diff --git a/web-ui/src/__tests__/components/tasks/TaskCard.test.tsx b/web-ui/src/__tests__/components/tasks/TaskCard.test.tsx
new file mode 100644
index 00000000..9e6dde65
--- /dev/null
+++ b/web-ui/src/__tests__/components/tasks/TaskCard.test.tsx
@@ -0,0 +1,96 @@
+import React from 'react';
+import { render, screen } from '@testing-library/react';
+import { TaskCard } from '@/components/tasks/TaskCard';
+import { STATUS_INFO } from '@/lib/taskStatusInfo';
+import type { Task } from '@/types';
+
+jest.mock('next/link', () => {
+  const MockLink = ({ href, children }: { href: string; children: React.ReactNode }) => (
+    <a href={href}>{children}</a>
+  );
+  MockLink.displayName = 'MockLink';
+  return MockLink;
+});
+
+// Radix UI tooltips use portals and pointer events that don't work in jsdom.
+// Replace with a simple always-visible version to test content.
+jest.mock('@/components/ui/tooltip', () => ({
+  TooltipProvider: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  Tooltip: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  TooltipTrigger: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  TooltipContent: ({ children }: { children: React.ReactNode }) => (
+    <div role="tooltip">{children}</div>
+  ),
+}));
+
+const baseTask: Task = {
+  id: 'task-1',
+  title: 'Test Task',
+  description: 'A test task description',
+  status: 'BACKLOG',
+  priority: 0,
+  depends_on: [],
+};
+
+const defaultProps = {
+  task: baseTask,
+  selectionMode: false,
+  selected: false,
+  onToggleSelect: jest.fn(),
+  onClick: jest.fn(),
+  onExecute: jest.fn(),
+  onMarkReady: jest.fn(),
+};
+
+describe('TaskCard status badge tooltip', () => {
+  it('renders the status badge label', () => {
+    render(<TaskCard {...defaultProps} />);
+    expect(screen.getByText('Backlog')).toBeInTheDocument();
+  });
+
+  it('renders tooltip with BACKLOG meaning', () => {
+    render(<TaskCard {...defaultProps} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.BACKLOG.meaning);
+  });
+
+  it('renders tooltip with BACKLOG next steps', () => {
+    render(<TaskCard {...defaultProps} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.BACKLOG.nextSteps);
+  });
+
+  it('renders tooltip with READY meaning', () => {
+    const task = { ...baseTask, status: 'READY' as const };
+    render(<TaskCard {...defaultProps} task={task} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.READY.meaning);
+  });
+
+  it('renders tooltip with FAILED meaning', () => {
+    const task = { ...baseTask, status: 'FAILED' as const };
+    render(<TaskCard {...defaultProps} task={task} onReset={jest.fn()} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.FAILED.meaning);
+  });
+
+  it('renders tooltip with IN_PROGRESS meaning', () => {
+    const task = { ...baseTask, status: 'IN_PROGRESS' as const };
+    render(<TaskCard {...defaultProps} task={task} onStop={jest.fn()} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.IN_PROGRESS.meaning);
+  });
+
+  it('renders tooltip with DONE meaning', () => {
+    const task = { ...baseTask, status: 'DONE' as const };
+    render(<TaskCard {...defaultProps} task={task} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.DONE.meaning);
+  });
+
+  it('renders tooltip with BLOCKED meaning', () => {
+    const task = { ...baseTask, status: 'BLOCKED' as const };
+    render(<TaskCard {...defaultProps} task={task} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.BLOCKED.meaning);
+  });
+
+  it('renders tooltip with MERGED meaning', () => {
+    const task = { ...baseTask, status: 'MERGED' as const };
+    render(<TaskCard {...defaultProps} task={task} />);
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.MERGED.meaning);
+  });
+});
diff --git a/web-ui/src/__tests__/components/tasks/TaskDetailModal.test.tsx b/web-ui/src/__tests__/components/tasks/TaskDetailModal.test.tsx
new file mode 100644
index 00000000..bcf60518
--- /dev/null
+++ b/web-ui/src/__tests__/components/tasks/TaskDetailModal.test.tsx
@@ -0,0 +1,161 @@
+import React from 'react';
+import { render, screen, waitFor } from '@testing-library/react';
+import { TaskDetailModal } from '@/components/tasks/TaskDetailModal';
+import { STATUS_INFO } from '@/lib/taskStatusInfo';
+import type { Task } from '@/types';
+
+// Radix UI tooltips use portals and pointer events that don't work in jsdom.
