diff --git a/packages/ui/src/components/chat/ChatContainer.tsx b/packages/ui/src/components/chat/ChatContainer.tsx
index 63489175..f508b65e 100644
--- a/packages/ui/src/components/chat/ChatContainer.tsx
+++ b/packages/ui/src/components/chat/ChatContainer.tsx
@@ -18,6 +18,7 @@ import { OverlayScrollbar } from '@/components/ui/OverlayScrollbar';
 import { TimelineDialog } from './TimelineDialog';
 import type { PermissionRequest } from '@/types/permission';
 import type { QuestionRequest } from '@/types/question';
+import { cn } from '@/lib/utils';
 
 const EMPTY_MESSAGES: Array<{ info: Message; parts: Part[] }> = [];
 const EMPTY_PERMISSIONS: PermissionRequest[] = [];
@@ -101,6 +102,7 @@ export const ChatContainer: React.FC = () => {
     const {
         isTimelineDialogOpen,
         setTimelineDialogOpen,
+        isExpandedInput,
     } = useUIStore();
 
     const sessionMessages = useSessionStore(
@@ -163,6 +165,7 @@ export const ChatContainer: React.FC = () => {
 
     const { isMobile } = useDeviceInfo();
     const draftOpen = Boolean(newSessionDraft?.open);
+    const isDesktopExpandedInput = isExpandedInput && !isMobile;
 
     React.useEffect(() => {
         if (!currentSessionId && !draftOpen) {
@@ -423,13 +426,22 @@ export const ChatContainer: React.FC = () => {
     if (!currentSessionId && draftOpen) {
         return (
             <div
-                className="flex flex-col h-full bg-background transform-gpu"
+                className="relative flex flex-col h-full bg-background transform-gpu"
                 style={isMobile ? { paddingBottom: 'var(--oc-keyboard-inset, 0px)' } : undefined}
             >
+                {!isDesktopExpandedInput ? (
                 <div className="flex-1 flex items-center justify-center">
                     <ChatEmptyState showDraftContext />
                 </div>
-                <div className="relative bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/80 z-10">
+                ) : null}
+                <div
+                    className={cn(
+                        'relative z-10',
+                        isDesktopExpandedInput
+                            ? 'flex-1 min-h-0 bg-background'
+                            : 'bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/80'
+                    )}
+                >
                     <ChatInput scrollToBottom={scrollToBottom} />
                 </div>
             </div>
@@ -470,13 +482,22 @@ export const ChatContainer: React.FC = () => {
     if (sessionMessages.length === 0 && !streamingMessageId) {
         return (
             <div
-                className="flex flex-col h-full bg-background transform-gpu"
+                className="relative flex flex-col h-full bg-background transform-gpu"
                 style={isMobile ? { paddingBottom: 'var(--oc-keyboard-inset, 0px)' } : undefined}
             >
+                {!isDesktopExpandedInput ? (
                 <div className="flex-1 flex items-center justify-center">
                     <ChatEmptyState />
                 </div>
-                <div className="relative bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/80 z-10">
+                ) : null}
+                <div
+                    className={cn(
+                        'relative z-10',
+                        isDesktopExpandedInput
+                            ? 'flex-1 min-h-0 bg-background'
+                            : 'bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/80'
+                    )}
+                >
                     <ChatInput scrollToBottom={scrollToBottom} />
                 </div>
             </div>
@@ -485,11 +506,18 @@ export const ChatContainer: React.FC = () => {
 
     return (
         <div
-            className="flex flex-col h-full bg-background"
+            className="relative flex flex-col h-full bg-background"
             style={isMobile ? { paddingBottom: 'var(--oc-keyboard-inset, 0px)' } : undefined}
         >
-            <div className="relative flex-1 min-h-0">
-
+            <div
+                className={cn(
+                    'relative min-h-0',
+                    isDesktopExpandedInput
+                        ? 'absolute inset-0 opacity-0 pointer-events-none'
+                        : 'flex-1'
+                )}
+                aria-hidden={isDesktopExpandedInput}
+            >
                 <div className="absolute inset-0">
                     <ScrollShadow
                         className="absolute inset-0 overflow-y-auto overflow-x-hidden z-0 chat-scroll overlay-scrollbar-target"
@@ -518,8 +546,15 @@ export const ChatContainer: React.FC = () => {
                 </div>
             </div>
 
