How to use the Apple Foundation Model from Node.js

Call Apple's on-device Foundation Model from Node.js using the official openai npm package, pointed at a local apfel --serve. 100% on-device, zero API cost.

Runnable scripts + tests: Arthur-Ficial/apfel-guides-lab/scripts/nodejs.

Prerequisites

• macOS 26+ Tahoe, Apple Silicon, Apple Intelligence enabled
• brew install apfel
• apfel --serve running (port 11434)
• Node.js 20+
• npm install openai
• "type": "module" in package.json (or use .mjs files)

1. One-shot chat completion

import OpenAI from "openai";

const client = new OpenAI({ baseURL: "http://localhost:11434/v1", apiKey: "not-needed" });

const response = await client.chat.completions.create({
  model: "apple-foundationmodel",
  messages: [{ role: "user", content: "In one sentence, what is the Swift programming language?" }],
  max_tokens: 80,
});

console.log((response.choices[0].message.content || "").trim());

Real output:

Swift is a modern, high-performance, and easy-to-learn programming language developed by Apple for building applications on iOS, macOS, watchOS, and tvOS.

Lab script: 01_oneshot.mjs.

2. Streaming

import OpenAI from "openai";

const client = new OpenAI({ baseURL: "http://localhost:11434/v1", apiKey: "not-needed" });

const stream = await client.chat.completions.create({
  model: "apple-foundationmodel",
  messages: [{ role: "user", content: "List three Apple silicon chips, one per line." }],
  max_tokens: 80,
  stream: true,
});

for await (const chunk of stream) {
  if (!chunk.choices || chunk.choices.length === 0) continue;
  const delta = chunk.choices[0].delta?.content ?? "";
  process.stdout.write(delta);
}
process.stdout.write("\n");

Real output:

Apple M1
Apple M2
Apple M2 Pro

Lab script: 02_stream.mjs.

3. JSON mode

import OpenAI from "openai";

const client = new OpenAI({ baseURL: "http://localhost:11434/v1", apiKey: "not-needed" });

const response = await client.chat.completions.create({
  model: "apple-foundationmodel",
  messages: [{
    role: "user",
    content: "Return JSON with fields 'chip', 'year', 'cores'. Describe the Apple M1 chip. Return ONLY JSON.",
  }],
  response_format: { type: "json_object" },
  max_tokens: 120,
});

let raw = (response.choices[0].message.content || "").trim();
raw = raw.replace(/^```(?:json)?\s*|\s*```$/gm, "").trim();
console.log(JSON.stringify(JSON.parse(raw), null, 2));

Real output:

{
  "chip": "Apple M1",
  "year": 2020,
  "cores": {
    "CPU": 8,
    "GPU": 8
  }
}

Lab script: 03_json.mjs.

4. Error handling

import OpenAI from "openai";

const client = new OpenAI({ baseURL: "http://localhost:11434/v1", apiKey: "not-needed" });

try {
  await client.embeddings.create({
    model: "apple-foundationmodel",
    input: "apfel runs 100% on-device.",
  });
} catch (err) {
  if (err instanceof OpenAI.APIError) {
    console.log(`Got expected error: HTTP ${err.status} - ${err.message}`);
  } else {
    throw err;
  }
}

Real output:

Got expected error: HTTP 501 - 501 Embeddings not supported by Apple's on-device model.

Lab script: 04_errors.mjs.

5. Tool calling

import OpenAI from "openai";

const client = new OpenAI({ baseURL: "http://localhost:11434/v1", apiKey: "not-needed" });

const tools = [{
  type: "function",
  function: {
    name: "get_weather",
    description: "Get the current temperature in Celsius for a city.",
    parameters: {
      type: "object",
      properties: { city: { type: "string", description: "City name" } },
      required: ["city"],
    },
  },
}];

function getWeather({ city }) {
  const fake = { Vienna: 14, Cupertino: 19, Tokyo: 11 };
  return JSON.stringify({ city, temp_c: fake[city] ?? 15 });
}

const messages = [{ role: "user", content: "What is the temperature in Vienna right now?" }];

const first = await client.chat.completions.create({
  model: "apple-foundationmodel", messages, tools, max_tokens: 256,
});
const msg = first.choices[0].message;
messages.push(msg);

if (msg.tool_calls?.length) {
  for (const call of msg.tool_calls) {
    const args = JSON.parse(call.function.arguments);
    messages.push({ role: "tool", tool_call_id: call.id, content: getWeather(args) });
  }
  const final = await client.chat.completions.create({
    model: "apple-foundationmodel", messages, max_tokens: 120,
  });
  console.log((final.choices[0].message.content || "").trim());
}

Real output:

The current temperature in Vienna is 14 degrees Celsius.

Lab script: 05_tools.mjs.

6. Real example - summarize stdin

import OpenAI from "openai";

const text = await new Promise((resolve) => {
  let buf = "";
  process.stdin.setEncoding("utf8");
  process.stdin.on("data", (c) => (buf += c));
  process.stdin.on("end", () => resolve(buf.trim()));
});

if (!text) {
  console.error("usage: cat file.txt | node 06_example.mjs");
  process.exit(1);
}

const client = new OpenAI({ baseURL: "http://localhost:11434/v1", apiKey: "not-needed" });

const response = await client.chat.completions.create({
  model: "apple-foundationmodel",
  messages: [
    { role: "system", content: "You are a concise summarizer. Reply with one short paragraph." },
    { role: "user", content: `Summarize:\n\n${text}` },
  ],
  max_tokens: 150,
});
console.log((response.choices[0].message.content || "").trim());

Real output (M1 paragraph):

The Apple M1 chip, released in November 2020, was Apple's first ARM-based system-on-a-chip for Mac computers. It uses an 8-core CPU with four performance and four efficiency cores, plus an integrated GPU with up to 8 cores. The chip unified CPU, GPU, memory, and neural engine on a single die, delivering significant performance-per-watt improvements over the Intel chips it replaced.

Lab script: 06_example.mjs.

Troubleshooting

• ECONNREFUSED - start apfel --serve before running your Node script.
• Missing choices[0] during streaming - handle the final usage chunk with the if (!chunk.choices || chunk.choices.length === 0) continue; guard above.
• TypeScript - same code works; npm install -D @types/node for Node types.

Tested with

• apfel v1.0.3 / macOS 26.3.1 Apple Silicon (original capture; the CLI and HTTP surfaces used here are release-gated by apfel's test suite on every version)
• Node.js v25.8.1 / openai 4.x
• Date: 2026-04-16

Runnable tests: tests/test_nodejs.py.

See also

python.md, ruby.md, php.md, bash-curl.md, apfel-guides-lab