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The Inference class is a thin, immutable facade over InferenceRuntime. It provides the unified entry point for configuring providers, building requests, and retrieving responses from any supported LLM.

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Creating an Instance

Choose the factory method that matches your level of control: 
<?php
use Cognesy\Polyglot\Inference\Inference;

// Use a named preset from your configuration
$inference = Inference::using('openai');

// Use the default provider
$inference = new Inference();

// Explicit configuration object
$inference = Inference::fromConfig($config);

// From a provider instance
$inference = Inference::fromProvider($provider);

// From a fully assembled runtime
$inference = Inference::fromRuntime($runtime);
// @doctest id="08b1"

​
Presets

The most common pattern is Inference::using(), which loads a named preset from your configuration files. Each preset defines the provider type, API key, base URL, default model, and other connection details: 
// Use different providers by switching the preset name
$openai    = Inference::using('openai');
$anthropic = Inference::using('anthropic');
$ollama    = Inference::using('ollama');
// @doctest id="dabd"

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Configuring a Request

The fluent API lets you build requests step by step. Every method returns a new immutable instance, so you can safely branch from a shared configuration:

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Messages and Model

$inference = Inference::using('openai')
    ->withMessages(Messages::fromString('Explain dependency injection in one paragraph.'))
    ->withModel('gpt-4.1-nano');
// @doctest id="2fd8"

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Tools and Response Format

use Cognesy\Polyglot\Inference\Data\ToolChoice;
use Cognesy\Polyglot\Inference\Data\ResponseFormat;

$inference = Inference::using('openai')
    ->withTools($toolDefinitions)
    ->withToolChoice(ToolChoice::auto())
    ->withResponseFormat(ResponseFormat::jsonObject());
// @doctest id="392b"

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Streaming and Token Limits

$inference = Inference::using('openai')
    ->withStreaming(true)
    ->withMaxTokens(256);
// @doctest id="581e"

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Provider-Specific Options

$inference = Inference::using('openai')
    ->withOptions(['temperature' => 0.5, 'top_p' => 0.9]);
// @doctest id="f332"

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The Combined with() Method

When you prefer a single call, use with() to set multiple fields at once: 
use Cognesy\Messages\Messages;
use Cognesy\Polyglot\Inference\Data\ToolChoice;
use Cognesy\Polyglot\Inference\Data\ResponseFormat;

$inference = Inference::using('openai')->with(
    messages: Messages::fromString('Hello'),
    model: 'gpt-4.1-nano',
    toolChoice: ToolChoice::auto(),
    responseFormat: ResponseFormat::text(),
    options: ['temperature' => 0.7],
);
// @doctest id="7f94"

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Full Method Reference

MethodPurpose
withMessages(...)Set conversation messages
withModel(...)Override the model
withTools(...)Attach tool/function definitions
withToolChoice(...)Control tool selection strategy
withResponseFormat(...)Specify the response format
withOptions(...)Set provider-specific options
withStreaming(...)Enable or disable streaming
withMaxTokens(...)Set maximum token count
withCachedContext(...)Attach reusable cached context
withRetryPolicy(...)Configure retry behavior
withResponseCachePolicy(...)Configure response caching
withRequest(...)Load all fields from an InferenceRequest
withRuntime(...)Replace the underlying runtime

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Executing Requests

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Response Shortcuts

These methods build the request, execute it, and return the result in a single step: 
<?php
use Cognesy\Polyglot\Inference\Inference;
use Cognesy\Messages\Messages;

$inference = Inference::using('openai')
    ->withMessages(Messages::fromString('What is PHP?'))
    ->withModel('gpt-4.1-nano');

// Plain text content
$text = $inference->get();

// Full InferenceResponse object (with usage, finish reason, etc.)
$response = $inference->response();

// JSON string extracted from the response
$json = $inference->asJson();

// Parsed JSON as an associative array
$data = $inference->asJsonData();

// JSON from a tool call response
$toolJson = $inference->asToolCallJson();

// Parsed tool call JSON as an array
$toolData = $inference->asToolCallJsonData();
// @doctest id="f51f"

​
Streaming

To receive partial results as they arrive from the provider: 
$stream = Inference::using('openai')
    ->withMessages(Messages::fromString('Write a short story about a robot.'))
    ->stream();

foreach ($stream->deltas() as $partial) {
    echo $partial->contentDelta;
}
// @doctest id="434e"

​
The Lazy Handle: PendingInference

If you need to defer execution or pass the handle to another part of your system, call create() to get a PendingInference instance. Execution happens only when you call a response method on it: 
$pending = Inference::using('openai')
    ->withMessages(Messages::fromString('Hello'))
    ->create();

// Nothing has been sent to the provider yet.
// Execution happens here:
$text = $pending->get();
// @doctest id="f68a"
PendingInference exposes the same response methods as Inference: get(), response(), asJson(), asJsonData(), asToolCallJson(), asToolCallJsonData(), and stream().

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Custom Drivers

To use a custom driver, implement the CanProvideInferenceDrivers contract and pass it to Inference::using() or Inference::fromConfig() via the drivers parameter: 
use Cognesy\Polyglot\Inference\Inference;

$response = Inference::using('custom-provider', drivers: $myDriverRegistry)
    ->withMessages(Messages::fromString('Hello from a custom driver.'))
    ->get();
// @doctest id="54c7"