diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 9b8c6fdd7a0c..38b810e139a6 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -3866,6 +3866,12 @@ importers:
 
   projects/packages/premium-analytics:
     dependencies:
+      '@automattic/jetpack-script-data':
+        specifier: workspace:*
+        version: link:../../js-packages/script-data
+      '@wordpress/api-fetch':
+        specifier: ^7.22.0
+        version: 7.46.0
       '@wordpress/boot':
         specifier: 0.13.0
         version: 0.13.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
@@ -3888,18 +3894,45 @@ importers:
         specifier: 18.3.1
         version: 18.3.1(react@18.3.1)
     devDependencies:
+      '@automattic/jetpack-webpack-config':
+        specifier: workspace:*
+        version: link:../../js-packages/webpack-config
       '@babel/core':
         specifier: 7.29.0
         version: 7.29.0
+      '@babel/preset-react':
+        specifier: 7.28.5
+        version: 7.28.5(@babel/core@7.29.0)
+      '@babel/preset-typescript':
+        specifier: 7.28.5
+        version: 7.28.5(@babel/core@7.29.0)
+      '@babel/runtime':
+        specifier: 7.29.2
+        version: 7.29.2
+      '@testing-library/dom':
+        specifier: 10.4.1
+        version: 10.4.1
+      '@testing-library/react':
+        specifier: 16.3.2
+        version: 16.3.2(@testing-library/dom@10.4.1)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@types/jest':
+        specifier: 30.0.0
+        version: 30.0.0
       '@typescript/native-preview':
         specifier: 7.0.0-dev.20260225.1
         version: 7.0.0-dev.20260225.1
       '@wordpress/build':
         specifier: 0.14.0
         version: 0.14.0(@babel/core@7.29.0)(@wordpress/boot@0.13.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1))(@wordpress/route@0.12.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1))(browserslist@4.28.2)
+      babel-jest:
+        specifier: 30.4.1
+        version: 30.4.1(@babel/core@7.29.0)
       browserslist:
         specifier: 4.28.2
         version: 4.28.2
+      jest:
+        specifier: 30.4.2
+        version: 30.4.2
 
   projects/packages/protect-models: {}
 
diff --git a/projects/packages/premium-analytics/changelog/add-site-sync b/projects/packages/premium-analytics/changelog/add-site-sync
new file mode 100644
index 000000000000..78c519e2c855
--- /dev/null
+++ b/projects/packages/premium-analytics/changelog/add-site-sync
@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+Add site-sync package (useSyncStatus hook) and configure apiFetch auth in init.
diff --git a/projects/packages/premium-analytics/jest.config.cjs b/projects/packages/premium-analytics/jest.config.cjs
new file mode 100644
index 000000000000..3769cabf2379
--- /dev/null
+++ b/projects/packages/premium-analytics/jest.config.cjs
@@ -0,0 +1,21 @@
+const baseConfig = require( 'jetpack-js-tools/jest/config.base.js' );
+
+module.exports = {
+	...baseConfig,
+	rootDir: '.',
+	collectCoverageFrom: [
+		'<rootDir>/packages/**/src/**/*.{js,jsx,ts,tsx}',
+		...baseConfig.collectCoverageFrom,
+	],
+	// Compile TS/JSX to CommonJS (rather than leaving native ESM). `jest.mock`
+	// hoisting relies on `require`, which is undefined when `.ts` runs as ESM
+	// under `--experimental-vm-modules`; emitting CJS keeps mocks working without
+	// that flag. Mirrors the shared transform used by js-packages/charts.
