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

# Why does my agent use gpt-5.4?

> Agents without a model default to OpenAIResponses with gpt-5.4. Set model explicitly to change this.

When an `Agent` is created without a `model`, Agno sets `OpenAIResponses(id="gpt-5.4")` as the default. You'll see this log line on the first run:

```
INFO Setting default model to OpenAI Responses
```

The default requires the `openai` package and the `OPENAI_API_KEY` environment variable. If the package is missing you'll get an `ImportError`, and if the key is missing the run fails.

## Set a Model Explicitly

Pass any model class to the `model` parameter:

```python theme={null}
from agno.agent import Agent
from agno.models.anthropic import Claude

agent = Agent(model=Claude(id="claude-sonnet-4-5"))
agent.print_response("What is the capital of France?")
```

Set the model explicitly in production. The default exists for quick experiments, and relying on it means your agent's behavior changes when Agno updates the default ID.

## Next Steps

* [Models overview](/models/overview)
* [OpenAI key request while using other models](/faq/openai-key-request-for-other-models)