diff --git a/src/Integrations/Divi/Design/ReferenceUsageQuery.php b/src/Integrations/Divi/Design/ReferenceUsageQuery.php
new file mode 100644
index 0000000..f4c512c
--- /dev/null
+++ b/src/Integrations/Divi/Design/ReferenceUsageQuery.php
@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Integrations\Divi\Design;
+
+use InvalidArgumentException;
+use LIT\MCP\Integrations\Divi\BlockTree\Container;
+use LIT\MCP\Integrations\Divi\BlockTree\MalformedMarkup;
+use LIT\MCP\Integrations\Divi\BlockTree\Parser;
+use LIT\MCP\Integrations\Divi\Library\UsageQuery;
+
+defined('ABSPATH') || exit;
+
+/**
+ * The posts that reference any of the global colors or variables $ids (GlobalUsages::reportFor(), ruling V8). Divi
+ * writes a reference as $variable({"type":"color"|"content","value":{"name":"<id>",…}})$ into block attributes, the
+ * quotes JSON-escaped in post_content (formats §1, §2). Fail closed (ruling P23): candidates contain an ID, a
+ * JSON-escaped hyphen after gcid/gvid or an escaped letter; a candidate matches when its raw content names an ID
+ * (also Divi 4 shortcodes), when the decoded attributes of any block do – the whole tree, also inside global modules,
+ * which NodeIndex does not descend into –, when a block's attributes cannot be read or when the parser rejects the
+ * markup.
+ */
+final class ReferenceUsageQuery implements UsageQuery
+{
+    /** MySQL REGEXP for "gcid"/"gvid" followed by a JSON-escaped hyphen ("\\u002d"), which LIKE does not find. */
+    public const ESCAPED_HYPHEN_REGEX = 'g[cv]id\\\\u002[dD]';
+
+    /** @var list<string> */
+    private array $ids;
+
+    /**
+     * @param list<string> $ids gcid-/gvid- IDs.
+     * @throws InvalidArgumentException Without an ID.
+     */
+    public function __construct(array $ids, private Parser $parser = new Parser())
+    {
+        $ids = array_values(array_unique(array_filter(
+            $ids,
+            static fn (mixed $id): bool => is_string($id) && $id !== ''
+        )));
+        if ($ids === []) {
+            throw new InvalidArgumentException('ReferenceUsageQuery needs at least one ID.');
+        }
+        $this->ids = $ids;
+    }
+
+    /**
+     * Whether a string inside $value (nested arrays included, keys not) contains one of $ids.
+     *
+     * @param list<string> $ids
+     */
+    public static function mentions(mixed $value, array $ids): bool
+    {
+        if (is_string($value)) {
+            foreach ($ids as $id) {
+                if (str_contains($value, $id)) {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+        if (is_array($value)) {
+            foreach ($value as $inner) {
+                if (self::mentions($inner, $ids)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    public function candidateCondition(\wpdb $db): string
+    {
+        $likes = array_map(static fn (string $id): string => '%' . $db->esc_like($id) . '%', $this->ids);
+
+        return (string) $db->prepare(
+            '(' . str_repeat('post_content LIKE %s OR ', count($likes))
+                . 'post_content REGEXP %s OR post_content REGEXP %s)',
+            ...array_merge($likes, [self::ESCAPED_HYPHEN_REGEX, self::ESCAPED_LETTER_REGEX])
+        );
+    }
+
+    public function matches(string $content): bool
+    {
+        if (self::mentions($content, $this->ids)) {
+            return true;
+        }
+
+        try {
+            return $this->inBlocks($this->parser->parse($content));
+        } catch (MalformedMarkup) {
+            return true;
+        }
+    }
+
+    private function inBlocks(Container $container): bool
+    {
+        foreach ($container->children() as $block) {
+            // The parser keeps attributes that are no JSON object as [] on an opaque block: unreadable, so it counts.
