diff --git a/packages/mosaic/src/cli.ts b/packages/mosaic/src/cli.ts
index e885b3e..7bf50ae 100644
--- a/packages/mosaic/src/cli.ts
+++ b/packages/mosaic/src/cli.ts
@@ -10,6 +10,7 @@ import { registerMemoryCommand } from '@mosaicstack/memory';
 import { registerQualityRails } from '@mosaicstack/quality-rails';
 import { registerQueueCommand } from '@mosaicstack/queue';
 import { registerStorageCommand } from '@mosaicstack/storage';
+import { registerTelemetryCommand } from './commands/telemetry.js';
 import { registerAgentCommand } from './commands/agent.js';
 import { registerConfigCommand } from './commands/config.js';
 import { registerMissionCommand } from './commands/mission.js';
@@ -382,6 +383,10 @@ registerQueueCommand(program);
 
 registerStorageCommand(program);
 
+// ─── telemetry ───────────────────────────────────────────────────────────────
+
+registerTelemetryCommand(program);
+
 // ─── update ─────────────────────────────────────────────────────────────
 
 program
diff --git a/packages/mosaic/src/commands/telemetry.spec.ts b/packages/mosaic/src/commands/telemetry.spec.ts
new file mode 100644
index 0000000..9e5b2da
--- /dev/null
+++ b/packages/mosaic/src/commands/telemetry.spec.ts
@@ -0,0 +1,426 @@
+/**
+ * CU-06-05 — Vitest tests for mosaic telemetry command
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { Command } from 'commander';
+import { registerTelemetryCommand } from './telemetry.js';
+import type { TelemetryConsent } from '../telemetry/consent-store.js';
+
+// ─── module mocks ─────────────────────────────────────────────────────────────
+
+// Mock consent-store so tests don't touch the filesystem.
+const mockConsent: TelemetryConsent = {
+  remoteEnabled: false,
+  optedInAt: null,
+  optedOutAt: null,
+  lastUploadAt: null,
+};
+
+vi.mock('../telemetry/consent-store.js', () => ({
+  readConsent: vi.fn(() => ({ ...mockConsent })),
+  writeConsent: vi.fn(),
+  optIn: vi.fn(() => ({
+    ...mockConsent,
+    remoteEnabled: true,
+    optedInAt: '2026-01-01T00:00:00.000Z',
+  })),
+  optOut: vi.fn(() => ({
+    ...mockConsent,
+    remoteEnabled: false,
+    optedOutAt: '2026-01-01T00:00:00.000Z',
+  })),
+  recordUpload: vi.fn(),
+}));
+
+// Mock the telemetry client shim.
+const mockClientInstance = {
+  init: vi.fn(),
+  captureEvent: vi.fn(),
+  upload: vi.fn().mockResolvedValue(undefined),
+  shutdown: vi.fn().mockResolvedValue(undefined),
+};
+
+vi.mock('../telemetry/client-shim.js', () => ({
+  getTelemetryClient: vi.fn(() => mockClientInstance),
+  setTelemetryClient: vi.fn(),
+  resetTelemetryClient: vi.fn(),
+}));
+
+// Mock @clack/prompts so tests don't require stdin.
+vi.mock('@clack/prompts', () => ({
+  confirm: vi.fn().mockResolvedValue(true),
+  intro: vi.fn(),
+  outro: vi.fn(),
+  isCancel: vi.fn().mockReturnValue(false),
+  cancel: vi.fn(),
+}));
+
+// ─── helpers ──────────────────────────────────────────────────────────────────
+
+function buildProgram(): Command {
+  const program = new Command();
+  program.exitOverride();
+  registerTelemetryCommand(program);
+  return program;
+}
+
+function getTelemetryCmd(program: Command): Command {
+  const found = program.commands.find((c) => c.name() === 'telemetry');
+  if (!found) throw new Error('telemetry command not found');
+  return found;
+}
+
+function getLocalCmd(telemetryCmd: Command): Command {
+  const found = telemetryCmd.commands.find((c) => c.name() === 'local');
+  if (!found) throw new Error('local subcommand not found');
+  return found;
+}
+
+// ─── CU-06-05 a: command structure smoke test ─────────────────────────────────
+
+describe('registerTelemetryCommand — structure', () => {
+  it('registers a "telemetry" command on the program', () => {
+    const program = buildProgram();
+    const names = program.commands.map((c) => c.name());
+    expect(names).toContain('telemetry');
+  });
+
+  it('registers the expected top-level subcommands', () => {
+    const program = buildProgram();
+    const tel = getTelemetryCmd(program);
+    const subs = tel.commands.map((c) => c.name()).sort();
+    expect(subs).toEqual(['local', 'opt-in', 'opt-out', 'status', 'test', 'upload']);
+  });
+
+  it('registers all three local subcommands', () => {
+    const program = buildProgram();
+    const local = getLocalCmd(getTelemetryCmd(program));
+    const subs = local.commands.map((c) => c.name()).sort();
+    expect(subs).toEqual(['jaeger', 'status', 'tail']);
+  });
+});
+
+// ─── CU-06-05 b: opt-in / opt-out ────────────────────────────────────────────
+
+describe('telemetry opt-in', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+
+    // Provide disabled consent so opt-in path is taken.
