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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/phpaisdk/xai/llms.txt

Use this file to discover all available pages before exploring further.

Every model in aisdk/xai exposes a structured capability system. When you call ->supports() or ->capability() on a model instance, the provider resolves the capability against three sources in order: any per-instance configured override, a custom ModelRegistry entry (if you registered a custom definition), and finally the bundled resources/models.json catalog. This layered resolution means the catalog acts as a sensible default while still allowing you to extend or override it for your own use cases.

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Capabilities table

The table below shows which capabilities are declared for each model family in the catalog.
Capabilitygrok-4*grok-3*grok-2*grok-imagine-image-quality
text_generation✓✓✓—
streaming✓✓✓—
tool_calling✓✓✓—
structured_output✓✓✓—
reasoning✓✓——
text_input✓✓✓✓
image_input✓✓✓✓
image_generation———✓
Key observations:
  • Reasoning is available on grok-4* and grok-3* only. The grok-2* family predates xAI’s reasoning API and does not expose this capability.
  • Image generation is exclusive to grok-imagine-image-quality.
  • All model families accept both text input and image input, making multimodal prompts possible across the entire range.
  • grok-imagine-image-quality has no streaming, tool calling, structured output, or text generation capabilities — it is a pure image-generation model.

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Checking capabilities at runtime

Use ->supports() for a simple boolean check, or ->capability() to retrieve a CapabilitySupport value that also carries metadata (such as the resolution source): 
use AiSdk\Capability;
use AiSdk\XAI;

$model = XAI::model('grok-4');

if ($model->supports(Capability::Reasoning)) {
    // safe to use reasoning
}

$support = $model->capability(Capability::ToolCalling);
CapabilitySupport::isSupported() returns true when the capability is present. The source property on the returned object tells you where the support was determined — catalog, registry, or unknown-model-fallback for unrecognised model IDs.

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The Capability enum

The PHP AI SDK exposes capabilities as a typed enum. The cases relevant to xAI models are:
Enum caseCatalog key
Capability::TextGenerationtext_generation
Capability::Streamingstreaming
Capability::ToolCallingtool_calling
Capability::StructuredOutputstructured_output
Capability::Reasoningreasoning
Capability::TextInputtext_input
Capability::ImageInputimage_input
Capability::ImageGenerationimage_generation
Always use the enum cases rather than raw strings when calling ->supports() or ->capability() so that your code benefits from IDE autocompletion and remains compatible with future SDK versions.

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Custom capability override

If the bundled catalog does not reflect the actual capabilities of a model you are using — for example, because xAI has extended an existing model with new functionality between aisdk/xai releases — you can register a custom definition via the ModelRegistry on a custom XAIProvider instance: 
use AiSdk\Capability;
use AiSdk\Support\ModelRegistry;
use AiSdk\XAI\XAIOptions;
use AiSdk\XAI\XAIProvider;

$registry = new ModelRegistry;
$registry->register('xai', 'grok-2-custom', [
    Capability::TextGeneration,
    Capability::Streaming,
    Capability::ToolCalling,
    Capability::Reasoning, // override: enable reasoning for this model
    Capability::TextInput,
    Capability::ImageInput,
]);

$provider = new XAIProvider(XAIOptions::fromArray(['apiKey' => '...']), $registry);
$model = $provider->textModel('grok-2-custom');
Any capability returned by the ModelRegistry takes precedence over the catalog, allowing per-instance overrides without modifying the shared catalog file.

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