diff --git a/app/src/features/human/HumanPage.test.tsx b/app/src/features/human/HumanPage.test.tsx
index 012300f6c..50ecd2014 100644
--- a/app/src/features/human/HumanPage.test.tsx
+++ b/app/src/features/human/HumanPage.test.tsx
@@ -11,6 +11,9 @@ import { act, fireEvent, render, screen } from '@testing-library/react';
 import { Provider } from 'react-redux';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
+import chatRuntimeReducer, { setToolTimelineForThread } from '../../store/chatRuntimeSlice';
+import mascotReducer from '../../store/mascotSlice';
+import threadReducer, { setSelectedThread } from '../../store/threadSlice';
 // ── Static import (after mocks are hoisted) ──────────────────────────────
 import HumanPage from './HumanPage';
 
@@ -20,22 +23,24 @@ vi.mock('../../pages/Conversations', () => ({
   default: () => <div data-testid="conversations-stub" />,
 }));
 
-vi.mock('./Mascot', () => ({ YellowMascot: () => <div data-testid="mascot-stub" /> }));
+vi.mock('./Mascot', () => ({
+  YellowMascot: () => <div data-testid="mascot-stub" />,
+  Ghosty: ({ face, bodyColor }: { face?: string; bodyColor?: string }) => (
+    <div data-testid="ghosty-submascot" data-face={face} data-body-color={bodyColor} />
+  ),
+}));
 
 vi.mock('./useHumanMascot', () => ({ useHumanMascot: () => ({ face: 'idle', visemes: [] }) }));
 
-vi.mock('../../store/hooks', () => ({ useAppSelector: () => 'yellow' }));
-
-vi.mock('../../store/mascotSlice', () => ({ selectMascotColor: () => 'yellow' }));
-
 const SPEAK_REPLIES_KEY = 'human.speakReplies';
 
 function buildMinimalStore() {
-  return configureStore({ reducer: { _noop: (_s: null = null) => _s } });
+  return configureStore({
+    reducer: { mascot: mascotReducer, thread: threadReducer, chatRuntime: chatRuntimeReducer },
+  });
 }
 
-function renderHumanPage() {
-  const store = buildMinimalStore();
+function renderHumanPage(store = buildMinimalStore()) {
   return render(
     <Provider store={store}>
       <HumanPage />
@@ -96,4 +101,39 @@ describe('HumanPage — speak-replies localStorage persistence', () => {
     expect(localStorage.getItem(SPEAK_REPLIES_KEY)).toBe('1');
     expect(checkbox).toBeChecked();
   });
+
+  it('renders sub-mascots for the selected thread subagent timeline', () => {
+    const store = buildMinimalStore();
+    store.dispatch(setSelectedThread('thread-subagents'));
+    store.dispatch(
+      setToolTimelineForThread({
+        threadId: 'thread-subagents',
+        entries: [
+          {
+            id: 'thread-subagents:subagent:sub-1:researcher',
+            name: 'subagent:researcher',
+            round: 1,
+            status: 'running',
+            detail: 'Research the latest docs and report back.',
+            subagent: {
+              taskId: 'sub-1',
+              agentId: 'researcher',
+              childIteration: 1,
+              childMaxIterations: 3,
+              toolCalls: [],
+            },
+          },
+        ],
+      })
+    );
+
+    renderHumanPage(store);
+
+    expect(screen.getByTestId('sub-mascot-layer')).toBeInTheDocument();
+    expect(
+      screen.getByRole('status', { name: /researcher subagent running/i })
+    ).toBeInTheDocument();
+    expect(screen.getByText('Researcher')).toBeInTheDocument();
+    expect(screen.getByText('Iteration 1/3')).toBeInTheDocument();
+  });
 });
diff --git a/app/src/features/human/HumanPage.tsx b/app/src/features/human/HumanPage.tsx
index 46a0d26f5..8def76542 100644
--- a/app/src/features/human/HumanPage.tsx
+++ b/app/src/features/human/HumanPage.tsx
@@ -2,13 +2,19 @@ import { useEffect, useState } from 'react';
 
 import { useT } from '../../lib/i18n/I18nContext';
 import Conversations from '../../pages/Conversations';
+import type { ToolTimelineEntry } from '../../store/chatRuntimeSlice';
 import { useAppSelector } from '../../store/hooks';
 import { selectMascotColor } from '../../store/mascotSlice';
 import { YellowMascot } from './Mascot';
+import { SubMascotLayer } from './SubMascotLayer';
 import { useHumanMascot } from './useHumanMascot';
 
 const SPEAK_REPLIES_KEY = 'human.speakReplies';
 
