diff --git a/apps/web/src/app-shell.tsx b/apps/web/src/app-shell.tsx
index 724d17e..87c1121 100644
--- a/apps/web/src/app-shell.tsx
+++ b/apps/web/src/app-shell.tsx
@@ -6,6 +6,7 @@ import { createEventStreamClient, type EventStreamClient } from './events/event-
 
 import { FleetPage, type FleetDataSource, type FleetSnapshot } from './fleet/fleet-page.js';
 import { createFleetApiDataSource } from './fleet/fleet-api-data-source.js';
+import { CallsModule, type CallsDataSource } from './instances/calls-module.js';
 import { CellularModule, type CellularDataSource } from './instances/cellular-module.js';
 import {
   DeviceNetworkModule,
@@ -13,6 +14,7 @@ import {
 } from './instances/device-network-module.js';
 import { OverviewSystemPage, type OverviewDataSource } from './instances/overview-system.js';
 import { InstanceEditor, type InstanceDataSource } from './instances/instance-crud.js';
+import { MessagesModule, type MessagesDataSource } from './instances/messages-module.js';
 import {
   InstanceDetail,
   INSTANCE_MODULE_LABELS,
@@ -70,6 +72,8 @@ export interface AppShellProps {
   overviewDataSource?: OverviewDataSource;
   cellularDataSource?: CellularDataSource;
   deviceNetworkDataSource?: DeviceNetworkDataSource;
+  messagesDataSource?: MessagesDataSource;
+  callsDataSource?: CallsDataSource;
   eventStreamClient?: EventStreamClient;
 }
 
@@ -140,6 +144,8 @@ function Page({
   overviewDataSource,
   cellularDataSource,
   deviceNetworkDataSource,
+  messagesDataSource,
+  callsDataSource,
   fleetRefreshSignal,
   detailRefreshSignal,
 }: {
@@ -153,6 +159,8 @@ function Page({
   overviewDataSource: OverviewDataSource | undefined;
   cellularDataSource: CellularDataSource | undefined;
   deviceNetworkDataSource: DeviceNetworkDataSource | undefined;
+  messagesDataSource: MessagesDataSource | undefined;
+  callsDataSource: CallsDataSource | undefined;
   fleetRefreshSignal: number;
   detailRefreshSignal: number;
 }): ReactNode {
@@ -229,6 +237,28 @@ function Page({
               ),
             }
           : {})}
+        {...(module === 'messages' && instance
+          ? {
+              moduleContent: (
+                <MessagesModule
+                  instance={instance}
+                  {...(messagesDataSource ? { dataSource: messagesDataSource } : {})}
+                  refreshSignal={detailRefreshSignal}
+                />
+              ),
+            }
+          : {})}
+        {...(module === 'calls' && instance
+          ? {
+              moduleContent: (
+                <CallsModule
+                  instance={instance}
+                  {...(callsDataSource ? { dataSource: callsDataSource } : {})}
+                  refreshSignal={detailRefreshSignal}
+                />
+              ),
+            }
+          : {})}
       />
     );
   }
@@ -262,6 +292,8 @@ export function AppShell({
   overviewDataSource,
   cellularDataSource,
   deviceNetworkDataSource,
+  messagesDataSource,
+  callsDataSource,
   eventStreamClient,
 }: AppShellProps) {
   const defaultEventStreamClient = useMemo(() => createEventStreamClient(), []);
@@ -317,6 +349,8 @@ export function AppShell({
             overviewDataSource={overviewDataSource}
             cellularDataSource={cellularDataSource}
             deviceNetworkDataSource={deviceNetworkDataSource}
+            messagesDataSource={messagesDataSource}
+            callsDataSource={callsDataSource}
             fleetRefreshSignal={refresh.fleet}
             detailRefreshSignal={refresh.detail}
           />
diff --git a/apps/web/src/index.ts b/apps/web/src/index.ts
index ed5b52a..8fc0307 100644
--- a/apps/web/src/index.ts
+++ b/apps/web/src/index.ts
@@ -91,4 +91,17 @@ export {
   type DeviceNetworkSnapshot,
 } from './instances/device-network-module.js';
 
+export {
+  CallsModule,
+  type CallsDataSource,
+  type CallsModuleProps,
+  type CallsSnapshot,
+} from './instances/calls-module.js';
+export {
+  MessagesModule,
+  type MessagesDataSource,
+  type MessagesModuleProps,
+  type MessagesSnapshot,
+} from './instances/messages-module.js';
+
 export const webWorkspaceReady = true;
diff --git a/apps/web/src/instances/calls-module.test.tsx b/apps/web/src/instances/calls-module.test.tsx
new file mode 100644
index 0000000..5aff5ae
--- /dev/null
+++ b/apps/web/src/instances/calls-module.test.tsx
