feat(2meet-data-optimizer): guard orphaned flat-table groups

- On init:1, re-register aeav_only groups whose flat table exists and whose definition is in wpdo_registry_meta but no active plugin registers them, so their data stays readable (routing only, never DDL)
- Keys owned by a live group, or with rows in native meta (newer data written while orphaned), are left alone; the native-meta check is cached for a day
- Surface restored groups via Site Health (wpdo_orphaned_entity_groups), the admin Doctor tab, and wp wpdo doctor
- Verify: EntityRegistryRestoreTest (9), OrphanGroupRestoreTest (7); core unit 622 / integration 439, HP 141/49, WC 10/22 OK; dry-run on dev20–22 restores 16/17/4 groups, keeps hp_taxonomy hp_sort_order/hp_icon on native
- PR: PR-018

admin/class-tmdo-admin.php

@@ -2990,7 +2990,7 @@ wpdo.getListings({ per_page: 3 }).then(r => console.log(r));'
 		?>
 		<h2><?php esc_html_e( '健康檢查（Doctor）', '2meet-data-optimizer' ); ?></h2>
 		<p class="description">
-			<?php esc_html_e( '8 項自我診斷檢查：schema 完整性、錯誤預算、hook 衝突、autoload 大小、postmeta 爆量、orphan zone rows、缺少快照、實體群組名稱衝突。', '2meet-data-optimizer' ); ?>
+			<?php esc_html_e( '9 項自我診斷檢查：schema 完整性、錯誤預算、hook 衝突、autoload 大小、postmeta 爆量、orphan zone rows、缺少快照、實體群組名稱衝突、孤兒實體群組。', '2meet-data-optimizer' ); ?>
 		</p>
 		<p>
 			<a class="button" href="<?php echo esc_url( admin_url( 'site-health.php' ) ); ?>">
@@ -3012,6 +3012,7 @@ wpdo.getListings({ per_page: 3 }).then(r => console.log(r));'
 			'wpdo_orphan_zone_rows'        => array( 'check_orphan_zone_rows', __( 'Orphan zone rows', '2meet-data-optimizer' ) ),
 			'wpdo_missing_snapshot'        => array( 'check_missing_snapshot', __( '缺少最近快照', '2meet-data-optimizer' ) ),
 			'wpdo_entity_group_collisions' => array( 'check_entity_group_collisions', __( '實體群組名稱衝突', '2meet-data-optimizer' ) ),
+			'wpdo_orphaned_entity_groups'  => array( 'check_orphaned_entity_groups', __( '孤兒實體群組', '2meet-data-optimizer' ) ),
 		);
 		?>
 		<table class="widefat striped">

admin/class-tmdo-help-tabs.php

@@ -184,7 +184,7 @@ class TMDO_Help_Tabs {
 	 * @return string
 	 */
 	private static function content_doctor(): string {
-		return '<p>' . esc_html__( '8 項自動健康檢查：', '2meet-data-optimizer' ) . '</p>'
+		return '<p>' . esc_html__( '9 項自動健康檢查：', '2meet-data-optimizer' ) . '</p>'
 			. '<ol class="wpdo-list-disc">'
 			. '<li><strong>schema_drift</strong> — ' . esc_html__( '所有 v2 表是否存在', '2meet-data-optimizer' ) . '</li>'
 			. '<li><strong>error_budget</strong> — ' . esc_html__( '7 天內 wp_wpdo_errors 行數', '2meet-data-optimizer' ) . '</li>'
@@ -194,6 +194,7 @@ class TMDO_Help_Tabs {
 			. '<li><strong>orphan_zone_rows</strong> — ' . esc_html__( '已 idle 的 module 但 zone 表還有資料', '2meet-data-optimizer' ) . '</li>'
 			. '<li><strong>missing_snapshot</strong> — ' . esc_html__( '在 cutover/cleanup/complete 但 7 天沒 snapshot', '2meet-data-optimizer' ) . '</li>'
 			. '<li><strong>entity_group_collisions</strong> — ' . esc_html__( '同名實體群組被不同外掛以不同欄位註冊（後者被忽略）', '2meet-data-optimizer' ) . '</li>'
+			. '<li><strong>orphaned_entity_groups</strong> — ' . esc_html__( '扁平表還在但已無外掛註冊的群組（已依保存的定義還原以維持可讀）', '2meet-data-optimizer' ) . '</li>'
 			. '</ol>'
 			. '<p>' . esc_html__( '結果有 5 分鐘 transient cache，剛操作完想立刻看新值請等下個週期。', '2meet-data-optimizer' ) . '</p>';
 	}

