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

# Core Concepts

> The durable resources behind every FaceTime experience.

<h2 id="resource-model">
  Resource model
</h2>

| Concept               | What it is                                                                                                          |
| --------------------- | ------------------------------------------------------------------------------------------------------------------- |
| **Line**              | A real FaceTime handle Chert operates. It has a status, answer policy, optional assistant, and one concurrent call. |
| **Worker**            | The infrastructure unit that operates a line, bridges media, and reports heartbeat and readiness.                   |
| **Assistant**         | An AI persona definition: system prompt, greeting, and avatar. Drafts publish into immutable versions.              |
| **Assistant version** | An immutable published snapshot. Lines resolve the active version at call time.                                     |
| **Call**              | One FaceTime conversation with direction, state, timings, terminal reason, and rollout metadata.                    |
| **Session**           | A live link between a FaceTime call and a LiveKit room for Models 2 and 3.                                          |
| **Answer policy**     | `auto_answer` or webhook-driven `customer_decides`.                                                                 |
| **Readiness**         | Named worker health stages. Any failed stage causes inbound calls to be declined.                                   |