+jest.mock('@/components/ui/tooltip', () => ({
+  TooltipProvider: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  Tooltip: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  TooltipTrigger: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  TooltipContent: ({ children }: { children: React.ReactNode }) => (
+    <div role="tooltip">{children}</div>
+  ),
+}));
+
+// ── Mocks ────────────────────────────────────────────────────────────────
+
+jest.mock('swr', () => ({
+  __esModule: true,
+  default: jest.fn(() => ({ data: { tasks: [] }, isLoading: false, error: null })),
+}));
+
+jest.mock('next/navigation', () => ({
+  useRouter: () => ({ push: jest.fn() }),
+}));
+
+jest.mock('next/link', () => {
+  const MockLink = ({ href, children }: { href: string; children: React.ReactNode }) => (
+    <a href={href}>{children}</a>
+  );
+  MockLink.displayName = 'MockLink';
+  return MockLink;
+});
+
+jest.mock('@/lib/api', () => ({
+  tasksApi: {
+    getOne: jest.fn(),
+    getAll: jest.fn(),
+    updateStatus: jest.fn(),
+  },
+}));
+
+jest.mock('@/hooks/useRequirementsLookup', () => ({
+  useRequirementsLookup: () => ({ requirementsMap: new Map(), isLoading: false }),
+}));
+
+import { tasksApi } from '@/lib/api';
+
+const makeTask = (overrides: Partial<Task> = {}): Task => ({
+  id: 'task-1',
+  title: 'Test Task',
+  description: 'A description',
+  status: 'BACKLOG',
+  priority: 0,
+  depends_on: [],
+  ...overrides,
+});
+
+const defaultProps = {
+  taskId: 'task-1',
+  workspacePath: '/ws',
+  open: true,
+  onClose: jest.fn(),
+  onExecute: jest.fn(),
+  onStatusChange: jest.fn(),
+};
+
+function renderModal(taskOverrides: Partial<Task> = {}) {
+  const task = makeTask(taskOverrides);
+  (tasksApi.getOne as jest.Mock).mockResolvedValue(task);
+  return render(<TaskDetailModal {...defaultProps} />);
+}
+
+describe('TaskDetailModal status badge tooltip', () => {
+  it('renders tooltip with BACKLOG meaning', async () => {
+    renderModal({ status: 'BACKLOG' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.BACKLOG.meaning);
+  });
+
+  it('renders tooltip with DONE meaning', async () => {
+    renderModal({ status: 'DONE' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.DONE.meaning);
+  });
+
+  it('renders tooltip with FAILED meaning', async () => {
+    renderModal({ status: 'FAILED' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByRole('tooltip')).toHaveTextContent(STATUS_INFO.FAILED.meaning);
+  });
+});
+
+describe('TaskDetailModal valid transition guidance', () => {
+  it('shows "Mark Ready" button for BACKLOG status', async () => {
+    renderModal({ status: 'BACKLOG' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByRole('button', { name: /mark ready/i })).toBeInTheDocument();
+  });
+
+  it('shows "Execute" button for READY status', async () => {
+    renderModal({ status: 'READY' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByRole('button', { name: /execute/i })).toBeInTheDocument();
+  });
+
+  it('shows next-step guidance for DONE status (no action button but guidance visible)', async () => {
+    renderModal({ status: 'DONE' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByTestId('status-next-step')).toBeInTheDocument();
+    expect(screen.getByTestId('status-next-step')).toHaveTextContent(STATUS_INFO.DONE.nextSteps);
+  });
+
+  it('shows next-step guidance for BLOCKED status', async () => {
+    renderModal({ status: 'BLOCKED' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByTestId('status-next-step')).toBeInTheDocument();
+    expect(screen.getByTestId('status-next-step')).toHaveTextContent(STATUS_INFO.BLOCKED.nextSteps);
+  });
+
+  it('shows next-step guidance for MERGED status', async () => {
+    renderModal({ status: 'MERGED' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByTestId('status-next-step')).toBeInTheDocument();
+    expect(screen.getByTestId('status-next-step')).toHaveTextContent(STATUS_INFO.MERGED.nextSteps);
+  });
+
+  it('shows next-step guidance for FAILED status via the alert panel', async () => {