@@ -0,0 +1,129 @@
+// @vitest-environment jsdom
+import { cleanup, render, screen, within } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import type { InstanceContext } from '../app-shell.js';
+import { CallsModule, type CallsDataSource, type CallsSnapshot } from './calls-module.js';
+
+afterEach(cleanup);
+
+const owner: InstanceContext = {
+  id: 'alpha',
+  name: 'Alpha',
+  origin: 'https://alpha.example',
+  status: 'online',
+  authentication: 'authenticated',
+  freshness: 'fresh',
+};
+
+const snapshot: CallsSnapshot = {
+  observedAt: '2026-07-17T12:30:00Z',
+  calls: { state: 'active', active: 2, ringing: 1, held: 0 },
+  devices: { state: 'available', total: 4, online: 3, busy: 2 },
+};
+
+function deferredSource() {
+  let resolvePending!: (value: CallsSnapshot) => void;
+  const load = vi.fn<CallsDataSource['load']>(
+    (_instanceId, _signal) =>
+      new Promise((done) => {
+        void _instanceId;
+        void _signal;
+        resolvePending = done;
+      }),
+  );
+  return { source: { load }, load, resolve: (value: CallsSnapshot) => resolvePending(value) };
+}
+
+describe('isolated Calls read module', () => {
+  it('loads only through the injected source and renders aggregate call and device status', async () => {
+    const pending = deferredSource();
+    render(<CallsModule instance={owner} dataSource={pending.source} />);
+    expect(screen.getByRole('status', { name: 'Calls loading status' })).toBeTruthy();
+    expect(pending.load).toHaveBeenCalledWith('alpha', expect.any(AbortSignal));
+    pending.resolve(snapshot);
+
+    const calls = await screen.findByRole('region', { name: 'Call status' });
+    const devices = screen.getByRole('region', { name: 'Device status' });
+    expect(within(calls).getByText('active')).toBeTruthy();
+    expect(within(calls).getByText('2')).toBeTruthy();
+    expect(within(devices).getByText('available')).toBeTruthy();
+    expect(screen.getByText(/Observed 2026-07-17T12:30:00Z/)).toBeTruthy();
+  });
+
+  it('strictly allowlists aggregate fields and exposes no phone numbers, audio, logs, or controls', async () => {
+    const unsafe = {
+      ...snapshot,
+      phoneNumber: '+1-555-0100',
+      audio: 'private recording body',
+      logBody: 'private call log body',
+      calls: { ...snapshot.calls, caller: '+1-555-0101', transcript: 'private transcript' },
+      devices: { ...snapshot.devices, phoneNumber: '+1-555-0102', audioUrl: 'secret-audio-url' },
+    } as CallsSnapshot;
+    render(<CallsModule instance={owner} dataSource={{ load: async () => unsafe }} />);
+    expect(await screen.findByText('available')).toBeTruthy();
+    expect(document.body.textContent).not.toMatch(/555|private|secret-audio/i);
+    expect(screen.queryByRole('button')).toBeNull();
+  });
+
+  it('fails closed without authentication or an injected source', async () => {
+    const load = vi.fn<CallsDataSource['load']>().mockResolvedValue(snapshot);
+    const { rerender } = render(
+      <CallsModule
+        instance={{ ...owner, authentication: 'auth-required' }}
+        dataSource={{ load }}
+      />,
+    );
+    expect(screen.getByRole('alert').textContent).toMatch(/authentication is required/i);
+    expect(load).not.toHaveBeenCalled();
+
+    rerender(<CallsModule instance={owner} />);
+    expect(screen.getByRole('status', { name: 'Calls unavailable' }).textContent).toMatch(
+      /no safe calls read data source.*will not invent.*production endpoint/i,
+    );
+  });
+
+  it('uses fixed safe errors, retries, and retains the same owner snapshot on refresh failure', async () => {
+    const user = userEvent.setup();
+    const load = vi
+      .fn<CallsDataSource['load']>()
+      .mockResolvedValueOnce(snapshot)
+      .mockRejectedValueOnce(new Error('secret endpoint and telephone'))
+      .mockResolvedValueOnce({ ...snapshot, calls: { ...snapshot.calls, active: 3 } });
+    const source = { load };
+    const { rerender } = render(
+      <CallsModule instance={owner} dataSource={source} refreshSignal={0} />,
+    );
+    expect(await screen.findByText('available')).toBeTruthy();
+    rerender(<CallsModule instance={owner} dataSource={source} refreshSignal={1} />);
+
+    const alert = await screen.findByRole('alert');
+    expect(alert.textContent).toMatch(/showing the last known Calls data/i);