+// Stable empty reference so useAppSelector's === equality doesn't force a re-render
+// of SubMascotLayer on every store update when no subagent timeline is active.
+const EMPTY_TIMELINE: ToolTimelineEntry[] = [];
+
 const HumanPage = () => {
   const { t } = useT();
   const [speakReplies, setSpeakReplies] = useState<boolean>(() => {
@@ -23,6 +29,12 @@ const HumanPage = () => {
   // Visemes are intentionally unused — the YellowMascot has its own talking lipsync.
   const { face } = useHumanMascot({ speakReplies });
   const mascotColor = useAppSelector(selectMascotColor);
+  const subMascotTimeline = useAppSelector(state => {
+    const threadId = state.thread.selectedThreadId ?? state.thread.activeThreadId;
+    return threadId
+      ? (state.chatRuntime.toolTimelineByThread[threadId] ?? EMPTY_TIMELINE)
+      : EMPTY_TIMELINE;
+  });
 
   // Sidebar reserves ~436px (420px panel + 16px gutter) on the right; the
   // mascot stage takes the remaining width so the two never overlap.
@@ -39,6 +51,7 @@ const HumanPage = () => {
       <div className="absolute inset-y-0 left-0 right-[436px] flex items-center justify-center">
         <div className="relative w-[min(80vh,90%)] aspect-square">
           <YellowMascot face={face} mascotColor={mascotColor} />
+          <SubMascotLayer entries={subMascotTimeline} />
         </div>
       </div>
 
