diff --git a/packages/ui/src/App.tsx b/packages/ui/src/App.tsx
index 250a3a8d..6c8d7949 100644
--- a/packages/ui/src/App.tsx
+++ b/packages/ui/src/App.tsx
@@ -222,6 +222,7 @@ function App({ apis }: AppProps) {
   const [initRetryExhausted, setInitRetryExhausted] = React.useState(false);
   const [initRetryEpoch, setInitRetryEpoch] = React.useState(0);
   const [manualInitRetrying, setManualInitRetrying] = React.useState(false);
+  const wideChatLayoutEnabled = useUIStore((state) => state.wideChatLayoutEnabled);
   const isDesktopRuntime = React.useMemo(() => isDesktopShell(), []);
   const setPlanModeEnabled = useFeatureFlagsStore((state) => state.setPlanModeEnabled);
   const [bootInjectionStatus, setBootInjectionStatus] = React.useState<BootInjectionStatus>(() => {
@@ -250,6 +251,13 @@ function App({ apis }: AppProps) {
     setIsVSCodeRuntime(apis.runtime.isVSCode);
   }, [apis.runtime.isVSCode]);
 
+  React.useEffect(() => {
+    document.documentElement.classList.toggle('wide-chat-layout', wideChatLayoutEnabled);
+    return () => {
+      document.documentElement.classList.remove('wide-chat-layout');
+    };
+  }, [wideChatLayoutEnabled]);
+
   React.useEffect(() => {
     registerRuntimeAPIs(apis);
     return () => registerRuntimeAPIs(null);
diff --git a/packages/ui/src/components/sections/openchamber/OpenChamberPage.tsx b/packages/ui/src/components/sections/openchamber/OpenChamberPage.tsx
index ff09e3c9..c3554787 100644
--- a/packages/ui/src/components/sections/openchamber/OpenChamberPage.tsx
+++ b/packages/ui/src/components/sections/openchamber/OpenChamberPage.tsx
@@ -128,7 +128,7 @@ const VisualSectionContent: React.FC = () => {
 
 // Chat section: User message rendering, Diff layout, Mobile status bar, Show reasoning traces, Queue mode, Persist draft
 const ChatSectionContent: React.FC = () => {
-    return <OpenChamberVisualSettings visibleSettings={['chatRenderMode', 'messageTransport', 'activityRenderMode', 'userMessageRendering', 'mermaidRendering', 'reasoning', 'showToolFileIcons', 'expandedTools', 'stickyUserHeader', 'splitAssistantMessageActions', 'diffLayout', 'mobileStatusBar', 'dotfiles', 'queueMode', 'persistDraft', 'inputSpellcheck']} />;
+    return <OpenChamberVisualSettings visibleSettings={['chatRenderMode', 'messageTransport', 'activityRenderMode', 'userMessageRendering', 'mermaidRendering', 'reasoning', 'showToolFileIcons', 'expandedTools', 'stickyUserHeader', 'wideChatLayout', 'splitAssistantMessageActions', 'diffLayout', 'mobileStatusBar', 'dotfiles', 'queueMode', 'persistDraft', 'inputSpellcheck']} />;
 };
 
 // Sessions section: Default model & agent, Session retention
diff --git a/packages/ui/src/components/sections/openchamber/OpenChamberVisualSettings.tsx b/packages/ui/src/components/sections/openchamber/OpenChamberVisualSettings.tsx
index 643ed74a..6ed0308b 100644
--- a/packages/ui/src/components/sections/openchamber/OpenChamberVisualSettings.tsx
+++ b/packages/ui/src/components/sections/openchamber/OpenChamberVisualSettings.tsx
@@ -220,7 +220,7 @@ const normalizeUserMessageRenderingMode = (mode: unknown): 'markdown' | 'plain'
     return mode === 'markdown' ? 'markdown' : 'plain';
 };
 
