Choose the chat model | Faustine Docs

The chat model is the model that answers users in a Web Agent's widget. It reads the persona, decides which actions to run and fills in their parameters. Each agent has its own chat model, set under AI Model in the agent's Assistant tab.

The chat model and the model provider

Two settings have similar names and do different jobs.

Setting	Where	What it decides
Model provider	Settings > Model Provider, once for the workspace	Whose account every AI request runs on and is billed to: the analysis, the editors and the chat.
Chat model	The agent's Assistant tab > AI Model, once for each agent	Which of that provider's models answers in this agent's widget.

The Provider cards under AI Model are Anthropic and OpenAI. They choose the family of models to list. They do not change the workspace's model provider. To set up or change the account itself, see Model providers.

Before you begin

Your workspace has a working model provider. The list of models comes from it.

Choose the model

To change an agent's chat model:

In the portal, go to Web Agents and select your agent.
Select the Assistant tab, then Provider & model.
In the Provider row, select Anthropic or OpenAI.
In the Model row, select a model. Each entry shows the model's ID and its context window. The entry marked Default is the platform default.
In the save bar, select Save changes.

The change applies to new messages once it is saved. The chat reads the model from the agent's settings, not from the version, so it does not wait for a publish and it applies to every environment.

To go back to the platform default, select the entry marked Default. An agent needs a model. With none selected, a conversation fails with a message that no chat model is configured.

Which model to choose

The list has only models that Faustine has vetted for agents. Among them, a more capable model follows the persona more closely, picks the right action more often and fills in parameters correctly. A smaller model answers faster and costs less.

Web search works with Anthropic models only.

Troubleshooting

Symptom	Cause	Fix
No OpenAI models mapped — map one in Settings to offer it for chat	Your model provider maps models by hand, and no OpenAI model is mapped.	Map one under Settings > Model Provider, or select Anthropic.
No chat models mapped for your provider	Your model provider has no chat model mapped.	Map the models under Settings > Model Provider.
The row shows a message that no API key is configured for the provider	Your workspace's model provider has no key for that family of models.	Select the other provider card. An Anthropic key is part of your model provider under Settings > Model Provider. To use OpenAI models, contact Faustine.
The selected model has the badge Current · not vetted	The model was selected before it left the vetted list.	Select a vetted model when you next change the setting.

Next steps

Model providers: the account the chat model runs on.
Write the agent's persona: the instructions the model reads.
Turn on web search: available with Anthropic models.