+	transform: {
+		...baseConfig.transform,
+		'\\.[jt]sx?$': require( 'jetpack-js-tools/jest/babel-jest-config-factory.js' )(
+			require.resolve
+		),
+	},
+	extensionsToTreatAsEsm: [],
+};
diff --git a/projects/packages/premium-analytics/package.json b/projects/packages/premium-analytics/package.json
index 31d5de969868..65413779079a 100644
--- a/projects/packages/premium-analytics/package.json
+++ b/projects/packages/premium-analytics/package.json
@@ -6,6 +6,7 @@
 	"scripts": {
 		"build": "wp-build && mkdir -p build/modules/boot && cp shims/boot-asset.php build/modules/boot/index.min.asset.php",
 		"build-production": "NODE_ENV=production wp-build && mkdir -p build/modules/boot && cp shims/boot-asset.php build/modules/boot/index.min.asset.php",
+		"test": "jest",
 		"typecheck": "tsgo --noEmit",
 		"watch": "wp-build --watch"
 	},
@@ -29,6 +30,8 @@
 		}
 	},
 	"dependencies": {
+		"@automattic/jetpack-script-data": "workspace:*",
+		"@wordpress/api-fetch": "^7.22.0",
 		"@wordpress/boot": "0.13.0",
 		"@wordpress/data": "10.46.0",
 		"@wordpress/i18n": "^6.9.0",
@@ -38,9 +41,18 @@
 		"react-dom": "18.3.1"
 	},
 	"devDependencies": {
+		"@automattic/jetpack-webpack-config": "workspace:*",
 		"@babel/core": "7.29.0",
+		"@babel/preset-react": "7.28.5",
+		"@babel/preset-typescript": "7.28.5",
+		"@babel/runtime": "7.29.2",
+		"@testing-library/dom": "10.4.1",
+		"@testing-library/react": "16.3.2",
+		"@types/jest": "30.0.0",
 		"@typescript/native-preview": "7.0.0-dev.20260225.1",
 		"@wordpress/build": "0.14.0",
-		"browserslist": "4.28.2"
+		"babel-jest": "30.4.1",
+		"browserslist": "4.28.2",
+		"jest": "30.4.2"
 	}
 }
diff --git a/projects/packages/premium-analytics/packages/init/package.json b/projects/packages/premium-analytics/packages/init/package.json
index 70de0aea9d5b..a9c75f14d5e4 100644
--- a/projects/packages/premium-analytics/packages/init/package.json
+++ b/projects/packages/premium-analytics/packages/init/package.json
@@ -7,6 +7,8 @@
 	"module": "build-module/index.mjs",
 	"wpScriptModuleExports": "./build-module/index.mjs",
 	"dependencies": {
+		"@automattic/jetpack-script-data": "workspace:*",
+		"@wordpress/api-fetch": "^7.22.0",
 		"@wordpress/boot": "0.13.0",
 		"@wordpress/data": "10.46.0",
 		"@wordpress/icons": "^13.0.0"
diff --git a/projects/packages/premium-analytics/packages/init/src/index.ts b/projects/packages/premium-analytics/packages/init/src/index.ts
index f4a5da3c37c8..3955304e7c49 100644
--- a/projects/packages/premium-analytics/packages/init/src/index.ts
+++ b/projects/packages/premium-analytics/packages/init/src/index.ts
@@ -1,6 +1,8 @@
 /**
  * External dependencies
  */
+import { getScriptData } from '@automattic/jetpack-script-data';
+import apiFetch from '@wordpress/api-fetch';
 import { store as bootStore } from '@wordpress/boot';
 import { dispatch } from '@wordpress/data';
 import { chartBar } from '@wordpress/icons';
@@ -10,6 +12,16 @@ import { chartBar } from '@wordpress/icons';
  * Runs before routes render.
  */
 export async function init(): Promise< void > {
+	// Point apiFetch at this site's REST API and authenticate requests. Required
+	// before any package (e.g. site-sync) calls apiFetch against /jetpack/v4/*.
