diff --git a/php-transformer/src/HtmlToBlocks/Elements/InertElements.php b/php-transformer/src/HtmlToBlocks/Elements/InertElements.php
new file mode 100644
index 000000000..3033dc6c2
--- /dev/null
+++ b/php-transformer/src/HtmlToBlocks/Elements/InertElements.php
@@ -0,0 +1,123 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Automattic\BlocksEngine\PhpTransformer\HtmlToBlocks\Elements;
+
+use Automattic\BlocksEngine\PhpTransformer\HtmlToBlocks\Classification\SourceElementClassifier;
+use Automattic\BlocksEngine\PhpTransformer\HtmlToBlocks\Style\SourceElementVisibility;
+use Automattic\BlocksEngine\PhpTransformer\HtmlToBlocks\Style\StyleResolver;
+use Automattic\BlocksEngine\PhpTransformer\HtmlToBlocks\Support\SourceDom;
+use DOMDocument;
+use DOMElement;
+
+/**
+ * Recognizes source elements that are inert on the page: runtime media
+ * placeholders that never paint, and hidden SVG sprite stores that only
+ * other SVG content consumes.
+ */
+final class InertElements
+{
+    public function __construct(
+        private readonly StyleResolver $styleResolver,
+        private readonly SourceElementClassifier $sourceElementClassifier,
+        private readonly SourceElementVisibility $sourceVisibility,
+        private readonly RuntimeIslandAnalyzer $runtimeIslands
+    ) {
+    }
+
+    public function isInertRuntimeMediaPlaceholder(DOMElement $element): bool
+    {
+        if ( ! $this->sourceElementClassifier->isRuntimeMediaSurfaceElement($element)
+            || ! str_contains(strtolower($element->tagName), '-')
+            || '' !== trim($element->textContent ?? '')
+        ) {
+            return false;
+        }
+
+        foreach ( array_merge(array( $element ), iterator_to_array($element->getElementsByTagName('*'))) as $candidate ) {
+            if ( ! $candidate instanceof DOMElement
+                || ! $this->runtimeIslands->isSafeTransparentCustomElement($candidate)
+                || '' !== trim(SourceDom::attr($candidate, 'role'))
+                || '' !== trim(SourceDom::attr($candidate, 'aria-label'))
+            ) {
+                return false;
+            }
+
+            foreach ( array( 'src', 'srcset', 'href', 'data-src', 'data-url' ) as $attribute ) {
+                if ( '' !== trim(SourceDom::attr($candidate, $attribute)) ) {
+                    return false;
+                }
+            }
+
+            foreach ( $candidate->attributes as $attribute ) {
+                if ( str_starts_with(strtolower($attribute->name), 'data-') && '' !== trim($attribute->value) ) {
+                    return false;
+                }
+            }
+
+            if ( $candidate !== $element && ! $this->sourceElementClassifier->isStructuralTransparentCustomWrapperChild($candidate) ) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    public function isInertHiddenSvgStorage(DOMElement $element): bool
+    {
+        $isDomStore = $element->hasAttribute('data-dom-store');
+        if ( ! $this->sourceVisibility->startsHidden($element)
+            || (! $isDomStore && (
+                $this->styleResolver->hasConditionalStyleFamily($element, 'layout')
+                || $this->styleResolver->hasConditionalStyleFamily($element, 'visibility')
+                || $this->styleResolver->hasConditionalStyleFamily($element, 'opacity')
+            ))
+            || '' !== trim(SourceDom::attr($element, 'aria-label'))
+            || '' !== trim(SourceDom::attr($element, 'aria-labelledby'))
+            || '' !== trim(SourceDom::attr($element, 'title'))
+            || ! $this->sourceElementClassifier->hasOnlySvgDefinitions($element)
+            || $this->hiddenSvgStoreHasNonSvgConsumer($element) ) {
+            return false;
+        }
+
+        return true;
+    }
+
+    private function hiddenSvgStoreHasNonSvgConsumer(DOMElement $store): bool
+    {
+        $ids = array();
+        foreach ( $store->getElementsByTagName('*') as $definition ) {
+            if ( $definition instanceof DOMElement && '' !== trim(SourceDom::attr($definition, 'id')) ) {
+                $ids[] = trim(SourceDom::attr($definition, 'id'));
+            }
+        }
+        if ( array() === $ids || ! $store->ownerDocument instanceof DOMDocument ) {
+            return false;
+        }
+
+        foreach ( $store->ownerDocument->getElementsByTagName('*') as $candidate ) {
+            if ( ! $candidate instanceof DOMElement || $this->sourceElementClassifier->isDescendantOf($candidate, $store) ) {
+                continue;
+            }
+            foreach ( $candidate->attributes as $attribute ) {
+                foreach ( $ids as $id ) {
+                    if ( preg_match('/(?:^|[\\s,(])(?:url\\(\\s*["\']?#' . preg_quote($id, '/') . '["\']?\\s*\\)|#' . preg_quote($id, '/') . '(?:$|[\\s,)]))/', $attribute->value)
+                        && 'svg' !== strtolower($candidate->tagName)
+                        && null === SourceDom::ancestorElement($candidate, 'svg') ) {
+                        return true;
+                    }
+                }
+            }
+            if ( 'style' === strtolower($candidate->tagName) ) {
+                foreach ( $ids as $id ) {
+                    if ( preg_match('/url\\(\\s*["\']?#' . preg_quote($id, '/') . '["\']?\\s*\\)/', $candidate->textContent ?? '') ) {
+                        return true;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+}
diff --git a/php-transformer/src/HtmlToBlocks/HtmlCompilation.php b/php-transformer/src/HtmlToBlocks/HtmlCompilation.php
index 1634d158e..506481c7f 100644
--- a/php-transformer/src/HtmlToBlocks/HtmlCompilation.php
+++ b/php-transformer/src/HtmlToBlocks/HtmlCompilation.php
@@ -315,6 +315,7 @@ final class HtmlCompilation extends SourceBlockCreator implements RichTextInline
     private readonly Elements\CustomImageHostLowering $customImageHosts;
     private readonly Elements\AnchorLowering $anchors;
     private readonly Elements\RenderNeutralElements $renderNeutral;
+    private readonly Elements\InertElements $inertElements;
     private readonly SourceProvenance $sourceProvenance;
 