+    renderModal({ status: 'FAILED' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByTestId('status-next-step')).toBeInTheDocument();
+    expect(screen.getByTestId('status-next-step')).toHaveTextContent(STATUS_INFO.FAILED.nextSteps);
+  });
+
+  it('does not show next-step guidance for BACKLOG (has action button)', async () => {
+    renderModal({ status: 'BACKLOG' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.queryByTestId('status-next-step')).not.toBeInTheDocument();
+  });
+
+  it('does not show next-step guidance for READY (has action button)', async () => {
+    renderModal({ status: 'READY' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.queryByTestId('status-next-step')).not.toBeInTheDocument();
+  });
+});
+
+describe('TaskDetailModal last changed timestamp', () => {
+  it('shows last changed date when updated_at is present', async () => {
+    renderModal({ status: 'DONE', updated_at: '2026-01-15T10:30:00Z' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.getByText(/last changed/i)).toBeInTheDocument();
+  });
+
+  it('does not show last changed when updated_at is absent', async () => {
+    renderModal({ status: 'BACKLOG' });
+    await waitFor(() => expect(screen.getByText('Test Task')).toBeInTheDocument());
+    expect(screen.queryByText(/last changed/i)).not.toBeInTheDocument();
+  });
+});
diff --git a/web-ui/src/components/tasks/TaskCard.tsx b/web-ui/src/components/tasks/TaskCard.tsx
index 70b6075a..01d72791 100644
--- a/web-ui/src/components/tasks/TaskCard.tsx
+++ b/web-ui/src/components/tasks/TaskCard.tsx
@@ -7,6 +7,7 @@ import { Badge } from '@/components/ui/badge';
 import { Button } from '@/components/ui/button';
 import { Checkbox } from '@/components/ui/checkbox';
 import { Tooltip, TooltipTrigger, TooltipContent, TooltipProvider } from '@/components/ui/tooltip';
+import { STATUS_INFO } from '@/lib/taskStatusInfo';
 import type { Task, TaskStatus, ProofRequirement } from '@/types';
 
 /** Map backend TaskStatus to badge variant name. */
@@ -80,6 +81,8 @@ export function TaskCard({
       aria-label={`View details for ${task.title}`}
     >
       <CardContent className="p-3">
+        {/* Single TooltipProvider for the entire card to avoid per-tooltip provider overhead */}
+        <TooltipProvider>
         {/* Top row: checkbox (if selection mode) + status badge */}
         <div className="mb-2 flex items-center justify-between gap-2">
           <div className="flex items-center gap-2">
@@ -91,26 +94,30 @@ export function TaskCard({
                 aria-label={`Select ${task.title}`}
               />
             )}
-            <Badge
-              variant={STATUS_BADGE_VARIANT[task.status] as never}
-            >
-              {STATUS_LABEL[task.status]}
-            </Badge>
+            <Tooltip>
+              <TooltipTrigger asChild>
+                <Badge variant={STATUS_BADGE_VARIANT[task.status] as never}>
+                  {STATUS_LABEL[task.status]}
+                </Badge>
+              </TooltipTrigger>
+              <TooltipContent className="max-w-[220px] space-y-1">
+                <p className="text-xs font-medium">{STATUS_INFO[task.status].meaning}</p>
+                <p className="text-xs text-muted-foreground">{STATUS_INFO[task.status].nextSteps}</p>
+              </TooltipContent>
+            </Tooltip>
           </div>
           {task.depends_on.length > 0 && (
-            <TooltipProvider>
-              <Tooltip>
-                <TooltipTrigger asChild>
-                  <span className="flex cursor-default items-center gap-1 text-xs text-muted-foreground">
-                    <LinkCircleIcon className="h-3.5 w-3.5" />
-                    {task.depends_on.length}
-                  </span>
-                </TooltipTrigger>
-                <TooltipContent>
-                  Depends on {task.depends_on.length} task{task.depends_on.length !== 1 ? 's' : ''}. This task will become READY when all dependencies complete.
