fix: stabilize admin editor and locale handling

src/payload/doc-locale-hook.ts

@@ -16,10 +16,20 @@ function normalizeLocale(value: unknown) {
     }
   }
   if (typeof value === 'string') {
-    if (/(^|[?&])locale=zh([&#]|$)/.test(value)) return 'zh'
-    if (/(^|[?&])locale=en([&#]|$)/.test(value)) return 'en'
-    if (/(^|\/)zh(\/|$)/.test(value)) return 'zh'
-    if (/(^|\/)en(\/|$)/.test(value)) return 'en'
+    if (value === 'en' || value === 'zh') return value
+
+    try {
+      const normalizedUrl = value.startsWith('http://') || value.startsWith('https://') ? value : `http://localhost${value.startsWith('/') ? '' : '/'}${value}`
+      const parsed = new URL(normalizedUrl)
+      const locale = parsed.searchParams.get('locale')
+      if (locale === 'en' || locale === 'zh') return locale
+
+      const firstSegment = parsed.pathname.split('/').filter(Boolean)[0]
+      if (firstSegment === 'en' || firstSegment === 'zh') return firstSegment
+    } catch {
+      const localeMatch = value.match(/(?:^|[?&])locale=(en|zh)(?:[&#]|$)/)
+      if (localeMatch?.[1] === 'en' || localeMatch?.[1] === 'zh') return localeMatch[1]
+    }
   }
   return null
 }