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An agent’s configuration controls everything about how it sounds and behaves during a conversation: the instructions it follows, the voice it speaks with, the language it uses, and the model driving its responses. All of these settings live together in a single configuration snapshot that is drafted, published, and versioned alongside your agent.

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Configuration fields

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System prompt

The system prompt defines your agent’s persona, goals, tone, and guardrails. For voice agents it’s the primary behavioral lever — write it for speech, not screen. See the System prompt guide for detailed authoring guidance.

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Prompt timezone

Set a prompt timezone to make the agent aware of the current date and time. When set, Zeptar appends a single line — the current date and time for that zone — to the system prompt at the start of every conversation, so the agent can answer questions like “what’s today’s date?” or apply business-hours logic.
  • Stored as a zone, evaluated at dispatch. The setting holds an IANA timezone (for example Europe/Paris), never a frozen timestamp. The actual date and time are computed when each conversation begins, so the agent always sees the real “now.”
  • Off by default. Leave it unset and nothing is added to the prompt.
  • Per-conversation override. Pass prompt_timezone in the conversation overrides to use a different zone for a single conversation, or null to turn the date/time line off for that conversation.

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First message

The first message is the opening line the agent speaks when a conversation starts. It frames the call and sets the caller’s expectations immediately.
  • Filled in — the agent speaks this line before the caller says anything.
  • Left empty — the agent waits for the caller to speak first. After the wait time elapses with no caller speech, the agent opens the conversation itself (generated from the system prompt).
Keep the first message short: one or two sentences that orient the caller without overwhelming them before they’ve said a word.

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Wait time

When the first message is empty, wait time controls how many seconds the agent waits for the caller to speak before it opens the conversation on its own.
  • A number — wait that many seconds, then speak. 0 opens immediately.
  • -1 — wait indefinitely; the agent never speaks first and always lets the caller lead.
  • Left blank — use the default of 7 seconds.
The agent computes the timeout at the start of each conversation; if the caller speaks within the window, the agent stays quiet and responds normally.

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Interruptible

When Interruptible is on (the default), the caller can talk over the agent and the agent stops to listen. Turn it off for flows where the agent must finish speaking — for example reading a required disclosure — before it accepts input.

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Language

The language setting controls which language the agent uses for speech recognition and synthesis.
  • Default language — the primary language for the conversation. The agent speaks in this language and optimises speech recognition for it.
  • Additional languages — optional list of secondary languages. When provided, the agent can detect and switch to any of the listed languages mid-conversation.
Setting a narrower language improves transcription accuracy for callers who speak that language. If your callers always speak a single language, set only the default and leave additional languages empty.

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LLM

The LLM setting selects the model that drives the agent’s reasoning and response generation. Zeptar’s model catalog spans multiple providers. You can pick any model listed in GET /v1/agent-config/catalog without changing anything else in your setup — Zeptar handles routing to the selected provider.
Leaving temperature blank tells Zeptar not to send a temperature parameter at all. The model runs with its own internal default, which may differ from what you’d get by setting 1.0 explicitly. If you need deterministic or creative output, set an explicit value.

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Voice

The voice setting selects the synthesis voice the agent speaks with. Like models, the voice catalog spans multiple providers. Browse available voices in GET /v1/agent-config/catalog and switch at any time — the change takes effect on the next published version.

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How to update your agent’s configuration

1

Open your agent

Navigate to Agents in the sidebar and select the agent you want to configure.
2

Go to the Agent tab

Inside the agent detail page, select the Agent tab. This is where system prompt, first message, language, model, and voice all live.
3

Make your changes

Edit any field. Changes autosave to your draft on the current branch as you type — there’s no explicit save button.
4

Publish to create a version

When your changes are ready, click Publish. Publishing commits your draft as a new immutable version on the current branch. Conversations that start after this point run against the new version.

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Configuration and versioning

Every configuration field — system prompt, first message, language, LLM, voice — is part of the versioned agent config. This means:
  • Edits autosave to your draft. Nothing reaches production until you publish.
  • Publishing creates an immutable version. Once created, a version is never changed or deleted.
  • Conversations pin to a version. A conversation started at version 3 stays on version 3 for its entire lifetime, even after you publish version 4.
  • Branches let you experiment safely. Fork a branch from any version, make bold changes to the configuration, publish, and test — Main is untouched until you merge.
See Versioning for the full branch-and-draft model, merge semantics, and version history tooling.