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: false,
+      optedInAt: null,
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+    vi.mocked(store.optIn).mockReturnValue({
+      remoteEnabled: true,
+      optedInAt: '2026-01-01T00:00:00.000Z',
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+
+    const clack = await import('@clack/prompts');
+    vi.mocked(clack.confirm).mockResolvedValue(true);
+    vi.mocked(clack.isCancel).mockReturnValue(false);
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+  });
+
+  it('calls optIn() when user confirms', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'opt-in']);
+
+    const store = await import('../telemetry/consent-store.js');
+    expect(vi.mocked(store.optIn)).toHaveBeenCalled();
+  });
+
+  it('does not call optIn() when user cancels', async () => {
+    const clack = await import('@clack/prompts');
+    vi.mocked(clack.confirm).mockResolvedValue(false);
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'opt-in']);
+
+    const store = await import('../telemetry/consent-store.js');
+    expect(vi.mocked(store.optIn)).not.toHaveBeenCalled();
+  });
+});
+
+describe('telemetry opt-out', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: true,
+      optedInAt: '2026-01-01T00:00:00.000Z',
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+    vi.mocked(store.optOut).mockReturnValue({
+      remoteEnabled: false,
+      optedInAt: '2026-01-01T00:00:00.000Z',
+      optedOutAt: '2026-02-01T00:00:00.000Z',
+      lastUploadAt: null,
+    });
+
+    const clack = await import('@clack/prompts');
+    vi.mocked(clack.confirm).mockResolvedValue(true);
+    vi.mocked(clack.isCancel).mockReturnValue(false);
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+  });
+
+  it('calls optOut() when user confirms', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'opt-out']);
+
+    const store = await import('../telemetry/consent-store.js');
+    expect(vi.mocked(store.optOut)).toHaveBeenCalled();
+  });
+
+  it('does not call optOut() when already disabled', async () => {
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: false,
+      optedInAt: null,
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'opt-out']);
+    expect(vi.mocked(store.optOut)).not.toHaveBeenCalled();
+  });
+});
+
+// ─── CU-06-05 c: status ──────────────────────────────────────────────────────
+
+describe('telemetry status', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+  });
+
+  it('shows disabled state when remote upload is off', async () => {
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: false,
+      optedInAt: null,
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'status']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('false');
+    expect(output).toContain('(never)');
+  });
+
+  it('shows enabled state and timestamps when opted in', async () => {
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: true,
+      optedInAt: '2026-01-01T00:00:00.000Z',
+      optedOutAt: null,
+      lastUploadAt: '2026-03-01T00:00:00.000Z',
+    });
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'status']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('true');
+    expect(output).toContain('2026-01-01');
+    expect(output).toContain('2026-03-01');
+  });
+
+  it('shows dry-run banner when MOSAIC_TELEMETRY_DRY_RUN=1', async () => {
+    process.env['MOSAIC_TELEMETRY_DRY_RUN'] = '1';
+
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: false,
+      optedInAt: null,
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'status']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('[dry-run]');
+
+    delete process.env['MOSAIC_TELEMETRY_DRY_RUN'];
+  });
+});
+
+// ─── CU-06-05 d: test / upload — dry-run assertions ──────────────────────────
+
+describe('telemetry test (dry-run)', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+  });
+
+  it('prints dry-run banner and does not call upload()', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'test']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('[dry-run]');
+    expect(mockClientInstance.upload).not.toHaveBeenCalled();
+  });
+
+  it('calls captureEvent() with a mosaic.cli.test event', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'test']);
+
+    expect(mockClientInstance.captureEvent).toHaveBeenCalledWith(
+      expect.objectContaining({ name: 'mosaic.cli.test' }),
+    );
+  });
+
+  it('does not make network calls in dry-run mode', async () => {
+    const fetchSpy = vi.spyOn(globalThis, 'fetch').mockResolvedValue(new Response());
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'test']);
+
+    expect(fetchSpy).not.toHaveBeenCalled();
+    fetchSpy.mockRestore();
+  });
+});
+
+describe('telemetry upload (dry-run default)', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+
+    // Remote disabled by default.