+	const site = getScriptData()?.site;
+	if ( site?.rest_root ) {
+		apiFetch.use( apiFetch.createRootURLMiddleware( site.rest_root ) );
+	}
+	if ( site?.rest_nonce ) {
+		apiFetch.use( apiFetch.createNonceMiddleware( site.rest_nonce ) );
+	}
+
 	dispatch( bootStore ).updateMenuItem( 'dashboard', {
 		icon: chartBar,
 	} );
diff --git a/projects/packages/premium-analytics/packages/site-sync/package.json b/projects/packages/premium-analytics/packages/site-sync/package.json
new file mode 100644
index 000000000000..bbf6d4b8f2a4
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/package.json
@@ -0,0 +1,18 @@
+{
+	"private": true,
+	"name": "@automattic/jetpack-premium-analytics-site-sync",
+	"version": "0.1.0",
+	"type": "module",
+	"wpScript": true,
+	"module": "build-module/index.mjs",
+	"wpScriptModuleExports": "./build-module/index.mjs",
+	"dependencies": {
+		"@automattic/jetpack-script-data": "workspace:*",
+		"@wordpress/api-fetch": "^7.22.0",
+		"@wordpress/i18n": "^6.9.0",
+		"react": "18.3.1"
+	},
+	"devDependencies": {
+		"@testing-library/react": "16.3.2"
+	}
+}
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/api/fetch-sync-status.ts b/projects/packages/premium-analytics/packages/site-sync/src/api/fetch-sync-status.ts
new file mode 100644
index 000000000000..017c6e5c9a7f
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/api/fetch-sync-status.ts
@@ -0,0 +1,18 @@
+/**
+ * External dependencies
+ */
+import apiFetch from '@wordpress/api-fetch';
+/**
+ * Internal dependencies
+ */
+import { SYNC_STATUS_PATH } from '../constants';
+import type { SyncStatusApiResponse } from '../types';
+
+/**
+ * Fetch the current sync status from Jetpack core.
+ *
+ * @return The current sync status.
+ */
+export function fetchSyncStatus(): Promise< SyncStatusApiResponse > {
+	return apiFetch( { path: SYNC_STATUS_PATH } );
+}
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/api/trigger-full-sync.ts b/projects/packages/premium-analytics/packages/site-sync/src/api/trigger-full-sync.ts
new file mode 100644
index 000000000000..ee16471a2d5b
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/api/trigger-full-sync.ts
@@ -0,0 +1,17 @@
+/**
+ * External dependencies
+ */
+import apiFetch from '@wordpress/api-fetch';
+/**
+ * Internal dependencies
+ */
+import { FULL_SYNC_PATH } from '../constants';
+
+/**
+ * Trigger a Jetpack full sync.
+ *
+ * @return The full-sync trigger response.
+ */
+export function triggerFullSync(): Promise< unknown > {
+	return apiFetch( { path: FULL_SYNC_PATH, method: 'POST' } );
+}
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/constants.ts b/projects/packages/premium-analytics/packages/site-sync/src/constants.ts
new file mode 100644
index 000000000000..a76673f5072c
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/constants.ts
@@ -0,0 +1,20 @@
+/**
+ * Polling interval in milliseconds.
+ */
+export const POLL_INTERVAL = 3_000;
+
+/**
+ * Jetpack core sync status endpoint (queue + full-sync state).
+ */
+export const SYNC_STATUS_PATH = '/jetpack/v4/sync/status';
+
+/**
+ * Jetpack core full-sync trigger endpoint.
+ */
+export const FULL_SYNC_PATH = '/jetpack/v4/sync/full-sync';
+
+/**
+ * Sync-module key whose progress gates the analytics dashboard. Mirrors the
+ * backend default (`Sync_Status_Tracker::ANALYTICS_SYNC_MODULE`).
