diff --git a/src/web-ui/src/app/components/NavPanel/MainNav.tsx b/src/web-ui/src/app/components/NavPanel/MainNav.tsx
index b5fb3ca2..dc07b95e 100644
--- a/src/web-ui/src/app/components/NavPanel/MainNav.tsx
+++ b/src/web-ui/src/app/components/NavPanel/MainNav.tsx
@@ -526,8 +526,7 @@ const MainNav: React.FC<MainNavProps> = ({
           aria-label={t('nav.items.persona')}
           title={t('nav.items.persona')}
         >
-          <img className="bitfun-nav-panel__workspace-bot-default" src="/panda_1.png" alt="" />
-          <img className="bitfun-nav-panel__workspace-bot-hover" src="/panda_2.png" alt="" />
+          <img className="bitfun-nav-panel__workspace-bot-logo" src="/Logo-ICON.png" alt="" />
         </button>
         <div className="bitfun-nav-panel__workspace-create-group">
           <button
diff --git a/src/web-ui/src/app/components/NavPanel/NavPanel.scss b/src/web-ui/src/app/components/NavPanel/NavPanel.scss
index 588de454..8fd1c452 100644
--- a/src/web-ui/src/app/components/NavPanel/NavPanel.scss
+++ b/src/web-ui/src/app/components/NavPanel/NavPanel.scss
@@ -161,18 +161,10 @@ $_section-header-height: 24px;
       left: 0;
     }
 
-    &-default {
+    &-logo {
       z-index: 1;
-    }
-
-    &-hover {
-      z-index: 2;
-      opacity: 0;
-      transition: opacity $motion-fast $easing-standard;
-    }
-
-    &:hover &-hover {
-      opacity: 1;
+      object-fit: contain !important;
+      padding: 6px;
     }
   }
 
diff --git a/src/web-ui/src/app/components/panels/base/FlexiblePanel.tsx b/src/web-ui/src/app/components/panels/base/FlexiblePanel.tsx
index ffe85521..8c8869fa 100644
--- a/src/web-ui/src/app/components/panels/base/FlexiblePanel.tsx
+++ b/src/web-ui/src/app/components/panels/base/FlexiblePanel.tsx
@@ -247,7 +247,7 @@ const FlexiblePanel: React.FC<ExtendedFlexiblePanelProps> = memo(({
         const markdownWorkspacePath = markdownEditorData.workspacePath || workspacePath;
         const markdownJumpToLine = markdownEditorData.jumpToLine;
         const markdownJumpToColumn = markdownEditorData.jumpToColumn;
-        
+
         return (
           <div className="bitfun-flexible-panel__markdown-editor">
             {markdownFilePath || markdownInitialContent !== undefined ? (
@@ -435,7 +435,7 @@ const FlexiblePanel: React.FC<ExtendedFlexiblePanelProps> = memo(({
         const fileName = editorData.fileName || content.title;
         const editorLanguage = editorData.language;
         const editorWorkspacePath = editorData.workspacePath || workspacePath;
-        
+
         return (
           <CodeEditor
             filePath={filePath}
diff --git a/src/web-ui/src/app/components/panels/content-canvas/editor-area/EditorGroup.tsx b/src/web-ui/src/app/components/panels/content-canvas/editor-area/EditorGroup.tsx
index 28aeb19b..48ff5c82 100644
--- a/src/web-ui/src/app/components/panels/content-canvas/editor-area/EditorGroup.tsx
+++ b/src/web-ui/src/app/components/panels/content-canvas/editor-area/EditorGroup.tsx
@@ -8,6 +8,8 @@ import { useTranslation } from 'react-i18next';
 import { TabBar } from '../tab-bar';
 import { DropZone } from './DropZone';
 import FlexiblePanel from '../../base/FlexiblePanel';
+import { createLogger } from '@/shared/utils/logger';
+const _dbgLog = createLogger('EditorGroup');
 import type { 
   EditorGroupId, 
   EditorGroupState, 
@@ -98,10 +100,11 @@ export const EditorGroup: React.FC<EditorGroupProps> = ({
   
