diff --git a/src/Sync/SyncContext.php b/src/Sync/SyncContext.php
new file mode 100644
index 0000000..7352e6f
--- /dev/null
+++ b/src/Sync/SyncContext.php
@@ -0,0 +1,92 @@
+<?php
+/**
+ * Immutable sync operation context.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Sync;
+
+final class SyncContext {
+	private const CONFLICT_STRATEGIES = array( 'last_write_wins', 'manual_review' );
+
+	private string $direction;
+	private string $operation_id;
+	private string $source_url;
+	private string $destination_url;
+	private string $conflict_strategy;
+
+	/** @var array<string, string> */
+	private array $url_mappings;
+
+	/**
+	 * @param array<string, string> $url_mappings URL mappings.
+	 */
+	private function __construct(
+		string $direction,
+		string $operation_id,
+		string $source_url,
+		string $destination_url,
+		string $conflict_strategy,
+		array $url_mappings
+	) {
+		$this->direction         = $direction;
+		$this->operation_id      = $operation_id;
+		$this->source_url        = $source_url;
+		$this->destination_url   = $destination_url;
+		$this->conflict_strategy = in_array( $conflict_strategy, self::CONFLICT_STRATEGIES, true ) ? $conflict_strategy : 'last_write_wins';
+		$this->url_mappings      = $url_mappings;
+	}
+
+	/**
+	 * @param array<string, mixed> $source            Source site metadata.
+	 * @param array<string, mixed> $destination       Destination site metadata.
+	 * @param string               $conflict_strategy Conflict strategy.
+	 * @param string               $operation_id      Operation ID.
+	 */
+	public static function forImport( array $source, array $destination, string $conflict_strategy, string $operation_id ): self {
+		$source_url      = esc_url_raw( (string) ( $source['site_url'] ?? '' ) );
+		$destination_url = esc_url_raw( (string) ( $destination['site_url'] ?? '' ) );
+		$url_mappings    = array();
+
+		if ( '' !== $source_url && '' !== $destination_url ) {
+			$url_mappings[ $source_url ] = $destination_url;
+		}
+
+		return new self(
+			'import',
+			sanitize_key( $operation_id ),
+			$source_url,
+			$destination_url,
+			$conflict_strategy,
+			$url_mappings
+		);
+	}
+
+	public function direction(): string {
+		return $this->direction;
+	}
+
+	public function operationId(): string {
+		return $this->operation_id;
+	}
+
+	public function sourceUrl(): string {
+		return $this->source_url;
+	}
+
+	public function destinationUrl(): string {
+		return $this->destination_url;
+	}
+
+	public function conflictStrategy(): string {
+		return $this->conflict_strategy;
+	}
+
+	/**
+	 * @return array<string, string>
+	 */
+	public function urlMappings(): array {
+		return $this->url_mappings;
+	}
+}
diff --git a/src/Sync/SyncOperationState.php b/src/Sync/SyncOperationState.php
new file mode 100644
index 0000000..b941876
--- /dev/null
+++ b/src/Sync/SyncOperationState.php
@@ -0,0 +1,78 @@
+<?php
+/**
+ * Immutable sync operation progress state.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Sync;
+
+final class SyncOperationState {
+	private string $operation_id;
+	private string $status;
+	private string $current_bucket;
+	private int $processed;
+	private int $total;
+
+	private function __construct( string $operation_id, string $status, string $current_bucket, int $processed, int $total ) {
+		$this->operation_id   = sanitize_key( $operation_id );
+		$this->status         = sanitize_key( $status );
+		$this->current_bucket = sanitize_key( $current_bucket );
+		$this->processed      = max( 0, $processed );
+		$this->total          = max( 0, $total );
+	}
+
+	public static function running( string $operation_id, string $current_bucket, int $processed, int $total ): self {
+		return new self( $operation_id, 'running', $current_bucket, $processed, $total );
+	}
+
+	public static function completed( string $operation_id, int $processed, int $total ): self {
+		return new self( $operation_id, 'completed', '', $processed, $total );
+	}
+
+	/**
+	 * @param array<string, mixed> $data State data.
