> For the complete documentation index, see [llms.txt](https://docs.zaia.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zaia.app/agents/agent-settings/model-selection.md).

# Model Selection

In Zaia Endless, each Agent can be powered by a specific **Provider** and **Model**.\
This configuration defines:

* Which **LLM** is used for reasoning
* How **billing and credit consumption** are handled

The model selection is part of the Agent configuration flow and is defined **after the Prompt**, ensuring that the Agent’s instructions are clear before choosing how it will reason.

***

### Where to Select the Model

The **Provider** and **Model** selector is located **below the main Prompt field** in the Agent configuration screen.

This positioning reflects the recommended workflow:

1. Define the Agent’s **Role**
2. Write the **Prompt**
3. Select the **Provider and Model**
4. Adjust behavioral settings (Temperature, Effort, Planning, Reasoning)

***

### How Providers Work

There are two ways to connect LLMs to your Agents.

#### Option 1 — Using Zaia Provider

When you select **Zaia** as the provider, your Agent uses models natively available on the platform (such as *Claude Sonnet 4.5*, *GPT-4o mini*, or *Grok 4.5*).

In this mode:

* You consume **Zaia platform credits** per execution
* Authentication and billing are fully managed by Zaia
* No API key configuration is required

This is the recommended option for most users who want a fully managed experience with instant access to multiple LLMs.

***

#### Option 2 — Adding a Custom Provider

You can also connect your **own LLM provider**, bypassing Zaia’s managed credits.

To configure a custom provider, go to:

```
Platform → Settings → Providers → Configure Provider
```

In this panel, you can:

* Set a **provider name** (e.g., “OpenAI Personal”, “Anthropic Enterprise”)
* Select the **provider type** (Anthropic, OpenAI, or Google AI)
* Paste your **API key**
* Optionally add an internal description for identification

Once saved, the provider becomes available in the **Provider** dropdown inside the Agent configuration.

When an Agent uses a custom provider:

* It consumes **your own API credits**
* Billing happens directly with the external provider
* Zaia does not charge credits for model execution

> 🔒 **Security note:** API tokens are stored in encrypted form and are only used when invoking the selected model for your Agent.

***

### Switching Models Per Agent

Model selection is **Agent-specific**.\
This allows you to:

* Use lightweight models for FAQs or simple Agents
* Assign more powerful models to complex, reasoning-heavy Agents
* Optimize cost, latency, and accuracy across your workspace

You can change the model at any time without modifying the Agent’s Prompt or logic.

***

### Best Practices

* Always define the **Prompt first**, then select the model
* Use **Zaia Provider** for faster setup and predictable billing
* Use **custom providers** when you need:
  * Cost optimization at scale
  * Enterprise contracts
  * Provider-specific features

***

👉 Choosing the right model ensures your Agent balances **performance, cost, and reasoning quality** according to its purpose.