+    expect(alert.textContent).not.toMatch(/secret endpoint|telephone/i);
+    expect(screen.getByText('available')).toBeTruthy();
+    await user.click(screen.getByRole('button', { name: 'Retry loading Calls' }));
+    expect(
+      await within(screen.getByRole('region', { name: 'Call status' })).findByText('3'),
+    ).toBeTruthy();
+  });
+
+  it('aborts superseded reads and fences late data from another owner', async () => {
+    const alpha = deferredSource();
+    const bravo = deferredSource();
+    const load = vi.fn<CallsDataSource['load']>((id, signal) =>
+      id === 'alpha' ? alpha.source.load(id, signal) : bravo.source.load(id, signal),
+    );
+    const source = { load };
+    const { rerender } = render(<CallsModule instance={owner} dataSource={source} />);
+    const alphaSignal = load.mock.calls[0]?.[1];
+    rerender(
+      <CallsModule instance={{ ...owner, id: 'bravo', name: 'Bravo' }} dataSource={source} />,
+    );
+    expect(alphaSignal?.aborted).toBe(true);
+    alpha.resolve({ ...snapshot, calls: { state: 'late-alpha' } });
+    bravo.resolve({ ...snapshot, calls: { state: 'current-bravo' } });
+    expect(await screen.findByText('current-bravo')).toBeTruthy();
+    expect(screen.queryByText('late-alpha')).toBeNull();
+  });
+});
diff --git a/apps/web/src/instances/calls-module.tsx b/apps/web/src/instances/calls-module.tsx
new file mode 100644
index 0000000..4779295
--- /dev/null
+++ b/apps/web/src/instances/calls-module.tsx
@@ -0,0 +1,218 @@
+import { useEffect, useRef, useState, type ReactNode } from 'react';
+
+import type { InstanceContext } from '../app-shell.js';
+
+/** Bounded values permitted in aggregate call/device status. */
+export type CallsStatusValue = string | number | boolean | null;
+
+/** Aggregate call state only. Per-call identity, phone numbers, logs, and media are unsupported. */
+export interface AggregateCallStatus {
+  readonly state?: CallsStatusValue;
+  readonly total?: CallsStatusValue;
+  readonly active?: CallsStatusValue;
+  readonly ringing?: CallsStatusValue;
+  readonly held?: CallsStatusValue;
+  readonly failed?: CallsStatusValue;
+}
+
+/** Aggregate device state only. Device phone numbers and media are intentionally unsupported. */
+export interface AggregateCallDeviceStatus {
+  readonly state?: CallsStatusValue;
+  readonly total?: CallsStatusValue;
+  readonly online?: CallsStatusValue;
+  readonly offline?: CallsStatusValue;
+  readonly busy?: CallsStatusValue;
+}
+
+export interface CallsSnapshot {
+  readonly observedAt?: string;
+  readonly calls: AggregateCallStatus;
+  readonly devices: AggregateCallDeviceStatus;
+}
+
+export interface CallsDataSource {
+  /** Supplied by the authenticated owner; this isolated module defines no production endpoint. */
+  load(instanceId: string, signal: AbortSignal): Promise<CallsSnapshot>;
+}
+
+export interface CallsModuleProps {
+  readonly instance: InstanceContext;
+  readonly dataSource?: CallsDataSource;
+  /** Change this owner-provided value to request another read. */
+  readonly refreshSignal?: unknown;
+}
+
+type OwnedSnapshot = { readonly ownerId: string; readonly value: CallsSnapshot };
+type ReadState =
+  | { kind: 'idle' }
+  | { kind: 'loading'; snapshot?: OwnedSnapshot }
+  | { kind: 'ready'; snapshot: OwnedSnapshot }
+  | { kind: 'error'; snapshot?: OwnedSnapshot };
+
+const SAFE_LOAD_ERROR = 'Calls data could not be loaded.';
+
+const CALL_FIELDS = [
+  ['State', 'state'],
+  ['Total', 'total'],
+  ['Active', 'active'],
+  ['Ringing', 'ringing'],
+  ['Held', 'held'],
+  ['Failed', 'failed'],
+] as const;
+
+const DEVICE_FIELDS = [
+  ['State', 'state'],
+  ['Total', 'total'],
+  ['Online', 'online'],
+  ['Offline', 'offline'],
+  ['Busy', 'busy'],
+] as const;
+
+function Section({ label, children }: { label: string; children: ReactNode }) {
+  return (
+    <section className="calls-card" aria-label={label}>
+      <h2>{label}</h2>
+      {children}
+    </section>
+  );
+}
+
+function AggregateFields({
+  values,
+  fields,
+}: {
+  values: object;
+  fields: readonly (readonly [label: string, key: string])[];
+}) {
+  const safeValues = values as Readonly<Record<string, CallsStatusValue | undefined>>;
+  const supplied = fields.filter(([, key]) => safeValues[key] !== undefined);