+ */
+export const ANALYTICS_SYNC_MODULE = 'woocommerce_analytics';
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/hooks/__tests__/use-sync-status.test.ts b/projects/packages/premium-analytics/packages/site-sync/src/hooks/__tests__/use-sync-status.test.ts
new file mode 100644
index 000000000000..5aabc33db11a
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/hooks/__tests__/use-sync-status.test.ts
@@ -0,0 +1,120 @@
+/**
+ * External dependencies
+ */
+import { getScriptData } from '@automattic/jetpack-script-data';
+import { renderHook, act, waitFor } from '@testing-library/react';
+/**
+ * Internal dependencies
+ */
+import { fetchSyncStatus } from '../../api/fetch-sync-status';
+import { triggerFullSync } from '../../api/trigger-full-sync';
+import { useSyncStatus } from '../use-sync-status';
+import type { SyncStatusApiResponse } from '../../types';
+
+jest.mock( '../../api/fetch-sync-status' );
+jest.mock( '../../api/trigger-full-sync' );
+jest.mock( '@automattic/jetpack-script-data' );
+
+const mockFetch = fetchSyncStatus as jest.MockedFunction< typeof fetchSyncStatus >;
+const mockTrigger = triggerFullSync as jest.MockedFunction< typeof triggerFullSync >;
+const mockScriptData = getScriptData as jest.MockedFunction< typeof getScriptData >;
+
+/**
+ * Build a raw sync-status API response for tests.
+ *
+ * @param overrides - Fields to override on the default running-analytics response.
+ * @return A raw sync-status API response.
+ */
+function rawStatus( overrides: Partial< SyncStatusApiResponse > = {} ): SyncStatusApiResponse {
+	return {
+		started: true,
+		finished: false,
+		progress: { woocommerce_analytics: { sent: 1, total: 2 } },
+		...overrides,
+	};
+}
+
+beforeEach( () => {
+	jest.useFakeTimers();
+	// Default: milestone not set.
+	mockScriptData.mockReturnValue( {
+		premium_analytics: { initial_full_sync_finished: 0 },
+	} as ReturnType< typeof getScriptData > );
+	mockFetch.mockResolvedValue( rawStatus() );
+	mockTrigger.mockResolvedValue( undefined );
+} );
+
+afterEach( () => {
+	jest.clearAllTimers();
+	jest.useRealTimers();
+	jest.clearAllMocks();
+} );
+
+describe( 'useSyncStatus', () => {
+	it( 'exposes normalized progress after the first poll', async () => {
+		const { result } = renderHook( () => useSyncStatus() );
+
+		await waitFor( () => expect( result.current.isLoading ).toBe( false ) );
+		expect( result.current.data?.percentage ).toBe( 50 );
+		expect( result.current.data?.isRunning ).toBe( true );
+		expect( result.current.error ).toBeNull();
+	} );
+
+	it( 'reports complete and stops polling when analytics reaches 100', async () => {
+		mockFetch.mockResolvedValue(
+			rawStatus( {
+				finished: true,
+				progress: { woocommerce_analytics: { sent: 2, total: 2 } },
+			} )
+		);
+		const { result } = renderHook( () => useSyncStatus() );
+
+		await waitFor( () => expect( result.current.isComplete ).toBe( true ) );
+		const callsAfterComplete = mockFetch.mock.calls.length;
+
+		await act( async () => {
+			jest.advanceTimersByTime( 10_000 );
+		} );
+		expect( mockFetch.mock.calls ).toHaveLength( callsAfterComplete );
+	} );
+
+	it( 'flags a stalled sync with an error', async () => {
+		mockFetch.mockResolvedValue(
+			rawStatus( {
+				started: true,
+				finished: true,
+				progress: { woocommerce_analytics: { sent: 1, total: 2 } },
+			} )
+		);
+		const { result } = renderHook( () => useSyncStatus() );
+
+		await waitFor( () => expect( result.current.isStalled ).toBe( true ) );
+		expect( result.current.error ).toBeInstanceOf( Error );
+	} );
+
+	it( 'surfaces fetch errors and never rejects triggerSync', async () => {
+		mockFetch.mockRejectedValueOnce( new Error( 'boom' ) );
+		const { result } = renderHook( () => useSyncStatus() );
+
+		await waitFor( () => expect( result.current.error ).toBeInstanceOf( Error ) );
+		expect( result.current.error?.message ).toBe( 'boom' );
+
+		// triggerSync resolves even if the trigger call fails.
