fix(api): handle hosts starting with http, HTTP errors on XHR and clearer connection errors

- buildBaseUrl treated any host starting with 'http' (e.g. httpbin.local) as having a scheme
- native streaming finished silently on 4xx/5xx; it now reports the status
- network failures now explain how to fix the connection instead of 'XHR streaming failed: 0'
- testConnection left its 5 s timer running on failure
- SSE parser accepts 'data:' without a space, as the spec allows

services/lmStudioApi.ts

@@ -9,12 +9,18 @@ import {
     StreamChunk,
 } from './types';
 
-function buildBaseUrl(config: ServerConfig): string {
+export function buildBaseUrl(config: ServerConfig): string {
     const host = config.host.replace(/\/+$/, '');
-    const protocol = host.startsWith('http') ? '' : 'http://';
+    const protocol = /^https?:\/\//i.test(host) ? '' : 'http://';
     return `${protocol}${host}:${config.port}/v1`;
 }
 
+function connectionError(baseUrl: string): Error {
+    return new Error(
+        `Could not reach the server at ${baseUrl}. Check the host and port in Settings and that LM Studio's local server is running.`,
+    );
+}
+
 function buildHeaders(config: ServerConfig): Record<string, string> {
     const headers: Record<string, string> = {
         'Content-Type': 'application/json',
@@ -26,19 +32,19 @@ function buildHeaders(config: ServerConfig): Record<string, string> {
 }
 
 export async function testConnection(config: ServerConfig): Promise<boolean> {
-    try {
-        const controller = new AbortController();
-        const timeout = setTimeout(() => controller.abort(), 5000);
+    const controller = new AbortController();
+    const timeout = setTimeout(() => controller.abort(), 5000);
 
+    try {
         const res = await fetch(`${buildBaseUrl(config)}/models`, {
             headers: buildHeaders(config),
             signal: controller.signal,
         });
-
-        clearTimeout(timeout);
         return res.ok;
     } catch {
         return false;
+    } finally {
+        clearTimeout(timeout);
     }
 }
 
@@ -84,7 +90,7 @@ export async function chatCompletion(
 }
 
 // Parse SSE lines from a text buffer
-function parseSSELines(
+export function parseSSELines(
     buffer: string,
     onChunk: (content: string) => void,
     onDone: () => void,
@@ -95,9 +101,9 @@ function parseSSELines(
 
     for (const line of lines) {
         const trimmed = line.trim();
-        if (!trimmed || !trimmed.startsWith('data: ')) continue;
+        if (!trimmed.startsWith('data:')) continue;
 
-        const payload = trimmed.slice(6);
+        const payload = trimmed.slice(5).trim();
         if (payload === '[DONE]') {
             isDone = true;
             onDone();
@@ -123,6 +129,7 @@ function streamWithXHR(
     url: string,
     headers: Record<string, string>,
     body: string,
+    baseUrl: string,
     onChunk: (content: string) => void,
     onDone: () => void,
     onError: (error: Error) => void,
@@ -146,6 +153,10 @@ function streamWithXHR(
     };
 
     xhr.onload = () => {
+        if (xhr.status < 200 || xhr.status >= 300) {
+            onError(new Error(`Stream failed: ${xhr.status} ${xhr.statusText}`));
+            return;
+        }
         // Process any remaining buffer
         if (buffer.trim()) {
             parseSSELines(buffer + '\n', onChunk, onDone);
@@ -154,7 +165,7 @@ function streamWithXHR(
     };
 
     xhr.onerror = () => {
-        onError(new Error(`XHR streaming failed: ${xhr.status} ${xhr.statusText}`));
+        onError(connectionError(baseUrl));
     };
 
     xhr.ontimeout = () => {
@@ -175,17 +186,23 @@ async function streamWithFetch(
     url: string,
     headers: Record<string, string>,
     body: string,
+    baseUrl: string,
     onChunk: (content: string) => void,
     onDone: () => void,
-    onError: (error: Error) => void,
     signal: AbortSignal,
 ): Promise<void> {
-    const res = await fetch(url, {
-        method: 'POST',
-        headers,
-        body,
-        signal,
-    });
+    let res: Response;
+    try {
+        res = await fetch(url, {
+            method: 'POST',
+            headers,
+            body,
+            signal,
+        });
+    } catch (err) {
+        if ((err as Error).name === 'AbortError') throw err;
+        throw connectionError(baseUrl);
+    }
 
     if (!res.ok) {
         throw new Error(`Stream failed: ${res.status} ${res.statusText}`);
@@ -229,7 +246,8 @@ export function chatCompletionStream(
         ...options,
     };
 
-    const url = `${buildBaseUrl(config)}/chat/completions`;
+    const baseUrl = buildBaseUrl(config);
+    const url = `${baseUrl}/chat/completions`;
     const headers = buildHeaders(config);
     const bodyStr = JSON.stringify(body);
 
@@ -245,7 +263,7 @@ export function chatCompletionStream(
         // Web: use fetch + ReadableStream
         const controller = new AbortController();
 
-        streamWithFetch(url, headers, bodyStr, onChunk, safeOnDone, onError, controller.signal)
+        streamWithFetch(url, headers, bodyStr, baseUrl, onChunk, safeOnDone, controller.signal)
             .catch((err) => {
                 if ((err as Error).name !== 'AbortError') {
                     onError(err as Error);
@@ -255,6 +273,6 @@ export function chatCompletionStream(
         return { abort: () => controller.abort() };
     } else {
         // Native: use XMLHttpRequest
-        return streamWithXHR(url, headers, bodyStr, onChunk, safeOnDone, onError);
+        return streamWithXHR(url, headers, bodyStr, baseUrl, onChunk, safeOnDone, onError);
     }
 }