cli/class-tmdo-cli.php

@@ -349,6 +349,21 @@ class TMDO_CLI {
 			$all_ok = false;
 		}
 
+		// ── Orphaned entity groups (restored from wpdo_registry_meta) ───────────
+		foreach ( TMDO_Entity_Registry::get_restored_groups() as $r ) {
+			WP_CLI::warning(
+				sprintf(
+					'  [ORPHAN] %s/%s — no active plugin registers it; restored %d field(s) from wpdo_registry_meta%s%s. Reactivate the owner or write the data back before removing it.',
+					$r['entity_type'],
+					$r['group'],
+					$r['fields'],
+					$r['skipped'] ? ' (skipped, owned by another group: ' . implode( ', ', $r['skipped'] ) . ')' : '',
+					$r['native'] ? ' (left on native meta, which has newer data: ' . implode( ', ', $r['native'] ) . ')' : ''
+				)
+			);
+			$all_ok = false;
+		}
+
 		// Check recent errors.
 		$errors = TMDO_Logger::get_recent( '', 5 );
 		if ( ! empty( $errors ) ) {

includes/class-tmdo-core.php

@@ -71,6 +71,12 @@ class TMDO_Core {
 					if ( class_exists( 'TMDO_Custom_Table_Registry' ) ) {
 						TMDO_Custom_Table_Registry::instance()->fire_registration();
 					}
+					// Every provider has registered by now: re-register groups whose flat
+					// table still holds data but whose plugin is gone, so aeav_only
+					// values keep reading back (routing only — never DDL).
+					if ( class_exists( 'TMDO_Schema_Manager' ) && class_exists( 'TMDO_Entity_Registry' ) ) {
+						TMDO_Schema_Manager::restore_orphaned_groups();
+					}
 					if ( class_exists( 'TMDO_Schema_Manager' ) && class_exists( 'TMDO_Entity_Registry' ) ) {
 						$pending = TMDO_Entity_Registry::get_pending_schemas();
 						if ( ! empty( $pending ) ) {

includes/diagnostic/class-tmdo-site-health.php

@@ -2,7 +2,7 @@
 /**
  * TMDO_Site_Health — WordPress Site Health integration (v2.2.0 M3).
  *
- * Registers 8 tests under Tools → Site Health → Status:
+ * Registers 9 tests under Tools → Site Health → Status:
  *   1. wpdo_schema_drift          (critical)
  *   2. wpdo_error_budget          (recommended)
  *   3. wpdo_hook_conflicts        (recommended)
@@ -11,6 +11,7 @@
  *   6. wpdo_orphan_zone_rows      (recommended)
  *   7. wpdo_missing_snapshot      (critical)
  *   8. wpdo_entity_group_collisions (recommended)
+ *   9. wpdo_orphaned_entity_groups  (recommended)
  *
  * Each test result is cached for 5 minutes to keep Site Health responsive.
  *
@@ -43,6 +44,7 @@ class TMDO_Site_Health {
 		'wpdo_orphan_zone_rows'        => 'check_orphan_zone_rows',
 		'wpdo_missing_snapshot'        => 'check_missing_snapshot',
 		'wpdo_entity_group_collisions' => 'check_entity_group_collisions',
+		'wpdo_orphaned_entity_groups'  => 'check_orphaned_entity_groups',
 	);
 
 	/**
@@ -55,7 +57,7 @@ class TMDO_Site_Health {
 	}
 
 	/**
-	 * Register the 8 tests with WP Site Health.
+	 * Register the 9 tests with WP Site Health.
 	 *
 	 * @param array $tests Existing tests.
 	 * @return array
@@ -86,6 +88,7 @@ class TMDO_Site_Health {
 			'wpdo_orphan_zone_rows'        => __( 'WPDO orphan zone rows', '2meet-data-optimizer' ),
 			'wpdo_missing_snapshot'        => __( 'WPDO missing snapshot', '2meet-data-optimizer' ),
 			'wpdo_entity_group_collisions' => __( 'WPDO entity group collisions', '2meet-data-optimizer' ),
+			'wpdo_orphaned_entity_groups'  => __( 'WPDO orphaned entity groups', '2meet-data-optimizer' ),
 		);
 		return $map[ $key ] ?? $key;
 	}
@@ -468,6 +471,46 @@ class TMDO_Site_Health {
 		);
 	}
 
