwenCloud.VoiceAgentAPIEvents.ResponseAudioTranscriptDelta,
            QwenCloud.VoiceAgentAPIEvents.ResponseAudioTranscriptDone,
            QwenCloud.VoiceAgentAPIEvents.ResponseAudioDone,
            QwenCloud.VoiceAgentAPIEvents.ResponseDone,
            QwenCloud.VoiceAgentAPIEvents.InputAudioBufferSpeechStopped,
            QwenCloud.VoiceAgentAPIEvents.InputAudioBufferCommitted,
            QwenCloud.VoiceAgentAPIEvents.ConversationItemCreated,
            QwenCloud.VoiceAgentAPIEvents.ConversationItemInputAudioTranscriptionCompleted,
            QwenCloud.VoiceAgentAPIEvents.Error,
            QwenCloud.VoiceAgentAPIEvents.WebSocketError,
            QwenCloud.VoiceAgentAPIEvents.Unknown,
        ].forEach((evtName) => {
            voiceAIClient.addEventListener(evtName, (e) => {
                Logger.write(`===${e.name}===>${JSON.stringify(e)}`);
            });
        });
    } catch (error) {
        Logger.write("===SOMETHING_WENT_WRONG===");
        Logger.write(JSON.stringify(error));
        VoxEngine.terminate();
    }
});