+  if (!supplied.length) return <p>No aggregate status was supplied.</p>;
+  return (
+    <dl>
+      {supplied.map(([label, key]) => (
+        <div key={key}>
+          <dt>{label}</dt>
+          <dd>{safeValues[key] == null ? 'Unavailable' : String(safeValues[key])}</dd>
+        </div>
+      ))}
+    </dl>
+  );
+}
+
+function SnapshotView({ snapshot }: { snapshot: CallsSnapshot }) {
+  return (
+    <>
+      {snapshot.observedAt ? <p>Observed {snapshot.observedAt}</p> : null}
+      <div className="calls-grid">
+        <Section label="Call status">
+          <AggregateFields values={snapshot.calls} fields={CALL_FIELDS} />
+        </Section>
+        <Section label="Device status">
+          <AggregateFields values={snapshot.devices} fields={DEVICE_FIELDS} />
+        </Section>
+      </div>
+    </>
+  );
+}
+
+export function CallsModule({ instance, dataSource, refreshSignal }: CallsModuleProps) {
+  const requestFence = useRef(0);
+  const [retry, setRetry] = useState(0);
+  const [state, setState] = useState<ReadState>({ kind: 'idle' });
+
+  useEffect(() => {
+    const request = ++requestFence.current;
+    const ownerId = instance.id;
+    const controller = new AbortController();
+
+    if (instance.authentication !== 'authenticated' || !dataSource) {
+      setState({ kind: 'idle' });
+      return () => controller.abort();
+    }
+
+    setState((current) => {
+      const snapshot =
+        current.kind !== 'idle' && current.snapshot?.ownerId === ownerId
+          ? current.snapshot
+          : undefined;
+      return { kind: 'loading', ...(snapshot ? { snapshot } : {}) };
+    });
+
+    void dataSource.load(ownerId, controller.signal).then(
+      (value) => {
+        if (request === requestFence.current && !controller.signal.aborted)
+          setState({ kind: 'ready', snapshot: { ownerId, value } });
+      },
+      (_reason: unknown) => {
+        void _reason;
+        if (request === requestFence.current && !controller.signal.aborted)
+          setState((current) => {
+            const snapshot =
+              current.kind === 'loading' && current.snapshot?.ownerId === ownerId
+                ? current.snapshot
+                : undefined;
+            return { kind: 'error', ...(snapshot ? { snapshot } : {}) };
+          });
+      },
+    );
+
+    return () => controller.abort();
+  }, [dataSource, instance.authentication, instance.id, refreshSignal, retry]);
+
+  if (instance.authentication !== 'authenticated')
+    return (
+      <div className="state-panel state-error" role="alert">
+        Authentication is required before Calls data can be read for this instance.
+      </div>
+    );
+
+  if (!dataSource)
+    return (
+      <div className="state-panel" role="status" aria-label="Calls unavailable">
+        No safe Calls read data source is available. This console will not invent or call an
+        uncontracted production endpoint.
+      </div>
+    );
+
+  const snapshot =
+    state.kind !== 'idle' && state.snapshot?.ownerId === instance.id ? state.snapshot : undefined;
+
+  if ((state.kind === 'idle' || state.kind === 'loading') && !snapshot)
+    return (
+      <p role="status" aria-label="Calls loading status">
+        Loading Calls…
+      </p>
+    );
+
+  if (state.kind === 'error' && !snapshot)
+    return (
+      <div className="state-panel state-error" role="alert">
+        <p>Unable to load Calls: {SAFE_LOAD_ERROR}</p>
+        <button type="button" onClick={() => setRetry((value) => value + 1)}>
+          Retry loading Calls
+        </button>
+      </div>
+    );
+
+  if (!snapshot) return null;
+
+  return (
+    <div className="calls-module">
+      {state.kind === 'loading' ? <p role="status">Refreshing Calls…</p> : null}
+      {state.kind === 'error' ? (
+        <div className="state-panel state-error" role="alert">
+          <p>Refresh failed; showing the last known Calls data.</p>
+          <button type="button" onClick={() => setRetry((value) => value + 1)}>
+            Retry loading Calls
+          </button>
+        </div>
+      ) : null}
+      {instance.freshness !== 'fresh' ? (
+        <p className="state-panel" role="status" aria-label="Calls freshness">
+          Calls data is {instance.freshness}; verify freshness before relying on these values.