   // Tabs to render (active + cached)
   const tabsToRender = useMemo(() => {
-    return group.tabs.filter(t => 
+    const result = group.tabs.filter(t => 
       !t.isHidden && 
       (t.id === group.activeTabId || cachedTabsRef.current.has(t.id))
     );
+    return result;
   }, [group.tabs, group.activeTabId]);
 
   const handleContentChange = useCallback((content: PanelContent | null) => {
diff --git a/src/web-ui/src/app/components/panels/content-canvas/hooks/useTabLifecycle.ts b/src/web-ui/src/app/components/panels/content-canvas/hooks/useTabLifecycle.ts
index d8809cfd..0d5e1704 100644
--- a/src/web-ui/src/app/components/panels/content-canvas/hooks/useTabLifecycle.ts
+++ b/src/web-ui/src/app/components/panels/content-canvas/hooks/useTabLifecycle.ts
@@ -14,6 +14,8 @@ import type { EditorGroupId, PanelContent, CreateTabEventDetail } from '../types
 import { TAB_EVENTS } from '../types';
 import { useI18n } from '@/infrastructure/i18n';
 import { drainPendingTabs } from '@/shared/services/pendingTabQueue';
+import { createLogger } from '@/shared/utils/logger';
+const _dbgLog = createLogger('useTabLifecycle');
 interface UseTabLifecycleOptions {
   /** App mode / target canvas */
   mode?: 'agent' | 'project' | 'git';
@@ -252,7 +254,7 @@ export const useTabLifecycle = (options: UseTabLifecycleOptions = {}): UseTabLif
         const existing = findTabByMetadata({ duplicateCheckKey });
         if (existing) {
           const hasJumpInfo = data?.jumpToRange || data?.jumpToLine || data?.jumpToColumn;
-          
+
           if (replaceExisting || hasJumpInfo) {
             // Update content
             updateTabContent(existing.tab.id, existing.groupId, content);
@@ -269,7 +271,7 @@ export const useTabLifecycle = (options: UseTabLifecycleOptions = {}): UseTabLif
       
       // Determine target group: use specified group when split enabled, otherwise active group
       const groupId = (enableSplitView && targetGroup) ? targetGroup : (targetGroup || activeGroupId);
-      
+
       // Open all tabs in active state by default (no preview replacement)
       addTab(content, 'active', groupId);
       
diff --git a/src/web-ui/src/app/layout/WorkspaceBody.scss b/src/web-ui/src/app/layout/WorkspaceBody.scss
index c7972bac..757e3af6 100644
--- a/src/web-ui/src/app/layout/WorkspaceBody.scss
+++ b/src/web-ui/src/app/layout/WorkspaceBody.scss
@@ -32,7 +32,7 @@ $_nav-collapsed-width: 80px;
 .bitfun-workspace-body__nav-area {
   display: flex;
   flex-direction: column;
-  width: $_nav-width;
+  width: var(--nav-width, $_nav-width);
   flex-shrink: 0;
   height: 100%;
   overflow: hidden;
@@ -46,6 +46,10 @@ $_nav-collapsed-width: 80px;
   }
 }
 
+.bitfun-is-resizing-nav .bitfun-workspace-body__nav-area {
+  transition: none;
+}
+
 .bitfun-workspace-body.is-entering .bitfun-workspace-body__nav-area:not(.is-collapsed) {
   animation: wb-nav-slide-in 560ms cubic-bezier(0.22, 1, 0.36, 1) both;
 }
@@ -71,6 +75,28 @@ $_nav-collapsed-width: 80px;
   height: 100%;
   cursor: ew-resize;
   z-index: 2;
+
+  &::after {
+    content: '';
+    position: absolute;
+    top: 0;
+    left: 50%;
+    transform: translateX(-50%);
+    width: 2px;
+    height: 100%;
+    background: var(--color-primary);
+    opacity: 0;
+    border-radius: 1px;
+    transition: opacity $motion-fast $easing-standard;
+  }
+
+  &:hover::after {
+    opacity: 0.35;
+  }
+}
+
+.bitfun-is-resizing-nav .bitfun-workspace-body__nav-divider::after {
+  opacity: 0.6;
 }
 