diff --git a/app/src/features/human/SubMascotLayer.test.tsx b/app/src/features/human/SubMascotLayer.test.tsx
new file mode 100644
index 000000000..1082fbfc7
--- /dev/null
+++ b/app/src/features/human/SubMascotLayer.test.tsx
@@ -0,0 +1,127 @@
+import { render, screen, within } from '@testing-library/react';
+import { describe, expect, it } from 'vitest';
+
+import type { ToolTimelineEntry } from '../../store/chatRuntimeSlice';
+import { SubMascotLayer, subMascotModelsFromTimeline } from './SubMascotLayer';
+
+function subagentEntry(overrides: Partial<ToolTimelineEntry> = {}): ToolTimelineEntry {
+  return {
+    id: 'thread-1:subagent:sub-1:researcher',
+    name: 'subagent:researcher',
+    round: 1,
+    status: 'running',
+    detail: 'Research the relevant docs.',
+    subagent: {
+      taskId: 'sub-1',
+      agentId: 'researcher',
+      childIteration: 1,
+      childMaxIterations: 4,
+      toolCalls: [],
+    },
+    ...overrides,
+  };
+}
+
+describe('subMascotModelsFromTimeline', () => {
+  it('builds visible models only from subagent timeline rows', () => {
+    const models = subMascotModelsFromTimeline([
+      { id: 'thread-1:tool:search', name: 'web_search', round: 1, status: 'running' },
+      subagentEntry(),
+    ]);
+
+    expect(models).toHaveLength(1);
+    expect(models[0]).toMatchObject({
+      agentId: 'researcher',
+      label: 'Researcher',
+      status: 'running',
+      face: 'thinking',
+      activity: 'Iteration 1/4',
+    });
+  });
+
+  it('uses child tool calls, completion, and failure as activity bubbles', () => {
+    const [running, success, error] = subMascotModelsFromTimeline([
+      subagentEntry({
+        id: 'thread-1:subagent:sub-1:code_executor',
+        name: 'subagent:code_executor',
+        subagent: {
+          taskId: 'sub-1',
+          agentId: 'code_executor',
+          toolCalls: [{ callId: 'call-1', toolName: 'read_file', status: 'running' }],
+        },
+      }),
+      subagentEntry({
+        id: 'thread-1:subagent:sub-2:researcher',
+        status: 'success',
+        subagent: { taskId: 'sub-2', agentId: 'researcher', outputChars: 512, toolCalls: [] },
+      }),
+      subagentEntry({
+        id: 'thread-1:subagent:sub-3:critic',
+        name: 'subagent:critic',
+        status: 'error',
+        subagent: { taskId: 'sub-3', agentId: 'critic', toolCalls: [] },
+      }),
+    ]);
+
+    expect(running?.activity).toBe('Using Read File');
+    expect(running?.face).toBe('thinking');
+    expect(success?.activity).toBe('Completed 512 chars');
+    expect(success?.face).toBe('happy');
+    expect(error?.activity).toBe('Needs attention');
+    expect(error?.face).toBe('concerned');
+  });
+});
+
+describe('<SubMascotLayer />', () => {
+  it('renders multiple colored sub-mascots with running, success, and failed states', () => {
+    render(
+      <SubMascotLayer
+        entries={[
+          subagentEntry(),
+          subagentEntry({
+            id: 'thread-1:subagent:sub-2:planner',
+            name: 'subagent:planner',
+            status: 'success',
+            subagent: { taskId: 'sub-2', agentId: 'planner', outputChars: 90, toolCalls: [] },
+          }),
+          subagentEntry({
+            id: 'thread-1:subagent:sub-3:critic',
+            name: 'subagent:critic',
+            status: 'error',
+            subagent: { taskId: 'sub-3', agentId: 'critic', toolCalls: [] },
+          }),
+        ]}
+      />
+    );
+
+    const mascots = screen.getAllByTestId('sub-mascot');
+    expect(mascots).toHaveLength(3);
+    expect(screen.getByRole('status', { name: /researcher subagent running/i })).toHaveAttribute(
+      'data-status',
+      'running'
+    );
+    expect(screen.getByRole('status', { name: /planner subagent success/i })).toHaveAttribute(
+      'data-status',
+      'success'
+    );
+    expect(screen.getByRole('status', { name: /critic subagent error/i })).toHaveAttribute(
+      'data-status',
+      'error'
+    );
+
+    const bubbles = screen.getAllByTestId('sub-mascot-bubble');
+    expect(within(bubbles[0]!).getByText('Researcher')).toBeInTheDocument();
+    expect(within(bubbles[1]!).getByText('Completed 90 chars')).toBeInTheDocument();
+    expect(within(bubbles[2]!).getByText('Needs attention')).toBeInTheDocument();
+  });
+
+  it('renders nothing when no subagent rows are present', () => {
+    const { container } = render(
+      <SubMascotLayer
+        entries={[{ id: 'tool-1', name: 'web_search', round: 1, status: 'running' }]}
+      />
+    );
+
+    expect(container).toBeEmptyDOMElement();
+  });
+});
diff --git a/app/src/features/human/SubMascotLayer.tsx b/app/src/features/human/SubMascotLayer.tsx
new file mode 100644
index 000000000..2e188de77
--- /dev/null
+++ b/app/src/features/human/SubMascotLayer.tsx
@@ -0,0 +1,187 @@
+import debug from 'debug';
+import { type FC, useMemo } from 'react';
+
+import type { ToolTimelineEntry, ToolTimelineEntryStatus } from '../../store/chatRuntimeSlice';
+import { Ghosty, type MascotFace } from './Mascot';
+
+const subMascotLog = debug('human:sub-mascots');
+
+const MAX_SUB_MASCOTS = 5;
+const ACTIVITY_LIMIT = 74;
+
+const SUB_MASCOT_COLORS = [
+  '#4A83DD',
+  '#5C9B75',
+  '#D9854B',
+  '#B8657A',
+  '#6E7BBD',
+  '#4A9A9A',
+] as const;
+
+const POSITIONS = [
+  { left: '72%', top: '18%' },
+  { left: '24%', top: '20%' },
+  { left: '80%', top: '62%' },
+  { left: '18%', top: '64%' },
+  { left: '50%', top: '10%' },
+] as const;
+
+export interface SubMascotModel {
+  id: string;
+  agentId: string;
+  label: string;
+  status: ToolTimelineEntryStatus;
+  face: MascotFace;
+  activity: string;
+  color: string;
+  position: (typeof POSITIONS)[number];
+}
+
+export interface SubMascotLayerProps {
+  entries: ToolTimelineEntry[];
+}
+