-            <div className="relative bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/80 z-10">
-                {showScrollButton && sessionMessages.length > 0 && (
+            <div
+                className={cn(
+                    'relative z-10',
+                    isDesktopExpandedInput
+                        ? 'flex-1 min-h-0 bg-background'
+                        : 'bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/80'
+                )}
+            >
+                {!isDesktopExpandedInput && showScrollButton && sessionMessages.length > 0 && (
                     <div className="absolute bottom-full left-1/2 -translate-x-1/2 mb-2">
                                 <Button
                                   variant="outline"
diff --git a/packages/ui/src/components/chat/ChatInput.tsx b/packages/ui/src/components/chat/ChatInput.tsx
index 257b5a87..63d6bcf6 100644
--- a/packages/ui/src/components/chat/ChatInput.tsx
+++ b/packages/ui/src/components/chat/ChatInput.tsx
@@ -6,6 +6,7 @@ import {
     RiAttachment2,
     RiCommandLine,
     RiFileUploadLine,
+    RiFullscreenLine,
     RiSendPlane2Line,
 } from '@remixicon/react';
 import { BrowserVoiceButton } from '@/components/voice';
@@ -21,7 +22,7 @@ import { QueuedMessageChips } from './QueuedMessageChips';
 import { FileMentionAutocomplete, type FileMentionHandle } from './FileMentionAutocomplete';
 import { CommandAutocomplete, type CommandAutocompleteHandle } from './CommandAutocomplete';
 import { SkillAutocomplete, type SkillAutocompleteHandle } from './SkillAutocomplete';
-import { cn } from '@/lib/utils';
+import { cn, isMacOS } from '@/lib/utils';
 import { ServerFilePicker } from './ServerFilePicker';
 import { ModelControls } from './ModelControls';
 import { UnifiedControlsDrawer } from './UnifiedControlsDrawer';
@@ -38,6 +39,7 @@ import { useMessageStore } from '@/stores/messageStore';
 import { isDesktopLocalOriginActive, isTauriShell, isVSCodeRuntime } from '@/lib/desktop';
 import { isIMECompositionEvent } from '@/lib/ime';
 import { StopIcon } from '@/components/icons/StopIcon';
+import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip';
 import type { MobileControlsPanel } from './mobileControlsUtils';
 import {
     DropdownMenu,
@@ -55,22 +57,49 @@ interface ChatInputProps {
     scrollToBottom?: (options?: { instant?: boolean; force?: boolean }) => void;
 }
 
-const CHAT_INPUT_DRAFT_KEY = 'openchamber_chat_input_draft';
+type AutocompleteOverlayPosition = {
+    top: number;
+    left: number;
+    place: 'above' | 'below';
+    maxHeight: number;
+};
 
-// Helper to safely read from localStorage
-const getStoredDraft = (): string => {
+// Per-session draft key — preserves in-progress messages across project switches
+const getDraftKey = (sessionId: string | null): string =>
+    `openchamber_chat_input_draft_${sessionId ?? 'new'}`;
+
+// Helper to safely read from localStorage for a given session
+const getStoredDraft = (sessionId: string | null): string => {
     try {
-        return localStorage.getItem(CHAT_INPUT_DRAFT_KEY) ?? '';
+        return localStorage.getItem(getDraftKey(sessionId)) ?? '';
     } catch {
         return '';
     }
 };
 
+// Helper to safely write/clear a per-session draft
+const saveStoredDraft = (sessionId: string | null, draft: string): void => {
+    try {
+        if (draft) {
+            localStorage.setItem(getDraftKey(sessionId), draft);
+        } else {
+            localStorage.removeItem(getDraftKey(sessionId));
+        }
+    } catch {
+        // Ignore localStorage errors
+    }
+};
+
 export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBottom }) => {
     // Track if we restored a draft on mount (for text selection)
     const initialDraftRef = React.useRef<string | null>(null);
+    // Track initial session ID (captured at mount time for draft restoration)
+    const initialSessionIdRef = React.useRef<string | null>(null);
     const [message, setMessage] = React.useState(() => {
-        const draft = getStoredDraft();
+        // Read per-session draft at mount time using the current session from the store
+        const sessionId = useSessionStore.getState().currentSessionId;
+        initialSessionIdRef.current = sessionId;
+        const draft = getStoredDraft(sessionId);
         if (draft) {
             initialDraftRef.current = draft;
         }
@@ -97,6 +126,8 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
     const mentionRef = React.useRef<FileMentionHandle>(null);
     const commandRef = React.useRef<CommandAutocompleteHandle>(null);
     const skillRef = React.useRef<SkillAutocompleteHandle>(null);
+    // Ref to track current message value without triggering re-renders in effects
+    const messageRef = React.useRef(message);
 