     private readonly RuntimeResourceElementConverter $runtimeResourceConverter;
@@ -607,6 +608,7 @@ function (DOMElement $element): array {
             $this->listStructure
         );
         $this->renderNeutral = new Elements\RenderNeutralElements($this->session, $this->styleResolver, $this->sourceElementClassifier, $this->sourceElementDescription, $this->runtimeIslands, $this->emptyElementFootprint);
+        $this->inertElements = new Elements\InertElements($this->styleResolver, $this->sourceElementClassifier, $this->sourceVisibility, $this->runtimeIslands);
         $this->customImageHosts = new Elements\CustomImageHostLowering($this, $this->blockFactory, $this->styleResolver, $this->session, $this->sourceElementClassifier, $this->sourceElementDescription, $this->imageLowering, $this->layoutShells, $this->runtimeIslands, $this->authorLayoutOwnership);
         $this->anchors = new Elements\AnchorLowering($this, $this, $this->styleResolver, $this->session, $this->sourceElementClassifier, $this->sourceElementDescription, $this->imageLowering, $this->imageUrls, $this->layoutShells, $this->linkWrapperPropagator, $this->runtimeIslands, $this->customImageHosts);
         $this->layoutTables = new Elements\LayoutTableLowering(
@@ -647,7 +649,7 @@ function (DOMElement $element): array {
         $this->textLeafConverter = new TextLeafElementConverter($this->richTextMaterializer, $this->runtime, $this, $this->styleResolver, $this->sourceElementClassifier, $this->createTextLeafElementContext());
         $this->richTextConverter = new RichTextElementConverter($this, $this->styleResolver, $this->richTextMaterializer, $this->runtime, $this->createRichTextElementContext());
         $svgConverter = new SvgElementConverter($this, $this->sourceElementClassifier, $this->styleResolver, new SvgElementContext(
-            fn (DOMElement $element): bool => $this->isInertHiddenSvgStorage($element),
+            fn (DOMElement $element): bool => $this->inertElements->isInertHiddenSvgStorage($element),
             fn (DOMElement $element): bool => $this->runtimeIslands->isRuntimeDomTarget($element),
             fn (DOMElement $element): string => $this->sanitizeInlineSvgMarkup($element),
             fn (string $html): bool => $this->isSafeSvgContent($html),
@@ -956,7 +958,7 @@ function (DOMElement $element, array &$fallbacks): array {
             $this,
             $this->runtimeIslands,
             $this->session,
-            fn (DOMElement $element): bool => $this->isInertRuntimeMediaPlaceholder($element),
+            fn (DOMElement $element): bool => $this->inertElements->isInertRuntimeMediaPlaceholder($element),
             fn (DOMElement $element): bool => $this->sourceVisibility->startsHidden($element),
             $this->sourceElementDescription
         );
@@ -1096,7 +1098,7 @@ function (DOMElement $element, array &$fallbacks): ?array {
                 fn (DOMElement $element): bool => $this->shouldPreserveEmptyVisualElement($element)
             ),
             $this->projectedNavigation,
-            new PhrasingSvgConverter($this->svgMaterializer, $this, fn (DOMElement $element): bool => $this->isInertHiddenSvgStorage($element)),
+            new PhrasingSvgConverter($this->svgMaterializer, $this, fn (DOMElement $element): bool => $this->inertElements->isInertHiddenSvgStorage($element)),
              $capturedDialogConverter,
              new CapturedChoiceGroupConverter(
                  $this->session,
@@ -3568,7 +3570,7 @@ private function convertElement(DOMElement $element, array &$fallbacks, bool $ca
             return $transparentCustomElement;
         }
 