+		mockTrigger.mockRejectedValueOnce( new Error( 'nope' ) );
+		await act( async () => {
+			await result.current.triggerSync();
+		} );
+		expect( result.current.error?.message ).toBe( 'nope' );
+	} );
+
+	it( 'starts complete and skips polling when the milestone is set', async () => {
+		mockScriptData.mockReturnValue( {
+			premium_analytics: { initial_full_sync_finished: 1_700_000_000 },
+		} as ReturnType< typeof getScriptData > );
+
+		const { result } = renderHook( () => useSyncStatus() );
+
+		await waitFor( () => expect( result.current.isComplete ).toBe( true ) );
+		expect( mockFetch ).not.toHaveBeenCalled();
+	} );
+} );
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/hooks/use-sync-status.ts b/projects/packages/premium-analytics/packages/site-sync/src/hooks/use-sync-status.ts
new file mode 100644
index 000000000000..8c79e2248a7d
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/hooks/use-sync-status.ts
@@ -0,0 +1,127 @@
+/**
+ * External dependencies
+ */
+import { getScriptData } from '@automattic/jetpack-script-data';
+import { __ } from '@wordpress/i18n';
+import { useState, useEffect, useRef, useCallback } from 'react';
+/**
+ * Internal dependencies
+ */
+import { fetchSyncStatus } from '../api/fetch-sync-status';
+import { triggerFullSync } from '../api/trigger-full-sync';
+import { POLL_INTERVAL } from '../constants';
+import { toSyncStatus, isSyncComplete, isSyncStalled } from '../status';
+import type { SyncStatus, UseSyncStatusReturn } from '../types';
+
+/**
+ * Read the page-load milestone injected by the backend Sync_Status_Tracker.
+ * Static for the lifetime of the page — never re-read while polling.
+ *
+ * @return The initial full-sync milestone (unix ts), or 0 if never finished.
+ */
+function readMilestone(): number {
+	return getScriptData()?.premium_analytics?.initial_full_sync_finished ?? 0;
+}
+
+/**
+ * Polls Jetpack's sync status and returns analytics-scoped progress.
+ *
+ * Polling auto-stops when the sync is complete, stalled, or errors. If the
+ * page-load milestone is already set, the dashboard is gated open immediately
+ * and no polling occurs. `triggerSync` POSTs the full-sync trigger and resumes
+ * polling; it never rejects (failures surface via `error`).
+ *
+ * @return The current sync state plus a `triggerSync` action.
+ */
+export function useSyncStatus(): UseSyncStatusReturn {
+	const milestoneRef = useRef< number >( readMilestone() );
+	const [ data, setData ] = useState< SyncStatus >();
+	const [ error, setError ] = useState< Error | null >( null );
+	const [ isStalled, setIsStalled ] = useState( false );
+
+	const intervalRef = useRef< ReturnType< typeof setInterval > | null >( null );
+	// Hold the latest `poll` in a ref so the interval always calls the current
+	// closure. Preserves the original package's pollRef pattern and keeps the
+	// interval stable if `poll`'s identity ever changes.