     const sendMessage = useSessionStore((state) => state.sendMessage);
     const currentSessionId = useSessionStore((state) => state.currentSessionId);
@@ -118,10 +149,12 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
     const { currentProviderId, currentModelId, currentVariant, currentAgentName, setAgent, getVisibleAgents } = useConfigStore();
     const agents = getVisibleAgents();
     const primaryAgents = React.useMemo(() => agents.filter((agent) => agent.mode === 'primary'), [agents]);
-    const { isMobile, inputBarOffset, isKeyboardOpen, setTimelineDialogOpen, cornerRadius, persistChatDraft } = useUIStore();
+    const { isMobile, inputBarOffset, isKeyboardOpen, setTimelineDialogOpen, cornerRadius, persistChatDraft, isExpandedInput, setExpandedInput } = useUIStore();
     const { working } = useAssistantStatus();
     const { currentTheme } = useThemeSystem();
     const [showAbortStatus, setShowAbortStatus] = React.useState(false);
+    const isDesktopExpanded = isExpandedInput && !isMobile;
+    const [autocompleteOverlayPosition, setAutocompleteOverlayPosition] = React.useState<AutocompleteOverlayPosition | null>(null);
     const abortTimeoutRef = React.useRef<ReturnType<typeof setTimeout> | null>(null);
     const prevWasAbortedRef = React.useRef(false);
 
@@ -177,6 +210,11 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
             .reverse(); // Most recent first
     }, [sessionMessages]);
 
+    // Keep messageRef in sync with message state
+    React.useEffect(() => {
+        messageRef.current = message;
+    }, [message]);
+
     // Handle initial draft restoration and text selection
     const hasHandledInitialDraftRef = React.useRef(false);
     React.useEffect(() => {
@@ -190,7 +228,7 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
             // Setting disabled - clear the restored draft
             setMessage('');
             try {
-                localStorage.removeItem(CHAT_INPUT_DRAFT_KEY);
+                localStorage.removeItem(getDraftKey(initialSessionIdRef.current));
             } catch {
                 // Ignore
             }
@@ -202,24 +240,31 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
         }
     }, [persistChatDraft]);
 
-    // Handle session switching: clear draft if persist disabled, select if enabled
+    // Handle session switching: save draft for old session, restore draft for new session
     const prevSessionIdRef = React.useRef(currentSessionId);
     React.useEffect(() => {
         if (prevSessionIdRef.current !== currentSessionId) {
+            const oldSessionId = prevSessionIdRef.current;
             prevSessionIdRef.current = currentSessionId;
             setInputMode('normal');
-            
-            if (!persistChatDraft) {
-                // Clear draft when switching sessions if persist is disabled
+
+            if (persistChatDraft) {
+                // Save current draft for the session we're leaving
+                saveStoredDraft(oldSessionId, messageRef.current);
+                // Restore draft for the session we're entering
+                const newDraft = getStoredDraft(currentSessionId);
+                setMessage(newDraft);
+                if (newDraft) {
+                    requestAnimationFrame(() => {
+                        textareaRef.current?.select();
+                    });
+                }
+            } else {
+                // Persist disabled: clear input without saving
                 setMessage('');
-            } else if (message) {
-                // Select text if there's any draft when switching sessions
-                requestAnimationFrame(() => {
-                    textareaRef.current?.select();
-                });
             }
         }
-    }, [currentSessionId, persistChatDraft, message]);
+    }, [currentSessionId, persistChatDraft]);
 
     // Focus textarea when new session draft is opened
     const prevNewSessionDraftOpenRef = React.useRef(newSessionDraftOpen);
@@ -238,27 +283,19 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
         prevNewSessionDraftOpenRef.current = newSessionDraftOpen;
     }, [newSessionDraftOpen, isMobile]);
 
-    // Persist chat input draft to localStorage (only if setting enabled)
+    // Persist chat input draft to localStorage per session (only if setting enabled)
     React.useEffect(() => {
         if (!persistChatDraft) {
-            // Clear stored draft when setting is disabled
+            // Clear stored draft for current session when setting is disabled
             try {
-                localStorage.removeItem(CHAT_INPUT_DRAFT_KEY);
+                localStorage.removeItem(getDraftKey(currentSessionId));
             } catch {
                 // Ignore
             }
             return;
         }
-        try {
-            if (message) {
-                localStorage.setItem(CHAT_INPUT_DRAFT_KEY, message);
-            } else {
-                localStorage.removeItem(CHAT_INPUT_DRAFT_KEY);
-            }
-        } catch {
-            // Ignore localStorage errors
-        }
-    }, [message, persistChatDraft]);
+        saveStoredDraft(currentSessionId, message);
+    }, [message, persistChatDraft, currentSessionId]);
 