-export type VisibleSetting = 'theme' | 'pwaInstallName' | 'pwaOrientation' | 'timeFormat' | 'weekStart' | 'fontSize' | 'terminalFontSize' | 'spacing' | 'inputBarOffset' | 'mermaidRendering' | 'userMessageRendering' | 'chatRenderMode' | 'messageTransport' | 'activityRenderMode' | 'stickyUserHeader' | 'splitAssistantMessageActions' | 'diffLayout' | 'mobileStatusBar' | 'dotfiles' | 'reasoning' | 'showToolFileIcons' | 'expandedTools' | 'queueMode' | 'terminalQuickKeys' | 'persistDraft' | 'inputSpellcheck' | 'reportUsage';
+export type VisibleSetting = 'theme' | 'pwaInstallName' | 'pwaOrientation' | 'timeFormat' | 'weekStart' | 'fontSize' | 'terminalFontSize' | 'spacing' | 'inputBarOffset' | 'mermaidRendering' | 'userMessageRendering' | 'chatRenderMode' | 'messageTransport' | 'activityRenderMode' | 'stickyUserHeader' | 'wideChatLayout' | 'splitAssistantMessageActions' | 'diffLayout' | 'mobileStatusBar' | 'dotfiles' | 'reasoning' | 'showToolFileIcons' | 'expandedTools' | 'queueMode' | 'terminalQuickKeys' | 'persistDraft' | 'inputSpellcheck' | 'reportUsage';
 
 interface OpenChamberVisualSettingsProps {
     /** Which settings to show. If undefined, shows all. */
@@ -242,6 +242,8 @@ export const OpenChamberVisualSettings: React.FC<OpenChamberVisualSettingsProps>
     const setUserMessageRenderingMode = useUIStore(state => state.setUserMessageRenderingMode);
     const stickyUserHeader = useUIStore(state => state.stickyUserHeader);
     const setStickyUserHeader = useUIStore(state => state.setStickyUserHeader);
+    const wideChatLayoutEnabled = useUIStore(state => state.wideChatLayoutEnabled);
+    const setWideChatLayoutEnabled = useUIStore(state => state.setWideChatLayoutEnabled);
     const chatRenderMode = useUIStore(state => state.chatRenderMode);
     const setChatRenderMode = useUIStore(state => state.setChatRenderMode);
     const activityRenderMode = useUIStore(state => state.activityRenderMode);
@@ -366,6 +368,11 @@ export const OpenChamberVisualSettings: React.FC<OpenChamberVisualSettingsProps>
         void updateDesktopSettings({ stickyUserHeader: enabled });
     }, [setStickyUserHeader]);
 
+    const handleWideChatLayoutChange = React.useCallback((enabled: boolean) => {
+        setWideChatLayoutEnabled(enabled);
+        void updateDesktopSettings({ wideChatLayoutEnabled: enabled });
+    }, [setWideChatLayoutEnabled]);
+
     const handleShowSplitAssistantMessageActionsChange = React.useCallback((enabled: boolean) => {
         setShowSplitAssistantMessageActions(enabled);
         void updateDesktopSettings({ showSplitAssistantMessageActions: enabled });
@@ -469,6 +476,7 @@ export const OpenChamberVisualSettings: React.FC<OpenChamberVisualSettingsProps>
         || shouldShow('messageTransport')
         || (shouldShow('activityRenderMode') && chatRenderMode === 'sorted')
         || shouldShow('stickyUserHeader')
+        || shouldShow('wideChatLayout')
         || shouldShow('splitAssistantMessageActions')
         || shouldShow('diffLayout')
         || (shouldShow('mobileStatusBar') && isMobile)
@@ -1451,7 +1459,7 @@ export const OpenChamberVisualSettings: React.FC<OpenChamberVisualSettingsProps>
                                 </div>
                             )}
 