+	const pollRef = useRef< () => void >();
+
+	const clearPolling = useCallback( () => {
+		if ( intervalRef.current ) {
+			clearInterval( intervalRef.current );
+			intervalRef.current = null;
+		}
+	}, [] );
+
+	const poll = useCallback( () => {
+		fetchSyncStatus()
+			.then( raw => {
+				const status = toSyncStatus( raw, milestoneRef.current );
+				setData( status );
+				setError( null );
+				setIsStalled( false );
+
+				if ( isSyncComplete( status ) ) {
+					clearPolling();
+					return;
+				}
+
+				if ( isSyncStalled( status ) ) {
+					clearPolling();
+					setIsStalled( true );
+					setError(
+						new Error( __( 'Sync has stalled. Please try again.', 'jetpack-premium-analytics' ) )
+					);
+				}
+			} )
+			.catch( ( e: unknown ) => {
+				clearPolling();
+				const message =
+					e instanceof Error
+						? e.message
+						: __( 'Unable to get sync status.', 'jetpack-premium-analytics' );
+				setError( new Error( message ) );
+			} );
+	}, [ clearPolling ] );
+
+	pollRef.current = poll;
+
+	const startPolling = useCallback( () => {
+		clearPolling();
+		intervalRef.current = setInterval( () => {
+			pollRef.current?.();
+		}, POLL_INTERVAL );
+	}, [ clearPolling ] );
+
+	const triggerSync = useCallback( async () => {
+		clearPolling();
+		setError( null );
+		setIsStalled( false );
+
+		try {
+			await triggerFullSync();
+			poll();
+			startPolling();
+		} catch ( e: unknown ) {
+			const message =
+				e instanceof Error ? e.message : __( 'Unable to start sync.', 'jetpack-premium-analytics' );
+			setError( new Error( message ) );
+		}
+	}, [ clearPolling, poll, startPolling ] );
+
+	useEffect( () => {
+		// Already finished before this page load — gate open, no polling needed.
+		if ( milestoneRef.current > 0 ) {
+			setData( toSyncStatus( {}, milestoneRef.current ) );
+			return;
+		}
+
+		poll();
+		startPolling();
+		return clearPolling;
+	}, [ poll, startPolling, clearPolling ] );
+
+	const isComplete = data ? isSyncComplete( data ) : false;
+	const isLoading = ! data && ! error;
+
+	return { data, error, isLoading, isComplete, isStalled, triggerSync };
+}
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/index.ts b/projects/packages/premium-analytics/packages/site-sync/src/index.ts
new file mode 100644
index 000000000000..db2c2897a38a
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/index.ts
@@ -0,0 +1,2 @@
+export { useSyncStatus } from './hooks/use-sync-status';
+export type { SyncStatus, SyncStatusApiResponse, UseSyncStatusReturn } from './types';
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/jetpack-script-data.d.ts b/projects/packages/premium-analytics/packages/site-sync/src/jetpack-script-data.d.ts
new file mode 100644
index 000000000000..f366df3d7891
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/jetpack-script-data.d.ts
@@ -0,0 +1,14 @@
+/**
+ * The backend `Sync_Status_Tracker` (jetpack PR #49211) injects this block into
+ * `window.JetpackScriptData` via the `jetpack_admin_js_script_data` filter. The
+ * base `@automattic/jetpack-script-data` types don't know about it, so augment.
+ */
+import '@automattic/jetpack-script-data';
+
+declare module '@automattic/jetpack-script-data' {
+	interface JetpackScriptData {
+		premium_analytics?: {
+			initial_full_sync_finished: number;
+		};
+	}
+}
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/status.test.ts b/projects/packages/premium-analytics/packages/site-sync/src/status.test.ts
new file mode 100644
index 000000000000..b5da2b27e181
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/status.test.ts
@@ -0,0 +1,160 @@
+import { toSyncStatus, isSyncComplete, isSyncStalled } from './status';
+
+describe( 'toSyncStatus', () => {
+	it( 'reports not-started when the sync has never run', () => {
+		const status = toSyncStatus( { started: false }, 0 );
+		expect( status ).toEqual( {
+			isStarted: false,
+			isRunning: false,
+			percentage: 0,
+			initialFullSyncFinished: 0,
+		} );
+	} );
+
+	it( 'computes analytics-scoped percentage from the module bucket', () => {
