diff --git a/services/web/frontend/js/features/source-editor/utils/tree-operations/projection.ts b/services/web/frontend/js/features/source-editor/utils/tree-operations/projection.ts
index 89681491e5..2be82c405a 100644
--- a/services/web/frontend/js/features/source-editor/utils/tree-operations/projection.ts
+++ b/services/web/frontend/js/features/source-editor/utils/tree-operations/projection.ts
@@ -1,6 +1,6 @@
 import { ensureSyntaxTree } from '@codemirror/language'
 import { EditorState, Transaction } from '@codemirror/state'
-import { IterMode, SyntaxNodeRef } from '@lezer/common'
+import { SyntaxNodeRef } from '@lezer/common'
 
 const TWENTY_MS = 20
 const FIVE_HUNDRED_MS = 500
@@ -144,7 +144,11 @@ export function getUpdatedProjection<T extends ProjectionItem>(
         }
         return enterNode(state, node, items, nodeIntersectsChange)
       },
-      mode: IterMode.IgnoreMounts | IterMode.IgnoreOverlays,
+      // Do not pass IgnoreMounts or IgnoreOverlays: mixed-language parsers
+      // (e.g. yamlFrontmatter wrapping Markdown) embed the content language
+      // as an overlay, and skipping overlays would hide all heading nodes.
+      // enterNode functions filter by node name, so visiting extra nodes from
+      // mounts/overlays in other languages is harmless.
     })
     // We know the exact projection. Return it.
     return {