+	// ─── Test 9: Orphaned entity groups ─────────────────────────────────
+
+	/**
+	 * Report flat-table groups kept alive from wpdo_registry_meta because no
+	 * active plugin registers them any more.
+	 *
+	 * Not cached for the same reason as check_entity_group_collisions().
+	 *
+	 * @return array Site Health result.
+	 */
+	public static function check_orphaned_entity_groups(): array {
+		$restored = class_exists( 'TMDO_Entity_Registry' ) ? TMDO_Entity_Registry::get_restored_groups() : array();
+		if ( empty( $restored ) ) {
+			return self::wrap( 'wpdo_orphaned_entity_groups', self::pass( __( 'Every flat-table group is registered by an active plugin.', '2meet-data-optimizer' ) ) );
+		}
+		$lines = array();
+		foreach ( $restored as $r ) {
+			$lines[] = sprintf(
+				'%s/%s (%d fields%s%s)',
+				$r['entity_type'],
+				$r['group'],
+				$r['fields'],
+				$r['skipped'] ? ', skipped: ' . implode( ',', $r['skipped'] ) : '',
+				$r['native'] ? ', left on native meta (newer data there): ' . implode( ',', $r['native'] ) : ''
+			);
+		}
+		return self::wrap(
+			'wpdo_orphaned_entity_groups',
+			self::fail(
+				__( 'WPDO entity groups restored from stored definitions', '2meet-data-optimizer' ),
+				sprintf(
+					/* translators: %s: list of entity/group names */
+					__( 'No active plugin registers these groups, so their stored definitions were re-applied to keep the flat-table data readable. Reactivate the owning plugin, or write the data back to native meta before removing it: %s', '2meet-data-optimizer' ),
+					implode( '; ', $lines )
+				),
+				'recommended'
+			)
+		);
+	}
+
 	/**
 	 * Wrap a raw check result with required Site Health envelope fields.
 	 *

includes/engine/class-tmdo-entity-registry.php

@@ -34,6 +34,9 @@ final class TMDO_Entity_Registry {
 	/** @var array<string, array> "entity/group" → 同名群組以不同定義重複註冊的紀錄 */
 	private static array $collisions = array();
 
+	/** @var array<string, array> "entity/group" → 從 wpdo_registry_meta 還原的孤兒群組 */
+	private static array $restored = array();
+
 	/** 合法的欄位型別 */
 	public const VALID_TYPES = array(
 		'text',
@@ -58,6 +61,7 @@ final class TMDO_Entity_Registry {
 		self::$field_index     = array();
 		self::$pending_schemas = array();
 		self::$collisions      = array();
+		self::$restored        = array();
 	}
 
 	// ─────────────────────────────────────────────────────────
@@ -109,7 +113,41 @@ final class TMDO_Entity_Registry {
 			return false;
 		}
 
-		// 驗證並正規化欄位定義
+		$normalized = self::normalize_fields( $entity_type, $group_name, $fields );
+
+		if ( empty( $normalized ) ) {
+			return false;
+		}
+
+		// 防重複登錄：相同定義（init:1 重新觸發）靜默略過；定義不同則記錄衝突，保留先註冊者。
+		if ( isset( self::$groups[ $entity_type ][ $group_name ] ) ) {
+			if ( self::$groups[ $entity_type ][ $group_name ] !== $normalized ) {
+				self::record_collision( $entity_type, $group_name, self::$groups[ $entity_type ][ $group_name ], $normalized );
+			}
+			return false;
+		}
+
+		// 建立索引以供快速查詢
+		foreach ( $normalized as $normalized_field ) {
+			self::$field_index[ $entity_type ][ $normalized_field['key'] ] = $normalized_field;
+		}
+
+		self::$groups[ $entity_type ][ $group_name ] = $normalized;
+
+		// 加入待建表佇列
+		self::$pending_schemas[] = array(
+			'type'   => $entity_type,
+			'group'  => $group_name,
+			'fields' => $normalized,
+		);
+
+		return true;
+	}
+
+	/**
+	 * 驗證並正規化欄位定義（略過缺 key/type 或型別不合法者）。
+	 */
+	private static function normalize_fields( string $entity_type, string $group_name, array $fields ): array {
 		$normalized = array();
 
 		foreach ( $fields as $field ) {
@@ -142,35 +180,79 @@ final class TMDO_Entity_Registry {
 			$normalized[] = $normalized_field;
 		}
 
-		if ( empty( $normalized ) ) {
+		return $normalized;
+	}
+
+	/**
+	 * 還原孤兒群組：依 wpdo_registry_meta 保存的定義重新登錄，只供讀寫路由用。
+	 *
+	 * 與 register_group() 的差異：不進 pending_schemas（絕不觸發 DDL），且已被
+	 * 其他存活群組管理的 key 一律略過，不覆蓋。$native_keys 列出原生 meta 仍有
+	 * 資料的 key：那些值比扁平表新（孤兒期間寫入），必須留在原生 meta。
+	 *
+	 * @param string[] $native_keys 原生 meta 仍有資料、不可還原的 key。
+	 * @return bool 有登錄任何欄位時為 true
+	 */
+	public static function restore_group( string $entity_type, string $group_name, array $fields, array $native_keys = array() ): bool {
+		if ( ! isset( self::$adapters[ $entity_type ] ) || isset( self::$groups[ $entity_type ][ $group_name ] ) ) {
 			return false;
 		}
 
