fix: session todo header display and mobile improvements

frontend/src/components/message/SessionTodoDisplay.test.tsx

@@ -0,0 +1,103 @@
+import { describe, it, expect, beforeEach } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { SessionTodoDisplay } from './SessionTodoDisplay'
+import { useSessionTodos } from '@/stores/sessionTodosStore'
+import type { Todo } from './SessionTodoDisplay'
+
+const activeTodos: Todo[] = [
+  { id: '1', content: 'Implement mobile header fix', status: 'in_progress', priority: 'high' },
+  { id: '2', content: 'Add regression tests', status: 'pending', priority: 'medium' },
+  { id: '3', content: 'Verify completed item grouping', status: 'completed', priority: 'low' },
+]
+
+const allCompletedTodos: Todo[] = [
+  { id: '1', content: 'Task one', status: 'completed', priority: 'high' },
+  { id: '2', content: 'Task two', status: 'completed', priority: 'medium' },
+]
+
+describe('SessionTodoDisplay', () => {
+  beforeEach(() => {
+    useSessionTodos.setState({ todos: new Map() })
+  })
+
+  it('renders collapsed by default', () => {
+    useSessionTodos.getState().setTodos('session-1', activeTodos)
+
+    render(<SessionTodoDisplay sessionID="session-1" />)
+
+    expect(screen.getByText('Tasks: 1/3 complete')).toBeInTheDocument()
+
+    expect(screen.queryByText('Implement mobile header fix')).not.toBeInTheDocument()
+    expect(screen.queryByText('Add regression tests')).not.toBeInTheDocument()
+  })
+
+  it('expands to show a small scrollable task preview when clicked', async () => {
+    const user = userEvent.setup()
+    useSessionTodos.getState().setTodos('session-1', activeTodos)
+
+    render(<SessionTodoDisplay sessionID="session-1" />)
+
+    const collapsedRow = screen.getByText('Tasks: 1/3 complete')
+    await user.click(collapsedRow)
+
+    expect(screen.getByText('Implement mobile header fix')).toBeInTheDocument()
+    expect(screen.getByText('Add regression tests')).toBeInTheDocument()
+    expect(screen.getByText('Verify completed item grouping')).toBeInTheDocument()
+
+    const expandedContainer = screen.getByTestId('todo-expanded-list')
+    expect(expandedContainer).toHaveClass('max-h-[80px]')
+    expect(expandedContainer).toHaveClass('sm:max-h-[160px]')
+    expect(expandedContainer).toHaveClass('overflow-y-auto')
+  })
+
+  it('collapses again when expanded header is clicked', async () => {
+    const user = userEvent.setup()
+    useSessionTodos.getState().setTodos('session-1', activeTodos)
+
+    render(<SessionTodoDisplay sessionID="session-1" />)
+
+    const collapsedRow = screen.getByText('Tasks: 1/3 complete')
+    await user.click(collapsedRow)
+
+    expect(screen.getByTestId('todo-expanded-list')).toBeInTheDocument()
+
+    const expandedHeader = screen.getByText('Tasks: 1/3 complete')
+    await user.click(expandedHeader)
+
+    expect(screen.queryByTestId('todo-expanded-list')).not.toBeInTheDocument()
+  })
+
+  it('does not render when all tasks are completed', () => {
+    useSessionTodos.getState().setTodos('session-1', allCompletedTodos)
+
+    const { container } = render(<SessionTodoDisplay sessionID="session-1" />)
+
+    expect(container.firstChild).toBeNull()
+  })
+
+  it('dismisses current todo signature and reappears when todo status changes', async () => {
+    const user = userEvent.setup()
+    useSessionTodos.getState().setTodos('session-1', activeTodos)
+
+    const { rerender } = render(<SessionTodoDisplay sessionID="session-1" />)
+
+    expect(screen.getByText('Tasks: 1/3 complete')).toBeInTheDocument()
+
+    const dismissButton = screen.getByLabelText('Dismiss tasks')
+    await user.click(dismissButton)
+
+    expect(screen.queryByText('Tasks: 1/3 complete')).not.toBeInTheDocument()
+
+    const updatedTodos: Todo[] = [
+      { id: '1', content: 'Implement mobile header fix', status: 'completed', priority: 'high' },
+      { id: '2', content: 'Add regression tests', status: 'pending', priority: 'medium' },
+      { id: '3', content: 'Verify completed item grouping', status: 'completed', priority: 'low' },
+    ]
+    useSessionTodos.getState().setTodos('session-1', updatedTodos)
+
+    rerender(<SessionTodoDisplay sessionID="session-1" />)
+
+    expect(screen.getByText('Tasks: 2/3 complete')).toBeInTheDocument()
+  })
+})

frontend/src/components/message/SessionTodoDisplay.tsx

@@ -15,7 +15,7 @@ const todoSignature = (todos: Todo[]) =>
 
 export function SessionTodoDisplay({ sessionID }: SessionTodoDisplayProps) {
   const todos = useSessionTodosForSession(sessionID)
-  const [isCollapsed, setIsCollapsed] = useState(false)
+  const [isCollapsed, setIsCollapsed] = useState(true)
   const [isDismissed, setIsDismissed] = useState(false)
   const dismissedSignatureRef = useRef<string>('')
 
@@ -129,7 +129,7 @@ export function SessionTodoDisplay({ sessionID }: SessionTodoDisplayProps) {
           <X className="w-3.5 h-3.5" />
         </button>
       </div>
-      <div className="max-h-[80px] sm:max-h-[160px] overflow-y-auto p-1.5 sm:p-2 bg-muted/30">
+      <div data-testid="todo-expanded-list" className="max-h-[80px] sm:max-h-[160px] overflow-y-auto p-1.5 sm:p-2 bg-muted/30">
         {renderGroup('In Progress', inProgress)}
         {renderGroup('Pending', pending)}
         {renderGroup('Completed', completedTodos)}

frontend/src/pages/SessionDetail.tsx

@@ -457,9 +457,10 @@ export function SessionDetail() {
       className="h-dvh max-h-dvh overflow-hidden bg-gradient-to-br from-background via-background to-background flex flex-col"
     >
       <div
+        data-testid="session-header-region"
         className={`flex-shrink-0 overflow-hidden bg-background transition-all duration-200 ease-out ${
           isHeaderVisible
-            ? 'max-h-40 opacity-100 translate-y-0'
+            ? 'max-h-72 sm:max-h-80 opacity-100 translate-y-0'
             : 'max-h-0 opacity-0 -translate-y-2'
         }`}
       >