Simple, reusable LM Studio client (OpenAI-compatible local API)

llmstudio-caller.js

// lmstudio.js
// Simple, reusable LM Studio client (OpenAI-compatible local API)

const LMSTUDIO_BASE_URL = "http://localhost:1234/v1";

/**
 * Non-streaming completion
 */
export async function lmChat({
  messages,
  temperature = 0.7,
  model = "local-model"
}) {
  const res = await fetch(`${LMSTUDIO_BASE_URL}/chat/completions`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json"
    },
    body: JSON.stringify({
      model,
      messages,
      temperature,
      stream: false
    })
  });

  if (!res.ok) {
    throw new Error(`LM Studio error: ${res.status}`);
  }

  const data = await res.json();
  return data.choices?.[0]?.message?.content || "";
}

/**
 * Streaming completion (token-by-token)
 */
export async function lmStream({
  messages,
  onToken,
  onDone,
  onError,
  model = "local-model"
}) {
  try {
    const res = await fetch(`${LMSTUDIO_BASE_URL}/chat/completions`, {
      method: "POST",
      headers: {
        "Content-Type": "application/json"
      },
      body: JSON.stringify({
        model,
        messages,
        stream: true
      })
    });

    if (!res.body) throw new Error("No response body");

    const reader = res.body.getReader();
    const decoder = new TextDecoder("utf-8");

    let buffer = "";

    while (true) {
      const { done, value } = await reader.read();
      if (done) break;

      buffer += decoder.decode(value, { stream: true });

      const lines = buffer.split("\n");
      buffer = lines.pop(); // keep incomplete line

      for (const line of lines) {
        if (!line.startsWith("data: ")) continue;

        const json = line.replace("data: ", "").trim();

        if (json === "[DONE]") {
          onDone && onDone();
          return;
        }

        try {
          const parsed = JSON.parse(json);
          const token = parsed.choices?.[0]?.delta?.content;

          if (token) {
            onToken && onToken(token);
          }
        } catch (err) {
          // ignore partial JSON
        }
      }
    }

    onDone && onDone();
  } catch (err) {
    onError && onError(err);
  }
}