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A voice call crosses more than one system. The caller arrives over SIP, the media lands on an SFU, an agent is dispatched into the room, and that agent calls three inference providers. When a call is slow or expensive, the answer can be in any of them.

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The three layers

Python 3.11 or later throughout.
Every voicegw subcommand needs the livekit extra, including ones with nothing to do with LiveKit. The CLI imports its LiveKit diagnostics at startup, so a bare pip install voicegateway leaves even voicegw --help failing with ModuleNotFoundError. Install voicegateway[livekit] even if you only run voicegw loadtest.
The agent layer stands alone. You can profile cost and latency without operating any infrastructure beyond your own agent process, and most people stay there. The SFU and SIP layers assume you already run the deployment under test, which is usually a different job and often a different person.

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The SIP layer works differently

VoiceGateway does not place calls and will not become a load generator. It is the evidence and reporting layer: something else drives the load, and this reads what it left behind.
You run the generator against your own trunk, then hand VoiceGateway the artifacts. voicegw loadtest import ingests and correlates them; voicegw loadtest report <run_id> judges the gates and writes the evidence bundle.

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How the layers join

Each layer is written by its own path: LiveKit webhooks fill calls and call_legs, the node scrape fills node_samples, and attach() writes sessions and requests. No single row joins all three. The joins are pairwise and deliberately conservative: GET /api/correlation reports the deployment-wide join rate so you can see how complete the picture is instead of assuming it.

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The per-call waterfall

The dashboard renders six layers per call. Two carry a number. The unmeasured rows render their reason rather than an empty bar. Per-modality inference timing does exist, from attach(), on the cost and latency views. It is not joined into this waterfall.

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What it does not do

  • It does not generate SIP load. Not one call.
  • It does generate SFU traffic when you ask: voicegw livekit latency places real agent turns, voicegw livekit sfu --load connects synthetic participants. Both are opt-in.
  • It does not provision infrastructure.
  • It does not claim a causal join. Node overlap means a sample fell inside a call’s window, not that the node served that call.