-        if ( $this->isInertRuntimeMediaPlaceholder($element) ) {
+        if ( $this->inertElements->isInertRuntimeMediaPlaceholder($element) ) {
             return null;
         }
 
@@ -3801,44 +3803,6 @@ private function recognizedNavigationHostBlock(DOMElement $element, array &$fall
     }
 
 
-    private function isInertRuntimeMediaPlaceholder(DOMElement $element): bool
-    {
-        if ( ! $this->sourceElementClassifier->isRuntimeMediaSurfaceElement($element)
-            || ! str_contains(strtolower($element->tagName), '-')
-            || '' !== trim($element->textContent ?? '')
-        ) {
-            return false;
-        }
-
-        foreach ( array_merge(array( $element ), iterator_to_array($element->getElementsByTagName('*'))) as $candidate ) {
-            if ( ! $candidate instanceof DOMElement
-                || ! $this->runtimeIslands->isSafeTransparentCustomElement($candidate)
-                || '' !== trim($this->attr($candidate, 'role'))
-                || '' !== trim($this->attr($candidate, 'aria-label'))
-            ) {
-                return false;
-            }
-
-            foreach ( array( 'src', 'srcset', 'href', 'data-src', 'data-url' ) as $attribute ) {
-                if ( '' !== trim($this->attr($candidate, $attribute)) ) {
-                    return false;
-                }
-            }
-
-            foreach ( $candidate->attributes as $attribute ) {
-                if ( str_starts_with(strtolower($attribute->name), 'data-') && '' !== trim($attribute->value) ) {
-                    return false;
-                }
-            }
-
-            if ( $candidate !== $element && ! $this->sourceElementClassifier->isStructuralTransparentCustomWrapperChild($candidate) ) {
-                return false;
-            }
-        }
-
-        return true;
-    }
-
     /**
      * @return array<string, mixed>|null
      */
@@ -6798,63 +6762,6 @@ private function containsExcludedMedia(DOMElement $element): bool
         return false;
     }
 
-    private function isInertHiddenSvgStorage(DOMElement $element): bool
-    {
-        $isDomStore = $element->hasAttribute('data-dom-store');
-        if ( ! $this->sourceVisibility->startsHidden($element)
-            || (! $isDomStore && (
-                $this->styleResolver->hasConditionalStyleFamily($element, 'layout')
-                || $this->styleResolver->hasConditionalStyleFamily($element, 'visibility')
-                || $this->styleResolver->hasConditionalStyleFamily($element, 'opacity')
-            ))
-            || '' !== trim($this->attr($element, 'aria-label'))
-            || '' !== trim($this->attr($element, 'aria-labelledby'))
-            || '' !== trim($this->attr($element, 'title'))
-            || ! $this->sourceElementClassifier->hasOnlySvgDefinitions($element)
-            || $this->hiddenSvgStoreHasNonSvgConsumer($element) ) {
-            return false;
-        }
-
-        return true;
-    }
-
-    private function hiddenSvgStoreHasNonSvgConsumer(DOMElement $store): bool
-    {
-        $ids = array();
-        foreach ( $store->getElementsByTagName('*') as $definition ) {
-            if ( $definition instanceof DOMElement && '' !== trim($this->attr($definition, 'id')) ) {
-                $ids[] = trim($this->attr($definition, 'id'));
-            }
-        }
-        if ( array() === $ids || ! $store->ownerDocument instanceof DOMDocument ) {
-            return false;
-        }
-
-        foreach ( $store->ownerDocument->getElementsByTagName('*') as $candidate ) {
-            if ( ! $candidate instanceof DOMElement || $this->sourceElementClassifier->isDescendantOf($candidate, $store) ) {
-                continue;
-            }
-            foreach ( $candidate->attributes as $attribute ) {
-                foreach ( $ids as $id ) {
-                    if ( preg_match('/(?:^|[\\s,(])(?:url\\(\\s*["\']?#' . preg_quote($id, '/') . '["\']?\\s*\\)|#' . preg_quote($id, '/') . '(?:$|[\\s,)]))/', $attribute->value)
-                        && 'svg' !== strtolower($candidate->tagName)
-                        && null === SourceDom::ancestorElement($candidate, 'svg') ) {
-                        return true;
-                    }
-                }
-            }
-            if ( 'style' === strtolower($candidate->tagName) ) {
-                foreach ( $ids as $id ) {
-                    if ( preg_match('/url\\(\\s*["\']?#' . preg_quote($id, '/') . '["\']?\\s*\\)/', $candidate->textContent ?? '') ) {
-                        return true;
-                    }
-                }
-            }
-        }
-
-        return false;
-    }
-
     /**
      * Whether an image's wrapping link is a lightbox trigger rather than a
      * destination: it has to point at an image resource and be marked as a