Crate fm_bindings 

Foundation Models Bindings for Rust

Rust bindings for Apple’s Foundation Models framework, providing access to on-device large language models (LLMs) that power Apple Intelligence.

Requirements

• macOS 26+ or iOS 26+
• Apple Intelligence enabled in System Settings

Features

• Blocking Response: Get complete responses with response()
• Streaming Response: Get real-time incremental updates with stream_response()
• Instructions: Configure model behavior with system prompts
• Transcript Persistence: Save and restore session state across app launches
• Type-safe error handling with Result<T, Error>

Examples

Basic Usage

use fm_bindings::LanguageModelSession;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let session = LanguageModelSession::new()?;
    let response = session.response("What is Rust?")?;
    println!("{}", response);
    Ok(())
}

With Instructions

use fm_bindings::LanguageModelSession;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let session = LanguageModelSession::with_instructions(
        "You are a friendly assistant. Keep responses brief and helpful."
    )?;
    let response = session.response("Hello!")?;
    println!("{}", response);
    Ok(())
}

Streaming Response

use fm_bindings::LanguageModelSession;
use std::io::{self, Write};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let session = LanguageModelSession::new()?;

    session.stream_response("Tell me a story", |chunk| {
        print!("{}", chunk);
        let _ = io::stdout().flush();
    })?;

    println!(); // newline after stream
    Ok(())
}

Persisting Sessions

use fm_bindings::LanguageModelSession;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create and use a session
    let session = LanguageModelSession::with_instructions("You are a travel guide.")?;
    let _ = session.response("Tell me about Paris")?;
    let _ = session.response("What about the food?")?;

    // Save the transcript
    let transcript = session.transcript_json()?;
    std::fs::write("session.json", &transcript)?;

    // Later: restore the session
    let saved = std::fs::read_to_string("session.json")?;
    let restored = LanguageModelSession::from_transcript_json(&saved)?;

    // Continue with full context
    let response = restored.response("Any restaurant recommendations?")?;
    println!("{}", response);
    Ok(())
}

Error Handling

use fm_bindings::{LanguageModelSession, Error};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let session = match LanguageModelSession::new() {
        Ok(s) => s,
        Err(Error::ModelNotAvailable) => {
            eprintln!("Apple Intelligence not enabled");
            return Ok(());
        }
        Err(e) => return Err(e.into()),
    };

    let response = session.response("Hello")?;
    println!("{}", response);
    Ok(())
}

Structs

LanguageModelSession

A session for interacting with Apple’s Foundation Models

Enums

Error

Errors that can occur when using Foundation Models

Type Aliases

Result

Result type alias for Foundation Models operations