     // Session activity for auto-send on idle
     const { phase: sessionPhase } = useCurrentSessionActivity();
@@ -528,12 +565,16 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
         }
         if (!queuedOnly) {
             setMessage('');
+            // Clear per-session draft on submit
+            saveStoredDraft(currentSessionId, '');
             // Reset message history navigation state
             setHistoryIndex(-1);
             setDraftMessage('');
             if (attachedFiles.length > 0) {
                 clearAttachedFiles();
             }
+            // Close expanded input overlay when submitting
+            setExpandedInput(false);
         }
 
         if (isMobile) {
@@ -728,6 +769,12 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
             }
         }
 
+        if (isDesktopExpanded && e.key === 'Escape') {
+            e.preventDefault();
+            setExpandedInput(false);
+            return;
+        }
+
         if (e.key === 'Tab' && !showCommandAutocomplete && !showFileMention) {
             e.preventDefault();
             handleCycleAgent();
@@ -812,6 +859,127 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
         }
     };
 
+    const measureCaretInTextarea = React.useCallback((textarea: HTMLTextAreaElement, cursorPosition: number) => {
+        const doc = textarea.ownerDocument;
+        const win = doc.defaultView;
+        if (!win) return null;
+
+        const style = win.getComputedStyle(textarea);
+        const mirror = doc.createElement('div');
+        const mirrorStyle = mirror.style;
+
+        mirrorStyle.position = 'absolute';
+        mirrorStyle.visibility = 'hidden';
+        mirrorStyle.pointerEvents = 'none';
+        mirrorStyle.whiteSpace = 'pre-wrap';
+        mirrorStyle.wordWrap = 'break-word';
+        mirrorStyle.overflow = 'hidden';
+        mirrorStyle.left = '-9999px';
+        mirrorStyle.top = '0';
+
+        mirrorStyle.width = `${textarea.clientWidth}px`;
+        mirrorStyle.font = style.font;
+        mirrorStyle.fontSize = style.fontSize;
+        mirrorStyle.fontFamily = style.fontFamily;
+        mirrorStyle.fontWeight = style.fontWeight;
+        mirrorStyle.fontStyle = style.fontStyle;
+        mirrorStyle.fontVariant = style.fontVariant;
+        mirrorStyle.letterSpacing = style.letterSpacing;
+        mirrorStyle.textTransform = style.textTransform;
+        mirrorStyle.textIndent = style.textIndent;
+        mirrorStyle.padding = style.padding;
+        mirrorStyle.border = style.border;
+        mirrorStyle.boxSizing = style.boxSizing;
+        mirrorStyle.lineHeight = style.lineHeight;
+        mirrorStyle.tabSize = style.tabSize;
+
+        mirror.textContent = textarea.value.slice(0, cursorPosition);
+        const marker = doc.createElement('span');
+        marker.textContent = textarea.value.slice(cursorPosition, cursorPosition + 1) || ' ';
+        mirror.appendChild(marker);
+
+        doc.body.appendChild(mirror);
+        const top = marker.offsetTop;
+        const left = marker.offsetLeft;
+        doc.body.removeChild(mirror);
+
+        return { top, left };
+    }, []);
+
+    const updateAutocompleteOverlayPosition = React.useCallback(() => {
+        if (!isDesktopExpanded) {
+            setAutocompleteOverlayPosition(null);
+            return;
+        }
+
+        if (!showCommandAutocomplete && !showSkillAutocomplete && !showFileMention) {
+            setAutocompleteOverlayPosition(null);
+            return;
+        }
+
+        const textarea = textareaRef.current;
+        const container = dropZoneRef.current;
+        if (!textarea || !container) return;
+
+        const cursor = textarea.selectionStart ?? message.length;
+        const caret = measureCaretInTextarea(textarea, cursor);
+        if (!caret) return;
+
+        const textareaRect = textarea.getBoundingClientRect();
+        const containerRect = container.getBoundingClientRect();
+
+        const caretY = textareaRect.top - containerRect.top + (caret.top - textarea.scrollTop);
+        const caretX = textareaRect.left - containerRect.left + (caret.left - textarea.scrollLeft);
+
+        const popupMargin = 8;
+        const estimatedPopupHeight = 260;
+        const spaceAbove = caretY - popupMargin;
+        const spaceBelow = containerRect.height - caretY - popupMargin;
+        const place: 'above' | 'below' = spaceBelow >= estimatedPopupHeight || spaceBelow >= spaceAbove ? 'below' : 'above';
+
+        const desiredWidth = showFileMention ? 520 : showCommandAutocomplete ? 450 : 360;
+        const clampedLeft = Math.max(
+            popupMargin,
+            Math.min(caretX - 24, containerRect.width - desiredWidth - popupMargin)
+        );
+
+        const maxHeight = Math.max(120, Math.min(estimatedPopupHeight, place === 'below' ? spaceBelow : spaceAbove));
+
+        setAutocompleteOverlayPosition({
+            top: place === 'below' ? caretY + 22 : caretY - 6,
+            left: clampedLeft,
+            place,
+            maxHeight,
+        });
+    }, [
+        isDesktopExpanded,
+        measureCaretInTextarea,
+        message.length,
+        showCommandAutocomplete,
+        showFileMention,
+        showSkillAutocomplete,
+    ]);
+
+    React.useLayoutEffect(() => {
+        updateAutocompleteOverlayPosition();
+    }, [
+        updateAutocompleteOverlayPosition,
+        message,
+        showCommandAutocomplete,
+        showSkillAutocomplete,
+        showFileMention,
+        isDesktopExpanded,
+    ]);
+
+    React.useEffect(() => {
+        if (!isDesktopExpanded) return;
+        const onResize = () => updateAutocompleteOverlayPosition();
+        window.addEventListener('resize', onResize);
+        return () => {
+            window.removeEventListener('resize', onResize);
+        };
+    }, [isDesktopExpanded, updateAutocompleteOverlayPosition]);
+
     const startAbortIndicator = React.useCallback(() => {
         if (abortTimeoutRef.current) {
             clearTimeout(abortTimeoutRef.current);
@@ -853,6 +1021,13 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
             return;
         }
 