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: false,
+      optedInAt: null,
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+    delete process.env['MOSAIC_TELEMETRY_DRY_RUN'];
+    delete process.env['MOSAIC_TELEMETRY_ENDPOINT'];
+  });
+
+  it('prints dry-run banner when remote upload is disabled', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'upload']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('[dry-run]');
+    expect(mockClientInstance.upload).not.toHaveBeenCalled();
+  });
+
+  it('prints dry-run banner when MOSAIC_TELEMETRY_DRY_RUN=1 even if opted in', async () => {
+    process.env['MOSAIC_TELEMETRY_DRY_RUN'] = '1';
+    process.env['MOSAIC_TELEMETRY_ENDPOINT'] = 'http://example.com/telemetry';
+
+    const store = await import('../telemetry/consent-store.js');
+    vi.mocked(store.readConsent).mockReturnValue({
+      remoteEnabled: true,
+      optedInAt: '2026-01-01T00:00:00.000Z',
+      optedOutAt: null,
+      lastUploadAt: null,
+    });
+
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'upload']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('[dry-run]');
+    expect(mockClientInstance.upload).not.toHaveBeenCalled();
+  });
+});
+
+// ─── local subcommand smoke tests ─────────────────────────────────────────────
+
+describe('telemetry local tail', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+  });
+
+  it('prints Jaeger UI URL and docker compose hint', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'local', 'tail']);
+
+    const output = consoleSpy.mock.calls.map((c) => c[0] as string).join('\n');
+    expect(output).toContain('Jaeger');
+    expect(output).toContain('docker compose');
+  });
+});
+
+describe('telemetry local jaeger', () => {
+  let consoleSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    consoleSpy = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+    delete process.env['JAEGER_UI_URL'];
+  });
+
+  afterEach(() => {
+    consoleSpy.mockRestore();
+  });
+
+  it('prints the default Jaeger URL', async () => {
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'local', 'jaeger']);
+    expect(consoleSpy).toHaveBeenCalledWith('http://localhost:16686');
+  });
+
+  it('respects JAEGER_UI_URL env var', async () => {
+    process.env['JAEGER_UI_URL'] = 'http://jaeger.example.com:16686';
+    const program = buildProgram();
+    await program.parseAsync(['node', 'mosaic', 'telemetry', 'local', 'jaeger']);
+    expect(consoleSpy).toHaveBeenCalledWith('http://jaeger.example.com:16686');
+    delete process.env['JAEGER_UI_URL'];
+  });
+});
diff --git a/packages/mosaic/src/commands/telemetry.ts b/packages/mosaic/src/commands/telemetry.ts
new file mode 100644
index 0000000..3a03504
--- /dev/null
+++ b/packages/mosaic/src/commands/telemetry.ts
@@ -0,0 +1,355 @@
+/**
+ * mosaic telemetry — CU-06-02 (local) + CU-06-03 (remote)
+ *
+ * Local half:  mosaic telemetry local {status, tail, jaeger}
+ * Remote half: mosaic telemetry {status, opt-in, opt-out, test, upload}
+ *
+ * Remote upload is DISABLED by default (dry-run mode).
+ * Per session-1 decision: ship upload/test in dry-run-only mode until
+ * the mosaicstack.dev server endpoint is live.
+ *
+ * Telemetry client: uses a forward-compat shim (see telemetry/client-shim.ts)
+ * because @mosaicstack/telemetry-client-js is not yet published.