-		// 防重複登錄：相同定義（init:1 重新觸發）靜默略過；定義不同則記錄衝突，保留先註冊者。
-		if ( isset( self::$groups[ $entity_type ][ $group_name ] ) ) {
-			if ( self::$groups[ $entity_type ][ $group_name ] !== $normalized ) {
-				self::record_collision( $entity_type, $group_name, self::$groups[ $entity_type ][ $group_name ], $normalized );
+		$kept    = array();
+		$skipped = array();
+		$native  = array();
+		foreach ( self::normalize_fields( $entity_type, $group_name, $fields ) as $field ) {
+			if ( isset( self::$field_index[ $entity_type ][ $field['key'] ] ) ) {
+				$skipped[] = (string) $field['key'];
+				continue;
+			}
+			if ( in_array( $field['key'], $native_keys, true ) ) {
+				$native[] = (string) $field['key'];
+				continue;
+			}
+			$kept[] = $field;
+		}
+
+		$id = $entity_type . '/' . $group_name;
+		if ( empty( $kept ) ) {
+			// 整組都留在原生 meta 時仍要回報：扁平表的舊資料需要人工處理。
+			if ( $native ) {
+				self::$restored[ $id ] = array(
+					'entity_type' => $entity_type,
+					'group'       => $group_name,
+					'fields'      => 0,
+					'skipped'     => $skipped,
+					'native'      => $native,
+				);
 			}
 			return false;
 		}
 
-		// 建立索引以供快速查詢
-		foreach ( $normalized as $normalized_field ) {
-			self::$field_index[ $entity_type ][ $normalized_field['key'] ] = $normalized_field;
+		foreach ( $kept as $field ) {
+			self::$field_index[ $entity_type ][ $field['key'] ] = $field;
 		}
+		self::$groups[ $entity_type ][ $group_name ] = $kept;
 
-		self::$groups[ $entity_type ][ $group_name ] = $normalized;
-
-		// 加入待建表佇列
-		self::$pending_schemas[] = array(
-			'type'   => $entity_type,
-			'group'  => $group_name,
-			'fields' => $normalized,
+		self::$restored[ $id ] = array(
+			'entity_type' => $entity_type,
+			'group'       => $group_name,
+			'fields'      => count( $kept ),
+			'skipped'     => $skipped,
+			'native'      => $native,
 		);
 
 		return true;
 	}
 
+	/**
+	 * 本請求從 wpdo_registry_meta 還原的孤兒群組。
+	 *
+	 * @return array<int, array{entity_type:string, group:string, fields:int, skipped:string[], native:string[]}>
+	 */
+	public static function get_restored_groups(): array {
+		return array_values( self::$restored );
+	}
+
 	/**
 	 * 記錄同名群組衝突（每個 entity/group 每請求一筆），並寫入 warning。
 	 *

