# Agent behavior

Agent behavior is the part of an agent configuration that controls what it is told, how it opens a conversation, which model it uses, and how long a text conversation can run.

## Behavior controls in Agent Studio

The Agent screen provides controls for:

- system prompt and optional first message;
- Indonesian or English as the default language;
- model selection and temperature when the model supports it;
- maximum conversation duration;
- the built-in friendly personality; and
- the built-in `end_call` tool.

The default personality is included unless **Default personality off** is selected. Turn it off when the system prompt defines the complete tone and behavior. When `end_call` is enabled, the agent can say goodbye and then close the conversation.

## How changes become active

Editing a behavior field changes your draft on the active branch. The autosave status confirms whether the draft reached the server. A draft can be tested without publishing, but only publishing Main updates the agent's active version.

An open test conversation keeps the configuration it started with. If the prompt or another behavior field changes, start a fresh conversation before comparing results.

## Where to go next

- Write the core instruction in [prompt and first message](/docs/agents/prompt-and-first-message).
- Select a runtime-ready option in [models](/docs/agents/models); selector presence alone does not prove an adapter is active.
- Set defaults in [language and conversation](/docs/agents/language-and-conversation).
- Learn the release boundary in [draft and publish](/docs/agents/draft-and-publish).