-                            {(shouldShow('stickyUserHeader') || shouldShow('splitAssistantMessageActions') || (shouldShow('mobileStatusBar') && isMobile) || shouldShow('dotfiles') || shouldShow('queueMode') || shouldShow('persistDraft') || shouldShow('showToolFileIcons') || (!isMobile && shouldShow('inputSpellcheck')) || shouldShow('reasoning')) && (
+                            {(shouldShow('stickyUserHeader') || shouldShow('wideChatLayout') || shouldShow('splitAssistantMessageActions') || (shouldShow('mobileStatusBar') && isMobile) || shouldShow('dotfiles') || shouldShow('queueMode') || shouldShow('persistDraft') || shouldShow('showToolFileIcons') || (!isMobile && shouldShow('inputSpellcheck')) || shouldShow('reasoning')) && (
                                 <section className="p-2 space-y-0.5">
                                     {shouldShow('reasoning') && (
                                         <div
@@ -1499,6 +1507,29 @@ export const OpenChamberVisualSettings: React.FC<OpenChamberVisualSettingsProps>
                                         </div>
                                     )}
 
+                                    {shouldShow('wideChatLayout') && (
+                                        <div
+                                            className="group flex cursor-pointer items-center gap-2 py-0.5"
+                                            role="button"
+                                            tabIndex={0}
+                                            aria-pressed={wideChatLayoutEnabled}
+                                            onClick={() => handleWideChatLayoutChange(!wideChatLayoutEnabled)}
+                                            onKeyDown={(event) => {
+                                                if (event.key === ' ' || event.key === 'Enter') {
+                                                    event.preventDefault();
+                                                    handleWideChatLayoutChange(!wideChatLayoutEnabled);
+                                                }
+                                            }}
+                                        >
+                                            <Checkbox
+                                                checked={wideChatLayoutEnabled}
+                                                onChange={handleWideChatLayoutChange}
+                                                ariaLabel={t('settings.openchamber.visual.field.wideChatLayoutAria')}
+                                            />
+                                            <span className="typography-ui-label text-foreground">{t('settings.openchamber.visual.field.wideChatLayout')}</span>
+                                        </div>
+                                    )}
+
                                     {shouldShow('splitAssistantMessageActions') && (
                                         <div
                                             className="group flex cursor-pointer items-center gap-2 py-0.5"
diff --git a/packages/ui/src/lib/desktop.ts b/packages/ui/src/lib/desktop.ts
index 38ded45c..52bcfb48 100644
--- a/packages/ui/src/lib/desktop.ts
+++ b/packages/ui/src/lib/desktop.ts
@@ -133,6 +133,7 @@ export type DesktopSettings = {
   mermaidRenderingMode?: 'svg' | 'ascii';
   userMessageRenderingMode?: 'markdown' | 'plain';
   stickyUserHeader?: boolean;
+  wideChatLayoutEnabled?: boolean;
   showSplitAssistantMessageActions?: boolean;
   fontSize?: number;
   terminalFontSize?: number;
diff --git a/packages/ui/src/lib/i18n/messages/en.settings.ts b/packages/ui/src/lib/i18n/messages/en.settings.ts
index 64f66584..50a1ed8e 100644