+ */
+
+import type { Command } from 'commander';
+import { confirm, intro, outro, isCancel, cancel } from '@clack/prompts';
+import { DEFAULT_MOSAIC_HOME } from '../constants.js';
+import { getTelemetryClient } from '../telemetry/client-shim.js';
+import { readConsent, optIn, optOut, recordUpload } from '../telemetry/consent-store.js';
+
+// ─── helpers ─────────────────────────────────────────────────────────────────
+
+function getMosaicHome(): string {
+  return process.env['MOSAIC_HOME'] ?? DEFAULT_MOSAIC_HOME;
+}
+
+function isDryRun(): boolean {
+  return process.env['MOSAIC_TELEMETRY_DRY_RUN'] === '1';
+}
+
+/** Try to open a URL — best-effort, does not fail if unsupported. */
+async function tryOpenUrl(url: string): Promise<void> {
+  try {
+    const { spawn } = await import('node:child_process');
+    // `start` is a Windows shell builtin — must be invoked via cmd /c.
+    const [bin, args] =
+      process.platform === 'darwin'
+        ? (['open', [url]] as [string, string[]])
+        : process.platform === 'win32'
+          ? (['cmd', ['/c', 'start', '', url]] as [string, string[]])
+          : (['xdg-open', [url]] as [string, string[]]);
+    spawn(bin, args, { detached: true, stdio: 'ignore' }).unref();
+  } catch {
+    // Best-effort — silently skip if unavailable.
+    console.log(`Open this URL in your browser: ${url}`);
+  }
+}
+
+// ─── local subcommands ───────────────────────────────────────────────────────
+
+function registerLocalCommand(parent: Command): void {
+  const local = parent
+    .command('local')
+    .description('Inspect the local OpenTelemetry stack')
+    .configureHelp({ sortSubcommands: true });
+
+  // ── telemetry local status ──────────────────────────────────────────────
+
+  local
+    .command('status')
+    .description('Report reachability of the local OTEL collector endpoint')
+    .action(async () => {
+      const endpoint = process.env['OTEL_EXPORTER_OTLP_ENDPOINT'] ?? 'http://localhost:4318';
+      const serviceName = process.env['OTEL_SERVICE_NAME'] ?? 'mosaic-gateway';
+      const exportInterval = '15000ms'; // matches tracing.ts PeriodicExportingMetricReader
+
+      console.log(`OTEL endpoint:     ${endpoint}`);
+      console.log(`Service name:      ${serviceName}`);
+      console.log(`Export interval:   ${exportInterval}`);
+      console.log('');
+
+      try {
+        const response = await fetch(endpoint, {
+          method: 'GET',
+          signal: AbortSignal.timeout(3000),
+        });
+        // OTLP collector typically returns 404 for GET on the root path —
+        // but a response means it's listening.
+        console.log(`Status: reachable (HTTP ${String(response.status)})`);
+      } catch (err) {
+        const msg = err instanceof Error ? err.message : String(err);
+        console.log(`Status: unreachable — ${msg}`);
+        console.log('');
+        console.log('Hint: start the local stack with `docker compose up -d`');
+      }
+    });
+
+  // ── telemetry local tail ────────────────────────────────────────────────
+
+  local
+    .command('tail')
+    .description('Explain how to view live traces from the local OTEL stack')
+    .action(() => {
+      const jaegerUrl = process.env['JAEGER_UI_URL'] ?? 'http://localhost:16686';
+
+      console.log('OTLP is a push protocol — there is no log tail.');
+      console.log('');
+      console.log('Traces flow: your service → OTEL Collector → Jaeger');
+      console.log('');
+      console.log(`Jaeger UI:  ${jaegerUrl}`);
+      console.log('Run `mosaic telemetry local jaeger` to print the URL (or open it).');
+      console.log('');
+      console.log('For raw collector output:');
+      console.log('  docker compose logs -f otel-collector');
+    });
+
+  // ── telemetry local jaeger ──────────────────────────────────────────────
+
+  local
+    .command('jaeger')
+    .description('Print the Jaeger UI URL (use --open to launch in browser)')
+    .option('--open', 'Open the Jaeger UI in the default browser')
+    .action(async (opts: { open?: boolean }) => {
+      const jaegerUrl = process.env['JAEGER_UI_URL'] ?? 'http://localhost:16686';
+      console.log(jaegerUrl);
+
+      if (opts.open) {
+        await tryOpenUrl(jaegerUrl);
+      }
+    });
+}
+
+// ─── remote subcommands ──────────────────────────────────────────────────────