+		const status = toSyncStatus(
+			{
+				started: true,
+				finished: false,
+				progress: { woocommerce_analytics: { sent: 1, total: 4 } },
+			},
+			0
+		);
+		expect( status.isRunning ).toBe( true );
+		expect( status.percentage ).toBe( 25 );
+	} );
+
+	it( 'ignores non-analytics modules when computing percentage', () => {
+		const status = toSyncStatus(
+			{
+				started: true,
+				finished: false,
+				progress: {
+					posts: { sent: 100, total: 100 },
+					woocommerce_analytics: { sent: 1, total: 2 },
+				},
+			},
+			0
+		);
+		expect( status.percentage ).toBe( 50 );
+	} );
+
+	it( 'is 100% when the page-load milestone is set', () => {
+		const status = toSyncStatus( { started: false }, 1_700_000_000 );
+		expect( status.percentage ).toBe( 100 );
+		expect( status.initialFullSyncFinished ).toBe( 1_700_000_000 );
+	} );
+
+	it( 'caps percentage at 100', () => {
+		const status = toSyncStatus(
+			{
+				started: true,
+				finished: false,
+				progress: { woocommerce_analytics: { sent: 9, total: 4 } },
+			},
+			0
+		);
+		expect( status.percentage ).toBe( 100 );
+	} );
+
+	it( 'is complete (and gates open) when analytics hits 100% even if finished is still false', () => {
+		const status = toSyncStatus(
+			{
+				started: true,
+				finished: false,
+				progress: { woocommerce_analytics: { sent: 2, total: 2 } },
+			},
+			0
+		);
+		expect( status.percentage ).toBe( 100 );
+		expect( status.isRunning ).toBe( true );
+		expect( isSyncComplete( status ) ).toBe( true );
+		expect( isSyncStalled( status ) ).toBe( false );
+	} );
+
+	it( 'treats a numeric finished timestamp as finished', () => {
+		const status = toSyncStatus(
+			{
+				started: true,
+				finished: 1_700_000_000,
+				progress: { woocommerce_analytics: { sent: 1, total: 2 } },
+			},
+			0
+		);
+		// total > 0 branch: floor(1/2 * 100) = 50; numeric finished coerces to true
+		// so isRunning = started && !finished = false.
+		expect( status.percentage ).toBe( 50 );
+		expect( status.isRunning ).toBe( false );
+		expect( isSyncStalled( status ) ).toBe( true );
+	} );
+} );
+
+describe( 'isSyncComplete', () => {
+	it( 'is complete when the milestone is set', () => {
+		expect(
+			isSyncComplete( {
+				isStarted: false,
+				isRunning: false,
+				percentage: 100,
+				initialFullSyncFinished: 1_700_000_000,
+			} )
+		).toBe( true );
+	} );
+
+	it( 'is complete when analytics progress reaches 100 this session', () => {
+		expect(
+			isSyncComplete( {
+				isStarted: true,
+				isRunning: false,
+				percentage: 100,
+				initialFullSyncFinished: 0,
+			} )
+		).toBe( true );
+	} );
+
+	it( 'is not complete mid-progress', () => {
+		expect(
+			isSyncComplete( {
+				isStarted: true,
+				isRunning: true,
+				percentage: 50,
+				initialFullSyncFinished: 0,
+			} )
+		).toBe( false );
+	} );
+} );
+
+describe( 'isSyncStalled', () => {
+	it( 'is stalled when started, no longer running, and not complete', () => {
+		expect(
+			isSyncStalled( {
+				isStarted: true,
+				isRunning: false,
+				percentage: 50,
+				initialFullSyncFinished: 0,
+			} )
+		).toBe( true );
+	} );
+
+	it( 'is not stalled when it never started', () => {
+		expect(
+			isSyncStalled( {
+				isStarted: false,
+				isRunning: false,
+				percentage: 0,
+				initialFullSyncFinished: 0,
+			} )
+		).toBe( false );
+	} );
+
+	it( 'is not stalled when complete', () => {
+		expect(
+			isSyncStalled( {
+				isStarted: true,
+				isRunning: false,
+				percentage: 100,
+				initialFullSyncFinished: 1_700_000_000,
+			} )
+		).toBe( false );
+	} );
+} );
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/status.ts b/projects/packages/premium-analytics/packages/site-sync/src/status.ts
new file mode 100644
index 000000000000..c88b416a4d55
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/status.ts
@@ -0,0 +1,56 @@
+/**
+ * Internal dependencies
+ */
+import { ANALYTICS_SYNC_MODULE } from './constants';
+import type { SyncStatus, SyncStatusApiResponse } from './types';
+
+/**
+ * Normalize Jetpack's raw sync status into the analytics-scoped shape.
