Point an agent at Gemini Live, and the caller talks to Google’s duplex speech-to-speech model directly. There is no separate transcriber or text-to-speech stage. The caller’s audio streams into one bidirectional session. The session listens and speaks on the same connection. Thus the agent starts to reply sooner, and barge-in feels instant. This is a shipped, first-class provider. ClutchCall Voice ships a native Gemini Live adapter. The adapter speaks Google’s BidiGenerateContent WebSocket protocol end to end. The adapter does these tasks:
  • It opens the session.
  • It upsamples the call’s audio to the rate that Gemini expects.
  • It streams the model’s spoken reply back onto the leg.
  • It connects Gemini’s server-side voice activity detection to barge-in.
To turn it on, name gemini as the provider in your agent config. There is no code to write.
Gemini Live is one of several duplex providers. For the shared model of how a speech-to-speech agent works, see BYO Speech-to-Speech Models. That page covers the single REALTIME node, the greeting behavior, and session budgets. This page covers the Gemini-specific config, voices, and behavior.

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Configure a Gemini Live agent

A duplex agent has a single node. Set the entry node to REALTIME. Name gemini as the provider. Select a model and a voice.
1

Name gemini in the agent spec

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string
required
Set to gemini to select the Gemini Live adapter.
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string
A Gemini Live model id, for example gemini-2.0-flash-exp. The adapter qualifies the id to Gemini’s required models/<id> form for you. Thus gemini-2.0-flash-exp and models/gemini-2.0-flash-exp both work.
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string
One of Gemini’s prebuilt voices: Aoede, Charon, Fenrir, Kore, or Puck. Leave the field empty to accept Google’s server default. The runtime defaults to Aoede when you omit the field.
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string
The system prompt. The adapter sends it as Gemini’s systemInstruction in the opening setup message. It also seeds the inbound greeting.
2

Supply your Gemini API key

The system stores credentials per tenant and never shares them across workspaces. Add your Gemini API key in the agent console at agent.clutchcall.dev, or through the control-plane API at portal.clutchcall.dev. The runtime reads the key when it opens the session. If there is no key, the provider returns no session. The call then falls back to a silent passthrough and does not drop.
3

Point a number at the agent and call

Save the agent. Attach a phone number or trunk to it. Place a call. ClutchCall Voice opens the Gemini Live WebSocket on the first inbound audio frame. It then streams audio in both directions.

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How the audio flows

You do not touch sample rates. The adapter does the conversions that Gemini requires:
1

Caller audio in

The adapter upsamples the call’s 8 kHz PCM16 to the 16 kHz PCM16 that Gemini Live expects on input. It streams the audio as realtimeInput.audio frames.
2

Model audio out

Gemini returns 24 kHz PCM16 audio. The runtime resamples the audio down and paces it back onto the call leg. A phone leg gets G.711. A browser leg gets Opus.
3

Barge-in

When the caller talks over the agent, Gemini’s server VAD emits an interrupted signal. The runtime cuts the in-flight reply immediately.

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Turn-taking

For a REALTIME entry node, the runtime defaults to server_vad. Gemini Live does its own endpointing and interruption detection. Thus you do not add a local turn detector. When Gemini reports an interruption, the runtime maps it to barge-in and stops the outgoing audio. See Turn Detection & Barge-In to tune how quickly the agent yields, or to learn the fallback behavior for models without server VAD.

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Greeting on inbound calls

Some carrier SBCs withhold RTP until they hear your RTP. On an inbound call, the runtime prompts Gemini to speak first. This opens the media path. The model greets from your instructions. This behavior is on by default for inbound direct-media calls. No extra config is required.

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Tools mid-conversation

The Gemini Live adapter renders your configured tools into Gemini’s functionDeclarations in the opening setup message. It receives toolCall events during a spoken turn. It returns your result as a toolResponse. Thus the model can call an HTTP or MCP tool and speak the outcome without leaving the call. Configure tools in the same way as for any agent. See Tool Calling.
Function calling over Gemini Live is newer than the OpenAI Realtime path. OpenAI Realtime is the most tested realtime adapter today. If your agent depends on complex multi-tool turns, check the behavior on a staging number before you route production traffic.

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Session budgets

Every realtime session is bounded. A stuck provider cannot run forever. The handshake gets a few seconds. After that, the runtime gives up and falls back. The runtime closes sessions at a 15-minute ceiling, even if the provider did not close them. Tune lifetime, idle re-engage, and hangup budgets on Session Lifecycle.

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Next steps

Speech-to-speech model

The shared duplex-agent model, greeting behavior, and provider matrix.

OpenAI Realtime

The most complete realtime adapter: server VAD, function calling, and greeting.

Turn detection

Tune barge-in, endpointing, and backchannel handling.

All runtime knobs

Models, codecs, budgets, and guardrails in one reference.