includes/engine/class-tmdo-schema-manager.php

@@ -268,6 +268,113 @@ final class TMDO_Schema_Manager {
 		);
 	}
 
+	/**
+	 * 還原孤兒群組：扁平表還在、定義存在 wpdo_registry_meta，但已沒有外掛註冊。
+	 *
+	 * 在所有註冊都完成後（init:1 晚綁定）呼叫。只處理 aeav_only 的實體：其他
+	 * 模式仍會寫原生 meta，孤兒 key 從原生讀取即正確；全部非 aeav_only 時不查資料庫。
+	 * 原生 meta 已有資料的 key（孤兒期間寫入，比扁平表新）留在原生，不還原。
+	 * 還原只影響讀寫路由，不會建立或修改任何資料表。
+	 *
+	 * @return int 還原的群組數
+	 */
+	public static function restore_orphaned_groups(): int {
+		global $wpdb;
+
+		if ( ! class_exists( 'TMDO_Mode_Manager' ) ) {
+			return 0;
+		}
+		$types = array_values(
+			array_filter(
+				TMDO_Entity_Registry::VALID_ENTITY_TYPES,
+				static fn( $type ) => TMDO_Mode_Manager::MODE_AEAV_ONLY === TMDO_Mode_Manager::get( $type )
+			)
+		);
+		if ( empty( $types ) ) {
+			return 0;
+		}
+
+		$meta_table   = $wpdb->prefix . TMDO_TABLE_PREFIX . 'registry_meta';
+		$placeholders = implode( ',', array_fill( 0, count( $types ), '%s' ) );
+		$rows         = $wpdb->get_results(
+			$wpdb->prepare( "SELECT entity_type, group_name, field_definitions FROM `{$meta_table}` WHERE entity_type IN ({$placeholders})", ...$types ),
+			ARRAY_A
+		);
+
+		$orphans = array();
+		foreach ( (array) $rows as $row ) {
+			if ( ! TMDO_Entity_Registry::get_group_fields( $row['entity_type'], $row['group_name'] ) ) {
+				$orphans[] = $row;
+			}
+		}
+		if ( empty( $orphans ) ) {
+			return 0;
+		}
+
+		// One SHOW TABLES for all candidates instead of one per orphan.
+		$existing = (array) $wpdb->get_col( $wpdb->prepare( 'SHOW TABLES LIKE %s', $wpdb->esc_like( $wpdb->prefix . TMDO_TABLE_PREFIX ) . '%' ) );
+
+		// "entity:key" → native meta has rows. Stable while the key is restored
+		// (aeav_only writes go to the flat table only), so a day-long cache is safe.
+		$native_cache = get_transient( 'tmdo_orphan_native_keys' );
+		$native_cache = is_array( $native_cache ) ? $native_cache : array();
+		$cache_dirty  = false;
+
+		$restored = 0;
+		foreach ( $orphans as $row ) {
+			if ( ! in_array( self::get_table_name( $row['entity_type'], $row['group_name'] ), $existing, true ) ) {
+				continue;
+			}
+			$fields = json_decode( (string) $row['field_definitions'], true );
+			if ( ! is_array( $fields ) ) {
+				continue;
+			}
+			$native_keys = array();
+			foreach ( $fields as $field ) {
+				$key = (string) ( $field['key'] ?? '' );
+				if ( '' === $key ) {
+					continue;
+				}
+				$cache_key = $row['entity_type'] . ':' . $key;
+				if ( ! array_key_exists( $cache_key, $native_cache ) ) {
+					$native_cache[ $cache_key ] = self::native_meta_has_key( $row['entity_type'], $key );
+					$cache_dirty                = true;
+				}
+				if ( $native_cache[ $cache_key ] ) {
+					$native_keys[] = $key;
+				}
+			}
+			if ( TMDO_Entity_Registry::restore_group( $row['entity_type'], $row['group_name'], $fields, $native_keys ) ) {
+				++$restored;
+			}
+		}
+
+		if ( $cache_dirty ) {
+			set_transient( 'tmdo_orphan_native_keys', $native_cache, DAY_IN_SECONDS );
+		}
+
+		return $restored;
+	}
+
+	/**
+	 * Whether the entity's native meta table holds any row for this key.
+	 */
+	private static function native_meta_has_key( string $entity_type, string $meta_key ): bool {
+		global $wpdb;
+		$tables = array(
+			'post'    => $wpdb->postmeta,
+			'user'    => $wpdb->usermeta,
+			'term'    => $wpdb->termmeta,
+			'comment' => $wpdb->commentmeta,
+		);
+		if ( empty( $tables[ $entity_type ] ) ) {
+			return false;
+		}
+		return (bool) $wpdb->get_var(
+			$wpdb->prepare( "SELECT 1 FROM `{$tables[ $entity_type ]}` WHERE meta_key = %s LIMIT 1", $meta_key )
+		);
+	}
+
 	/**
 	 * 取得已儲存的 Schema hash
 	 */

