diff --git a/apps/desktop/src/components/editor/EditorSettingsDialog.vue b/apps/desktop/src/components/editor/EditorSettingsDialog.vue
index bc6662f6f1..3ef7a00ffa 100644
--- a/apps/desktop/src/components/editor/EditorSettingsDialog.vue
+++ b/apps/desktop/src/components/editor/EditorSettingsDialog.vue
@@ -3755,6 +3755,9 @@ watch(previewRef, async (el) => {
       previewLineNumbersComp.of(buildPreviewLineNumbersExtension(ss.showLineNumbers)),
       highlightActiveLineGutter(),
       previewBasicSetup,
+      EditorState.readOnly.of(true),
+      EditorView.editable.of(false),
+      EditorView.contentAttributes.of({ tabindex: "0" }),
       sql({ dialect: MySQL }),
       themeComp.of(themeExt),
       fontThemeComp.of(editorFontTheme(EditorView, ss.fontSize, ss.fontFamily)),
@@ -3943,6 +3946,9 @@ onUnmounted(() => {
                 <div class="rounded-md border overflow-auto max-w-full" :class="editTheme === 'vscode-light' || editTheme === 'duotone-light' || editTheme === 'xcode' ? 'border-border' : 'border-border/50'">
                   <div ref="previewRef" style="min-width: 100%" />
                 </div>
+                <p v-if="editSqlSemanticDiagnosticsEnabled" class="text-xs text-muted-foreground">
+                  {{ t("settings.previewSyntaxErrorHint") }}
+                </p>
               </div>
 
               <Separator />
diff --git a/apps/desktop/src/components/editor/__tests__/EditorSettingsDialog.previewPosition.spec.ts b/apps/desktop/src/components/editor/__tests__/EditorSettingsDialog.previewPosition.spec.ts
index 0a5530d986..fbb1b02162 100644
--- a/apps/desktop/src/components/editor/__tests__/EditorSettingsDialog.previewPosition.spec.ts
+++ b/apps/desktop/src/components/editor/__tests__/EditorSettingsDialog.previewPosition.spec.ts
@@ -38,4 +38,21 @@ describe("EditorSettingsDialog live preview placement", () => {
     expect(dialogSource).toContain("previewLineNumbersComp.reconfigure(buildPreviewLineNumbersExtension(ss.showLineNumbers))");
     expect(dialogSource).toContain("return buildQueryEditorLineNumbersExtension(previewLineNumbersFactory, enabled");
   });
+
+  it("creates the preview editor as read-only so demo edits cannot desync the Apply buttons", () => {
+    expect(dialogSource).toContain("EditorState.readOnly.of(true)");
+    expect(dialogSource).toContain("EditorView.editable.of(false)");
+    expect(dialogSource).toContain('EditorView.contentAttributes.of({ tabindex: "0" })');
+  });
+
+  it("explains the intentional syntax-error demo below the preview when diagnostics are enabled", () => {
+    const preview = editorSection.indexOf('ref="previewRef"');
+    expect(editorSection).toContain('v-if="editSqlSemanticDiagnosticsEnabled"');
+    expect(editorSection.indexOf('t("settings.previewSyntaxErrorHint")')).toBeGreaterThan(preview);
+  });
+
+  it.each(["en", "zh-CN", "zh-TW", "es", "pt-BR", "it", "ja", "ko"])("locale %s translates settings.previewSyntaxErrorHint", (locale) => {
+    const localeSource = readFileSync(new URL(`../../../i18n/locales/${locale}.ts`, import.meta.url), "utf8");
+    expect(localeSource).toMatch(/previewSyntaxErrorHint: ".+"/);
+  });
 });
diff --git a/apps/desktop/src/i18n/locales/en.ts b/apps/desktop/src/i18n/locales/en.ts
index 1a4e9f9321..7f15826a67 100644
--- a/apps/desktop/src/i18n/locales/en.ts
+++ b/apps/desktop/src/i18n/locales/en.ts
@@ -6661,6 +6661,7 @@ export default {
     shortcutConflict: "This shortcut conflicts with another action in the same scope.",
     shortcutClear: "Clear shortcut",
     preview: "Live Preview",
+    previewSyntaxErrorHint: "Read-only preview. The FOM typo in the demo SQL is intentional and demonstrates syntax-error highlighting.",
     customTheme: "Custom Theme",
     customThemeConfigure: "Configure Custom Theme",
     customThemeTitle: "Custom Theme Configuration",
diff --git a/apps/desktop/src/i18n/locales/es.ts b/apps/desktop/src/i18n/locales/es.ts
index 6435b10b79..3c4d0c4bfb 100644
--- a/apps/desktop/src/i18n/locales/es.ts
+++ b/apps/desktop/src/i18n/locales/es.ts
@@ -6332,6 +6332,7 @@ export default withEnglishFallback({
     shortcutConflict: "Este atajo entra en conflicto con otra acción del mismo ámbito.",