+
+function registerRemoteStatusCommand(cmd: Command): void {
+  cmd
+    .command('status')
+    .description('Print the remote telemetry upload status and consent state')
+    .action(() => {
+      const mosaicHome = getMosaicHome();
+      const consent = readConsent(mosaicHome);
+      const remoteEndpoint = process.env['MOSAIC_TELEMETRY_ENDPOINT'] ?? '(not configured)';
+      const dryRunActive = isDryRun();
+
+      console.log('Remote telemetry status');
+      console.log('─────────────────────────────────────────────');
+      console.log(`  Remote upload enabled: ${String(consent.remoteEnabled)}`);
+      console.log(`  Remote endpoint:       ${remoteEndpoint}`);
+      if (consent.optedInAt) {
+        console.log(`  Opted in:              ${consent.optedInAt}`);
+      }
+      if (consent.optedOutAt) {
+        console.log(`  Opted out:             ${consent.optedOutAt}`);
+      }
+      if (consent.lastUploadAt) {
+        console.log(`  Last upload:           ${consent.lastUploadAt}`);
+      } else {
+        console.log('  Last upload:           (never)');
+      }
+      if (dryRunActive) {
+        console.log('');
+        console.log('  [dry-run] MOSAIC_TELEMETRY_DRY_RUN=1 is set — uploads are suppressed');
+      }
+      console.log('');
+      console.log('Local OTEL stack always active (see `mosaic telemetry local status`).');
+    });
+}
+
+function registerOptInCommand(cmd: Command): void {
+  cmd
+    .command('opt-in')
+    .description('Enable remote telemetry upload (requires explicit consent)')
+    .action(async () => {
+      const mosaicHome = getMosaicHome();
+      const current = readConsent(mosaicHome);
+
+      if (current.remoteEnabled) {
+        console.log('Remote telemetry upload is already enabled.');
+        console.log(`Opted in: ${current.optedInAt ?? '(unknown)'}`);
+        return;
+      }
+
+      intro('Mosaic remote telemetry opt-in');
+
+      console.log('');
+      console.log('What gets uploaded:');
+      console.log('  - CLI command names and completion status (no arguments / values)');
+      console.log('  - Error types (no stack traces or user data)');
+      console.log('  - Mosaic version and platform metadata');
+      console.log('');
+      console.log('What is NEVER uploaded:');
+      console.log('  - File contents, code, or credentials');
+      console.log('  - Personal information or agent conversation data');
+      console.log('');
+      console.log('Note: remote upload is currently in dry-run mode until');
+      console.log('      the mosaicstack.dev telemetry endpoint is live.');
+      console.log('');
+
+      const confirmed = await confirm({
+        message: 'Enable remote telemetry upload?',
+      });
+
+      if (isCancel(confirmed) || !confirmed) {
+        cancel('Opt-in cancelled — no changes made.');
+        return;
+      }
+
+      const consent = optIn(mosaicHome);
+      outro(`Remote telemetry enabled. Opted in at ${consent.optedInAt ?? ''}`);
+    });
+}
+
+function registerOptOutCommand(cmd: Command): void {
+  cmd
+    .command('opt-out')
+    .description('Disable remote telemetry upload')
+    .action(async () => {
+      const mosaicHome = getMosaicHome();
+      const current = readConsent(mosaicHome);
+
+      if (!current.remoteEnabled) {
+        console.log('Remote telemetry upload is already disabled.');
+        return;
+      }
+
+      intro('Mosaic remote telemetry opt-out');
+      console.log('');
+      console.log('This will disable remote upload of anonymised usage data.');
+      console.log('Local OTEL tracing (to Jaeger) will remain active — it is');
+      console.log('independent of this consent state.');
+      console.log('');
+
+      const confirmed = await confirm({
+        message: 'Disable remote telemetry upload?',
+      });
+
+      if (isCancel(confirmed) || !confirmed) {
+        cancel('Opt-out cancelled — no changes made.');
+        return;
+      }
+
+      const consent = optOut(mosaicHome);
+      outro(`Remote telemetry disabled. Opted out at ${consent.optedOutAt ?? ''}`);
+      console.log('Local OTEL stack (Jaeger) remains active.');
+    });
+}
+
+function registerTestCommand(cmd: Command): void {
+  cmd
+    .command('test')
+    .description('Synthesise a fake event and print the payload that would be sent (dry-run)')