tests/integration/OrphanGroupRestoreTest.php

@@ -0,0 +1,192 @@
+<?php
+declare(strict_types=1);
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Orphaned flat-table groups stay readable.
+ *
+ * Scenario: a plugin registered an entity group, its flat table was created
+ * (definition persisted in wpdo_registry_meta), data landed there, and then
+ * the plugin went away. In aeav_only mode the values exist only in the flat
+ * table, so without the group registration reads come back empty.
+ */
+class OrphanGroupRestoreTest extends TestCase {
+
+	private const GROUP = 'orphan_itest';
+	private const TABLE = 'wp_itest_wpdo_user_orphan_itest';
+
+	public static function setUpBeforeClass(): void {
+		$base = WPDO_PLUGIN_DIR;
+		foreach ( array(
+			'includes/adapters/interface-entity-adapter.php',
+			'includes/engine/class-tmdo-type-caster.php',
+			'includes/engine/class-tmdo-schema-manager.php',
+			'includes/engine/class-tmdo-entity-registry.php',
+			'includes/engine/class-tmdo-mode-manager.php',
+			'includes/engine/class-tmdo-cache-orchestrator.php',
+			'includes/adapters/class-tmdo-adapter-user.php',
+			'includes/engine/class-tmdo-hook-bus.php',
+		) as $file ) {
+			require_once $base . $file;
+		}
+		WPDO_Installer::install_v2_tables();
+
+		global $wpdb;
+		$wpdb->query(
+			"CREATE TABLE IF NOT EXISTS `{$wpdb->usermeta}` (
+				umeta_id   BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+				user_id    BIGINT(20) UNSIGNED NOT NULL DEFAULT 0,
+				meta_key   VARCHAR(255) DEFAULT NULL,
+				meta_value LONGTEXT,
+				PRIMARY KEY (umeta_id),
+				KEY meta_key (meta_key(191))
+			) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4"
+		);
+	}
+
+	protected function setUp(): void {
+		global $wpdb;
+		self::drop_fixture();
+		$GLOBALS['_wp_options']    = array();
+		$GLOBALS['_wp_cache']      = array();
+		$GLOBALS['_wp_transients'] = array();
+		self::reset_statics();
+
+		// A provider registered the group earlier: its flat table exists and the
+		// normalized definition was persisted to registry_meta (what
+		// Schema_Manager::create_or_upgrade_table() leaves behind — built by hand
+		// here because that method needs the real wp-admin upgrade.php).
+		WPDO_Entity_Registry::init();
+		WPDO_Entity_Registry::register_adapter( 'user', new WPDO_Adapter_User() );
+		WPDO_Entity_Registry::register_group( 'user', self::GROUP, array( array( 'key' => 'orphan_note', 'type' => 'text' ) ) );
+		$wpdb->query(
+			'CREATE TABLE `' . self::TABLE . '` (
+				`id` BIGINT(20) NOT NULL AUTO_INCREMENT,
+				`user_id` BIGINT(20) NOT NULL,
+				`orphan_note` VARCHAR(255) DEFAULT NULL,
+				`created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+				`updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+				PRIMARY KEY (`id`),
+				UNIQUE KEY `uk_entity` (`user_id`)
+			) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4'
+		);
+		$wpdb->insert(
+			$wpdb->prefix . 'wpdo_registry_meta',
+			array(
+				'entity_type'       => 'user',
+				'group_name'        => self::GROUP,
+				'schema_hash'       => 'itest',
+				'field_definitions' => wp_json_encode( WPDO_Entity_Registry::get_group_fields( 'user', self::GROUP ) ),
+			)
+		);
+		$wpdb->insert( self::TABLE, array( 'user_id' => 77, 'orphan_note' => 'kept' ) );
+
+		// The provider goes away: next request starts with an empty registry.
+		WPDO_Entity_Registry::init();
+		WPDO_Entity_Registry::register_adapter( 'user', new WPDO_Adapter_User() );
+		self::reset_statics();
+	}
+
+	protected function tearDown(): void {
+		self::drop_fixture();
+		WPDO_Entity_Registry::init();
+		self::set_modes( null );
+	}
+
+	public function test_orphaned_group_is_unreadable_before_restore(): void {
+		self::set_modes( 'aeav_only' );
+
+		$this->assertNull( WPDO_Hook_Bus::intercept_get( null, 77, 'orphan_note', true, 'user' ) );
