fix(config): resolve common config sync issues across frontend and backend

- Fix backfill pollution: extract custom config from live when common config enabled
- Fix proxy backup: merge common config before backup to preserve full config
- Unify null override semantics: null no longer overrides in both frontend and backend
- Add missing i18n keys for common config UI
- Hide format button in readonly JsonEditor
- Add mapGeminiWarningToI18n for user-friendly warning messages

src/components/JsonEditor.tsx

@@ -280,7 +280,7 @@ const JsonEditor: React.FC<JsonEditorProps> = ({
         style={{ width: "100%", height: isFullHeight ? undefined : "auto" }}
         className={isFullHeight ? "flex-1 min-h-0" : ""}
       />
-      {language === "json" && (
+      {language === "json" && !readOnly && (
         <button
           type="button"
           onClick={handleFormat}

src/components/providers/EditProviderDialog.tsx

@@ -12,7 +12,10 @@ import {
 import { providersApi, vscodeApi, configApi, type AppId } from "@/lib/api";
 import { extractDifference, isPlainObject } from "@/utils/configMerge";
 import { extractTomlDifference } from "@/utils/tomlConfigMerge";
-import { parseGeminiCommonConfigSnippet } from "@/utils/providerConfigUtils";
+import {
+  parseGeminiCommonConfigSnippet,
+  mapGeminiWarningToI18n,
+} from "@/utils/providerConfigUtils";
 
 interface EditProviderDialogProps {
   open: boolean;
@@ -138,7 +141,7 @@ export function EditProviderDialog({
                       } else {
                         // Show warning toast if keys were filtered
                         if (parseResult.warning) {
-                          toast.warning(parseResult.warning);
+                          toast.warning(mapGeminiWarningToI18n(parseResult.warning, t));
                         }
 
                         if (

src/components/providers/forms/ProviderForm.tsx

@@ -38,7 +38,10 @@ import { applyTemplateValues } from "@/utils/providerConfigUtils";
 import { mergeProviderMeta } from "@/utils/providerMetaUtils";
 import { extractDifference, isPlainObject } from "@/utils/configMerge";
 import { extractTomlDifference } from "@/utils/tomlConfigMerge";
-import { parseGeminiCommonConfigSnippet } from "@/utils/providerConfigUtils";
+import {
+  parseGeminiCommonConfigSnippet,
+  mapGeminiWarningToI18n,
+} from "@/utils/providerConfigUtils";
 import { getCodexCustomTemplate } from "@/config/codexTemplates";
 import CodexConfigEditor from "./CodexConfigEditor";
 import { CommonConfigEditor } from "./CommonConfigEditor";
@@ -979,7 +982,7 @@ export function ProviderForm({
           );
           // Show warning toast if keys were filtered
           if (warning) {
-            toast.warning(warning);
+            toast.warning(mapGeminiWarningToI18n(warning, t));
           }
           if (isPlainObject(envObj) && isPlainObject(commonEnvObj)) {
             const { customConfig } = extractDifference(envObj, commonEnvObj);

src/i18n/locales/en.json

@@ -36,7 +36,8 @@
     "search": "Search",
     "reset": "Reset",
     "actions": "Actions",
-    "deleting": "Deleting..."
+    "deleting": "Deleting...",
+    "readonly": "Read-only"
   },
   "apiKeyInput": {
     "placeholder": "Enter API Key",
@@ -58,7 +59,12 @@
     "extractFromCurrent": "Extract from Editor",
     "extractNoCommonConfig": "No common config available to extract from editor",
     "extractFailed": "Extract failed: {{error}}",
-    "saveFailed": "Save failed: {{error}}"
+    "saveFailed": "Save failed: {{error}}",
+    "hidePreview": "Hide merged preview",
+    "showPreview": "Show merged preview",
+    "customConfig": "Custom config (overrides common)",
+    "mergedPreview": "Merged preview (read-only)",
+    "mergedPreviewHint": "Common config + Custom config = Final config"
   },
   "header": {
     "viewOnGithub": "View on GitHub",
@@ -553,7 +559,8 @@
     "commonConfigInvalidValues": "Common config snippet values must be strings",
     "noCommonConfigToApply": "Common config snippet is empty or has no applicable entries",
     "configMergeFailed": "Config merge failed: {{error}}",
-    "configReplaceFailed": "Config replace failed: {{error}}"
+    "configReplaceFailed": "Config replace failed: {{error}}",
+    "forbiddenKeysWarning": "The following keys were filtered (not allowed in common config): {{keys}}"
   },
   "opencode": {
     "npmPackage": "API Format",

