diff --git a/backend/chainlit/translations/ar-SA.json b/backend/chainlit/translations/ar-SA.json
index b98b427d23..b5de794c3d 100644
--- a/backend/chainlit/translations/ar-SA.json
+++ b/backend/chainlit/translations/ar-SA.json
@@ -68,6 +68,7 @@
     "favorites": {
       "use": "استخدام رسالة مفضلة",
       "headline": "الرسائل المفضلة",
+      "remove": "إزالة من المفضلة",
       "empty": {
         "title": "لا توجد رسائل محفوظة بعد",
         "description": "ابدأ بإرسال رسالة وقم بتمييزها بنجمة أو ميّز رسالة من محادثاتك السابقة"
diff --git a/backend/chainlit/translations/da-DK.json b/backend/chainlit/translations/da-DK.json
index aba214e617..8c9e8607b0 100644
--- a/backend/chainlit/translations/da-DK.json
+++ b/backend/chainlit/translations/da-DK.json
@@ -68,6 +68,7 @@
     "favorites": {
       "use": "Brug en favorit besked",
       "headline": "Favorit beskeder",
+      "remove": "Fjern favorit",
       "empty": {
         "title": "Ingen gemte prompts endnu",
         "description": "Start med at sende en prompt og markere den med en stjerne, eller vælg en prompt fra tidligere samtaler"
diff --git a/backend/chainlit/translations/de-DE.json b/backend/chainlit/translations/de-DE.json
index db5934b6f1..1469a3f569 100644
--- a/backend/chainlit/translations/de-DE.json
+++ b/backend/chainlit/translations/de-DE.json
@@ -249,6 +249,12 @@
   "components": {
     "MultiSelectInput": {
       "placeholder": "Wähle aus..."
+    },
+    "DatePickerInput": {
+      "placeholder": {
+        "single": "Datum auswählen",
+        "range": "Datumsbereich auswählen"
+      }
     }
   }
 }
diff --git a/backend/chainlit/translations/it.json b/backend/chainlit/translations/it.json
index 69021fe630..bad83ea185 100644
--- a/backend/chainlit/translations/it.json
+++ b/backend/chainlit/translations/it.json
@@ -249,6 +249,12 @@
   "components": {
     "MultiSelectInput": {
       "placeholder": "Seleziona..."
+    },
+    "DatePickerInput": {
+      "placeholder": {
+        "single": "Seleziona una data",
+        "range": "Seleziona un intervallo di date"
+      }
     }
   }
 }
diff --git a/backend/chainlit/translations/ja.json b/backend/chainlit/translations/ja.json
index b1ea49659b..2762908e41 100644
--- a/backend/chainlit/translations/ja.json
+++ b/backend/chainlit/translations/ja.json
@@ -86,6 +86,7 @@
     },
     "fileUpload": {
       "dragDrop": "ここにファイルをドラッグ＆ドロップ",
+      "browse": "ファイルを選択",
       "sizeLimit": "制限：",
       "errors": {
         "failed": "アップロードに失敗しました",
diff --git a/backend/chainlit/translations/ko.json b/backend/chainlit/translations/ko.json
index f05622faf1..3a0cca3bf2 100644
--- a/backend/chainlit/translations/ko.json
+++ b/backend/chainlit/translations/ko.json
@@ -249,6 +249,12 @@
   "components": {
     "MultiSelectInput": {
       "placeholder": "선택..."
+    },
+    "DatePickerInput": {
+      "placeholder": {
+        "single": "날짜 선택",
+        "range": "날짜 범위 선택"
+      }
     }
   }
 }
diff --git a/backend/tests/test_translations.py b/backend/tests/test_translations.py
index 6e517c4748..6b852b87d8 100644
--- a/backend/tests/test_translations.py
+++ b/backend/tests/test_translations.py
@@ -1,8 +1,11 @@
+import json
+import os
 from io import StringIO
 from unittest.mock import patch
 
 import pytest
 
+from chainlit.config import TRANSLATIONS_DIR
 from chainlit.translations import compare_json_structures, lint_translation_json
 
 
@@ -384,3 +387,40 @@ def test_compare_preserves_error_order(self):
         missing_errors = [e for e in errors if "Missing" in e]
         assert len(extra_errors) == 2
         assert len(missing_errors) == 3
+
+
+def _load_translation(filename):
+    with open(os.path.join(TRANSLATIONS_DIR, filename), encoding="utf-8") as f:
+        return json.load(f)
+
+
+_TRUTH_LOCALE = "en-US.json"
+_LOCALE_FILES = sorted(f for f in os.listdir(TRANSLATIONS_DIR) if f.endswith(".json"))
+
+
+class TestTranslationFileParity:
+    """Every shipped locale file must carry every key in en-US.json.
+
+    This walks the real backend/chainlit/translations/ directory rather than
+    synthetic dictionaries, so a PR that adds a key to en-US.json without
+    updating the other locales fails here instead of shipping silently.
+    """
+
+    @pytest.mark.parametrize("locale_file", _LOCALE_FILES)
+    def test_locale_has_no_missing_or_mismatched_keys(self, locale_file):
+        truth = _load_translation(_TRUTH_LOCALE)
+        # Comparing en-US.json to itself is expected to be trivially clean —
+        # it is both a locale file and the ground truth.
+        to_compare = _load_translation(locale_file)
+
+        errors = compare_json_structures(truth, to_compare)
+        # "Extra key" is excluded: a locale carrying a key en-US.json doesn't
+        # (yet) have is not a rendering regression. Missing keys and structure
+        # mismatches both are — a key present as the wrong shape (e.g. an
+        # object where en-US.json has a string) breaks rendering exactly like
+        # a missing key does, so both must fail here.
+        relevant = [e for e in errors if "Extra" not in e]
+
+        assert relevant == [], (
+            f"{locale_file} diverges from {_TRUTH_LOCALE}: {relevant}"
+        )