+        </p>
+      ) : null}
+      <SnapshotView snapshot={snapshot.value} />
+    </div>
+  );
+}
diff --git a/apps/web/src/instances/messages-module.test.tsx b/apps/web/src/instances/messages-module.test.tsx
new file mode 100644
index 0000000..9acc783
--- /dev/null
+++ b/apps/web/src/instances/messages-module.test.tsx
@@ -0,0 +1,215 @@
+// @vitest-environment jsdom
+import { cleanup, render, screen, within } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import type { InstanceContext } from '../app-shell.js';
+import {
+  MessagesModule,
+  type MessagesDataSource,
+  type MessagesSnapshot,
+} from './messages-module.js';
+
+afterEach(cleanup);
+
+const owner: InstanceContext = {
+  id: 'alpha',
+  name: 'Alpha',
+  origin: 'https://alpha.example',
+  status: 'online',
+  authentication: 'authenticated',
+  freshness: 'fresh',
+};
+
+const snapshot: MessagesSnapshot = {
+  observedAt: '2026-07-17T12:00:00Z',
+  sms: {
+    total: 42,
+    inbound: 25,
+    outbound: 17,
+    unread: 3,
+    failed: 2,
+    queued: 1,
+    lastActivityAt: '2026-07-17T11:55:00Z',
+    // Deliberate excess fields: payloads and recipient data must never reach the DOM.
+    body: 'private message body',
+    content: 'private message content',
+    recipient: '+15550199',
+    recipientCredential: 'secret-recipient-token',
+  },
+  devices: [
+    {
+      deviceId: 'modem-1',
+      label: 'Primary modem',
+      state: 'online',
+      total: 30,
+      inbound: 18,
+      outbound: 12,
+      unread: 2,
+      failed: 1,
+      queued: 0,
+      lastActivityAt: '2026-07-17T11:54:00Z',
+      body: 'device body must not render',
+      phoneNumber: '+15550123',
+      password: 'device credential',
+    },
+  ],
+};
+
+function deferredSource() {
+  let resolve!: (value: MessagesSnapshot) => void;
+  let reject!: (reason: unknown) => void;
+  const load = vi.fn<MessagesDataSource['load']>(
+    (_instanceId, _signal) =>
+      new Promise((done, fail) => {
+        void _instanceId;
+        void _signal;
+        resolve = done;
+        reject = fail;
+      }),
+  );
+  return {
+    source: { load },
+    load,
+    resolve: (value: MessagesSnapshot) => resolve(value),
+    reject: (reason: unknown) => reject(reason),
+  };
+}
+
+describe('Messages isolated read module', () => {
+  it('loads only through the injected exact-owner source and renders aggregate SMS/device metadata', async () => {
+    const pending = deferredSource();
+    render(<MessagesModule instance={owner} dataSource={pending.source} />);
+
+    expect(screen.getByRole('status', { name: 'Messages loading status' })).toBeTruthy();
+    expect(pending.load).toHaveBeenCalledWith('alpha', expect.any(AbortSignal));
+    pending.resolve(snapshot);
+
+    const sms = await screen.findByRole('region', { name: 'SMS aggregate' });
+    expect(within(sms).getByText('42')).toBeTruthy();
+    expect(within(sms).getByText('2026-07-17T11:55:00Z')).toBeTruthy();
+    const devices = screen.getByRole('region', { name: 'Device message aggregates' });
+    expect(within(devices).getByText('modem-1')).toBeTruthy();
+    expect(within(devices).getByText('Primary modem')).toBeTruthy();
+    expect(screen.getByText(/Observed 2026-07-17T12:00:00Z/)).toBeTruthy();
+  });
+
+  it('uses an explicit safe allowlist and exposes no bodies, content, recipients, credentials, or write actions', async () => {
+    render(<MessagesModule instance={owner} dataSource={{ load: async () => snapshot }} />);
+    expect(await screen.findByText('Primary modem')).toBeTruthy();
+    const text = document.body.textContent ?? '';
+    for (const secret of [
+      'private message body',
+      'private message content',
+      '+15550199',
+      'secret-recipient-token',
+      'device body must not render',
+      '+15550123',
+      'device credential',
+    ]) {
+      expect(text).not.toContain(secret);
+    }
+    expect(screen.queryByText(/recipient|phone number|password/i)).toBeNull();