+    .option('--upload', 'Actually upload (requires consent + MOSAIC_TELEMETRY_ENDPOINT)')
+    .action(async (opts: { upload?: boolean }) => {
+      const mosaicHome = getMosaicHome();
+      const consent = readConsent(mosaicHome);
+      const dryRunActive = isDryRun() || !opts.upload;
+
+      if (!dryRunActive && !consent.remoteEnabled) {
+        console.error('Remote upload is not enabled. Run `mosaic telemetry opt-in` first.');
+        process.exit(1);
+      }
+
+      const fakeEvent = {
+        name: 'mosaic.cli.test',
+        properties: {
+          command: 'telemetry test',
+          version: process.env['npm_package_version'] ?? 'unknown',
+          platform: process.platform,
+        },
+        timestamp: new Date().toISOString(),
+      };
+
+      const endpoint = process.env['MOSAIC_TELEMETRY_ENDPOINT'];
+      const client = getTelemetryClient();
+
+      client.init({
+        endpoint,
+        dryRun: dryRunActive,
+        labels: { source: 'mosaic-cli' },
+      });
+
+      client.captureEvent(fakeEvent);
+
+      if (dryRunActive) {
+        console.log('[dry-run] telemetry test — payload that would be sent:');
+        console.log(JSON.stringify(fakeEvent, null, 2));
+        console.log('');
+        console.log('No network call made. Pass --upload to attempt real delivery.');
+      } else {
+        try {
+          await client.upload();
+          recordUpload(mosaicHome);
+          console.log('Event delivered.');
+        } catch (err) {
+          // The shim throws when a real POST is attempted — make it clear nothing was sent.
+          console.error(err instanceof Error ? err.message : String(err));
+          process.exit(1);
+        }
+      }
+    });
+}
+
+function registerUploadCommand(cmd: Command): void {
+  cmd
+    .command('upload')
+    .description('Send pending telemetry events to the remote endpoint')
+    .action(async () => {
+      const mosaicHome = getMosaicHome();
+      const consent = readConsent(mosaicHome);
+      const dryRunActive = isDryRun();
+
+      if (!consent.remoteEnabled) {
+        console.log('[dry-run] telemetry upload — no network call made');
+        console.log('Remote upload is disabled. Run `mosaic telemetry opt-in` to enable.');
+        return;
+      }
+
+      const endpoint = process.env['MOSAIC_TELEMETRY_ENDPOINT'];
+
+      if (dryRunActive || !endpoint) {
+        console.log('[dry-run] telemetry upload — no network call made');
+        if (!endpoint) {
+          console.log('MOSAIC_TELEMETRY_ENDPOINT is not set — running in dry-run mode.');
+        }
+        if (dryRunActive) {
+          console.log('MOSAIC_TELEMETRY_DRY_RUN=1 — uploads suppressed.');
+        }
+        console.log('');
+        console.log('Dry-run is the default until the mosaicstack.dev telemetry endpoint is live.');
+        return;
+      }
+
+      const client = getTelemetryClient();
+      client.init({ endpoint, dryRun: false, labels: { source: 'mosaic-cli' } });
+
+      try {
+        await client.upload();
+        recordUpload(mosaicHome);
+        console.log('Upload complete.');
+      } catch (err) {
+        // The shim throws when a real POST is attempted — make it clear nothing was sent.
+        console.error(err instanceof Error ? err.message : String(err));
+        process.exit(1);
+      }
+    });
+}
+
+// ─── public registration ──────────────────────────────────────────────────────
+
+export function registerTelemetryCommand(program: Command): void {
+  const cmd = program
+    .command('telemetry')
+    .description('Inspect and manage telemetry (local OTEL stack + remote upload)')
+    .configureHelp({ sortSubcommands: true });
+
+  // ── local subgroup ──────────────────────────────────────────────────────
+  registerLocalCommand(cmd);
+
+  // ── remote subcommands ──────────────────────────────────────────────────
+  registerRemoteStatusCommand(cmd);
+  registerOptInCommand(cmd);
+  registerOptOutCommand(cmd);
+  registerTestCommand(cmd);
+  registerUploadCommand(cmd);
+}
diff --git a/packages/mosaic/src/telemetry/client-shim.ts b/packages/mosaic/src/telemetry/client-shim.ts
new file mode 100644
index 0000000..de9e60f
--- /dev/null
+++ b/packages/mosaic/src/telemetry/client-shim.ts
@@ -0,0 +1,132 @@
+/**
+ * Forward-compat shim for @mosaicstack/telemetry-client-js.
