diff --git a/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.test.tsx b/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.test.tsx
index 4a60db7375..ed91f573a5 100644
--- a/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.test.tsx
+++ b/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.test.tsx
@@ -7,10 +7,16 @@ import { sessionSceneWorkspaceKey } from '@/app/services/sessionSceneTarget';
 import { useContentResourceStore } from '@/app/workbench/contentResourceStore';
 import { activateSurface } from '@/infrastructure/peer-device/deviceSurface';
 
-const state = vi.hoisted(() => ({ grouping: 'all', activeWorkspaceId: null as string | null, workspaces: [
-  { id: 'assistant', name: 'Assistant', workspaceKind: 'assistant' },
-  { id: 'project', name: 'Project', workspaceKind: 'normal' },
-] }));
+const state = vi.hoisted(() => {
+  const assistant = { id: 'assistant', name: 'Assistant', workspaceKind: 'assistant' };
+  const project = { id: 'project', name: 'Project', workspaceKind: 'normal' };
+  return {
+    grouping: 'all',
+    activeWorkspaceId: null as string | null,
+    workspaces: [assistant, project],
+    defaultWorkspaces: [assistant, project],
+  };
+});
 vi.mock('@/infrastructure/i18n', () => ({ useI18n: () => ({ t: (key: string) => key }) }));
 vi.mock('@/shared/notification-system', () => ({ notificationService: { error: vi.fn() } }));
 vi.mock('@/infrastructure/contexts/WorkspaceContext', () => ({
@@ -29,11 +35,19 @@ vi.mock('../../workspaceSessionView', () => ({
   useWorkspaceSessionViewStore: (selector: (value: typeof state) => unknown) => selector(state),
 }));
 vi.mock('./WorkspaceItem', () => ({
-  default: ({ workspace, isActive, isSelected }: {
+  default: ({ workspace, isActive, isSelected, draggable }: {
     workspace: { id: string };
     isActive: boolean;
     isSelected: boolean;
-  }) => <div data-owner-row={workspace.id} data-context-active={isActive} data-selected={isSelected} />,
+    draggable?: boolean;
+  }) => (
+    <div
+      data-owner-row={workspace.id}
+      data-context-active={isActive}
+      data-selected={isSelected}
+      data-row-draggable={draggable ? 'true' : 'false'}
+    />
+  ),
 }));
 vi.mock('../sessions/SessionsSection', () => ({
   default: ({ workspaceScopes }: { workspaceScopes: { workspaceId: string }[] }) => (
@@ -52,11 +66,124 @@ function sessionTab(workspaceId: string, surfaceId = 'local'): SceneTab {
 afterEach(() => {
   state.grouping = 'all';
   state.activeWorkspaceId = null;
+  state.workspaces = [...state.defaultWorkspaces];
   useSceneStore.setState({ activeTabId: null, openTabs: [] });
   useContentResourceStore.setState({ resources: {} });
   activateSurface('local');
 });
 