     shortcutClear: "Borrar atajo",
     preview: "Vista previa en tiempo real",
+    previewSyntaxErrorHint: "Vista previa de solo lectura. El error FOM en el SQL de ejemplo es intencionado y demuestra el resaltado de errores de sintaxis.",
     customTheme: "Tema personalizado",
     customThemeConfigure: "Configurar tema personalizado",
     customThemeTitle: "Configuración de tema personalizado",
diff --git a/apps/desktop/src/i18n/locales/it.ts b/apps/desktop/src/i18n/locales/it.ts
index 355e4a9a3c..ccff441484 100644
--- a/apps/desktop/src/i18n/locales/it.ts
+++ b/apps/desktop/src/i18n/locales/it.ts
@@ -6332,6 +6332,7 @@ export default withEnglishFallback({
     shortcutConflict: "Questa scorciatoia è in conflitto con un'altra azione nello stesso ambito.",
     shortcutClear: "Cancella scorciatoia",
     preview: "Anteprima in tempo reale",
+    previewSyntaxErrorHint: "Anteprima di sola lettura. L'errore FOM nell'SQL di esempio è intenzionale e mostra l'evidenziazione degli errori di sintassi.",
     customTheme: "Tema personalizzato",
     customThemeConfigure: "Configura tema personalizzato",
     customThemeTitle: "Configurazione tema personalizzato",
diff --git a/apps/desktop/src/i18n/locales/ja.ts b/apps/desktop/src/i18n/locales/ja.ts
index 59026d3999..b6a613c9f1 100644
--- a/apps/desktop/src/i18n/locales/ja.ts
+++ b/apps/desktop/src/i18n/locales/ja.ts
@@ -6343,6 +6343,7 @@ export default withEnglishFallback({
     shortcutConflict: "このショートカットは同じスコープ内の別のアクションと競合しています。",
     shortcutClear: "ショートカットをクリア",
     preview: "ライブプレビュー",
+    previewSyntaxErrorHint: "プレビューは読み取り専用です。デモ SQL 内の FOM は意図的な構文エラーで、エラーのハイライトを示しています。",
     customTheme: "カスタムテーマ",
     customThemeConfigure: "カスタムテーマを設定",
     customThemeTitle: "カスタムテーマ設定",
diff --git a/apps/desktop/src/i18n/locales/ko.ts b/apps/desktop/src/i18n/locales/ko.ts
index 0524695860..fb5df000b9 100644
--- a/apps/desktop/src/i18n/locales/ko.ts
+++ b/apps/desktop/src/i18n/locales/ko.ts
@@ -6036,6 +6036,7 @@ export default withEnglishFallback({
     shortcutConflict: "이 단축키는 같은 범위의 다른 작업과 충돌합니다.",
     shortcutClear: "단축키 지우기",
     preview: "실시간 미리보기",
+    previewSyntaxErrorHint: "미리보기는 읽기 전용입니다. 데모 SQL의 FOM 오타는 의도적인 구문 오류이며 오류 강조 표시를 보여줍니다.",
     customTheme: "사용자 지정 테마",
     customThemeConfigure: "사용자 지정 테마 설정",
     customThemeTitle: "사용자 지정 테마 구성",
diff --git a/apps/desktop/src/i18n/locales/pt-BR.ts b/apps/desktop/src/i18n/locales/pt-BR.ts
index b647e4cb91..4f3d2002ba 100644
--- a/apps/desktop/src/i18n/locales/pt-BR.ts
+++ b/apps/desktop/src/i18n/locales/pt-BR.ts
@@ -6334,6 +6334,7 @@ export default withEnglishFallback({
     shortcutConflict: "Este atalho conflita com outra ação no mesmo escopo.",
     shortcutClear: "Limpar atalho",
     preview: "Pré-visualização ao vivo",
+    previewSyntaxErrorHint: "Pré-visualização somente leitura. O erro FOM no SQL de exemplo é intencional e demonstra o destaque de erros de sintaxe.",
     customTheme: "Tema personalizado",
     customThemeConfigure: "Configurar tema personalizado",
     customThemeTitle: "Configuração do tema personalizado",
diff --git a/apps/desktop/src/i18n/locales/zh-CN.ts b/apps/desktop/src/i18n/locales/zh-CN.ts
index ab9437acb7..835bd2b921 100644
--- a/apps/desktop/src/i18n/locales/zh-CN.ts
+++ b/apps/desktop/src/i18n/locales/zh-CN.ts
@@ -6647,6 +6647,7 @@ export default withEnglishFallback({
     shortcutConflict: "这个快捷键与同一作用域内的其他操作冲突。",
     shortcutClear: "清除快捷键",
     preview: "实时预览",
+    previewSyntaxErrorHint: "预览为只读。示例 SQL 中的 FOM 拼写是故意设置的语法错误，用于演示错误高亮效果。",
     customTheme: "自定义主题",
     customThemeConfigure: "自定义主题配置",
     customThemeTitle: "自定义主题配置",
diff --git a/apps/desktop/src/i18n/locales/zh-TW.ts b/apps/desktop/src/i18n/locales/zh-TW.ts
index b2b46207db..0636bd4d90 100644
--- a/apps/desktop/src/i18n/locales/zh-TW.ts
+++ b/apps/desktop/src/i18n/locales/zh-TW.ts
@@ -5639,6 +5639,7 @@ export default withEnglishFallback({
     shortcutConflict: "這個快速鍵與同一作用域內的其他操作衝突。",
     shortcutClear: "清除快速鍵",
     preview: "即時預覽",
+    previewSyntaxErrorHint: "預覽為唯讀。範例 SQL 中的 FOM 拼寫是刻意設置的語法錯誤，用於示範錯誤高亮效果。",
     customTheme: "自定義主題",
     customThemeConfigure: "自定義主題配置",
     customThemeTitle: "自定義主題配置",