+ *
+ * @param raw       - Raw GET /jetpack/v4/sync/status response.
+ * @param milestone - Page-load milestone (unix ts, or 0 if never finished).
+ * @return Analytics-scoped sync status.
+ */
+export function toSyncStatus( raw: SyncStatusApiResponse, milestone: number ): SyncStatus {
+	const started = Boolean( raw.started );
+	const finished = Boolean( raw.finished );
+	const bucket = raw.progress?.[ ANALYTICS_SYNC_MODULE ];
+	const total = bucket?.total ?? 0;
+	const sent = bucket?.sent ?? 0;
+
+	let percentage = 0;
+	if ( total > 0 ) {
+		percentage = Math.min( 100, Math.floor( ( sent / total ) * 100 ) );
+	} else if ( milestone > 0 || finished ) {
+		// No analytics bucket in this batch, but the sync has finished (now or
+		// before) — treat analytics as fully synced.
+		percentage = 100;
+	}
+
+	return {
+		isStarted: started,
+		isRunning: started && ! finished,
+		percentage,
+		initialFullSyncFinished: milestone,
+	};
+}
+
+/**
+ * The analytics initial sync has finished — either before this page load
+ * (milestone) or analytics progress reached 100 during this session.
+ * @param status - Normalized sync status.
+ * @return Whether the analytics initial sync has finished.
+ */
+export function isSyncComplete( status: SyncStatus ): boolean {
+	return status.initialFullSyncFinished > 0 || status.percentage >= 100;
+}
+
+/**
+ * Stalled = the sync started but is no longer running and hasn't completed. A
+ * sync that never started is NOT stalled — it just needs to be triggered.
+ * @param status - Normalized sync status.
+ * @return Whether the sync has stalled.
+ */
+export function isSyncStalled( status: SyncStatus ): boolean {
+	return status.isStarted && ! status.isRunning && ! isSyncComplete( status );
+}
diff --git a/projects/packages/premium-analytics/packages/site-sync/src/types.ts b/projects/packages/premium-analytics/packages/site-sync/src/types.ts
new file mode 100644
index 000000000000..07262f6da459
--- /dev/null
+++ b/projects/packages/premium-analytics/packages/site-sync/src/types.ts
@@ -0,0 +1,39 @@
+/**
+ * Subset of Jetpack core's GET /jetpack/v4/sync/status response that this
+ * package consumes. `progress` is keyed by sync-module name; each module
+ * reports items `sent` of `total`.
+ */
+export type SyncStatusApiResponse = {
+	started?: boolean;
+	finished?: boolean | number;
+	progress?: Record< string, { sent?: number; total?: number } >;
+};
+
+/**
+ * Normalized, analytics-scoped sync status.
+ */
+export type SyncStatus = {
+	isStarted: boolean;
+	isRunning: boolean;
+	/** Analytics-module progress, 0–100, computed client-side. */
+	percentage: number;
+	/** Page-load milestone: unix ts when the initial analytics sync first finished, else 0. */
+	initialFullSyncFinished: number;
+};
+
+/**
+ * Return type for the useSyncStatus hook.
+ */
+export type UseSyncStatusReturn = {
+	data: SyncStatus | undefined;
+	error: Error | null;
+	isLoading: boolean;
+	isComplete: boolean;
+	isStalled: boolean;
+	/**
+	 * POST the full-sync trigger and resume polling. The returned promise always
+	 * resolves; failures surface via `error` so callers can `void triggerSync()`
+	 * from event handlers without an unhandled rejection.
+	 */
+	triggerSync: () => Promise< void >;
+};