+function renderList() {
+  const container = document.createElement('div');
+  const root = createRoot(container);
+  act(() => root.render(<WorkspaceListSection variant="all" />));
+  return {
+    container,
+    ownerRows: () => Array.from(container.querySelectorAll('[data-owner-row]'))
+      .map(row => row.getAttribute('data-owner-row')),
+    unmount: () => act(() => root.unmount()),
+  };
+}
+
+describe('assistant pinning', () => {
+  it('pins the assistant above the project workspaces regardless of the stored order', () => {
+    state.grouping = 'grouped';
+    // The persisted workspace order lists the project first.
+    state.workspaces = [...state.defaultWorkspaces].reverse();
+
+    const list = renderList();
+    try {
+      expect(list.ownerRows()).toEqual(['assistant', 'project']);
+      const pinnedRow = list.container.querySelector('[data-session-group-pinned="true"]');
+      expect(pinnedRow?.getAttribute('data-workspace-id')).toBe('assistant');
+      expect(pinnedRow?.getAttribute('data-session-group-kind')).toBe('assistant');
+      expect(pinnedRow?.querySelector('[data-owner-row="assistant"]')).not.toBeNull();
+    } finally {
+      list.unmount();
+    }
+  });
+
+  it('keeps the pinned assistant out of the project drag order', () => {
+    state.grouping = 'grouped';
+    state.workspaces = [
+      { id: 'assistant', name: 'Assistant', workspaceKind: 'assistant' },
+      { id: 'first-project', name: 'First', workspaceKind: 'normal' },
+      { id: 'second-project', name: 'Second', workspaceKind: 'normal' },
+    ];
+
+    const list = renderList();
+    try {
+      expect(list.ownerRows()).toEqual(['assistant', 'first-project', 'second-project']);
+      const draggable = (id: string) => list.container
+        .querySelector(`[data-owner-row="${id}"]`)?.getAttribute('data-row-draggable');
+      expect(draggable('assistant')).toBe('false');
+      expect(draggable('first-project')).toBe('true');
+      expect(draggable('second-project')).toBe('true');
+    } finally {
+      list.unmount();
+    }
+  });
+
+  it('keeps the pin above the flat session list without rendering project rows', () => {
+    state.grouping = 'all';
+
+    const list = renderList();
+    try {
+      expect(list.ownerRows()).toEqual(['assistant']);
+      expect(list.container.querySelector('[data-session-group-pinned="true"]')
+        ?.getAttribute('data-workspace-id')).toBe('assistant');
+      expect(list.container.querySelector('[data-session-scopes]')?.getAttribute('data-session-scopes'))
+        .toBe('project');
+    } finally {
+      list.unmount();
+    }
+  });
+
+  it('renders no pin when the assistant is not created or has been hidden', () => {
+    state.grouping = 'grouped';
+    // A hidden assistant is not an opened workspace, so it must not leave an
+    // empty pinned slot behind.
+    state.workspaces = state.defaultWorkspaces.filter(workspace => workspace.workspaceKind !== 'assistant');
+
+    const list = renderList();
+    try {
+      expect(list.ownerRows()).toEqual(['project']);
+      expect(list.container.querySelector('[data-session-group-pinned="true"]')).toBeNull();
+      expect(list.container.querySelector('[data-testid="nav-workspace-list-empty"]')).toBeNull();
+    } finally {
+      list.unmount();
+    }
+  });
+
+  it('leaves the flat session list in place when no assistant is open', () => {
+    state.grouping = 'all';
+    state.workspaces = state.defaultWorkspaces.filter(workspace => workspace.workspaceKind !== 'assistant');
+
+    const list = renderList();
+    try {
+      expect(list.ownerRows()).toEqual([]);
+      expect(list.container.querySelector('[data-session-group-pinned="true"]')).toBeNull();
+      expect(list.container.querySelector('[data-testid="nav-workspace-list-empty"]')).toBeNull();
+      expect(list.container.querySelector('[data-session-scopes]')?.getAttribute('data-session-scopes'))
+        .toBe('project');
+    } finally {
+      list.unmount();
+    }
+  });
+
+  it('keeps the empty state when no session group is open', () => {
+    state.grouping = 'grouped';
+    state.workspaces = [];
+
+    const list = renderList();
+    try {
+      expect(list.ownerRows()).toEqual([]);
+      expect(list.container.querySelector('[data-testid="nav-workspace-list-empty"]')).not.toBeNull();
+    } finally {
+      list.unmount();
+    }
+  });
+});
+
 describe('assistant navigation across grouping modes', () => {
   it.each(['all', 'grouped'])('keeps the assistant entry and excludes its sessions from the %s list', grouping => {
     state.grouping = grouping;
diff --git a/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.tsx b/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.tsx
index 807edb50d8..0a0fff6dea 100644
--- a/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.tsx
+++ b/src/web-ui/src/app/components/NavPanel/sections/workspaces/WorkspaceListSection.tsx
@@ -13,6 +13,7 @@ import {
   isWorkspaceBackedSessionGroupSelected,
   projectWorkspaceBackedSessionGroups,
   type SessionNavigationScope,
+  type WorkspaceBackedSessionGroup,
 } from '../../sessionNavigationProjection';
 import './WorkspaceListSection.scss';
 
@@ -31,6 +32,13 @@ const WORKSPACE_DRAG_MIME_TYPE = 'application/x-openbitfun-workspace';
 const WORKSPACE_DROP_SETTLE_MS = 160;
 const WORKSPACE_DROP_EASING = 'cubic-bezier(0.22, 1, 0.36, 1)';
 