--- a/packages/ui/src/lib/i18n/messages/en.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/en.settings.ts
@@ -1394,6 +1394,8 @@ export const settingsDict = {
   'settings.openchamber.visual.field.showReasoningTraces': 'Show Reasoning Traces',
   'settings.openchamber.visual.field.stickyUserHeaderAria': 'Sticky user header',
   'settings.openchamber.visual.field.stickyUserHeader': 'Sticky User Header',
+  'settings.openchamber.visual.field.wideChatLayoutAria': 'Wide chat layout',
+  'settings.openchamber.visual.field.wideChatLayout': 'Wide Chat Layout',
   'settings.openchamber.visual.field.showSplitAssistantMessageActionsAria': 'Inline assistant actions',
   'settings.openchamber.visual.field.showSplitAssistantMessageActions': 'Inline Assistant Actions',
   'settings.openchamber.visual.field.showSplitAssistantMessageActionsTooltip': 'Show Copy Answer, Save as image, and Read aloud on assistant text blocks that appear before later tool calls in the same response.',
diff --git a/packages/ui/src/lib/i18n/messages/es.settings.ts b/packages/ui/src/lib/i18n/messages/es.settings.ts
index 14e24e93..84d51980 100644
--- a/packages/ui/src/lib/i18n/messages/es.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/es.settings.ts
@@ -1394,6 +1394,8 @@ export const settingsDict = {
   "settings.openchamber.visual.field.showReasoningTraces": "Mostrar trazas de razonamiento",
   "settings.openchamber.visual.field.stickyUserHeaderAria": "Encabezado del usuario fijo",
   "settings.openchamber.visual.field.stickyUserHeader": "Encabezado de usuario fijo",
+  "settings.openchamber.visual.field.wideChatLayoutAria": "Diseño de chat ancho",
+  "settings.openchamber.visual.field.wideChatLayout": "Diseño de chat ancho",
   "settings.openchamber.visual.field.showSplitAssistantMessageActionsAria": "Acciones en línea del asistente",
   "settings.openchamber.visual.field.showSplitAssistantMessageActions": "Acciones en línea del asistente",
   "settings.openchamber.visual.field.showSplitAssistantMessageActionsTooltip": "Muestra Copiar respuesta, Guardar como imagen y Leer en voz alta en bloques de texto del asistente que aparecen antes de llamadas a herramientas posteriores dentro de la misma respuesta.",
diff --git a/packages/ui/src/lib/i18n/messages/ko.settings.ts b/packages/ui/src/lib/i18n/messages/ko.settings.ts
index 932ae118..870656a7 100644
--- a/packages/ui/src/lib/i18n/messages/ko.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/ko.settings.ts
@@ -1394,6 +1394,8 @@ export const settingsDict = {
   'settings.openchamber.visual.field.showReasoningTraces': 'Reasoning Trace 표시',
   'settings.openchamber.visual.field.stickyUserHeaderAria': '고정 사용자 헤더',
   'settings.openchamber.visual.field.stickyUserHeader': '고정 사용자 헤더',
+  'settings.openchamber.visual.field.wideChatLayoutAria': '넓은 채팅 레이아웃',
+  'settings.openchamber.visual.field.wideChatLayout': '넓은 채팅 레이아웃',
   'settings.openchamber.visual.field.showSplitAssistantMessageActionsAria': '인라인 어시스턴트 작업',
   'settings.openchamber.visual.field.showSplitAssistantMessageActions': '인라인 어시스턴트 작업',
   'settings.openchamber.visual.field.showSplitAssistantMessageActionsTooltip': '같은 응답에서 이후 도구 호출 앞에 나타나는 어시스턴트 텍스트 블록에 답변 복사, 이미지로 저장, 소리 내어 읽기 작업을 표시합니다.',
diff --git a/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts b/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts
index bf7a3ab5..dcd6f16d 100644
--- a/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/pt-BR.settings.ts
@@ -1394,6 +1394,8 @@ export const settingsDict = {
   "settings.openchamber.visual.field.showReasoningTraces": "Mostrar rastros de raciocínio",
   "settings.openchamber.visual.field.stickyUserHeaderAria": "Cabeçalho do usuário fixo",
