diff --git a/web/.env.example b/web/.env.example
index 2c5cdb153..f954e347f 100644
--- a/web/.env.example
+++ b/web/.env.example
@@ -1 +1,5 @@
-VITE_API_BASE_URL=http://localhost:5300
+# Leave empty in development to use Vite's same-origin proxy. This keeps API,
+# login, and WebSocket requests working when the UI is opened from another
+# device on the local network.
+VITE_API_BASE_URL=
+VITE_API_PROXY_TARGET=http://127.0.0.1:5300
diff --git a/web/vite.config.ts b/web/vite.config.ts
index d1023070a..d2899a62f 100644
--- a/web/vite.config.ts
+++ b/web/vite.config.ts
@@ -1,18 +1,35 @@
-import { defineConfig } from 'vite';
+import { defineConfig, loadEnv } from 'vite';
 import react from '@vitejs/plugin-react';
 import path from 'path';
 
-export default defineConfig({
-  plugins: [react()],
-  resolve: {
-    alias: {
-      '@': path.resolve(__dirname, './src'),
+export default defineConfig(({ mode }) => {
+  const env = loadEnv(mode, process.cwd(), '');
+  const apiProxyTarget = env.VITE_API_PROXY_TARGET || 'http://127.0.0.1:5300';
+
+  return {
+    plugins: [react()],
+    resolve: {
+      alias: {
+        '@': path.resolve(__dirname, './src'),
+      },
     },
-  },
-  server: {
-    port: 3000,
-  },
-  build: {
-    outDir: 'dist',
-  },
+    server: {
+      host: '0.0.0.0',
+      port: 3000,
+      proxy: {
+        '/api': {
+          target: apiProxyTarget,
+          changeOrigin: true,
+          ws: true,
+        },
+        '/mcp': {
+          target: apiProxyTarget,
+          changeOrigin: true,
+        },
+      },
+    },
+    build: {
+      outDir: 'dist',
+    },
+  };
 });