-                </TooltipContent>
-              </Tooltip>
-            </TooltipProvider>
+            <Tooltip>
+              <TooltipTrigger asChild>
+                <span className="flex cursor-default items-center gap-1 text-xs text-muted-foreground">
+                  <LinkCircleIcon className="h-3.5 w-3.5" />
+                  {task.depends_on.length}
+                </span>
+              </TooltipTrigger>
+              <TooltipContent>
+                Depends on {task.depends_on.length} task{task.depends_on.length !== 1 ? 's' : ''}. This task will become READY when all dependencies complete.
+              </TooltipContent>
+            </Tooltip>
           )}
         </div>
 
@@ -215,6 +222,7 @@ export function TaskCard({
             )}
           </div>
         )}
+        </TooltipProvider>
       </CardContent>
     </Card>
   );
diff --git a/web-ui/src/components/tasks/TaskDetailModal.tsx b/web-ui/src/components/tasks/TaskDetailModal.tsx
index c64ef7a5..7a6bca62 100644
--- a/web-ui/src/components/tasks/TaskDetailModal.tsx
+++ b/web-ui/src/components/tasks/TaskDetailModal.tsx
@@ -13,6 +13,7 @@ import {
   BookOpen01Icon,
   Alert02Icon,
   CheckListIcon,
+  InformationCircleIcon,
 } from '@hugeicons/react';
 import {
   Dialog,
@@ -22,6 +23,8 @@ import {
   DialogDescription,
   DialogFooter,
 } from '@/components/ui/dialog';
+import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from '@/components/ui/tooltip';
+import { STATUS_INFO } from '@/lib/taskStatusInfo';
 import { Badge } from '@/components/ui/badge';
 import { Button } from '@/components/ui/button';
 import useSWR from 'swr';
@@ -152,9 +155,19 @@ export function TaskDetailModal({
           <>
             <DialogHeader>
               <div className="flex items-center gap-2">
-                <Badge variant={STATUS_BADGE_VARIANT[task.status] as never}>
-                  {STATUS_LABEL[task.status]}
-                </Badge>
+                <TooltipProvider>
+                  <Tooltip>
+                    <TooltipTrigger asChild>
+                      <Badge variant={STATUS_BADGE_VARIANT[task.status] as never}>
+                        {STATUS_LABEL[task.status]}
+                      </Badge>
+                    </TooltipTrigger>
+                    <TooltipContent className="max-w-[240px] space-y-1">
+                      <p className="text-xs font-medium">{STATUS_INFO[task.status].meaning}</p>
+                      <p className="text-xs text-muted-foreground">{STATUS_INFO[task.status].nextSteps}</p>
+                    </TooltipContent>
+                  </Tooltip>
+                </TooltipProvider>
                 {task.priority > 0 && (
                   <span className="text-xs text-muted-foreground">
                     Priority {task.priority}
@@ -188,6 +201,12 @@ export function TaskDetailModal({
                   {task.estimated_hours}h estimated
                 </span>
               )}
+              {task.updated_at && (
+                <span className="flex items-center gap-1">
+                  <Time01Icon className="h-3.5 w-3.5" />
+                  Last changed: {new Date(task.updated_at).toLocaleDateString('en-US', { month: 'short', day: 'numeric', year: 'numeric' })}
+                </span>
+              )}
             </div>
 
             {/* Dependencies — full list with status highlights and navigation */}
@@ -263,24 +282,34 @@ export function TaskDetailModal({
               </div>
             )}
 
-            {/* FAILED-state guidance panel */}
+            {/* FAILED-state guidance panel — testid enables status-next-step checks */}
             {task.status === 'FAILED' && (
-              <div className="rounded-md border border-destructive/40 bg-destructive/5 px-3 py-2.5">
+              <div className="rounded-md border border-destructive/40 bg-destructive/5 px-3 py-2.5" data-testid="status-next-step">
                 <div className="flex items-start gap-2">
                   <Alert02Icon className="mt-0.5 h-4 w-4 shrink-0 text-destructive" />
                   <div className="space-y-0.5">
                     <p className="text-xs font-medium text-destructive">Task failed during execution</p>
                     <p className="text-xs text-muted-foreground">
-                      Check PROOF9 gates to identify which quality requirements need attention.