+ *
+ * @mosaicstack/telemetry-client-js is not yet published to the Gitea npm
+ * registry (returns 404 as of 2026-04-04). This shim mirrors the minimal
+ * interface that the real client will expose so that all telemetry wiring
+ * can be implemented now and swapped for the real package when it lands.
+ *
+ * TODO: replace this shim with `import { ... } from '@mosaicstack/telemetry-client-js'`
+ *       once the package is published.
+ */
+
+export interface TelemetryEvent {
+  /** Event name / category */
+  name: string;
+  /** Arbitrary key-value payload */
+  properties?: Record<string, unknown>;
+  /** ISO timestamp — defaults to now if omitted */
+  timestamp?: string;
+}
+
+/**
+ * Minimal interface mirroring what @mosaicstack/telemetry-client-js exposes.
+ */
+export interface TelemetryClient {
+  /** Initialise the client (must be called before captureEvent / upload). */
+  init(options: TelemetryClientOptions): void;
+  /** Queue a telemetry event for eventual upload. */
+  captureEvent(event: TelemetryEvent): void;
+  /**
+   * Flush all queued events to the remote endpoint.
+   * In dry-run mode the client must print instead of POST.
+   */
+  upload(): Promise<void>;
+  /** Flush and release resources. */
+  shutdown(): Promise<void>;
+}
+
+export interface TelemetryClientOptions {
+  /** Remote OTLP / telemetry endpoint URL */
+  endpoint?: string;
+  /** Dry-run: print payloads instead of posting */
+  dryRun?: boolean;
+  /** Extra labels attached to every event */
+  labels?: Record<string, string>;
+}
+
+// ─── Shim implementation ─────────────────────────────────────────────────────
+
+/**
+ * A no-network shim that buffers events and pretty-prints them in dry-run mode.
+ * This is the ONLY implementation used until the real package is published.
+ */
+class TelemetryClientShim implements TelemetryClient {
+  private options: TelemetryClientOptions = {};
+  private queue: TelemetryEvent[] = [];
+
+  init(options: TelemetryClientOptions): void {
+    // Merge options without clearing the queue — buffered events must survive
+    // re-initialisation so that `telemetry upload` can flush them.
+    this.options = options;
+  }
+
+  captureEvent(event: TelemetryEvent): void {
+    this.queue.push({
+      ...event,
+      timestamp: event.timestamp ?? new Date().toISOString(),
+    });
+  }
+
+  async upload(): Promise<void> {
+    const isDryRun = this.options.dryRun !== false; // dry-run is default
+
+    if (isDryRun) {
+      console.log('[dry-run] telemetry upload — no network call made');
+      for (const evt of this.queue) {
+        console.log(JSON.stringify({ ...evt, labels: this.options.labels }, null, 2));
+      }
+      this.queue = [];
+      return;
+    }
+
+    // Real upload path — placeholder until real client replaces this shim.
+    const endpoint = this.options.endpoint;
+    if (!endpoint) {
+      console.log('[dry-run] telemetry upload — no endpoint configured, no network call made');
+      for (const evt of this.queue) {
+        console.log(JSON.stringify(evt, null, 2));
+      }
+      this.queue = [];
+      return;
+    }
+
+    // The real client is not yet published — throw so callers know no data
+    // was actually sent. This prevents the CLI from marking an upload as
+    // successful when only the shim is present.
+    // TODO: remove once @mosaicstack/telemetry-client-js replaces this shim.
+    throw new Error(
+      `[shim] telemetry-client-js is not yet available — cannot POST to ${endpoint}. ` +
+        'Remote upload is supported only after the mosaicstack.dev endpoint is live.',
+    );
+  }
+
+  async shutdown(): Promise<void> {
+    await this.upload();
+  }
+}
+
+/** Singleton client instance. */
+let _client: TelemetryClient | null = null;
+
+/** Return (or lazily create) the singleton telemetry client. */
+export function getTelemetryClient(): TelemetryClient {
+  if (!_client) {
+    _client = new TelemetryClientShim();
+  }
+  return _client;
+}
+
+/**
+ * Replace the singleton — used in tests to inject a mock.
+ */
+export function setTelemetryClient(client: TelemetryClient): void {
+  _client = client;
+}
+
+/**
+ * Reset the singleton to null (useful in tests).