+/**
+ * WorkspaceListSection — the session section's group list.
+ *
+ * Projects and assistants are both workspace-backed, but they are not peers in
+ * navigation: the assistant identity is pinned above the workspace list and
+ * never joins the workspace order (see `pinnedGroups`).
+ */
 
 const WorkspaceListSection: React.FC<WorkspaceListSectionProps> = ({ variant }) => {
   const { t } = useI18n('common');
@@ -86,9 +94,32 @@ const WorkspaceListSection: React.FC<WorkspaceListSectionProps> = ({ variant })
         }))
       : []
   ), [variant, sessionGroups]);
-  const visibleGroups = grouping === 'all' && variant !== 'assistants'
+  /**
+   * The assistant is a product-level identity, not one workspace among many. It
+   * is pinned above the workspace list and stays out of the workspace order, so
+   * the persisted and draggable order only ever describes project workspaces.
+   *
+   * A hidden, deleted, or never-created assistant has no opened workspace and
+   * therefore produces no pinned row: the pin appears and disappears with the
+   * assistant itself, and the workspace list is untouched either way.
+   */
+  const pinnedGroups = variant === 'all'
     ? sessionGroups.filter(group => group.kind === 'assistant')
+    : [];
+  const reorderableGroups = variant === 'all'
+    ? sessionGroups.filter(group => group.kind === 'project')
     : sessionGroups;
+  // The flat view folds every project session into one aggregate list, so only
+  // the pinned assistant rows stay above it.
+  const visibleReorderableGroups = grouping === 'all' && variant !== 'assistants'
+    ? []
+    : reorderableGroups;
+  const canReorderGroups = visibleReorderableGroups.length > 1;
+  /**
+   * Pinned assistants sit outside the drag order, so a project drag rewrites
+   * project positions only and leaves the assistant's stored slot untouched.
+   */
+  const reorderSection = variant === 'all' ? 'projects' : variant;
 
   const workspaceSignature = sessionGroups.map(group => group.groupId).join(':');
 
@@ -227,7 +258,7 @@ const WorkspaceListSection: React.FC<WorkspaceListSectionProps> = ({ variant })
     );
 
     try {
-      await reorderOpenedWorkspacesInSection(variant, payload.workspaceId, workspaceId, position);
+      await reorderOpenedWorkspacesInSection(reorderSection, payload.workspaceId, workspaceId, position);
     } catch (error) {
       pendingDropRectsRef.current = null;
       notificationService.error(
@@ -237,7 +268,62 @@ const WorkspaceListSection: React.FC<WorkspaceListSectionProps> = ({ variant })
     } finally {
       setDraggedWorkspaceId(null);
     }
-  }, [reorderOpenedWorkspacesInSection, t, variant]);
+  }, [reorderOpenedWorkspacesInSection, reorderSection, t, variant]);
+
+  /**
+   * One session-group row. Pinned assistants and project workspaces share the
+   * same box, but only project rows join the drag group: an assistant row never
+   * becomes a drop target, so dropping a project near it cannot reorder it.
+   */
+  const renderGroupRow = (group: WorkspaceBackedSessionGroup, pinned: boolean) => {
+    const workspace = group.workspace;
+    const isActive = isWorkspaceBackedSessionGroupActive(workspace, activeWorkspace);
+    const isSelected = isWorkspaceBackedSessionGroupSelected(workspace, {
+      activeTab, contentScope, surfaceId, activeWorkspaceId,
+    });
+    const draggable = !pinned && canReorderGroups;
+    return (
+      <div
+        data-openbitfun-component="workspace-list-section"
+        data-openbitfun-part="item"
+        data-openbitfun-state={isSelected ? 'selected' : undefined}
+        key={workspace.id}
+        ref={pinned ? undefined : (element) => {
+          if (element) workspaceRowRefs.current.set(workspace.id, element);
+          else workspaceRowRefs.current.delete(workspace.id);
+        }}
+        className={[
+          'openbitfun-nav-panel__workspace-drop-target',
+          draggable && draggedWorkspaceId && draggedWorkspaceId !== workspace.id && 'is-drag-active',
+          dropTarget?.workspaceId === workspace.id && 'is-drop-target',
+          dropTarget?.workspaceId === workspace.id && dropTarget.position === 'before' && 'is-before',
+          dropTarget?.workspaceId === workspace.id && dropTarget.position === 'after' && 'is-after',
+        ].filter(Boolean).join(' ')}
+        data-testid={pinned ? 'nav-workspace-pinned-item' : 'nav-workspace-drop-target'}
+        data-workspace-id={workspace.id}
+        data-workspace-list={variant}
+        data-session-group-kind={group.kind}
+        data-session-group-pinned={pinned ? 'true' : undefined}
+        onDragOver={draggable ? handleDragOver(workspace.id) : undefined}
+        onDragLeave={draggable ? handleDragLeave(workspace.id) : undefined}
+        onDrop={draggable ? (event) => { void handleDrop(workspace.id)(event); } : undefined}
+      >
+        <WorkspaceItem
+          workspace={workspace}
+          isActive={isActive}
+          isSelected={isSelected}
+          isSingle={!draggable}
+          draggable={draggable}
+          isDragging={draggedWorkspaceId === workspace.id}
+          onDragStart={draggable ? handleDragStart(workspace.id) : undefined}
+          onDragEnd={draggable ? handleDragEnd : undefined}
+        />
+        {dropTarget?.workspaceId === workspace.id ? (
+          <div data-openbitfun-component="workspace-list-section" data-openbitfun-part="dropLine" className="openbitfun-nav-panel__workspace-drop-line" aria-hidden="true" />
+        ) : null}
+      </div>
+    );
+  };
 
