diff --git a/packages/wp-build/CHANGELOG.md b/packages/wp-build/CHANGELOG.md
index 23e33c1cdca137..d801aa55d1c6ae 100644
--- a/packages/wp-build/CHANGELOG.md
+++ b/packages/wp-build/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Bug Fixes
 
+-   Preserve the non-enumerable `__esModule` marker on `window.wp.*` IIFE globals so that external webpack consumers (e.g. WooCommerce) can still default-import `@wordpress/*` packages exposed as webpack externals.
 -   Remove the incorrect `#wpwrap` background from wp-admin critical CSS to prevent a black flash before hydration; rely on the existing `body` background instead ([#78493](https://github.com/WordPress/gutenberg/pull/78493)).
 
 ## 0.15.0 (2026-05-27)
diff --git a/packages/wp-build/lib/build.mjs b/packages/wp-build/lib/build.mjs
index 0ae6c549245942..e35dc30054a4df 100755
--- a/packages/wp-build/lib/build.mjs
+++ b/packages/wp-build/lib/build.mjs
@@ -585,10 +585,14 @@ async function bundlePackage( packageName, options = {} ) {
 		}
 		if ( globalName ) {
 			// esbuild marks the getters non-configurable, so we can't rewrite
-			// them in place; replacing the whole namespace with a shallow
-			// copy is the simplest way to materialize each value once.
+			// them in place; replacing the whole namespace with a shallow copy
+			// is the simplest way to materialize each value once.
+			//
+			// Seed the copy with a non-enumerable `__esModule` flag so that
+			// bundlers treat it as an ESM module, triggering interop
+			// conventions for default exports.
 			footerParts.push(
-				`if(${ globalName }&&typeof ${ globalName }==='object'){${ globalName }=Object.assign({},${ globalName });}`
+				`if(${ globalName }&&typeof ${ globalName }==='object'){${ globalName }=Object.assign(Object.defineProperty({},'__esModule',{value:true,writable:true}),${ globalName });}`
 			);
 		}
 		if ( footerParts.length ) {