+	 */
+	public static function fromArray( array $data ): self {
+		return new self(
+			(string) ( $data['operation_id'] ?? '' ),
+			(string) ( $data['status'] ?? '' ),
+			(string) ( $data['current_bucket'] ?? '' ),
+			(int) ( $data['processed'] ?? 0 ),
+			(int) ( $data['total'] ?? 0 )
+		);
+	}
+
+	public function operationId(): string {
+		return $this->operation_id;
+	}
+
+	public function status(): string {
+		return $this->status;
+	}
+
+	public function currentBucket(): string {
+		return $this->current_bucket;
+	}
+
+	public function processed(): int {
+		return $this->processed;
+	}
+
+	public function total(): int {
+		return $this->total;
+	}
+
+	/**
+	 * @return array<string, mixed>
+	 */
+	public function toArray(): array {
+		return array(
+			'operation_id'   => $this->operation_id,
+			'status'         => $this->status,
+			'current_bucket' => $this->current_bucket,
+			'processed'      => $this->processed,
+			'total'          => $this->total,
+		);
+	}
+}
diff --git a/src/Sync/SyncStateRepository.php b/src/Sync/SyncStateRepository.php
new file mode 100644
index 0000000..495ea1d
--- /dev/null
+++ b/src/Sync/SyncStateRepository.php
@@ -0,0 +1,38 @@
+<?php
+/**
+ * Sync operation state persistence.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Sync;
+
+final class SyncStateRepository {
+	private const DEFAULT_EXPIRATION = 86400;
+
+	public function save( SyncOperationState $state ): void {
+		set_transient( $this->key( $state->operationId() ), $state->toArray(), $this->expiration() );
+	}
+
+	public function get( string $operation_id ): ?SyncOperationState {
+		$value = get_transient( $this->key( $operation_id ) );
+
+		if ( ! is_array( $value ) ) {
+			return null;
+		}
+
+		return SyncOperationState::fromArray( $value );
+	}
+
+	public function delete( string $operation_id ): void {
+		delete_transient( $this->key( $operation_id ) );
+	}
+
+	private function key( string $operation_id ): string {
+		return 'wpcs_sync_state_' . sanitize_key( $operation_id );
+	}
+
+	private function expiration(): int {
+		return defined( 'DAY_IN_SECONDS' ) ? (int) DAY_IN_SECONDS : self::DEFAULT_EXPIRATION;
+	}
+}
diff --git a/tests/Unit/Sync/SyncContextTest.php b/tests/Unit/Sync/SyncContextTest.php
new file mode 100644
index 0000000..cc2a6fd
--- /dev/null
+++ b/tests/Unit/Sync/SyncContextTest.php
@@ -0,0 +1,38 @@
+<?php
+/**
+ * Tests for sync operation context.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Tests\Unit\Sync;
+
+use PHPUnit\Framework\TestCase;
+use WPContentSync\Sync\SyncContext;
+
+class SyncContextTest extends TestCase {
+	public function test_it_builds_import_context_from_package_sites(): void {
+		$context = SyncContext::forImport(
+			array( 'site_url' => 'https://source.test' ),
+			array( 'site_url' => 'https://destination.test' ),
+			'last_write_wins',
+			'operation-1'
+		);
+
+		self::assertSame( 'import', $context->direction() );
+		self::assertSame( 'operation-1', $context->operationId() );
+		self::assertSame( 'last_write_wins', $context->conflictStrategy() );
+		self::assertSame( 'https://source.test', $context->sourceUrl() );
+		self::assertSame( 'https://destination.test', $context->destinationUrl() );
+		self::assertSame(
+			array( 'https://source.test' => 'https://destination.test' ),
+			$context->urlMappings()
+		);
+	}
+
+	public function test_it_falls_back_to_last_write_wins_for_invalid_strategy(): void {
+		$context = SyncContext::forImport( array(), array(), 'surprise', 'operation-2' );