 // ── Right column: rounded scene card (SceneBar + SceneViewport) ───
@@ -128,14 +154,14 @@ $_nav-collapsed-width: 80px;
     opacity: 0;
   }
   to {
-    width: $_nav-width;
+    width: var(--nav-width, $_nav-width);
     opacity: 1;
   }
 }
 
 @keyframes wb-nav-slide-out {
   from {
-    width: $_nav-width;
+    width: var(--nav-width, $_nav-width);
     opacity: 1;
   }
   to {
diff --git a/src/web-ui/src/app/layout/WorkspaceBody.tsx b/src/web-ui/src/app/layout/WorkspaceBody.tsx
index 1fc0889b..b0b10f6d 100644
--- a/src/web-ui/src/app/layout/WorkspaceBody.tsx
+++ b/src/web-ui/src/app/layout/WorkspaceBody.tsx
@@ -10,7 +10,7 @@
  *     SceneViewport (flex:1 — active scene content)
  */
 
-import React, { useCallback, useRef } from 'react';
+import React, { useCallback, useRef, useState } from 'react';
 import { useCurrentWorkspace } from '../../infrastructure/contexts/WorkspaceContext';
 import { NavBar } from '../components/NavBar';
 import NavPanel from '../components/NavPanel/NavPanel';
@@ -19,6 +19,11 @@ import { SceneViewport } from '../scenes';
 import { useApp } from '../hooks/useApp';
 import './WorkspaceBody.scss';
 
+const NAV_DEFAULT_WIDTH = 240;
+const NAV_MIN_WIDTH = 240;
+const NAV_MAX_WIDTH = 480;
+const COLLAPSE_THRESHOLD = 64;
+
 interface WorkspaceBodyProps {
   className?: string;
   isEntering?: boolean;
@@ -42,40 +47,48 @@ const WorkspaceBody: React.FC<WorkspaceBodyProps> = ({
 }) => {
   const { workspace: currentWorkspace } = useCurrentWorkspace();
   const { state, toggleLeftPanel } = useApp();
-  const collapseDragRef = useRef<{ startX: number; hasCollapsed: boolean } | null>(null);
   const isNavCollapsed = state.layout.leftPanelCollapsed;
+  const [navWidth, setNavWidth] = useState(NAV_DEFAULT_WIDTH);
 
   const handleNavCollapseDragStart = useCallback((event: React.MouseEvent<HTMLDivElement>) => {
     if (event.button !== 0 || isNavCollapsed) return;
     event.preventDefault();
 
-    const COLLAPSE_THRESHOLD = 64;
-    collapseDragRef.current = { startX: event.clientX, hasCollapsed: false };
+    const startX = event.clientX;
+    const startWidth = navWidth;
+    let hasCollapsed = false;
+
     document.body.classList.add('bitfun-is-dragging-nav-collapse');
+    document.body.classList.add('bitfun-is-resizing-nav');
 
     const cleanup = () => {
-      collapseDragRef.current = null;
       document.body.classList.remove('bitfun-is-dragging-nav-collapse');
+      document.body.classList.remove('bitfun-is-resizing-nav');
       window.removeEventListener('mousemove', handleMouseMove);
       window.removeEventListener('mouseup', handleMouseUp);
     };
 
     const handleMouseMove = (moveEvent: MouseEvent) => {
-      const dragState = collapseDragRef.current;
-      if (!dragState || dragState.hasCollapsed) return;
-      const deltaX = moveEvent.clientX - dragState.startX;
-      if (deltaX <= -COLLAPSE_THRESHOLD) {
-        dragState.hasCollapsed = true;
+      if (hasCollapsed) return;
+      const deltaX = moveEvent.clientX - startX;
+      const rawWidth = startWidth + deltaX;
+
+      // Collapse only after the width hits minimum AND continues left by COLLAPSE_THRESHOLD
+      if (rawWidth <= NAV_MIN_WIDTH - COLLAPSE_THRESHOLD) {
+        hasCollapsed = true;
         toggleLeftPanel();
         cleanup();
+        return;
       }
+      const newWidth = Math.min(NAV_MAX_WIDTH, Math.max(NAV_MIN_WIDTH, rawWidth));
+      setNavWidth(newWidth);
     };
 