+        if (isDesktopExpanded) {
+            textarea.style.height = '100%';
+            textarea.style.maxHeight = 'none';
+            setTextareaSize(null);
+            return;
+        }
+
         textarea.style.height = 'auto';
 
         const view = textarea.ownerDocument?.defaultView;
@@ -879,7 +1054,7 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
             }
             return { height: nextHeight, maxHeight };
         });
-    }, []);
+    }, [isDesktopExpanded]);
 
     React.useLayoutEffect(() => {
         adjustTextareaHeight();
@@ -1856,11 +2031,12 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
     }, []);
 
     return (
-
+        <>
         <form
             onSubmit={(e) => { e.preventDefault(); handlePrimaryAction(); }}
             className={cn(
                 "relative pt-0 pb-4",
+                isDesktopExpanded && 'flex h-full min-h-0 flex-col pt-4',
                 isMobile && isKeyboardOpen ? "ios-keyboard-safe-area" : "bottom-safe-area"
             )}
             data-keyboard-avoid="true"
@@ -1879,7 +2055,7 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                     showAbortStatus={showAbortStatus}
                 />
             </div>
-            <div className="chat-column relative overflow-visible">
+            <div className={cn('chat-column relative overflow-visible', isDesktopExpanded && 'flex flex-1 min-h-0 flex-col')}>
                 <AttachedFilesList />
                 <QueuedMessageChips
                     onEditMessage={(content) => {
@@ -1908,6 +2084,7 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                 <div
                     className={cn(
                         "flex flex-col relative overflow-visible",
+                        isDesktopExpanded && 'flex-1 min-h-0',
                         "border border-border/80",
                         "focus-within:ring-1",
                         inputMode === 'shell'
@@ -1953,6 +2130,16 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                             activeTab={autocompleteTab}
                             onTabSelect={handleAutocompleteTabSelect}
                             onClose={() => setShowCommandAutocomplete(false)}
+                            style={isDesktopExpanded && autocompleteOverlayPosition
+                                ? {
+                                    left: `${autocompleteOverlayPosition.left}px`,
+                                    top: `${autocompleteOverlayPosition.top}px`,
+                                    bottom: 'auto',
+                                    width: `min(450px, calc(100% - ${autocompleteOverlayPosition.left + 8}px))`,
+                                    maxHeight: `${autocompleteOverlayPosition.maxHeight}px`,
+                                    transform: autocompleteOverlayPosition.place === 'above' ? 'translateY(-100%)' : undefined,
+                                }
+                                : undefined}
                         />
                     )}
                     { }
@@ -1962,6 +2149,16 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                             searchQuery={skillQuery}
                             onSkillSelect={handleSkillSelect}
                             onClose={() => setShowSkillAutocomplete(false)}
+                            style={isDesktopExpanded && autocompleteOverlayPosition
+                                ? {
+                                    left: `${autocompleteOverlayPosition.left}px`,
+                                    top: `${autocompleteOverlayPosition.top}px`,
+                                    bottom: 'auto',
+                                    width: `min(360px, calc(100% - ${autocompleteOverlayPosition.left + 8}px))`,
+                                    maxHeight: `${autocompleteOverlayPosition.maxHeight}px`,
+                                    transform: autocompleteOverlayPosition.place === 'above' ? 'translateY(-100%)' : undefined,
+                                }
+                                : undefined}
                         />
                     )}
 
