> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fish.audio/llms.txt
> Use this file to discover all available pages before exploring further.

# Preview Calls

> Talk to your draft agent in a live voice call, right in the Builder

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.

## Start a preview call

<Steps>
  <Step title="Open your agent in the Builder">
    Preview works from any Builder section — Configuration, Tools, Knowledge
    base, and so on.
  </Step>

  <Step title="Click Test call">
    The **Test call** button in the top bar opens the Preview panel on the right
    side of the Builder.
  </Step>

  <Step title="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.
  </Step>

  <Step title="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](/agents/build/configuration), and the conversation begins.
  </Step>
</Steps>

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.

## During the call

### 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.

### Tool calls

When the agent invokes a [tool](/agents/build/tools), 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.

<Warning>
  Preview calls run your real configuration. [Webhook
  tools](/agents/build/webhook-tools) send real HTTP requests to your endpoints
  — point them at a staging environment if you want to avoid side effects while
  testing.
</Warning>

### Controls

| Control  | Behavior                                                                                                                                       |
| -------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
| Mute     | Toggles your microphone without ending the call                                                                                                |
| End call | Ends the call and returns the panel to its ready state                                                                                         |
| Timer    | Shows elapsed time; preview calls are capped at 10 minutes (600 seconds) — or the agent's configured maximum call duration, whichever is lower |

## Drafts, not published versions

Preview calls and production sessions read different configurations:

| Session            | Configuration used                                       |
| ------------------ | -------------------------------------------------------- |
| Preview call       | Latest draft, autosaved as you edit in the Builder       |
| Production session | The published version, unchanged until you publish again |

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](/agents/deploy/versions-publishing).

<Tip>
  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.
</Tip>

## 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](/agents/monitor/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](/agents/monitor/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](/agents/monitor/webhooks), so Builder debugging doesn't push analysis results to your production systems.

## Going further

<CardGroup cols={2}>
  <Card title="Agent tests" icon="vial" href="/agents/test/agent-tests">
    Scripted conversations with automated Pass/Fail judging — catch regressions
    without listening by ear.
  </Card>

  <Card title="Versions & publishing" icon="rocket" href="/agents/deploy/versions-publishing">
    Ship the draft you just previewed as an immutable published version.
  </Card>

  <Card title="Post-call analysis" icon="chart-simple" href="/agents/monitor/post-call-analysis">
    Configure summaries, data extraction, and success criteria — results show up
    in the preview panel.
  </Card>

  <Card title="Web SDK" icon="code" href="/agents/deploy/web-sdk">
    Put the same voice conversation in your own app.
  </Card>
</CardGroup>