+    expect(screen.queryByRole('button')).toBeNull();
+    expect(screen.getByText(/aggregate metadata only/i)).toBeTruthy();
+    expect(
+      screen.getByText(/sending, deleting, and changing messages are unavailable/i),
+    ).toBeTruthy();
+  });
+
+  it('does not invent an endpoint when no source is injected', () => {
+    render(<MessagesModule instance={owner} />);
+    expect(screen.getByRole('status', { name: 'Messages unavailable' }).textContent).toMatch(
+      /no safe messages read data source.*uncontracted production endpoint/i,
+    );
+  });
+
+  it('requires the exact owner to remain authenticated and clears prior owner data', async () => {
+    const load = vi.fn<MessagesDataSource['load']>().mockResolvedValue(snapshot);
+    const { rerender } = render(<MessagesModule instance={owner} dataSource={{ load }} />);
+    expect(await screen.findByText('Primary modem')).toBeTruthy();
+
+    rerender(
+      <MessagesModule
+        instance={{ ...owner, id: 'bravo', name: 'Bravo', authentication: 'auth-required' }}
+        dataSource={{ load }}
+      />,
+    );
+    expect(screen.getByRole('alert').textContent).toMatch(/authentication is required/i);
+    expect(screen.queryByText('Primary modem')).toBeNull();
+    expect(load).toHaveBeenCalledTimes(1);
+  });
+
+  it('uses a fixed safe error and retries without exposing rejection details', async () => {
+    const user = userEvent.setup();
+    const load = vi
+      .fn<MessagesDataSource['load']>()
+      .mockRejectedValueOnce(new Error('secret URL and recipient credential'))
+      .mockResolvedValueOnce(snapshot);
+    render(<MessagesModule instance={owner} dataSource={{ load }} />);
+
+    const alert = await screen.findByRole('alert');
+    expect(alert.textContent).toContain('Messages data could not be loaded.');
+    expect(alert.textContent).not.toContain('secret URL');
+    await user.click(screen.getByRole('button', { name: 'Retry loading Messages' }));
+    expect(await screen.findByText('Primary modem')).toBeTruthy();
+    expect(load).toHaveBeenCalledTimes(2);
+  });
+
+  it('retains only the same owner last-good snapshot during refresh and after refresh failure', async () => {
+    const user = userEvent.setup();
+    const load = vi
+      .fn<MessagesDataSource['load']>()
+      .mockResolvedValueOnce(snapshot)
+      .mockRejectedValueOnce(new Error('unsafe detail'))
+      .mockResolvedValueOnce({ ...snapshot, devices: [{ label: 'Replacement modem', total: 4 }] });
+    const source = { load };
+    const { rerender } = render(
+      <MessagesModule instance={owner} dataSource={source} refreshSignal={0} />,
+    );
+    expect(await screen.findByText('Primary modem')).toBeTruthy();
+
+    rerender(<MessagesModule instance={owner} dataSource={source} refreshSignal={1} />);
+    expect(screen.getByText('Primary modem')).toBeTruthy();
+    expect((await screen.findByRole('alert')).textContent).toMatch(/showing the last known/i);
+    expect(screen.getByText('Primary modem')).toBeTruthy();
+    await user.click(screen.getByRole('button', { name: 'Retry loading Messages' }));
+    expect(await screen.findByText('Replacement modem')).toBeTruthy();
+  });
+
+  it('aborts replaced reads and fences late responses from another owner', async () => {
+    const alpha = deferredSource();
+    const bravo = deferredSource();
+    const load = vi.fn<MessagesDataSource['load']>((instanceId, signal) =>
+      instanceId === 'alpha'
+        ? alpha.source.load(instanceId, signal)
+        : bravo.source.load(instanceId, signal),
+    );
+    const source = { load };
+    const { rerender } = render(<MessagesModule instance={owner} dataSource={source} />);
+    const alphaSignal = load.mock.calls[0]?.[1];
+
+    rerender(
+      <MessagesModule instance={{ ...owner, id: 'bravo', name: 'Bravo' }} dataSource={source} />,
+    );
+    expect(alphaSignal?.aborted).toBe(true);
+    expect(screen.queryByText('Primary modem')).toBeNull();
