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# 01.05.2026: Appended Messages for Playground Experiments

> Available in Phoenix 13.0+

<Update label="01.05.2026">

## Appended Messages for A/B Testing

<video controls autoPlay={false} loop={false} width="100%">
  <source src="https://storage.googleapis.com/arize-phoenix-assets/assets/videos/append_messages_on_playground.mp4" type="video/mp4" />
</video>

The Prompt Playground now supports appending conversation history from dataset examples to your prompts, enabling powerful A/B testing workflows for models and system prompts.

### Key Features

- **Append Conversation History**: Specify a dot-notation path to messages in your dataset examples (e.g., `messages` or `input.messages`)
- **OpenAI Message Format**: Full support for user, assistant, system, and tool messages
- **A/B Testing Models**: Compare how different models respond to the same conversation history
- **Testing System Prompts**: Evaluate different system prompts against identical user conversations

### How to Use

1. Load a dataset containing conversation messages in OpenAI format
2. Click the **settings button** (gear icon) in the experiment toolbar
3. Enter the path to your messages (e.g., `messages`)
4. Run your experiment to see results across all prompt variants

### Example Dataset Format

```json
{
  "messages": [
    {"role": "user", "content": "What is the weather in San Francisco?"},
    {"role": "assistant", "content": "Let me check that for you."},
    {"role": "user", "content": "Thanks! Also, what about New York?"}
  ]
}
```

<Card title="Using the Playground" href="/docs/phoenix/prompt-engineering/how-to-prompts/using-the-playground#appending-conversation-history" icon="book" horizontal>
Learn more about appending conversation history
</Card>

<Card title="Test a Prompt" href="/docs/phoenix/prompt-engineering/how-to-prompts/test-a-prompt#ab-testing-models-and-system-prompts" icon="flask" horizontal>
See A/B testing examples
</Card>

</Update>