# Provider Interoperability

When working with Prism, you might need to customize requests based on which provider you're using. Different providers have unique capabilities, configuration options, and requirements that can affect how you structure your requests for optimal results.

## Using the `whenProvider` Method

The `whenProvider` method lets you easily customize your requests for specific providers while maintaining clean, readable code.

```php
$response = Prism::text()
    ->using(Provider::OpenAI, 'gpt-4o')
    ->withPrompt('Who are you?')
    ->whenProvider(
        Provider::Anthropic,
        fn ($request) => $request
            ->withProviderOptions([
                'cacheType' => 'ephemeral',
            ])
    )
    ->asText();
```

In this example, the `withProviderOptions` settings will only be applied when using Anthropic's provider. If you're using OpenAI (as specified in the `using` method), these customizations are simply skipped.

## Key Benefits

- **Cleaner Code**: Keep your provider-specific customizations encapsulated and only apply them when needed
- **Easy Provider Switching**: Swap between providers without rewriting your configuration code
- **Maintainable Applications**: Define provider-specific behaviors in one place

## Advanced Usage

You can chain multiple `whenProvider` calls to handle different provider scenarios:

```php
$response = Prism::text()
    ->using(Provider::OpenAI, 'gpt-4o')
    ->withPrompt('Generate a creative story about robots.')
    ->whenProvider(
        Provider::Anthropic,
        fn ($request) => $request
            ->withMaxTokens(4000)
            ->withProviderOptions(['cacheType' => 'ephemeral'])
    )
    ->whenProvider(
        Provider::OpenAI,
        fn ($request) => $request
            ->withMaxTokens(2000)
            ->withProviderOptions(['response_format' => ['type' => 'text']])
    )
    ->asText();
```

## Using Invokable Classes

For more complex provider-specific configurations, you can use invokable classes instead of closures:

```php
class AnthropicConfigurator
{
    public function __invoke($request)
    {
        return $request
            ->withMaxTokens(4000)
            ->withProviderOptions([
                'cacheType' => 'ephemeral',
                'citations' => true,
            ]);
    }
}

$response = Prism::text()
    ->using(Provider::Anthropic, 'claude-3-sonnet')
    ->withPrompt('Explain the theory of relativity.')
    ->whenProvider(Provider::Anthropic, new AnthropicConfigurator())
    ->asText();
```

This approach can be especially helpful when you have complex or reusable provider configurations.

> [!TIP]
> The `whenProvider` method works with all request types in Prism including text, structured output, and embeddings requests.

## Best Practices

### Avoiding SystemMessages with Multiple Providers

When working with multiple providers, it's best to avoid using `SystemMessages` directly in your `withMessages` array. Instead, use the `withSystemPrompt` method as it offers better provider interoperability.

```php
// Avoid this when switching between providers
$response = Prism::text()
    ->using(Provider::OpenAI, 'gpt-4o')
    ->withMessages([
        new SystemMessage('You are a helpful assistant.'),
        new UserMessage('Tell me about AI'),
    ])
    ->asText();

// Prefer this instead
$response = Prism::text()
    ->using(Provider::OpenAI, 'gpt-4o')
    ->withSystemPrompt('You are a helpful assistant.')
    ->withPrompt('Tell me about AI')
    ->asText();
```

This approach allows Prism to handle the provider-specific formatting of system messages, making your code more portable across different LLM providers.