+    alpha.resolve(snapshot);
+    bravo.resolve({ ...snapshot, devices: [{ label: 'Bravo modem', total: 9 }] });
+    expect(await screen.findByText('Bravo modem')).toBeTruthy();
+    expect(screen.queryByText('Primary modem')).toBeNull();
+  });
+
+  it('marks owner-declared stale data while preserving aggregates', async () => {
+    render(
+      <MessagesModule
+        instance={{ ...owner, freshness: 'stale' }}
+        dataSource={{ load: async () => snapshot }}
+      />,
+    );
+    expect((await screen.findByRole('status', { name: 'Messages freshness' })).textContent).toMatch(
+      /stale/i,
+    );
+    expect(screen.getByText('Primary modem')).toBeTruthy();
+  });
+});
diff --git a/apps/web/src/instances/messages-module.tsx b/apps/web/src/instances/messages-module.tsx
new file mode 100644
index 0000000..7292064
--- /dev/null
+++ b/apps/web/src/instances/messages-module.tsx
@@ -0,0 +1,247 @@
+import { useEffect, useRef, useState, type ReactNode } from 'react';
+
+import type { InstanceContext } from '../app-shell.js';
+
+/** Bounded primitives permitted at the Messages presentation boundary. */
+export type MessageMetadataValue = string | number | boolean | null;
+
+/** Aggregate SMS metadata only. Message bodies, content, recipients, and credentials are absent. */
+export interface SmsAggregate {
+  readonly total?: number | null;
+  readonly inbound?: number | null;
+  readonly outbound?: number | null;
+  readonly unread?: number | null;
+  readonly failed?: number | null;
+  readonly queued?: number | null;
+  readonly lastActivityAt?: string | null;
+}
+
+/** Non-sensitive device identity/status and aggregate counts only. */
+export interface DeviceMessageAggregate extends SmsAggregate {
+  readonly deviceId?: string | null;
+  readonly label?: string | null;
+  readonly state?: string | null;
+}
+
+export interface MessagesSnapshot {
+  readonly observedAt?: string;
+  readonly sms: SmsAggregate;
+  readonly devices: readonly DeviceMessageAggregate[];
+}
+
+export interface MessagesDataSource {
+  /** Supplied by the authenticated owner; this isolated module defines no network endpoint. */
+  load(instanceId: string, signal: AbortSignal): Promise<MessagesSnapshot>;
+}
+
+export interface MessagesModuleProps {
+  readonly instance: InstanceContext;
+  readonly dataSource?: MessagesDataSource;
+  /** Change this owner-provided value to request another read. */
+  readonly refreshSignal?: unknown;
+}
+
+type ReadState =
+  | { kind: 'idle'; ownerId: string }
+  | { kind: 'loading'; ownerId: string; snapshot?: MessagesSnapshot }
+  | { kind: 'ready'; ownerId: string; snapshot: MessagesSnapshot }
+  | { kind: 'error'; ownerId: string; snapshot?: MessagesSnapshot };
+
+const SAFE_LOAD_ERROR = 'Messages data could not be loaded.';
+
+const AGGREGATE_FIELDS = [
+  ['Total', 'total'],
+  ['Inbound', 'inbound'],
+  ['Outbound', 'outbound'],
+  ['Unread', 'unread'],
+  ['Failed', 'failed'],
+  ['Queued', 'queued'],
+  ['Last activity', 'lastActivityAt'],
+] as const;
+
+function display(value: MessageMetadataValue | undefined): string {
+  return value == null ? 'Unavailable' : String(value);
+}
+
+function Fields({
+  values,
+}: {
+  values: readonly (readonly [label: string, value: MessageMetadataValue | undefined])[];
+}) {
+  return (
+    <dl>
+      {values.map(([label, value]) => (
+        <div key={label}>
+          <dt>{label}</dt>
+          <dd>{display(value)}</dd>
+        </div>
+      ))}
+    </dl>
+  );
+}
+
+function Section({ label, children }: { label: string; children: ReactNode }) {
+  return (
+    <section className="messages-card" aria-label={label}>
+      <h2>{label}</h2>
+      {children}
+    </section>
+  );
+}
+
+function aggregateFields(
+  aggregate: SmsAggregate,
+): readonly (readonly [string, MessageMetadataValue | undefined])[] {
+  // This constant-key projection is the presentation allowlist. Never enumerate source objects.
