diff --git a/apps/desktop/src/settings/DesktopClientSettings.test.ts b/apps/desktop/src/settings/DesktopClientSettings.test.ts
index ea7ec6e1512..d8db331d785 100644
--- a/apps/desktop/src/settings/DesktopClientSettings.test.ts
+++ b/apps/desktop/src/settings/DesktopClientSettings.test.ts
@@ -20,6 +20,7 @@ const clientSettings: ClientSettings = {
   diffIgnoreWhitespace: true,
   favorites: [],
   providerModelPreferences: {},
+  previewDisableWebSecurity: false,
   sidebarProjectGroupingMode: "repository_path",
   sidebarProjectGroupingOverrides: {
     "environment-1:/tmp/project-a": "separate",
diff --git a/apps/web/src/browser/HostedBrowserWebview.tsx b/apps/web/src/browser/HostedBrowserWebview.tsx
index a72da49c6fa..05ec2670bb9 100644
--- a/apps/web/src/browser/HostedBrowserWebview.tsx
+++ b/apps/web/src/browser/HostedBrowserWebview.tsx
@@ -6,6 +6,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 
 import { previewBridge } from "~/components/preview/previewBridge";
 import { usePreviewBridge } from "~/components/preview/usePreviewBridge";
+import { getClientSettings, useClientSettingsHydrated } from "~/hooks/useSettings";
 import { cn } from "~/lib/utils";
 
 import { stopBrowserRecording, useActiveBrowserRecordingTabId } from "./browserRecording";
@@ -43,6 +44,14 @@ export function HostedBrowserWebview(props: {
   const { threadRef, tabId, initialUrl, viewport, zoomFactor } = props;
   const config = usePreviewWebviewConfig(threadRef.environmentId);
   const [initialSrc] = useState(() => initialUrl ?? "about:blank");
+  // Freeze once hydration lands so a startup/session-restore webview reads the
+  // persisted value, not the default `false` snapshot. Electron reads the
+  // attribute only at guest attach, so the value stays frozen afterwards.
+  const settingsHydrated = useClientSettingsHydrated();
+  const [disableWebSecurity, setDisableWebSecurity] = useState<boolean | null>(null);
+  if (disableWebSecurity === null && settingsHydrated) {
+    setDisableWebSecurity(getClientSettings().previewDisableWebSecurity);
+  }
   const tabLeaseRef = useRef<AcquiredDesktopTab | null>(null);
   const wrapperRef = useRef<HTMLDivElement | null>(null);
   const webviewRef = useRef<ElectronWebview | null>(null);
@@ -174,7 +183,7 @@ export function HostedBrowserWebview(props: {
     wrapper.scrollTo({ left: 0, top: 0 });
   }, [tabId, viewport._tag, viewportHeight, viewportWidth]);
 
-  if (!config) return null;
+  if (!config || disableWebSecurity === null) return null;
 
   const wrapperStyle = resolveHostedBrowserWebviewWrapperStyle({
     active,
@@ -206,6 +215,10 @@ export function HostedBrowserWebview(props: {
           partition={config.partition}
           webpreferences={config.webPreferences}
           {...(config.preloadUrl ? { preload: config.preloadUrl } : {})}
+          {...(disableWebSecurity
+            ? // string, not boolean: React omits boolean values on this unknown attribute
+              { disablewebsecurity: "true" as unknown as boolean }
+            : {})}
           data-preview-tab={tabId}
           data-preview-viewport-mode={effectiveViewport._tag}
           data-preview-viewport-key={browserViewportSettingKey(effectiveViewport)}
diff --git a/apps/web/src/components/preview/PreviewMoreMenu.tsx b/apps/web/src/components/preview/PreviewMoreMenu.tsx
index 13ddcf57e9e..9b8e6501a37 100644
--- a/apps/web/src/components/preview/PreviewMoreMenu.tsx
+++ b/apps/web/src/components/preview/PreviewMoreMenu.tsx
@@ -3,8 +3,17 @@
 import { Minus, MoreVertical, Plus as PlusIcon, RotateCcw } from "lucide-react";
 
 import { Button } from "~/components/ui/button";
-import { Menu, MenuItem, MenuPopup, MenuSeparator, MenuTrigger } from "~/components/ui/menu";
+import {
+  Menu,
+  MenuCheckboxItem,
+  MenuItem,
+  MenuPopup,
+  MenuSeparator,
+  MenuTrigger,
+} from "~/components/ui/menu";
+import { stackedThreadToast, toastManager } from "~/components/ui/toast";
 import { Tooltip, TooltipPopup, TooltipTrigger } from "~/components/ui/tooltip";
+import { useClientSettings, useUpdateClientSettings } from "~/hooks/useSettings";
 
 import { previewBridge } from "./previewBridge";
 
@@ -37,6 +46,8 @@ export function PreviewMoreMenu({
   deviceToolbarVisible,
   onToggleDeviceToolbar,
 }: Props) {
+  const disableWebSecurity = useClientSettings((settings) => settings.previewDisableWebSecurity);
+  const updateClientSettings = useUpdateClientSettings();
   if (!previewBridge) return null;
   const bridge = previewBridge;
   const tabDisabled = !tabId || !hasWebContents;
@@ -127,6 +138,27 @@ export function PreviewMoreMenu({
         <MenuItem onClick={() => void bridge.clearCache().catch(() => undefined)}>
           Clear cache
         </MenuItem>
+        <MenuSeparator />
+        <MenuCheckboxItem
+          variant="switch"
+          closeOnClick={false}
+          checked={disableWebSecurity}
+          onCheckedChange={(checked) => {
+            const enabled = Boolean(checked);
+            updateClientSettings({ previewDisableWebSecurity: enabled });
+            toastManager.add(
+              stackedThreadToast({
+                type: "info",
+                title: enabled ? "Browser WebSecurity disabled" : "Browser WebSecurity enabled",
+                description: enabled
+                  ? "CORS is off for preview tabs opened from now on. Reopen this tab to apply."
+                  : "Applies to preview tabs opened from now on. Reopen this tab to apply.",
+              }),
+            );
+          }}
+        >
+          Disable browser WebSecurity
+        </MenuCheckboxItem>
       </MenuPopup>
     </Menu>
   );
diff --git a/packages/contracts/src/settings.ts b/packages/contracts/src/settings.ts
index 6ccd65533dd..be164005e0a 100644
--- a/packages/contracts/src/settings.ts
+++ b/packages/contracts/src/settings.ts
@@ -72,6 +72,7 @@ export const ClientSettingsSchema = Schema.Struct({
       modelOrder: Schema.Array(Schema.String).pipe(Schema.withDecodingDefault(Effect.succeed([]))),
     }),
   ).pipe(Schema.withDecodingDefault(Effect.succeed({}))),
+  previewDisableWebSecurity: Schema.Boolean.pipe(Schema.withDecodingDefault(Effect.succeed(false))),
   sidebarProjectGroupingMode: SidebarProjectGroupingMode.pipe(
     Schema.withDecodingDefault(Effect.succeed(DEFAULT_SIDEBAR_PROJECT_GROUPING_MODE)),
   ),
@@ -559,6 +560,7 @@ export const ClientSettingsPatch = Schema.Struct({
       }),
     ),
   ),
+  previewDisableWebSecurity: Schema.optionalKey(Schema.Boolean),
   sidebarProjectGroupingMode: Schema.optionalKey(SidebarProjectGroupingMode),
   sidebarProjectGroupingOverrides: Schema.optionalKey(
     Schema.Record(TrimmedNonEmptyString, SidebarProjectGroupingMode),