     const handleMouseUp = () => cleanup();
 
     window.addEventListener('mousemove', handleMouseMove);
     window.addEventListener('mouseup', handleMouseUp);
-  }, [isNavCollapsed, toggleLeftPanel]);
+  }, [isNavCollapsed, navWidth, toggleLeftPanel]);
 
   return (
     <div className={`bitfun-workspace-body${isEntering ? ' is-entering' : ''}${isExiting ? ' is-exiting' : ''} ${className}`}>
@@ -86,7 +99,10 @@ const WorkspaceBody: React.FC<WorkspaceBodyProps> = ({
       )}
 
       {/* Left: nav history bar + navigation sidebar — always rendered for slide animation */}
-      <div className={`bitfun-workspace-body__nav-area${isNavCollapsed ? ' is-collapsed' : ''}`}>
+      <div
+        className={`bitfun-workspace-body__nav-area${isNavCollapsed ? ' is-collapsed' : ''}`}
+        style={isNavCollapsed ? undefined : { '--nav-width': `${navWidth}px` } as React.CSSProperties}
+      >
         <NavBar onExpandNav={toggleLeftPanel} onMaximize={onMaximize} />
         <NavPanel className="bitfun-workspace-body__nav-panel" />
         {!isNavCollapsed && (
diff --git a/src/web-ui/src/shared/services/ide-control/PanelController.ts b/src/web-ui/src/shared/services/ide-control/PanelController.ts
index 09b59ecd..56f06c60 100644
--- a/src/web-ui/src/shared/services/ide-control/PanelController.ts
+++ b/src/web-ui/src/shared/services/ide-control/PanelController.ts
@@ -170,6 +170,19 @@ export class PanelController implements IdeController {
           },
         };
 
+      case 'code-editor':
+      case 'file-viewer':
+      case 'markdown-editor':
+      case 'plan-viewer':
+        return {
+          ...baseDetail,
+          data: {
+            ...baseDetail.data,
+            filePath: config.file_path,
+            workspacePath: config.workspace_path,
+          },
+        };
+
       default:
         return baseDetail;
     }
diff --git a/src/web-ui/src/tools/editor/components/CodeEditor.tsx b/src/web-ui/src/tools/editor/components/CodeEditor.tsx
index a6fc4617..b3d5919a 100644
--- a/src/web-ui/src/tools/editor/components/CodeEditor.tsx
+++ b/src/web-ui/src/tools/editor/components/CodeEditor.tsx
@@ -926,7 +926,10 @@ const CodeEditor: React.FC<CodeEditorProps> = ({
 
   // Load file content
   const loadFileContent = useCallback(async () => {
-    if (!filePath) return;
+    if (!filePath) {
+      setLoading(false);
+      return;
+    }
 
     // If Model already has content, skip file loading to avoid overwriting unsaved changes (e.g. switching back to open tab)
     if (modelRef.current && modelRef.current.getValue()) {
@@ -949,7 +952,10 @@ const CodeEditor: React.FC<CodeEditorProps> = ({
       setHasChanges(false);
       hasChangesRef.current = false;
       
-      onContentChange?.(fileContent, false);
+      // NOTE: Do NOT call onContentChange here during initial load.
+      // Calling it triggers parent re-render which unmounts this component,
+      // causing an infinite loop. onContentChange should only be called
+      // when user actually edits the content.
       
       // Sync versionId after Model update
       queueMicrotask(() => {
@@ -1124,9 +1130,18 @@ const CodeEditor: React.FC<CodeEditorProps> = ({
     }
   }, [filePath, hasChanges, monacoReady]);
 
-  // Initial file load
+  // Initial file load - only run once when filePath changes
+  const loadFileContentCalledRef = useRef(false);
   useEffect(() => {
-    loadFileContent();
+    // Reset the flag when filePath changes
+    loadFileContentCalledRef.current = false;
+  }, [filePath]);
+  
+  useEffect(() => {
+    if (!loadFileContentCalledRef.current) {
+      loadFileContentCalledRef.current = true;
+      loadFileContent();
+    }
   }, [loadFileContent]);
 
