diff --git a/src/renderer/src/lib/browser-cookie-import-toast.test.ts b/src/renderer/src/lib/browser-cookie-import-toast.test.ts
index 23e04c53034..8ed73b8b8f8 100644
--- a/src/renderer/src/lib/browser-cookie-import-toast.test.ts
+++ b/src/renderer/src/lib/browser-cookie-import-toast.test.ts
@@ -73,6 +73,26 @@ describe('emitBrowserCookieImportToast', () => {
     expect(message).not.toContain('export')
   })
 
+  it('uses the generic warning for a reason added by a newer runtime host', () => {
+    emitBrowserCookieImportToast(
+      {
+        ...summary,
+        warning: {
+          code: 'cookies-undecryptable',
+          failedCookies: 3,
+          reason: 'newer-runtime-reason'
+        }
+      } as unknown as BrowserCookieImportSummary,
+      'Imported 0 cookies.',
+      'Remote Mac'
+    )
+
+    expect(warningToastMock).toHaveBeenCalledWith(
+      '3 cookies could not be decrypted and were skipped. Close the source browser completely and try the import again.'
+    )
+    expect(successToastMock).not.toHaveBeenCalled()
+  })
+
   it('shows separate host-specific Google guidance after success', () => {
     emitBrowserCookieImportToast(
       { ...summary, importedCookies: 2, skippedCookies: 1, googleCookiesSkipped: 1 },
diff --git a/src/renderer/src/lib/browser-cookie-import-toast.ts b/src/renderer/src/lib/browser-cookie-import-toast.ts
index a8fa4aa6bae..70cb6da3a9a 100644
--- a/src/renderer/src/lib/browser-cookie-import-toast.ts
+++ b/src/renderer/src/lib/browser-cookie-import-toast.ts
@@ -4,6 +4,14 @@ import { translate } from '@/i18n/i18n'
 
 type CookieImportWarning = NonNullable<BrowserCookieImportSummary['warning']>
 
+function formatUnknownCookieImportWarning(failedCookies: number): string {
+  return translate(
+    'auto.lib.browser.cookie.import.toast.undecryptableUnknown',
+    '{{value0}} cookies could not be decrypted and were skipped. Close the source browser completely and try the import again.',
+    { value0: failedCookies }
+  )
+}
+
 function formatCookieImportWarning(warning: CookieImportWarning): string {
   switch (warning.code) {
     case 'restart-fallback-unavailable':
@@ -48,12 +56,10 @@ function formatCookieImportWarning(warning: CookieImportWarning): string {
                 { value0: warning.failedCookies }
               )
         case 'unknown':
-          return translate(
-            'auto.lib.browser.cookie.import.toast.undecryptableUnknown',
-            '{{value0}} cookies could not be decrypted and were skipped. Close the source browser completely and try the import again.',
-            { value0: warning.failedCookies }
-          )
+          return formatUnknownCookieImportWarning(warning.failedCookies)
       }
+      // Older clients can receive a reason added by a newer runtime host before their types know it.
+      return formatUnknownCookieImportWarning(warning.failedCookies)
   }
 }