+	}
+
+	public function test_restore_makes_aeav_only_data_readable_again(): void {
+		self::set_modes( 'aeav_only' );
+
+		$this->assertSame( 1, WPDO_Schema_Manager::restore_orphaned_groups() );
+
+		$this->assertSame( array( 'kept' ), WPDO_Hook_Bus::intercept_get( null, 77, 'orphan_note', true, 'user' ) );
+		$this->assertSame( array(), WPDO_Entity_Registry::get_pending_schemas(), 'Restoring must not queue DDL.' );
+	}
+
+	public function test_restore_only_applies_to_aeav_only(): void {
+		// dual_write / shadow_read still write native meta, so an orphaned key
+		// keeps reading correctly from there — nothing to restore.
+		foreach ( array( 'disabled', 'dual_write', 'shadow_read' ) as $mode ) {
+			self::set_modes( $mode );
+			$this->assertSame( 0, WPDO_Schema_Manager::restore_orphaned_groups(), $mode );
+			$this->assertNull( WPDO_Entity_Registry::get_field( 'user', 'orphan_note' ), $mode );
+		}
+	}
+
+	public function test_key_with_native_meta_rows_stays_on_native(): void {
+		global $wpdb;
+		self::set_modes( 'aeav_only' );
+		// Written to native meta while the group was unregistered — newer than the flat copy.
+		$wpdb->insert( $wpdb->usermeta, array( 'user_id' => 5, 'meta_key' => 'orphan_note', 'meta_value' => 'native' ) );
+
+		$this->assertSame( 0, WPDO_Schema_Manager::restore_orphaned_groups() );
+
+		$this->assertNull( WPDO_Hook_Bus::intercept_get( null, 5, 'orphan_note', true, 'user' ), 'Native meta must keep serving this key.' );
+		$this->assertSame( array( 'orphan_note' ), WPDO_Entity_Registry::get_restored_groups()[0]['native'] );
+	}
+
+	public function test_native_meta_check_is_cached(): void {
+		self::set_modes( 'aeav_only' );
+		WPDO_Schema_Manager::restore_orphaned_groups();
+
+		$this->assertSame( array( 'user:orphan_note' => false ), get_transient( 'tmdo_orphan_native_keys' ) );
+	}
+
+	public function test_restore_skips_groups_whose_table_is_gone(): void {
+		global $wpdb;
+		self::set_modes( 'aeav_only' );
+		$wpdb->query( 'DROP TABLE IF EXISTS `' . self::TABLE . '`' );
+		self::reset_statics();
+
+		$this->assertSame( 0, WPDO_Schema_Manager::restore_orphaned_groups() );
+	}
+
+	public function test_registered_group_is_left_alone(): void {
+		self::set_modes( 'aeav_only' );
+		WPDO_Entity_Registry::register_group( 'user', self::GROUP, array( array( 'key' => 'orphan_note', 'type' => 'text' ) ) );
+
+		$this->assertSame( 0, WPDO_Schema_Manager::restore_orphaned_groups() );
+		$this->assertSame( array(), WPDO_Entity_Registry::get_restored_groups() );
+	}
+
+	// ── Helpers ──────────────────────────────────────────────────────────────
+
+	private static function drop_fixture(): void {
+		global $wpdb;
+		$wpdb->query( 'DROP TABLE IF EXISTS `' . self::TABLE . '`' );
+		$wpdb->delete( $wpdb->prefix . 'wpdo_registry_meta', array( 'entity_type' => 'user', 'group_name' => self::GROUP ) );
+		$wpdb->delete( $wpdb->usermeta, array( 'meta_key' => 'orphan_note' ) );
+	}
+
+	/** Clear Schema_Manager's table_exists cache and the Cache_Orchestrator L1. */
+	private static function reset_statics(): void {
+		$ref = new ReflectionProperty( WPDO_Schema_Manager::class, 'table_exists_cache' );
+		$ref->setAccessible( true );
+		$ref->setValue( null, array() );
+
+		$l1 = new ReflectionProperty( WPDO_Cache_Orchestrator::class, 'l1_cache' );
+		$l1->setAccessible( true );
+		$l1->setValue( null, array() );
+	}
+
+	/** Inject the user mode straight into Mode_Manager's cache (null = reset). */
+	private static function set_modes( ?string $user_mode ): void {
+		$ref = new ReflectionProperty( WPDO_Mode_Manager::class, 'cache' );
+		$ref->setAccessible( true );
+		$ref->setValue(
+			null,
+			null === $user_mode ? null : array(
+				'user'    => $user_mode,
+				'post'    => 'disabled',
+				'term'    => 'disabled',
+				'comment' => 'disabled',
+			)
+		);
+	}
+}