   return (
     <div data-openbitfun-component="workspace-list-section" data-openbitfun-part="root" data-openbitfun-state={draggedWorkspaceId ? 'dragging' : undefined}
@@ -256,53 +342,10 @@ const WorkspaceListSection: React.FC<WorkspaceListSectionProps> = ({ variant })
           {emptyLabel}
         </div>
       ) : (
-        visibleGroups.map(group => {
-          const workspace = group.workspace;
-          const isActive = isWorkspaceBackedSessionGroupActive(workspace, activeWorkspace);
-          const isSelected = isWorkspaceBackedSessionGroupSelected(workspace, {
-            activeTab, contentScope, surfaceId, activeWorkspaceId,
-          });
-          return (
-            <div
-              data-openbitfun-component="workspace-list-section"
-              data-openbitfun-part="item"
-              data-openbitfun-state={isSelected ? 'selected' : undefined}
-              key={workspace.id}
-              ref={(element) => {
-                if (element) workspaceRowRefs.current.set(workspace.id, element);
-                else workspaceRowRefs.current.delete(workspace.id);
-              }}
-              className={[
-                'openbitfun-nav-panel__workspace-drop-target',
-                draggedWorkspaceId && draggedWorkspaceId !== workspace.id && 'is-drag-active',
-                dropTarget?.workspaceId === workspace.id && 'is-drop-target',
-                dropTarget?.workspaceId === workspace.id && dropTarget.position === 'before' && 'is-before',
-                dropTarget?.workspaceId === workspace.id && dropTarget.position === 'after' && 'is-after',
-              ].filter(Boolean).join(' ')}
-              data-testid="nav-workspace-drop-target"
-              data-workspace-id={workspace.id}
-              data-workspace-list={variant}
-              data-session-group-kind={group.kind}
-              onDragOver={handleDragOver(workspace.id)}
-              onDragLeave={handleDragLeave(workspace.id)}
-              onDrop={(event) => { void handleDrop(workspace.id)(event); }}
-            >
-              <WorkspaceItem
-                workspace={workspace}
-                isActive={isActive}
-                isSelected={isSelected}
-                isSingle={workspaces.length === 1}
-                draggable={workspaces.length > 1}
-                isDragging={draggedWorkspaceId === workspace.id}
-                onDragStart={handleDragStart(workspace.id)}
-                onDragEnd={handleDragEnd}
-              />
-              {dropTarget?.workspaceId === workspace.id ? (
-                <div data-openbitfun-component="workspace-list-section" data-openbitfun-part="dropLine" className="openbitfun-nav-panel__workspace-drop-line" aria-hidden="true" />
-              ) : null}
-            </div>
-          );
-        })
+        <>
+          {pinnedGroups.map(group => renderGroupRow(group, true))}
+          {visibleReorderableGroups.map(group => renderGroupRow(group, false))}
+        </>
       )}
       {grouping === 'all' && workspaceScopes.length > 0 && (
         <div className="openbitfun-nav-panel__workspace-all-sessions" data-testid="nav-workspace-all-sessions">
diff --git a/tests/e2e/specs/l0-navigation.spec.ts b/tests/e2e/specs/l0-navigation.spec.ts
index 006d4c4d52..4a95da66ab 100644
--- a/tests/e2e/specs/l0-navigation.spec.ts
+++ b/tests/e2e/specs/l0-navigation.spec.ts
@@ -202,8 +202,11 @@ describe('L0 Navigation Panel', () => {
         );
         if (!list) return null;
 
+        // The pinned assistant row is a peer group in the same column even
+        // though it never joins the workspace drag order.
         const groups = Array.from(list.querySelectorAll<HTMLElement>(
-          ':scope > [data-testid="nav-workspace-drop-target"]',
+          ':scope > [data-testid="nav-workspace-pinned-item"], '
+          + ':scope > [data-testid="nav-workspace-drop-target"]',
         )).filter(group => group.getBoundingClientRect().height > 0);
         const groupWithSession = groups.find(group => group.querySelector(
           '[data-testid="nav-session-item"][data-session-level="0"]',