@@ -1976,6 +2173,16 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                             activeTab={autocompleteTab}
                             onTabSelect={handleAutocompleteTabSelect}
                             onClose={() => setShowFileMention(false)}
+                            style={isDesktopExpanded && autocompleteOverlayPosition
+                                ? {
+                                    left: `${autocompleteOverlayPosition.left}px`,
+                                    top: `${autocompleteOverlayPosition.top}px`,
+                                    bottom: 'auto',
+                                    width: `min(520px, calc(100% - ${autocompleteOverlayPosition.left + 8}px))`,
+                                    maxHeight: `${autocompleteOverlayPosition.maxHeight}px`,
+                                    transform: autocompleteOverlayPosition.place === 'above' ? 'translateY(-100%)' : undefined,
+                                }
+                                : undefined}
                         />
                     )}
                     <Textarea
@@ -1989,6 +2196,10 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                         onDragOver={handleDragOver}
                         onDrop={handleDrop}
                         onPointerDownCapture={handleTextareaPointerDownCapture}
+                        onKeyUp={updateAutocompleteOverlayPosition}
+                        onClick={updateAutocompleteOverlayPosition}
+                        onScroll={updateAutocompleteOverlayPosition}
+                        onSelect={updateAutocompleteOverlayPosition}
                         placeholder={currentSessionId || newSessionDraftOpen
                             ? inputMode === 'shell'
                                 ? "Enter shell command..."
@@ -1998,16 +2209,20 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                         autoCorrect={isMobile ? "on" : "off"}
                         autoCapitalize={isMobile ? "sentences" : "off"}
                         spellCheck={isMobile}
-                        outerClassName="focus-within:ring-0"
+                        outerClassName={cn('focus-within:ring-0', isDesktopExpanded && 'flex-1 min-h-0')}
                         className={cn(
                             'min-h-[52px] resize-none border-0 px-3 rounded-b-none appearance-none hover:border-transparent bg-transparent',
+                            isDesktopExpanded
+                                ? 'h-full min-h-0 py-4'
+                                : isMobile
+                                    ? 'py-2.5'
+                                    : 'pt-4 pb-2',
                             inputMode === 'shell' && 'font-mono',
-                            isMobile ? "py-2.5" : "pt-4 pb-2"
                         )}
                         style={{
-                            flex: 'none',
-                            height: textareaSize ? `${textareaSize.height}px` : undefined,
-                            maxHeight: textareaSize ? `${textareaSize.maxHeight}px` : undefined,
+                            flex: isDesktopExpanded ? '1 1 auto' : 'none',
+                            height: !isDesktopExpanded && textareaSize ? `${textareaSize.height}px` : undefined,
+                            maxHeight: !isDesktopExpanded && textareaSize ? `${textareaSize.maxHeight}px` : undefined,
                             borderTopLeftRadius: cornerRadius,
                             borderTopRightRadius: cornerRadius,
                         }}
@@ -2060,6 +2275,36 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                             <>
                                 <div className={cn("flex items-center flex-shrink-0", footerGapClass)}>
                                     {attachmentsControls}
+                                    <Tooltip delayDuration={600}>
+                                        <TooltipTrigger asChild>
+                                            <button
+                                                type="button"
+                                                className={cn(
+                                                    footerIconButtonClass,
+                                                    'rounded-md',
+                                                    isExpandedInput
+                                                        ? 'text-primary'
+                                                        : 'text-muted-foreground hover:bg-[var(--interactive-hover)]/40 hover:text-foreground'
+                                                )}
+                                                onMouseDown={(event) => {
+                                                    event.preventDefault();
+                                                }}
+                                                onClick={() => setExpandedInput(!isExpandedInput)}
+                                                aria-label="Toggle focus mode"
+                                                aria-pressed={isExpandedInput}
+                                            >
+                                                <RiFullscreenLine className={cn(iconSizeClass)} />
+                                            </button>
+                                        </TooltipTrigger>
+                                        <TooltipContent side="top" sideOffset={8}>
+                                            <div className="flex flex-col gap-0.5 text-center">
+                                                <span>Focus mode</span>
+                                                <span className="font-mono opacity-60">
+                                                    {isMacOS() ? '⌘⇧E' : 'Ctrl+Shift+E'}
+                                                </span>
+                                            </div>
+                                        </TooltipContent>
+                                    </Tooltip>
                                 </div>
                                 <div className={cn('flex items-center flex-1 justify-end', footerGapClass, 'md:gap-x-3')}>
                                     <ModelControls className={cn('flex-1 min-w-0 justify-end')} />
@@ -2075,5 +2320,6 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                 </div>
             </div>
         </form>
+        </>
     );
 };
diff --git a/packages/ui/src/components/chat/CommandAutocomplete.tsx b/packages/ui/src/components/chat/CommandAutocomplete.tsx
index 842d4688..548dec65 100644
--- a/packages/ui/src/components/chat/CommandAutocomplete.tsx
+++ b/packages/ui/src/components/chat/CommandAutocomplete.tsx
@@ -30,6 +30,7 @@ interface CommandAutocompleteProps {
   showTabs?: boolean;
   activeTab?: AutocompleteTab;
   onTabSelect?: (tab: AutocompleteTab) => void;
+  style?: React.CSSProperties;
 }
 
