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LLMs

Large Language Models (LLMs) are a core component of LangChain. LangChain does not serve its own LLMs, but rather provides a standard interface for interacting with many different LLMs.

All LLMs implement the llms.Model interface:

// Model is an interface multi-modal models implement.
type Model interface {
	// GenerateContent asks the model to generate content from a sequence of
	// messages. It's the most general interface for multi-modal LLMs that support
	// chat-like interactions.
	GenerateContent(ctx context.Context, messages []MessageContent, options ...CallOption) (*ContentResponse, error)

	// Call is a simplified interface for a text-only Model, generating a single
	// string response from a single string prompt.
	//
	// Deprecated: this method is retained for backwards compatibility. Use the
	// more general [GenerateContent] instead.
	Call(ctx context.Context, prompt string, options ...CallOption) (string, error)
}

The interface provides two methods:

GenerateContent: The modern, recommended method that supports multi-modal inputs and complex message sequences
Call: A legacy method for simple text-to-text generation (deprecated but still supported)

For backwards compatibility, llms.LLM is provided as a type alias:

// LLM is an alias for model, for backwards compatibility.
// Deprecated: This alias may be removed in the future; please use Model instead.
type LLM = Model