diff --git a/npm_install.py b/npm_install.py
index 705f177..36ecb30 100644
--- a/npm_install.py
+++ b/npm_install.py
@@ -2312,6 +2312,12 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
             os.chdir(src_frontend)
             _prepare_sass(src_frontend)
 
+            # Clean Yarn 4.x PnP files that can cause stale patch resolution
+            for pnp_file in [".pnp.cjs", ".pnp.d.ts", ".pnp.loader.mjs"]:
+                p = src_frontend / pnp_file
+                if p.exists():
+                    p.unlink()
+
             shutil.rmtree(src_frontend / ".yarn", ignore_errors=True)
             shutil.rmtree(src_frontend / "node_modules", ignore_errors=True)
             run(yarn_cmd + ["cache", "clean", "--all"], check=False)
@@ -2344,6 +2350,10 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
                 node_modules = src_frontend / "node_modules"
                 if node_modules.exists():
                     shutil.rmtree(node_modules, ignore_errors=True)
+                for pnp_file in [".pnp.cjs", ".pnp.d.ts", ".pnp.loader.mjs"]:
+                    p = src_frontend / pnp_file
+                    if p.exists():
+                        p.unlink()
                 run(install_cmd, timeout=1200)
                 
         except Exception as e:
diff --git a/npm_install_multiversion.py b/npm_install_multiversion.py
index cbd71ac..35e67ae 100644
--- a/npm_install_multiversion.py
+++ b/npm_install_multiversion.py
@@ -2034,6 +2034,12 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
         except Exception:
             pass
 
+        # Clean Yarn 4.x PnP files that can cause stale patch resolution
+        for pnp_file in [".pnp.cjs", ".pnp.d.ts", ".pnp.loader.mjs"]:
+            p = src_frontend / pnp_file
+            if p.exists():
+                p.unlink()
+
         # Clean cache
         try:
             run(yarn_cmd + ["cache", "clean"], check=False)