+  return AGGREGATE_FIELDS.map(([label, key]) => [label, aggregate[key]] as const);
+}
+
+function SnapshotView({ snapshot }: { snapshot: MessagesSnapshot }) {
+  return (
+    <>
+      {snapshot.observedAt ? <p>Observed {snapshot.observedAt}</p> : null}
+      <p>Aggregate metadata only; sensitive payload and addressing details are excluded.</p>
+      <div className="messages-grid">
+        <Section label="SMS aggregate">
+          <Fields values={aggregateFields(snapshot.sms)} />
+        </Section>
+        <Section label="Device message aggregates">
+          {snapshot.devices.length ? (
+            snapshot.devices.map((device, index) => (
+              <article key={`${device.deviceId ?? device.label ?? 'device'}-${index}`}>
+                <Fields
+                  values={[
+                    ['Device ID', device.deviceId],
+                    ['Label', device.label],
+                    ['State', device.state],
+                    ...aggregateFields(device),
+                  ]}
+                />
+              </article>
+            ))
+          ) : (
+            <p>No device message aggregates were supplied.</p>
+          )}
+        </Section>
+      </div>
+      <section className="state-panel" aria-label="Messages actions">
+        <h2>Messages actions</h2>
+        <p>Sending, deleting, and changing messages are unavailable in this read-only module.</p>
+      </section>
+    </>
+  );
+}
+
+export function MessagesModule({ instance, dataSource, refreshSignal }: MessagesModuleProps) {
+  const requestOwner = useRef(0);
+  const [retry, setRetry] = useState(0);
+  const [state, setState] = useState<ReadState>({ kind: 'idle', ownerId: instance.id });
+
+  useEffect(() => {
+    const request = ++requestOwner.current;
+    const ownerId = instance.id;
+    const controller = new AbortController();
+
+    if (instance.authentication !== 'authenticated' || !dataSource) {
+      setState({ kind: 'idle', ownerId });
+      return () => controller.abort();
+    }
+
+    setState((current) => ({
+      kind: 'loading',
+      ownerId,
+      ...(current.ownerId === ownerId &&
+      (current.kind === 'ready' || current.kind === 'error') &&
+      current.snapshot
+        ? { snapshot: current.snapshot }
+        : {}),
+    }));
+
+    void dataSource.load(ownerId, controller.signal).then(
+      (snapshot) => {
+        if (request === requestOwner.current && !controller.signal.aborted) {
+          setState({ kind: 'ready', ownerId, snapshot });
+        }
+      },
+      (_reason: unknown) => {
+        void _reason;
+        if (request === requestOwner.current && !controller.signal.aborted) {
+          setState((current) => ({
+            kind: 'error',
+            ownerId,
+            ...(current.ownerId === ownerId && current.kind === 'loading' && current.snapshot
+              ? { snapshot: current.snapshot }
+              : {}),
+          }));
+        }
+      },
+    );
+
+    return () => controller.abort();
+  }, [dataSource, instance.authentication, instance.id, refreshSignal, retry]);
+
+  if (instance.authentication !== 'authenticated') {
+    return (
+      <div className="state-panel state-error" role="alert">
+        Authentication is required before Messages data can be read for this instance.
+      </div>
+    );
+  }
+
+  if (!dataSource) {
+    return (
+      <div className="state-panel" role="status" aria-label="Messages unavailable">
+        No safe Messages read data source is available. This console will not invent or call an
+        uncontracted production endpoint.
+      </div>
+    );
+  }
+
+  const retainedSnapshot =
+    state.ownerId === instance.id && (state.kind === 'loading' || state.kind === 'error')
+      ? state.snapshot
+      : undefined;
+
+  if ((state.kind === 'idle' || state.kind === 'loading') && !retainedSnapshot) {
+    return (
+      <p role="status" aria-label="Messages loading status">
+        Loading Messages…
+      </p>
+    );
+  }
+
+  if (state.kind === 'error' && !retainedSnapshot) {
+    return (
+      <div className="state-panel state-error" role="alert">
+        <p>Unable to load Messages: {SAFE_LOAD_ERROR}</p>
+        <button type="button" onClick={() => setRetry((value) => value + 1)}>
+          Retry loading Messages
+        </button>
+      </div>
+    );
+  }
+
+  const currentSnapshot =
+    state.kind === 'ready' && state.ownerId === instance.id ? state.snapshot : retainedSnapshot;
+  if (!currentSnapshot) return null;
+
+  return (
+    <div className="messages-module">
+      {state.kind === 'loading' ? <p role="status">Refreshing Messages…</p> : null}
+      {state.kind === 'error' ? (
+        <div className="state-panel state-error" role="alert">
+          <p>Refresh failed; showing the last known Messages data.</p>
+          <button type="button" onClick={() => setRetry((value) => value + 1)}>
+            Retry loading Messages
+          </button>
+        </div>
+      ) : null}
+      {instance.freshness !== 'fresh' ? (
+        <p className="state-panel" role="status" aria-label="Messages freshness">
+          Messages data is {instance.freshness}; verify freshness before relying on these values.
+        </p>
+      ) : null}
+      <SnapshotView snapshot={currentSnapshot} />
+    </div>
+  );
+}