+ */
+export function resetTelemetryClient(): void {
+  _client = null;
+}
diff --git a/packages/mosaic/src/telemetry/consent-store.ts b/packages/mosaic/src/telemetry/consent-store.ts
new file mode 100644
index 0000000..b2bc049
--- /dev/null
+++ b/packages/mosaic/src/telemetry/consent-store.ts
@@ -0,0 +1,112 @@
+/**
+ * Persistent consent store for remote telemetry upload.
+ *
+ * State is stored in $MOSAIC_HOME/telemetry.json (not inside the markdown
+ * config files — those are template-rendered and would lose structured data).
+ *
+ * Schema:
+ *   {
+ *     remoteEnabled: boolean,
+ *     optedInAt:     string | null,   // ISO timestamp
+ *     optedOutAt:    string | null,   // ISO timestamp
+ *     lastUploadAt:  string | null    // ISO timestamp
+ *   }
+ */
+
+import { existsSync, readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { atomicWrite } from '../platform/file-ops.js';
+import { DEFAULT_MOSAIC_HOME } from '../constants.js';
+
+export interface TelemetryConsent {
+  remoteEnabled: boolean;
+  optedInAt: string | null;
+  optedOutAt: string | null;
+  lastUploadAt: string | null;
+}
+
+const TELEMETRY_FILE = 'telemetry.json';
+
+const DEFAULT_CONSENT: TelemetryConsent = {
+  remoteEnabled: false,
+  optedInAt: null,
+  optedOutAt: null,
+  lastUploadAt: null,
+};
+
+function consentFilePath(mosaicHome?: string): string {
+  return join(mosaicHome ?? getMosaicHome(), TELEMETRY_FILE);
+}
+
+function getMosaicHome(): string {
+  return process.env['MOSAIC_HOME'] ?? DEFAULT_MOSAIC_HOME;
+}
+
+/**
+ * Read the current consent state. Returns defaults if file doesn't exist.
+ */
+export function readConsent(mosaicHome?: string): TelemetryConsent {
+  const filePath = consentFilePath(mosaicHome);
+  if (!existsSync(filePath)) {
+    return { ...DEFAULT_CONSENT };
+  }
+  try {
+    const raw = readFileSync(filePath, 'utf-8');
+    const parsed = JSON.parse(raw) as Partial<TelemetryConsent>;
+    return {
+      remoteEnabled: parsed.remoteEnabled ?? false,
+      optedInAt: parsed.optedInAt ?? null,
+      optedOutAt: parsed.optedOutAt ?? null,
+      lastUploadAt: parsed.lastUploadAt ?? null,
+    };
+  } catch {
+    return { ...DEFAULT_CONSENT };
+  }
+}
+
+/**
+ * Persist a full or partial consent update.
+ */
+export function writeConsent(update: Partial<TelemetryConsent>, mosaicHome?: string): void {
+  const current = readConsent(mosaicHome);
+  const next: TelemetryConsent = { ...current, ...update };
+  atomicWrite(consentFilePath(mosaicHome), JSON.stringify(next, null, 2) + '\n');
+}
+
+/**
+ * Mark opt-in: enable remote upload and record timestamp.
+ */
+export function optIn(mosaicHome?: string): TelemetryConsent {
+  const now = new Date().toISOString();
+  const next: TelemetryConsent = {
+    remoteEnabled: true,
+    optedInAt: now,
+    optedOutAt: null,
+    lastUploadAt: readConsent(mosaicHome).lastUploadAt,
+  };
+  writeConsent(next, mosaicHome);
+  return next;
+}
+
+/**
+ * Mark opt-out: disable remote upload and record timestamp.
+ */
+export function optOut(mosaicHome?: string): TelemetryConsent {
+  const now = new Date().toISOString();
+  const current = readConsent(mosaicHome);
+  const next: TelemetryConsent = {
+    remoteEnabled: false,
+    optedInAt: current.optedInAt,
+    optedOutAt: now,
+    lastUploadAt: current.lastUploadAt,
+  };
+  writeConsent(next, mosaicHome);
+  return next;
+}
+
+/**
+ * Record a successful upload timestamp.
+ */
+export function recordUpload(mosaicHome?: string): void {
+  writeConsent({ lastUploadAt: new Date().toISOString() }, mosaicHome);
+}