   "settings.openchamber.visual.field.stickyUserHeader": "Cabeçalho do usuário fixo",
+  "settings.openchamber.visual.field.wideChatLayoutAria": "Layout de chat amplo",
+  "settings.openchamber.visual.field.wideChatLayout": "Layout de chat amplo",
   "settings.openchamber.visual.field.showSplitAssistantMessageActionsAria": "Ações inline do assistente",
   "settings.openchamber.visual.field.showSplitAssistantMessageActions": "Ações inline do assistente",
   "settings.openchamber.visual.field.showSplitAssistantMessageActionsTooltip": "Mostra Copiar resposta, Salvar como imagem e Ler em voz alta em blocos de texto do assistente que aparecem antes de chamadas de ferramenta posteriores na mesma resposta.",
diff --git a/packages/ui/src/lib/i18n/messages/uk.settings.ts b/packages/ui/src/lib/i18n/messages/uk.settings.ts
index 91ce8bd6..bff60512 100644
--- a/packages/ui/src/lib/i18n/messages/uk.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/uk.settings.ts
@@ -1394,6 +1394,8 @@ export const settingsDict = {
   "settings.openchamber.visual.field.showReasoningTraces": "Показати сліди міркувань",
   "settings.openchamber.visual.field.stickyUserHeaderAria": "Закріплений заголовок користувача",
   "settings.openchamber.visual.field.stickyUserHeader": "Закріплений заголовок користувача",
+  "settings.openchamber.visual.field.wideChatLayoutAria": "Широкий макет чату",
+  "settings.openchamber.visual.field.wideChatLayout": "Широкий макет чату",
   "settings.openchamber.visual.field.showSplitAssistantMessageActionsAria": "Вбудовані дії асистента",
   "settings.openchamber.visual.field.showSplitAssistantMessageActions": "Вбудовані дії асистента",
   "settings.openchamber.visual.field.showSplitAssistantMessageActionsTooltip": "Показує «Скопіювати відповідь», «Зберегти як зображення» та озвучення для текстових блоків асистента, які з’являються перед пізнішими викликами інструментів у тій самій відповіді.",
diff --git a/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts b/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts
index dd676c17..5e0ec20a 100644
--- a/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-CN.settings.ts
@@ -1394,6 +1394,8 @@ export const settingsDict = {
   'settings.openchamber.visual.field.showReasoningTraces': '显示推理轨迹',
   'settings.openchamber.visual.field.stickyUserHeaderAria': '固定用户消息头',
   'settings.openchamber.visual.field.stickyUserHeader': '固定用户消息头',
+  'settings.openchamber.visual.field.wideChatLayoutAria': '宽聊天布局',
+  'settings.openchamber.visual.field.wideChatLayout': '宽聊天布局',
   'settings.openchamber.visual.field.showSplitAssistantMessageActionsAria': '内联助手操作',
   'settings.openchamber.visual.field.showSplitAssistantMessageActions': '内联助手操作',
   'settings.openchamber.visual.field.showSplitAssistantMessageActionsTooltip': '在同一条回复中，如果助手文本块后面还有工具调用，则显示“复制回答”“保存为图片”和“朗读”操作。',
diff --git a/packages/ui/src/lib/persistence.ts b/packages/ui/src/lib/persistence.ts
index 23080d3e..fac42d34 100644
--- a/packages/ui/src/lib/persistence.ts
+++ b/packages/ui/src/lib/persistence.ts
@@ -431,6 +431,9 @@ const applyDesktopUiPreferences = (settings: DesktopSettings) => {
   if (typeof settings.stickyUserHeader === 'boolean' && settings.stickyUserHeader !== store.stickyUserHeader) {
     store.setStickyUserHeader(settings.stickyUserHeader);
   }
+  if (typeof settings.wideChatLayoutEnabled === 'boolean' && settings.wideChatLayoutEnabled !== store.wideChatLayoutEnabled) {
+    store.setWideChatLayoutEnabled(settings.wideChatLayoutEnabled);
+  }
   if (
     typeof settings.showSplitAssistantMessageActions === 'boolean'
     && settings.showSplitAssistantMessageActions !== store.showSplitAssistantMessageActions
