i think i got step one working

frontend/src/lib/tauri-bridge.ts

@@ -0,0 +1,71 @@
+/**
+ * tauri-bridge.ts
+ *
+ * Polyfills window.electronAPI with Tauri equivalents so all existing
+ * call-sites in App.tsx, hooks, and stores continue to work unchanged.
+ *
+ * Imported once at the top of main.tsx.
+ */
+
+import { invoke } from '@tauri-apps/api/core';
+import { open, save } from '@tauri-apps/plugin-dialog';
+import { readTextFile, writeTextFile } from '@tauri-apps/plugin-fs';
+
+const VIDEO_FILTERS = [
+  { name: 'Video Files', extensions: ['mp4', 'avi', 'mov', 'mkv', 'webm'] },
+  { name: 'Audio Files', extensions: ['m4a', 'wav', 'mp3', 'flac'] },
+  { name: 'All Files', extensions: ['*'] },
+];
+
+const PROJECT_FILTERS = [
+  { name: 'TalkEdit Project', extensions: ['aive'] },
+];
+
+const EXPORT_FILTERS = [
+  { name: 'Video Files', extensions: ['mp4', 'mov', 'webm'] },
+  { name: 'Project Files', extensions: ['aive'] },
+];
+
+window.electronAPI = {
+  openFile: async (_options?: Record<string, unknown>): Promise<string | null> => {
+    const result = await open({
+      multiple: false,
+      filters: VIDEO_FILTERS,
+    });
+    return typeof result === 'string' ? result : null;
+  },
+
+  saveFile: async (_options?: Record<string, unknown>): Promise<string | null> => {
+    const result = await save({ filters: EXPORT_FILTERS });
+    return result ?? null;
+  },
+
+  openProject: async (): Promise<string | null> => {
+    const result = await open({
+      multiple: false,
+      filters: PROJECT_FILTERS,
+    });
+    return typeof result === 'string' ? result : null;
+  },
+
+  getBackendUrl: (): Promise<string> => {
+    return invoke<string>('get_backend_url');
+  },
+
+  encryptString: (data: string): Promise<string> => {
+    return invoke<string>('encrypt_string', { data });
+  },
+
+  decryptString: (encrypted: string): Promise<string> => {
+    return invoke<string>('decrypt_string', { encrypted });
+  },
+
+  readFile: (path: string): Promise<string> => {
+    return readTextFile(path);
+  },
+
+  writeFile: async (path: string, content: string): Promise<boolean> => {
+    await writeTextFile(path, content);
+    return true;
+  },
+};

frontend/src/main.tsx

@@ -1,5 +1,7 @@
 import React from 'react';
 import ReactDOM from 'react-dom/client';
+// Must be imported before App so window.electronAPI is patched before any component runs.
+import './lib/tauri-bridge';
 import App from './App';
 import './index.css';