+function hashString(value: string): number {
+  let hash = 0;
+  for (let i = 0; i < value.length; i += 1) {
+    hash = (hash * 31 + value.charCodeAt(i)) >>> 0;
+  }
+  return hash;
+}
+
+function truncateActivity(value: string): string {
+  const trimmed = value.trim().replace(/\s+/g, ' ');
+  if (trimmed.length <= ACTIVITY_LIMIT) return trimmed;
+  return `${trimmed.slice(0, ACTIVITY_LIMIT - 3).trimEnd()}...`;
+}
+
+function humanizeIdentifier(value: string): string {
+  const cleaned = value
+    .replace(/^subagent:/, '')
+    .replace(/[_-]+/g, ' ')
+    .trim();
+  if (!cleaned) return 'Subagent';
+  return cleaned.replace(/\b\w/g, ch => ch.toUpperCase());
+}
+
+function faceForStatus(status: ToolTimelineEntryStatus): MascotFace {
+  switch (status) {
+    case 'success':
+      return 'happy';
+    case 'error':
+      return 'concerned';
+    case 'running':
+    default:
+      return 'thinking';
+  }
+}
+
+function activityForEntry(entry: ToolTimelineEntry): string {
+  const subagent = entry.subagent;
+  if (!subagent) return 'Starting';
+
+  if (entry.status === 'success') {
+    return subagent.outputChars ? `Completed ${subagent.outputChars} chars` : 'Completed';
+  }
+
+  if (entry.status === 'error') {
+    return 'Needs attention';
+  }
+
+  const lastRunningTool = [...subagent.toolCalls].reverse().find(call => call.status === 'running');
+  if (lastRunningTool) {
+    return `Using ${humanizeIdentifier(lastRunningTool.toolName)}`;
+  }
+
+  if (subagent.childIteration) {
+    return subagent.childMaxIterations
+      ? `Iteration ${subagent.childIteration}/${subagent.childMaxIterations}`
+      : `Iteration ${subagent.childIteration}`;
+  }
+
+  if (entry.detail?.trim()) {
+    return truncateActivity(entry.detail);
+  }
+
+  return 'Starting';
+}
+
+export function subMascotModelsFromTimeline(entries: ToolTimelineEntry[]): SubMascotModel[] {
+  return entries
+    .filter(entry => entry.subagent && entry.name.startsWith('subagent:'))
+    .slice(-MAX_SUB_MASCOTS)
+    .map((entry, index) => {
+      const subagent = entry.subagent!;
+      const agentId = subagent.agentId || entry.name.replace(/^subagent:/, '') || 'subagent';
+      const colorIndex = hashString(`${subagent.taskId}:${agentId}`) % SUB_MASCOT_COLORS.length;
+      return {
+        id: entry.id,
+        agentId,
+        label: humanizeIdentifier(agentId),
+        status: entry.status,
+        face: faceForStatus(entry.status),
+        activity: activityForEntry(entry),
+        color: SUB_MASCOT_COLORS[colorIndex],
+        position: POSITIONS[index % POSITIONS.length],
+      };
+    });
+}
+
+export const SubMascotLayer: FC<SubMascotLayerProps> = ({ entries }) => {
+  const models = useMemo(() => subMascotModelsFromTimeline(entries), [entries]);
+
+  if (models.length === 0) return null;
+
+  subMascotLog(
+    'render count=%d states=%o',
+    models.length,
+    models.map(model => `${model.agentId}:${model.status}`)
+  );
+
+  return (
+    <div
+      className="pointer-events-none absolute inset-0 z-10"
+      data-testid="sub-mascot-layer"
+      aria-live="polite">
+      {models.map(model => (
+        <div
+          key={model.id}
+          role="status"
+          aria-label={`${model.label} subagent ${model.status}`}
+          data-testid="sub-mascot"
+          data-status={model.status}
+          className="absolute w-[clamp(78px,18%,128px)]"
+          style={{
+            left: model.position.left,
+            top: model.position.top,
+            transform: 'translate(-50%, -50%)',
+          }}>
+          <div
+            className={[
+              'relative transition-opacity duration-500',
+              model.status === 'running' ? 'opacity-100' : 'opacity-85',
+            ].join(' ')}>
+            <div className="drop-shadow-[0_10px_20px_rgba(15,23,42,0.22)]">
+              <Ghosty
+                size="100%"
+                idPrefix={`sub-mascot-${model.id.replace(/[^a-zA-Z0-9_-]/g, '-')}`}
+                bodyColor={model.color}
+                face={model.face}
+              />
+            </div>
+            <div
+              className="absolute left-1/2 top-[78%] w-[min(168px,42vw)] -translate-x-1/2 rounded-lg border border-white/70 bg-white/90 px-2 py-1 text-center text-[11px] leading-tight text-stone-700 shadow-soft backdrop-blur dark:border-neutral-700 dark:bg-neutral-900/90 dark:text-neutral-100"
+              data-testid="sub-mascot-bubble">
+              <div className="truncate font-medium">{model.label}</div>
+              <div
+                className="mt-0.5 overflow-hidden text-[10px] text-stone-500 dark:text-neutral-300"
+                style={{ display: '-webkit-box', WebkitLineClamp: 2, WebkitBoxOrient: 'vertical' }}>
+                {model.activity}
+              </div>
+            </div>
+          </div>
+        </div>
+      ))}
+    </div>
+  );
+};
diff --git a/docs/TEST-COVERAGE-MATRIX.md b/docs/TEST-COVERAGE-MATRIX.md
index 8d3b1db9e..e861a41bf 100644
--- a/docs/TEST-COVERAGE-MATRIX.md
+++ b/docs/TEST-COVERAGE-MATRIX.md
@@ -189,6 +189,7 @@ Canonical mapping of every product feature to its test source(s). Drives gap-fil
 | 4.3.1 | Tool Trigger via Chat      | WD    | `skill-execution-flow.spec.ts`, `skill-multi-round.spec.ts` | ✅     |       |
 | 4.3.2 | Permission-Based Execution | RU+WD | `src/openhuman/tools/`, `skill-execution-flow.spec.ts`      | ✅     |       |
 | 4.3.3 | Tool Failure Handling      | WD    | `skill-execution-flow.spec.ts`                              | ✅     |       |
+| 4.3.4 | Subagent Mascot Visualization | VU | `app/src/features/human/SubMascotLayer.test.tsx`, `app/src/features/human/HumanPage.test.tsx` | ✅ | Renders spawned/completed/failed subagent timeline rows as colored companion mascots with activity bubbles |
 