@@ -859,6 +862,9 @@ const sanitizeWebSettings = (payload: unknown): DesktopSettings | null => {
   if (typeof candidate.stickyUserHeader === 'boolean') {
     result.stickyUserHeader = candidate.stickyUserHeader;
   }
+  if (typeof candidate.wideChatLayoutEnabled === 'boolean') {
+    result.wideChatLayoutEnabled = candidate.wideChatLayoutEnabled;
+  }
   if (typeof candidate.showSplitAssistantMessageActions === 'boolean') {
     result.showSplitAssistantMessageActions = candidate.showSplitAssistantMessageActions;
   }
diff --git a/packages/ui/src/stores/useUIStore.ts b/packages/ui/src/stores/useUIStore.ts
index e2165ab7..cda78712 100644
--- a/packages/ui/src/stores/useUIStore.ts
+++ b/packages/ui/src/stores/useUIStore.ts
@@ -563,6 +563,7 @@ interface UIStore {
   showTerminalQuickKeysOnDesktop: boolean;
   persistChatDraft: boolean;
   inputSpellcheckEnabled: boolean;
+  wideChatLayoutEnabled: boolean;
   showToolFileIcons: boolean;
   showExpandedBashTools: boolean;
   showExpandedEditTools: boolean;
@@ -689,6 +690,7 @@ interface UIStore {
   setMaxLastMessageLength: (value: number) => void;
   setPersistChatDraft: (value: boolean) => void;
   setInputSpellcheckEnabled: (value: boolean) => void;
+  setWideChatLayoutEnabled: (value: boolean) => void;
   setShowToolFileIcons: (value: boolean) => void;
   setShowExpandedBashTools: (value: boolean) => void;
   setShowExpandedEditTools: (value: boolean) => void;
@@ -811,6 +813,7 @@ export const useUIStore = create<UIStore>()(
         showTerminalQuickKeysOnDesktop: false,
         persistChatDraft: true,
         inputSpellcheckEnabled: false,
+        wideChatLayoutEnabled: false,
         showToolFileIcons: true,
         showExpandedBashTools: false,
         showExpandedEditTools: false,
@@ -1804,6 +1807,9 @@ export const useUIStore = create<UIStore>()(
         setInputSpellcheckEnabled: (value) => {
           set({ inputSpellcheckEnabled: value });
         },
+        setWideChatLayoutEnabled: (value) => {
+          set({ wideChatLayoutEnabled: value });
+        },
         setShowToolFileIcons: (value) => {
           set({ showToolFileIcons: value });
         },
@@ -2025,6 +2031,7 @@ export const useUIStore = create<UIStore>()(
           maxLastMessageLength: state.maxLastMessageLength,
           persistChatDraft: state.persistChatDraft,
           inputSpellcheckEnabled: state.inputSpellcheckEnabled,
+          wideChatLayoutEnabled: state.wideChatLayoutEnabled,
           showToolFileIcons: state.showToolFileIcons,
           showExpandedBashTools: state.showExpandedBashTools,
           showExpandedEditTools: state.showExpandedEditTools,
diff --git a/packages/ui/src/styles/typography.css b/packages/ui/src/styles/typography.css
index 3d26a381..cd4dd21c 100644
--- a/packages/ui/src/styles/typography.css
+++ b/packages/ui/src/styles/typography.css
@@ -25,11 +25,15 @@
   }
 
   .chat-column {
-    width: min(100%, 64rem);
+    width: min(100%, 48rem);
     margin-inline: auto;
     padding-inline: calc(clamp(0.75rem, 2.5vw, 1rem) * var(--padding-scale, 1));
   }
 
+  .wide-chat-layout .chat-column {
+    width: min(100%, 64rem);
+  }
+
   .chat-input-column {
     width: min(100%, 48rem);
     margin-inline: auto;
@@ -37,11 +41,15 @@
   }
 
   .chat-message-column {
-    width: min(100%, 64rem);
+    width: min(100%, 48rem);
     margin-inline: auto;
     padding-inline: calc(clamp(0.75rem, 2.5vw, 1rem) * var(--padding-scale, 1));
   }
 
+  .wide-chat-layout .chat-message-column {
+    width: min(100%, 64rem);
+  }
+
   @media (min-width: 1024px) {
     .chat-column {
       padding-inline: calc(clamp(1rem, 2.5vw, 1.5rem) * var(--padding-scale, 1));