+
+		self::assertSame( 'last_write_wins', $context->conflictStrategy() );
+	}
+}
diff --git a/tests/Unit/Sync/SyncStateRepositoryTest.php b/tests/Unit/Sync/SyncStateRepositoryTest.php
new file mode 100644
index 0000000..4be7c04
--- /dev/null
+++ b/tests/Unit/Sync/SyncStateRepositoryTest.php
@@ -0,0 +1,46 @@
+<?php
+/**
+ * Tests for sync state persistence.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Tests\Unit\Sync;
+
+use PHPUnit\Framework\TestCase;
+use WPContentSync\Sync\SyncOperationState;
+use WPContentSync\Sync\SyncStateRepository;
+
+class SyncStateRepositoryTest extends TestCase {
+	protected function tearDown(): void {
+		unset( $GLOBALS['wpcs_test_transients'], $GLOBALS['wpcs_test_transient_expiration'] );
+
+		parent::tearDown();
+	}
+
+	public function test_it_saves_and_reads_operation_state(): void {
+		$repository = new SyncStateRepository();
+		$state      = SyncOperationState::running( 'operation-1', 'posts', 2, 10 );
+
+		$repository->save( $state );
+
+		$loaded = $repository->get( 'operation-1' );
+
+		self::assertInstanceOf( SyncOperationState::class, $loaded );
+		self::assertSame( 'operation-1', $loaded->operationId() );
+		self::assertSame( 'posts', $loaded->currentBucket() );
+		self::assertSame( 2, $loaded->processed() );
+		self::assertSame( 10, $loaded->total() );
+		self::assertSame( 'running', $loaded->status() );
+	}
+
+	public function test_it_deletes_operation_state(): void {
+		$repository = new SyncStateRepository();
+		$repository->save( SyncOperationState::completed( 'operation-1', 10, 10 ) );
+
+		$repository->delete( 'operation-1' );
+
+		self::assertNull( $repository->get( 'operation-1' ) );
+		self::assertArrayNotHasKey( 'wpcs_sync_state_operation-1', $GLOBALS['wpcs_test_transient_expiration'] );
+	}
+}
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index d6903a4..648ecf6 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -51,6 +51,18 @@ if ( ! function_exists( 'sanitize_text_field' ) ) {
 	}
 }
 
+if ( ! function_exists( 'sanitize_key' ) ) {
+	/**
+	 * Minimal WordPress-compatible key sanitizer for unit tests.
+	 *
+	 * @param mixed $key Key to sanitize.
+	 * @return string
+	 */
+	function sanitize_key( $key ) {
+		return strtolower( preg_replace( '/[^a-zA-Z0-9_\-]/', '', (string) $key ) );
+	}
+}
+
 if ( ! function_exists( 'wp_strip_all_tags' ) ) {
 	/**
 	 * Minimal tag stripper for unit tests.
@@ -223,6 +235,36 @@ if ( ! function_exists( 'delete_transient' ) ) {
 	 */
 	function delete_transient( $name ) {
 		unset( $GLOBALS['wpcs_test_transients'][ $name ] );
+		unset( $GLOBALS['wpcs_test_transient_expiration'][ $name ] );
+
+		return true;
+	}
+}
+
+if ( ! function_exists( 'get_transient' ) ) {
+	/**
+	 * Minimal WordPress transient reader for unit tests.
+	 *
+	 * @param string $name Transient name.
+	 * @return mixed
+	 */
+	function get_transient( $name ) {
+		return $GLOBALS['wpcs_test_transients'][ $name ] ?? false;
+	}
+}
+
+if ( ! function_exists( 'set_transient' ) ) {
+	/**
+	 * Minimal WordPress transient writer for unit tests.
+	 *
+	 * @param string $name       Transient name.
+	 * @param mixed  $value      Transient value.
+	 * @param int    $expiration Expiration in seconds.
+	 * @return bool
+	 */
+	function set_transient( $name, $value, $expiration = 0 ) {
+		$GLOBALS['wpcs_test_transients'][ $name ]           = $value;
+		$GLOBALS['wpcs_test_transient_expiration'][ $name ] = $expiration;
 
 		return true;
 	}