 export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, CommandAutocompleteProps>(({
@@ -38,7 +39,8 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
   onClose,
   showTabs,
   activeTab = 'commands',
-  onTabSelect
+  onTabSelect,
+  style,
 }, ref) => {
   const { hasMessagesInCurrentSession, currentSessionId } = useSessionStore(
     useShallow((state) => {
@@ -251,6 +253,7 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
     <div
       ref={containerRef}
       className="absolute z-[100] min-w-0 w-full max-w-[450px] max-h-64 bg-background border-2 border-border/60 rounded-xl shadow-md bottom-full mb-2 left-0 flex flex-col"
+      style={style}
     >
       {showTabs ? (
         <div className="px-2 pt-2 pb-1 border-b border-border/60">
diff --git a/packages/ui/src/components/chat/FileMentionAutocomplete.tsx b/packages/ui/src/components/chat/FileMentionAutocomplete.tsx
index df86cf7e..3c3ad059 100644
--- a/packages/ui/src/components/chat/FileMentionAutocomplete.tsx
+++ b/packages/ui/src/components/chat/FileMentionAutocomplete.tsx
@@ -32,6 +32,7 @@ interface FileMentionAutocompleteProps {
   showTabs?: boolean;
   activeTab?: AutocompleteTab;
   onTabSelect?: (tab: AutocompleteTab) => void;
+  style?: React.CSSProperties;
 }
 
 export const FileMentionAutocomplete = React.forwardRef<FileMentionHandle, FileMentionAutocompleteProps>(({
@@ -42,6 +43,7 @@ export const FileMentionAutocomplete = React.forwardRef<FileMentionHandle, FileM
   showTabs,
   activeTab = 'files',
   onTabSelect,
+  style,
 }, ref) => {
   const { currentDirectory } = useDirectoryStore();
   const { addServerFile } = useSessionStore();
@@ -367,6 +369,7 @@ export const FileMentionAutocomplete = React.forwardRef<FileMentionHandle, FileM
       <div
         ref={containerRef}
         className="absolute z-[100] min-w-0 w-full max-w-[520px] max-h-64 bg-background border-2 border-border/60 rounded-xl shadow-md bottom-full mb-2 left-0 flex flex-col"
+        style={style}
       >
         {showTabs ? (
           <div className="px-2 pt-2 pb-1 border-b border-border/60">
diff --git a/packages/ui/src/components/chat/SkillAutocomplete.tsx b/packages/ui/src/components/chat/SkillAutocomplete.tsx
index a9fba70b..41059509 100644
--- a/packages/ui/src/components/chat/SkillAutocomplete.tsx
+++ b/packages/ui/src/components/chat/SkillAutocomplete.tsx
@@ -17,12 +17,14 @@ interface SkillAutocompleteProps {
   searchQuery: string;
   onSkillSelect: (skillName: string) => void;
   onClose: () => void;
+  style?: React.CSSProperties;
 }
 