tests/unit/EntityRegistryRestoreTest.php

@@ -0,0 +1,116 @@
+<?php
+declare(strict_types=1);
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Restoring orphaned entity groups from their persisted definition.
+ *
+ * When the plugin that registered a group is gone, its flat table keeps the
+ * data but nothing maps the meta keys to it any more — in aeav_only mode the
+ * values read back as empty. restore_group() re-registers the stored
+ * definition for read/write routing only: it must never queue DDL and must
+ * not take over keys another live group already manages.
+ */
+class EntityRegistryRestoreTest extends TestCase {
+
+	protected function setUp(): void {
+		if ( ! class_exists( 'TMDO_Site_Health' ) ) {
+			require_once TMDO_PATH . 'includes/diagnostic/class-tmdo-site-health.php';
+		}
+		TMDO_Entity_Registry::init();
+		TMDO_Entity_Registry::register_adapter( 'user', $this->createMock( TMDO_Entity_Adapter_Interface::class ) );
+	}
+
+	private function stored_definition(): array {
+		return array(
+			array( 'key' => 'orphan_note', 'type' => 'text', 'group' => 'orphan', 'entity_type' => 'user' ),
+			array( 'key' => 'orphan_score', 'type' => 'integer', 'searchable' => true, 'group' => 'orphan', 'entity_type' => 'user' ),
+		);
+	}
+
+	public function test_restore_registers_fields_for_routing(): void {
+		$this->assertTrue( TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() ) );
+
+		$this->assertSame( 'orphan', TMDO_Entity_Registry::get_field( 'user', 'orphan_note' )['group'] );
+		$this->assertSame( array( 'orphan_note', 'orphan_score' ), TMDO_Entity_Registry::get_group_keys( 'user', 'orphan' ) );
+	}
+
+	public function test_restore_never_queues_ddl(): void {
+		TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() );
+
+		$this->assertSame( array(), TMDO_Entity_Registry::get_pending_schemas() );
+	}
+
+	public function test_restore_skips_keys_managed_by_a_live_group(): void {
+		TMDO_Entity_Registry::register_group( 'user', 'live', array( array( 'key' => 'orphan_note', 'type' => 'text' ) ) );
+
+		TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() );
+
+		$this->assertSame( 'live', TMDO_Entity_Registry::get_field( 'user', 'orphan_note' )['group'] );
+		$this->assertSame( array( 'orphan_score' ), TMDO_Entity_Registry::get_group_keys( 'user', 'orphan' ) );
+		$restored = TMDO_Entity_Registry::get_restored_groups();
+		$this->assertSame( array( 'orphan_note' ), $restored[0]['skipped'] );
+	}
+
+	public function test_restore_leaves_keys_with_native_data_on_native_meta(): void {
+		TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition(), array( 'orphan_note' ) );
+
+		$this->assertNull( TMDO_Entity_Registry::get_field( 'user', 'orphan_note' ) );
+		$this->assertSame( array( 'orphan_score' ), TMDO_Entity_Registry::get_group_keys( 'user', 'orphan' ) );
+		$this->assertSame( array( 'orphan_note' ), TMDO_Entity_Registry::get_restored_groups()[0]['native'] );
+	}
+
+	public function test_group_left_entirely_on_native_is_still_reported(): void {
+		$this->assertFalse( TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition(), array( 'orphan_note', 'orphan_score' ) ) );
+
+		$this->assertNotContains( 'orphan', TMDO_Entity_Registry::get_groups_for_type( 'user' ) );
+		$restored = TMDO_Entity_Registry::get_restored_groups();
+		$this->assertSame( 0, $restored[0]['fields'] );
+		$this->assertSame( array( 'orphan_note', 'orphan_score' ), $restored[0]['native'] );
+	}
+
+	public function test_restore_is_refused_when_group_is_registered(): void {
+		TMDO_Entity_Registry::register_group( 'user', 'orphan', array( array( 'key' => 'orphan_note', 'type' => 'text' ) ) );
+
+		$this->assertFalse( TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() ) );
+		$this->assertSame( array(), TMDO_Entity_Registry::get_restored_groups() );
+	}
+
+	public function test_restore_is_refused_when_every_key_is_taken(): void {
+		TMDO_Entity_Registry::register_group(
+			'user',
+			'live',
+			array(
+				array( 'key' => 'orphan_note', 'type' => 'text' ),
+				array( 'key' => 'orphan_score', 'type' => 'integer' ),
+			)
+		);
+
+		$this->assertFalse( TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() ) );
+		$this->assertNotContains( 'orphan', TMDO_Entity_Registry::get_groups_for_type( 'user' ) );
+	}
+
+	public function test_restored_groups_are_listed_and_cleared_by_init(): void {
+		TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() );
+
+		$restored = TMDO_Entity_Registry::get_restored_groups();
+		$this->assertSame( 'user', $restored[0]['entity_type'] );
+		$this->assertSame( 'orphan', $restored[0]['group'] );
+		$this->assertSame( 2, $restored[0]['fields'] );
+
+		TMDO_Entity_Registry::init();
+		$this->assertSame( array(), TMDO_Entity_Registry::get_restored_groups() );
+	}
+
+	public function test_site_health_reports_restored_groups(): void {
+		$this->assertSame( 'good', TMDO_Site_Health::check_orphaned_entity_groups()['status'] );
+
+		TMDO_Entity_Registry::restore_group( 'user', 'orphan', $this->stored_definition() );
+
+		$result = TMDO_Site_Health::check_orphaned_entity_groups();
+		$this->assertSame( 'recommended', $result['status'] );
+		$this->assertStringContainsString( 'user/orphan', $result['description'] );
+		$this->assertArrayHasKey( 'wpdo_orphaned_entity_groups', TMDO_Site_Health::register_tests( array() )['direct'] );
+	}
+}