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Preview calls let you hold a live voice conversation with your agent without leaving the Builder. Every call runs against your current draft configuration — edit the system prompt, pick a different voice, and call again to hear the difference immediately, no publish required.

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Start a preview call

1

Open your agent in the Builder

Preview works from any Builder section — Configuration, Tools, Knowledge base, and so on.
2

Click Test call

The Test call button in the top bar opens the Preview panel on the right side of the Builder.
3

Click Start call

Your browser asks for microphone access the first time. The call cannot start without a microphone — if you deny permission, the panel tells you to allow access in your browser settings and try again.
4

Talk to your agent

Once connected, the status pill shows Live with a running call timer. The agent opens the call according to your first message settings, and the conversation begins.
The panel stays connected while you switch between Builder sections, so you can read your configuration mid-call. Navigating away from the Builder — back to the agent list, for example — hangs up. If the call fails to connect, the panel shows an error state and lets you retry; a connection drop mid-call simply ends the call.

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During the call

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Live transcript

The panel shows both sides of the conversation as it happens:
  • Your speech appears as it is transcribed, updating in place while you talk and settling when you finish a turn.
  • Agent replies stream in as text while the agent speaks them aloud.

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Tool calls

When the agent invokes a tool, the call appears inline in the transcript as a compact entry that flips from running to done or failed. Expand an entry to inspect the exact arguments the model sent and the response it received, as formatted JSON truncated at 4 KB.
Preview calls run your real configuration. Webhook tools send real HTTP requests to your endpoints — point them at a staging environment if you want to avoid side effects while testing.

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Controls

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Drafts, not published versions

Preview calls and production sessions read different configurations: This makes preview the fast inner loop: tweak the prompt, call, listen, repeat. Your published version — and every live integration using it — is untouched until you decide the draft is ready and publish it.
After a config change, hang up and start a new call. A preview call reflects the draft as it stood when the session was created.

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After the call

Preview sessions are built for iteration, not record-keeping:
  • Post-call analysis runs in the panel. If you have post-call analysis configured, ending the call triggers it and the results — summary, extracted data fields, and per-criterion success / failure / unknown verdicts — appear directly in the panel. Analysis runs however the call ends — including the automatic time limit or closing the tab mid-call — but results are viewable only in the panel, so close the tab and you won’t see them.
  • Nothing enters conversation history. Preview calls never appear in conversation history, and the transcript is not preserved after you hang up.
  • No post-call webhook fires. Preview sessions never trigger the call.analyzed post-call webhook, so Builder debugging doesn’t push analysis results to your production systems.

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Going further

Agent tests

Scripted conversations with automated Pass/Fail judging — catch regressions without listening by ear.

Versions & publishing

Ship the draft you just previewed as an immutable published version.

Post-call analysis

Configure summaries, data extraction, and success criteria — results show up in the preview panel.

Web SDK

Put the same voice conversation in your own app.