 export const SkillAutocomplete = React.forwardRef<SkillAutocompleteHandle, SkillAutocompleteProps>(({
   searchQuery,
   onSkillSelect,
   onClose,
+  style,
 }, ref) => {
   const containerRef = React.useRef<HTMLDivElement | null>(null);
   const [selectedIndex, setSelectedIndex] = React.useState(0);
@@ -147,6 +149,7 @@ export const SkillAutocomplete = React.forwardRef<SkillAutocompleteHandle, Skill
     <div
       ref={containerRef}
       className="absolute z-[100] min-w-0 w-full max-w-[360px] max-h-60 bg-background border-2 border-border/60 rounded-xl shadow-md bottom-full mb-2 left-0 flex flex-col"
+      style={style}
     >
       <ScrollableOverlay outerClassName="flex-1 min-h-0" className="px-0 pb-2" fillContainer={false}>
         {filteredSkills.length ? (
diff --git a/packages/ui/src/hooks/useKeyboardShortcuts.ts b/packages/ui/src/hooks/useKeyboardShortcuts.ts
index 94d0c1e0..689c680d 100644
--- a/packages/ui/src/hooks/useKeyboardShortcuts.ts
+++ b/packages/ui/src/hooks/useKeyboardShortcuts.ts
@@ -20,10 +20,12 @@ export const useKeyboardShortcuts = () => {
     setRightSidebarTab,
     toggleBottomTerminal,
     setBottomTerminalExpanded,
+    isMobile,
     setSessionSwitcherOpen,
     setActiveMainTab,
     setSettingsDialogOpen,
     setModelSelectorOpen,
+    toggleExpandedInput,
     shortcutOverrides,
   } = useUIStore();
   const { themeMode, setThemeMode } = useThemeSystem();
@@ -286,6 +288,15 @@ export const useKeyboardShortcuts = () => {
         return;
       }
 
+      if (eventMatchesShortcut(e, combo('expand_input'))) {
+        if (isMobile) {
+          return;
+        }
+        e.preventDefault();
+        toggleExpandedInput();
+        return;
+      }
+
       if (e.key === 'Escape') {
         const target = e.target as Element | null;
         const isInsideDialog = Boolean(target?.closest('[role="dialog"]'));
@@ -376,10 +387,12 @@ export const useKeyboardShortcuts = () => {
     setRightSidebarTab,
     toggleBottomTerminal,
     setBottomTerminalExpanded,
+    isMobile,
     setSessionSwitcherOpen,
     setActiveMainTab,
     setSettingsDialogOpen,
     setModelSelectorOpen,
+    toggleExpandedInput,
     setThemeMode,
     working,
     armAbortPrompt,
diff --git a/packages/ui/src/lib/shortcuts.ts b/packages/ui/src/lib/shortcuts.ts
index 9c6e392e..925fe7e6 100644
--- a/packages/ui/src/lib/shortcuts.ts
+++ b/packages/ui/src/lib/shortcuts.ts
@@ -284,6 +284,13 @@ const SHORTCUT_ACTIONS: ReadonlyArray<ShortcutAction> = [
     label: 'Cycle thinking variant',
     description: 'Cycle thinking variant while in chat',
   },
+  {
+    id: 'expand_input',
+    defaultCombo: 'mod+shift+e',
+    label: 'Expand input',
+    description: 'Toggle focus mode for the chat input',
+    customizable: true,
+  },
   {
     id: 'abort_run',
     defaultCombo: 'escape',
diff --git a/packages/ui/src/stores/useUIStore.ts b/packages/ui/src/stores/useUIStore.ts
index a8e0a4ef..5dd239d6 100644
--- a/packages/ui/src/stores/useUIStore.ts
+++ b/packages/ui/src/stores/useUIStore.ts
@@ -215,6 +215,8 @@ interface UIStore {
   persistChatDraft: boolean;
   isMobileSessionStatusBarCollapsed: boolean;
 
+  isExpandedInput: boolean;
+
   shortcutOverrides: Record<string, ShortcutCombo>;
 
   setTheme: (theme: 'light' | 'dark' | 'system') => void;
@@ -298,6 +300,8 @@ interface UIStore {
   setMaxLastMessageLength: (value: number) => void;
   setPersistChatDraft: (value: boolean) => void;
   setIsMobileSessionStatusBarCollapsed: (value: boolean) => void;
+  toggleExpandedInput: () => void;
+  setExpandedInput: (value: boolean) => void;
   openMultiRunLauncher: () => void;
   openMultiRunLauncherWithPrompt: (prompt: string) => void;
   setShortcutOverride: (actionId: string, combo: ShortcutCombo) => void;
@@ -390,6 +394,7 @@ export const useUIStore = create<UIStore>()(
         showTerminalQuickKeysOnDesktop: false,
         persistChatDraft: true,
         isMobileSessionStatusBarCollapsed: false,
+        isExpandedInput: false,
         shortcutOverrides: {},
 
         setTheme: (theme) => {
@@ -1131,6 +1136,14 @@ export const useUIStore = create<UIStore>()(
         resetAllShortcutOverrides: () => {
           set({ shortcutOverrides: {} });
         },
+
+        toggleExpandedInput: () => {
+          set((state) => ({ isExpandedInput: !state.isExpandedInput }));
+        },
+
+        setExpandedInput: (value) => {
+          set({ isExpandedInput: value });
+        },
       }),
       {
         name: 'ui-store',