 ---
 
diff --git a/gitbooks/developing/architecture/frontend.md b/gitbooks/developing/architecture/frontend.md
index 606ce3351..a90604f18 100644
--- a/gitbooks/developing/architecture/frontend.md
+++ b/gitbooks/developing/architecture/frontend.md
@@ -843,6 +843,34 @@ test('SocketProvider connects when token is available', () => {
 
 ***
 
+## Human Mascot Surface
+
+The Human page (`app/src/features/human/HumanPage.tsx`) renders the main
+`YellowMascot` beside the conversation sidebar. The mascot face still comes
+from `useHumanMascot`, which subscribes to chat lifecycle events for thinking,
+speaking, acknowledgement, and error states.
+
+Sub-agent delegation is visualized by `SubMascotLayer`. It does not introduce a
+new socket protocol. Instead, it reads the selected or active thread's
+`chatRuntime.toolTimelineByThread` entries that `ChatRuntimeProvider` already
+builds from `subagent_spawned`, `subagent_completed`, `subagent_failed`,
+`subagent_iteration_start`, `subagent_tool_call`, and `subagent_tool_result`.
+
+Lifecycle mapping:
+
+| Runtime timeline state | Sub-mascot state |
+| ---------------------- | ---------------- |
+| `running`              | Small colored mascot in a thinking face with a short activity bubble |
+| `success`              | Same mascot resolves to a happy face and completion bubble |
+| `error`                | Same mascot resolves to a concerned face and failure bubble |
+
+Activity bubble text is intentionally compact: current child tool call, child
+iteration, the delegation prompt excerpt, or final status. The thread timeline
+remains the authoritative detailed view; sub-mascots are only the glanceable
+orchestration layer around the main mascot.
+
+***
+
 ## Pages & Routing
 
 The application uses HashRouter with protected and public route guards.
diff --git a/src/openhuman/about_app/catalog.rs b/src/openhuman/about_app/catalog.rs
index f7c1696d1..1052e1faa 100644
--- a/src/openhuman/about_app/catalog.rs
+++ b/src/openhuman/about_app/catalog.rs
@@ -159,6 +159,16 @@ const CAPABILITIES: &[Capability] = &[
         status: CapabilityStatus::Beta,
         privacy: None,
     },
+    Capability {
+        id: "conversation.subagent_mascots",
+        name: "Subagent Mascots",
+        domain: "conversation",
+        category: CapabilityCategory::Conversation,
+        description: "Show delegated sub-agents as colored companion mascots with compact activity bubbles and running, completed, or failed states.",
+        how_to: "Human > ask the assistant to delegate work to sub-agents",
+        status: CapabilityStatus::Beta,
+        privacy: None,
+    },
     Capability {
         id: "conversation.label_filter",
         name: "Thread Label Filters",
diff --git a/src/openhuman/about_app/catalog_tests.rs b/src/openhuman/about_app/catalog_tests.rs
index 33eb45392..26532fb82 100644
--- a/src/openhuman/about_app/catalog_tests.rs
+++ b/src/openhuman/about_app/catalog_tests.rs
@@ -102,6 +102,7 @@ fn catalog_includes_additional_user_facing_surfaces() {
         "meet_agent.live_loop",
         "intelligence.mcp_server",
         "intelligence.tool_registry",
+        "conversation.subagent_mascots",
     ] {
         assert!(
             ids.contains(expected),