src/i18n/locales/ja.json

@@ -36,7 +36,8 @@
     "search": "検索",
     "reset": "リセット",
     "actions": "操作",
-    "deleting": "削除中..."
+    "deleting": "削除中...",
+    "readonly": "読み取り専用"
   },
   "apiKeyInput": {
     "placeholder": "API Key を入力",
@@ -58,7 +59,12 @@
     "extractFromCurrent": "編集内容から抽出",
     "extractNoCommonConfig": "編集内容から抽出できる共通設定がありません",
     "extractFailed": "抽出に失敗しました: {{error}}",
-    "saveFailed": "保存に失敗しました: {{error}}"
+    "saveFailed": "保存に失敗しました: {{error}}",
+    "hidePreview": "マージプレビューを非表示",
+    "showPreview": "マージプレビューを表示",
+    "customConfig": "カスタム設定（共通設定を上書き）",
+    "mergedPreview": "マージプレビュー（読み取り専用）",
+    "mergedPreviewHint": "共通設定 + カスタム設定 = 最終設定"
   },
   "header": {
     "viewOnGithub": "GitHub で見る",
@@ -553,7 +559,8 @@
     "commonConfigInvalidValues": "共通設定スニペットの値は文字列である必要があります",
     "noCommonConfigToApply": "共通設定スニペットが空、または適用できる項目がありません",
     "configMergeFailed": "設定のマージに失敗しました: {{error}}",
-    "configReplaceFailed": "設定の置換に失敗しました: {{error}}"
+    "configReplaceFailed": "設定の置換に失敗しました: {{error}}",
+    "forbiddenKeysWarning": "以下のキーはフィルタされました（共通設定では許可されていません）：{{keys}}"
   },
   "opencode": {
     "npmPackage": "API フォーマット",

src/i18n/locales/zh.json

@@ -36,7 +36,8 @@
     "search": "查询",
     "reset": "重置",
     "actions": "操作",
-    "deleting": "删除中..."
+    "deleting": "删除中...",
+    "readonly": "只读"
   },
   "apiKeyInput": {
     "placeholder": "请输入API Key",
@@ -58,7 +59,12 @@
     "extractFromCurrent": "从编辑内容提取",
     "extractNoCommonConfig": "当前编辑内容没有可提取的通用配置",
     "extractFailed": "提取失败: {{error}}",
-    "saveFailed": "保存失败: {{error}}"
+    "saveFailed": "保存失败: {{error}}",
+    "hidePreview": "隐藏合并预览",
+    "showPreview": "显示合并预览",
+    "customConfig": "自定义配置（覆盖通用配置）",
+    "mergedPreview": "合并预览（只读）",
+    "mergedPreviewHint": "通用配置 + 自定义配置 = 最终配置"
   },
   "header": {
     "viewOnGithub": "在 GitHub 上查看",
@@ -553,7 +559,8 @@
     "commonConfigInvalidValues": "通用配置片段的值必须是字符串",
     "noCommonConfigToApply": "通用配置片段为空或没有可写入的内容",
     "configMergeFailed": "配置合并失败: {{error}}",
-    "configReplaceFailed": "配置替换失败: {{error}}"
+    "configReplaceFailed": "配置替换失败: {{error}}",
+    "forbiddenKeysWarning": "以下密钥已被自动过滤（禁止在通用配置中设置）：{{keys}}"
   },
   "opencode": {
     "npmPackage": "接口格式",

src/utils/configMerge.ts

@@ -73,7 +73,7 @@ export const deepEqual = (a: unknown, b: unknown): boolean => {
  * - 嵌套对象：递归合并
  * - 数组：source 完全替换 target（不做元素级合并）
  * - 原始值：source 覆盖 target
- * - undefined：不覆盖
+ * - undefined/null：不覆盖（与后端 config_merge.rs 保持一致）
  */
 export const deepMerge = <T extends Record<string, unknown>>(
   target: T,
@@ -85,8 +85,8 @@ export const deepMerge = <T extends Record<string, unknown>>(
     const sourceValue = source[key];
     const targetValue = result[key];
 
-    // undefined 不覆盖
-    if (sourceValue === undefined) {
+    // undefined 和 null 都不覆盖（与后端保持一致）
+    if (sourceValue === undefined || sourceValue === null) {
       continue;
     }
 

src/utils/providerConfigUtils.ts

@@ -1201,3 +1201,26 @@ export function parseGeminiCommonConfigSnippet(
     warning: warnings.length > 0 ? warnings.join("; ") : undefined,
   };
 }
+
+/**
+ * Map Gemini common config warning to i18n-friendly message.
+ *
+ * @param warning - The raw warning string from parseGeminiCommonConfigSnippet
+ * @param t - The i18n translation function
+ * @returns Translated warning message
+ */
+export function mapGeminiWarningToI18n(
+  warning: string,
+  t: (key: string, options?: { keys?: string; defaultValue?: string }) => string,
+): string {
+  if (warning.startsWith(GEMINI_CONFIG_ERROR_CODES.FORBIDDEN_KEYS)) {
+    // Extract key list: "GEMINI_CONFIG_FORBIDDEN_KEYS: KEY1, KEY2" -> "KEY1, KEY2"
+    const keys = warning.replace(
+      `${GEMINI_CONFIG_ERROR_CODES.FORBIDDEN_KEYS}: `,
+      "",
+    );
+    return t("geminiConfig.forbiddenKeysWarning", { keys });
+  }
+  // Other warnings: return as-is
+  return warning;
+}