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Preview is the test

There is no separate “test mode” and no phone number needed. The Preview tab runs a live voice session against your current playbook using the same AgentRunner that serves a production call. What you hear here is what a caller hears.
Your microphone streams up at 16 kHz; the agent’s synthesized voice streams back at 24 kHz. The audio rides a WebSocket bridge; the transcript and checkpoint arrive on a separate side channel, so the transcript stays accurate even when audio is under load.

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Step 1 - Set the voice and model

The Preview header has the run controls:

Voice profile

Pick the voice the agent speaks in - the same voice a real caller would hear. Each profile shows its language, its STT + TTS providers, an estimated cost per turn, and a WER (word-error-rate) quality hint.

Model

Choose the LLM the agent runs on for this test (separate from the builder model in the chat). The picker shows speed/cost hints like GPT-4.1 mini · fast. BYOK lets you run on your own provider key.
Preview voice test: a voice profile dropdown listing Anika, Neha, Shagun, Riya, Zara, Pooja - each with a language tag, STT and TTS provider, cost per turn, and WER - next to a large Press to talk mic orb with 'Try saying:' chips.

Voice profile picker - language, STT/TTS stack, cost per turn, and WER for each voice

If Press to talk is disabled, the header tells you why - usually a missing voice profile or an unsaved playbook. Pick a voice and save, and the control unlocks.

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Step 2 - Press to talk

The center of the Preview is a single Press to talk control.
1

Idle

You see the orb plus a row of “Try saying:” opener chips - example first lines pulled from your playbook. They are prompts for you; they are not injected into the agent.
2

Connect and speak

Press it, allow the mic, and talk as a caller would. The session connects and the agent answers in the voice you chose.
3

Live

The transcript fills in turn by turn with timestamps, a slim pipeline readout shows the current stage, and level meters confirm audio is flowing.
Preview tab showing the voice pipeline in action

Connected - each turn runs through the same STT -> DialogMachine.turn() -> TTS pipeline a live caller hits

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Step 3 - Read the live signal

While you talk, three things tell you whether the playbook works:

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What to actually check

  • The persona and voice sound right to a caller.
  • Checkpoints advance on the conditions you wrote (done_when / advance_when) - not too early, not too late.
  • Slot collection works: the agent captures what it needs (order number, callback) before moving on.
  • Interrupts fire from any step - saying “goodbye” or “I’m busy” ends the call gracefully.

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Step 4 - Dig in when something is off

Open the advanced drawer below the call for the detailed console: the EVENTS log, traces, and per-turn LLM calls. Use it to see why a checkpoint did not advance - the Director’s judgment and any tool calls are all there.
The console shows the engine’s own events and never leaks raw provider errors. If a turn fails, you get a clean surface here, not a stack trace.

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The tight loop

Testing is meant to feed straight back into authoring - both panes stay mounted, so a turn in flight survives a tab switch:
1

Hear a problem in Preview

e.g. the agent offers 5pm before the caller declines 4pm.
2

Fix it in chat or the Editor

“Only offer 5pm after the caller says 4pm doesn’t work.” The YAML updates.
3

Press to talk again

Re-test the same path. Repeat until it behaves.

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Next step

When it behaves on the paths you tried by hand, let the optimizer stress it against many simulated callers.

Optimize the playbook

Run generated personas, score goal completion, and harden the weak spots automatically.