-                      {(task.requirement_ids ?? []).length === 0 && (
-                        <> Use the button below to view all gates.</>
-                      )}
+                      {STATUS_INFO.FAILED.nextSteps}
                     </p>
                   </div>
                 </div>
               </div>
             )}
 
+            {/* Next-step guidance for statuses with no action buttons */}
+            {(task.status === 'DONE' || task.status === 'BLOCKED' || task.status === 'MERGED') && (
+              <div className="rounded-md border bg-muted/40 px-3 py-2.5" data-testid="status-next-step">
+                <div className="flex items-start gap-2">
+                  <InformationCircleIcon className="mt-0.5 h-4 w-4 shrink-0 text-muted-foreground" />
+                  <div className="space-y-0.5">
+                    <p className="text-xs font-medium text-foreground">What&apos;s next?</p>
+                    <p className="text-xs text-muted-foreground">{STATUS_INFO[task.status].nextSteps}</p>
+                  </div>
+                </div>
+              </div>
+            )}
+
             <DialogFooter>
               {task.status === 'BACKLOG' && (
                 <Button
diff --git a/web-ui/src/lib/taskStatusInfo.ts b/web-ui/src/lib/taskStatusInfo.ts
new file mode 100644
index 00000000..69751eee
--- /dev/null
+++ b/web-ui/src/lib/taskStatusInfo.ts
@@ -0,0 +1,48 @@
+import type { TaskStatus } from '@/types';
+
+export interface StatusInfo {
+  /** One-sentence explanation of what this status means. */
+  meaning: string;
+  /** How the task entered this state. */
+  enteredWhen: string;
+  /** What the user should do next. */
+  nextSteps: string;
+}
+
+export const STATUS_INFO: Record<TaskStatus, StatusInfo> = {
+  BACKLOG: {
+    meaning: 'Task identified but not yet ready to work on.',
+    enteredWhen: 'Created, or moved back from Ready.',
+    nextSteps: 'Mark Ready when prerequisites are met to enable execution.',
+  },
+  READY: {
+    meaning: 'Task is queued and ready for AI agent execution.',
+    enteredWhen: 'Marked Ready manually or promoted from Backlog.',
+    nextSteps: 'Click Execute to start the AI agent on this task.',
+  },
+  IN_PROGRESS: {
+    meaning: 'AI agent is actively executing this task.',
+    enteredWhen: 'Execution was started.',
+    nextSteps: 'Watch execution output — or Stop to cancel.',
+  },
+  DONE: {
+    meaning: 'Task completed — all verification gates passed.',
+    enteredWhen: 'Agent finished with all quality gates passing.',
+    nextSteps: 'Review changes and create a PR to merge.',
+  },
+  BLOCKED: {
+    meaning: 'Agent needs human input before it can continue.',
+    enteredWhen: 'Agent detected it cannot proceed without an answer.',
+    nextSteps: 'Answer the blocker to resume execution.',
+  },
+  FAILED: {
+    meaning: 'Execution failed due to a technical error.',
+    enteredWhen: 'Agent exceeded retry limit or hit an unrecoverable error.',
+    nextSteps: 'Check PROOF9 gates for details, then Reset to retry.',
+  },
+  MERGED: {
+    meaning: 'Task changes have been merged. No further actions.',
+    enteredWhen: 'PR was merged.',
+    nextSteps: 'This task is complete.',
+  },
+};