fix: Drag-and-drop file attach broken (#1620)

## Problem

Drag and drop to attach files is broken.

<!-- Who is this for and what problem does it solve? -->

<!-- Closes #ISSUE_ID -->

## Changes

1. Expose webUtils.getPathForFile from preload via contextBridge
2. Add getFilePath utility that uses the bridge with a File.path fallback
3. Replace all File.path casts in drop handlers (SessionView, TaskInput, useTiptapEditor, AttachmentMenu)
4. Add Window.electronUtils type declaration

<!-- What did you change and why? -->

<!-- If there are frontend changes, include screenshots. -->

## How did you test this?

Manually

<!-- Describe what you tested -- manual steps, automated tests, or both. -->

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Author: charlesvien

apps/code/src/main/preload.ts

@@ -1,6 +1,11 @@
 import { exposeElectronTRPC } from "@posthog/electron-trpc/main";
+import { contextBridge, webUtils } from "electron";
 import "electron-log/preload";
 
+contextBridge.exposeInMainWorld("electronUtils", {
+  getPathForFile: (file: File) => webUtils.getPathForFile(file),
+});
+
 process.once("loaded", async () => {
   exposeElectronTRPC();
 });

apps/code/src/renderer/features/message-editor/components/AttachmentMenu.tsx

@@ -4,6 +4,7 @@ import { IconButton, Popover } from "@radix-ui/themes";
 import { trpcClient, useTRPC } from "@renderer/trpc/client";
 import { toast } from "@renderer/utils/toast";
 import { useQuery } from "@tanstack/react-query";
+import { getFilePath } from "@utils/getFilePath";
 import { getFileName } from "@utils/path";
 import { useRef, useState } from "react";
 import type { FileAttachment, MentionChip } from "../utils/content";
@@ -69,7 +70,7 @@ export function AttachmentMenu({
     try {
       const attachments = await Promise.all(
         files.map(async (file) => {
-          const filePath = (file as globalThis.File & { path?: string }).path;
+          const filePath = getFilePath(file);
           if (filePath) {
             return { id: filePath, label: file.name } satisfies FileAttachment;
           }

apps/code/src/renderer/features/message-editor/tiptap/useTiptapEditor.ts

@@ -4,6 +4,7 @@ import { toast } from "@renderer/utils/toast";
 import { useSettingsStore } from "@stores/settingsStore";
 import type { EditorView } from "@tiptap/pm/view";
 import { useEditor } from "@tiptap/react";
+import { getFilePath } from "@utils/getFilePath";
 import type React from "react";
 import { useCallback, useEffect, useRef, useState } from "react";
 import { usePromptHistoryStore } from "../stores/promptHistoryStore";
@@ -270,8 +271,7 @@ export function useTiptapEditor(options: UseTiptapEditorOptions) {
           const newAttachments: FileAttachment[] = [];
           for (let i = 0; i < files.length; i++) {
             const file = files[i];
-            // In Electron, File objects have a 'path' property
-            const path = (file as unknown as { path?: string }).path;
+            const path = getFilePath(file);
             if (path) {
               newAttachments.push({ id: path, label: file.name });
             }

apps/code/src/renderer/features/sessions/components/SessionView.tsx

@@ -20,6 +20,7 @@ import {
   isJsonRpcNotification,
   isJsonRpcResponse,
 } from "@shared/types/session-events";
+import { getFilePath } from "@utils/getFilePath";
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { useHotkeys } from "react-hotkeys-hook";
 import { getSessionService } from "../service/service";
@@ -328,7 +329,7 @@ export function SessionView({
 
     for (let i = 0; i < files.length; i++) {
       const file = files[i];
-      const filePath = (file as File & { path?: string }).path;
+      const filePath = getFilePath(file);
       if (filePath) {
         editorRef.current?.addAttachment({
           id: filePath,

apps/code/src/renderer/features/task-detail/components/TaskInput.tsx

@@ -29,6 +29,7 @@ import { useAuthStore } from "@renderer/features/auth/stores/authStore";
 import { useTRPC } from "@renderer/trpc/client";
 import { useNavigationStore } from "@stores/navigationStore";
 import { useQuery } from "@tanstack/react-query";
+import { getFilePath } from "@utils/getFilePath";
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { useHotkeys } from "react-hotkeys-hook";
 import { usePreviewConfig } from "../hooks/usePreviewConfig";
@@ -344,7 +345,7 @@ export function TaskInput({
 
     for (let i = 0; i < files.length; i++) {
       const file = files[i];
-      const filePath = (file as File & { path?: string }).path;
+      const filePath = getFilePath(file);
       if (filePath) {
         editorRef.current?.addAttachment({
           id: filePath,

apps/code/src/renderer/types/electron.d.ts

@@ -1,3 +1,11 @@
 import "@main/services/types";
 
 // No legacy IPC interfaces - all communication now uses tRPC
+
+declare global {
+  interface Window {
+    electronUtils?: {
+      getPathForFile: (file: File) => string;
+    };
+  }
+}

apps/code/src/renderer/utils/getFilePath.ts

@@ -0,0 +1,13 @@
+/**
+ * Get the filesystem path for a File from a drag-and-drop or file input event.
+ *
+ * In Electron 32+ with contextIsolation, File.path is empty. The preload
+ * script exposes webUtils.getPathForFile as window.electronUtils.getPathForFile
+ * to bridge this gap.
+ */
+export function getFilePath(file: File): string {
+  if (window.electronUtils?.getPathForFile) {
+    return window.electronUtils.getPathForFile(file);
+  }
+  return (file as File & { path?: string }).path ?? "";
+}