+            $unreadable = $block->isOpaque() && $block->attrs() === [] && str_contains((string) $block->rawOpen(), '{');
+            if ($unreadable || self::mentions($block->attrs(), $this->ids) || $this->inBlocks($block)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
diff --git a/tests/Unit/Integrations/Divi/Design/ReferenceUsageQueryTest.php b/tests/Unit/Integrations/Divi/Design/ReferenceUsageQueryTest.php
new file mode 100644
index 0000000..b40a3f3
--- /dev/null
+++ b/tests/Unit/Integrations/Divi/Design/ReferenceUsageQueryTest.php
@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Tests\Unit\Integrations\Divi\Design;
+
+use InvalidArgumentException;
+use LIT\MCP\Integrations\Divi\Design\ReferenceUsageQuery;
+use LIT\MCP\Tests\Unit\TestCase;
+use Mockery;
+
+final class ReferenceUsageQueryTest extends TestCase
+{
+    /** A color reference as post_content holds it: quotes JSON-escaped (formats §2). */
+    private const COLOR_REF = '$variable({"type":"color","value":{"name":'
+        . '"gcid-holz000001","settings":{}}})$';
+
+    public function testCandidatesContainAnIdAnEscapedHyphenOrAnEscapedLetter(): void
+    {
+        $db = Mockery::mock(\wpdb::class);
+        $db->allows('esc_like')->andReturnUsing(static fn (string $text): string => $text);
+        $db->expects('prepare')
+            ->with(
+                '(post_content LIKE %s OR post_content LIKE %s OR post_content REGEXP %s OR post_content REGEXP %s)',
+                '%gcid-holz000001%',
+                '%gvid-radius0001%',
+                'g[cv]id\\\\u002[dD]',
+                '\\\\u00[4-7][0-9a-fA-F]'
+            )
+            ->andReturn('(prepared)');
+
+        $query = new ReferenceUsageQuery(['gcid-holz000001', 'gvid-radius0001', 'gcid-holz000001']);
+
+        self::assertSame('(prepared)', $query->candidateCondition($db));
+    }
+
+    public function testNeedsAnId(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new ReferenceUsageQuery(['']);
+    }
+
+    public function testFindsAReferenceInTheAttributesOfAnyBlock(): void
+    {
+        $query = new ReferenceUsageQuery(['gcid-holz000001', 'gvid-radius0001']);
+
+        self::assertTrue($query->matches('<!-- wp:divi/text {"module":{"decoration":{"background":{"desktop":'
+            . '{"value":{"color":"' . self::COLOR_REF . '"}}}}}} /-->'));
+        self::assertTrue($query->matches('<!-- wp:divi/text {"x":"gvid-radius0001"} /-->'));
+        self::assertFalse($query->matches('<!-- wp:divi/text {"module":{"decoration":{"background":{"desktop":'
+            . '{"value":{"color":"#ffffff"}}}}}} /-->'));
+        self::assertFalse($query->matches('<!-- wp:divi/text {"x":"gcid-anders0001"} /-->'));
+        self::assertFalse($query->matches('<p>Keine Verweise</p>'));
+    }
+
+    public function testFindsAnIdWrittenWithJsonEscapesAlsoInsideGlobalModules(): void
+    {
+        $query = new ReferenceUsageQuery(['gcid-holz000001']);
+
+        self::assertTrue($query->matches('<!-- wp:divi/text {"x":"gcid-holz000001"} /-->'));
+        self::assertTrue($query->matches('<!-- wp:divi/section {"globalModule":"12"} -->'
+            . '<!-- wp:divi/text {"x":"gcid-holz000001"} /--><!-- /wp:divi/section -->'));
+        self::assertFalse($query->matches('<!-- wp:divi/text {"x":"gcid-anders0001"} /-->'));
+    }
+
+    public function testUnreadableMarkupAndDivi4ContentCount(): void
+    {
+        $query = new ReferenceUsageQuery(['gcid-holz000001']);
+
+        self::assertTrue($query->matches('<!-- wp:divi/section --><!-- wp:divi/text {"x":1} /-->'), 'never closed');
+        self::assertTrue($query->matches('<!-- wp:divi/text {"x":"gcid-holz000001",} /-->'), 'attrs no JSON');
+        self::assertTrue($query->matches('[et_pb_text background_color="gcid-holz000001"]x[/et_pb_text]'), 'Divi 4');
+    }
+
+    public function testMentionsLooksIntoNestedStrings(): void
+    {
+        self::assertTrue(ReferenceUsageQuery::mentions(['a' => ['b' => 'x gvid-radius0001 y']], ['gvid-radius0001']));
+        self::assertFalse(ReferenceUsageQuery::mentions(['gvid-radius0001' => 1], ['gvid-radius0001']), 'keys');
+        self::assertFalse(ReferenceUsageQuery::mentions(12, ['gvid-radius0001']));
+    }
+}