   // Periodic file modification check
diff --git a/src/web-ui/src/tools/editor/components/MarkdownEditor.tsx b/src/web-ui/src/tools/editor/components/MarkdownEditor.tsx
index b309d0c6..ec1e1cb9 100644
--- a/src/web-ui/src/tools/editor/components/MarkdownEditor.tsx
+++ b/src/web-ui/src/tools/editor/components/MarkdownEditor.tsx
@@ -109,9 +109,9 @@ const MarkdownEditor: React.FC<MarkdownEditorProps> = ({
         setTimeout(() => {
           editorRef.current?.setInitialContent?.(fileContent);
         }, 0);
-        if (onContentChangeRef.current) {
-          onContentChangeRef.current(fileContent, false);
-        }
+        // NOTE: Do NOT call onContentChange here during initial load.
+        // Calling it triggers parent re-render which unmounts this component,
+        // causing an infinite loop.
       }
     } catch (err) {
       if (!isUnmountedRef.current) {
@@ -132,18 +132,28 @@ const MarkdownEditor: React.FC<MarkdownEditorProps> = ({
     }
   }, [filePath, t]);
 
+  // Initial file load - only run once when filePath changes
+  const loadFileContentCalledRef = useRef(false);
+  useEffect(() => {
+    // Reset the flag when filePath changes
+    loadFileContentCalledRef.current = false;
+  }, [filePath]);
+  
   useEffect(() => {
     if (filePath) {
-      loadFileContent();
+      if (!loadFileContentCalledRef.current) {
+        loadFileContentCalledRef.current = true;
+        loadFileContent();
+      }
     } else if (initialContent !== undefined) {
       setContent(initialContent);
       setHasChanges(false);
       setTimeout(() => {
         editorRef.current?.setInitialContent?.(initialContent);
       }, 0);
-      if (onContentChangeRef.current) {
-        onContentChangeRef.current(initialContent, false);
-      }
+      // NOTE: Do NOT call onContentChange here during initial load.
+      // Calling it triggers parent re-render which unmounts this component,
+      // causing an infinite loop.
     }
   }, [filePath, initialContent, loadFileContent]);
 
@@ -195,10 +205,7 @@ const MarkdownEditor: React.FC<MarkdownEditorProps> = ({
 
   const handleDirtyChange = useCallback((isDirty: boolean) => {
     setHasChanges(isDirty);
-    if (onContentChangeRef.current) {
-      onContentChangeRef.current(content, isDirty);
-    }
-  }, [content]);
+  }, []);
 
   const handleSave = useCallback((_value: string) => {
     saveFileContent();
diff --git a/src/web-ui/src/tools/editor/components/PlanViewer.tsx b/src/web-ui/src/tools/editor/components/PlanViewer.tsx
index a73ac69b..92da1137 100644
--- a/src/web-ui/src/tools/editor/components/PlanViewer.tsx
+++ b/src/web-ui/src/tools/editor/components/PlanViewer.tsx
@@ -115,7 +115,10 @@ const PlanViewer: React.FC<PlanViewerProps> = ({
   }, []);
 
   const loadFileContent = useCallback(async () => {
-    if (!filePath || isUnmountedRef.current) return;
+    if (!filePath || isUnmountedRef.current) {
+      if (!isUnmountedRef.current) setLoading(false);
+      return;
+    }
 
     if (planBuildStateService.isFileWriting(filePath)) {
       return;
diff --git a/src/web-ui/src/tools/editor/utils/monacoPathHelper.ts b/src/web-ui/src/tools/editor/utils/monacoPathHelper.ts
index 510ac880..ee6483bd 100644
--- a/src/web-ui/src/tools/editor/utils/monacoPathHelper.ts
+++ b/src/web-ui/src/tools/editor/utils/monacoPathHelper.ts
@@ -17,7 +17,8 @@ export function getMonacoPath(): string {
   const isDev = import.meta.env.DEV;
   
   if (isDev) {
-    return 'http://localhost:1422/monaco-editor/vs';
+    // In dev mode, use node_modules path served by Vite
+    return '/node_modules/monaco-editor/min/vs';
   } else {
     return './monaco-editor/vs';
   }