diff --git a/npm_install.py b/npm_install.py
index 9988575..b3fc20a 100644
--- a/npm_install.py
+++ b/npm_install.py
@@ -2232,35 +2232,54 @@ def _build_frontend(src_frontend: Path, dest_frontend: Path):
                     if DEBUG:
                         print(f"   ⚠ 'yarn set version' failed: {e}")
             
-            # METHOD 3: npm install yarn@berry
+            # METHOD 3: npm install @yarnpkg/cli (yarn 4.x)
             try:
-                run(["npm", "install", "-g", "yarn@berry"], check=False)
+                run(["npm", "install", "-g", "@yarnpkg/cli"], check=False)
                 
                 if shutil.which("yarn"):
                     major = _get_yarn_major_version(["yarn"])
                     
                     if major and major >= 4:
                         if DEBUG:
-                            print(f"   ✓ Yarn {major}.x installed via npm")
+                            print(f"   ✓ Yarn {major}.x installed via @yarnpkg/cli")
                         return True
             except Exception as e:
                 if DEBUG:
-                    print(f"   ⚠ npm install yarn@berry failed: {e}")
+                    print(f"   ⚠ npm install @yarnpkg/cli failed: {e}")
             
-            # METHOD 4: Force install latest yarn
-            try:
-                run(["npm", "install", "-g", "yarn@latest", "--force"], check=False)
-                
-                if shutil.which("yarn"):
-                    major = _get_yarn_major_version(["yarn"])
+            # METHOD 4: yarn set version stable (requires yarn 1.x)
+            # First install yarn 1.x if not present
+            if not shutil.which("yarn"):
+                try:
+                    run(["npm", "install", "-g", "yarn@1"], check=False)
+                except Exception:
+                    pass
+            
+            if shutil.which("yarn"):
+                try:
+                    # Uninstall any global yarn 4.x first
+                    run(["npm", "uninstall", "-g", "@yarnpkg/cli"], check=False,
+                        stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
                     
-                    if major and major >= 4:
-                        if DEBUG:
-                            print(f"   ✓ Yarn {major}.x installed via npm --force")
-                        return True
-            except Exception as e:
-                if DEBUG:
-                    print(f"   ⚠ npm install --force failed: {e}")
+                    # yarn 1.x can upgrade itself to 4.x
+                    result = subprocess.run(
+                        ["yarn", "set", "version", "stable"],
+                        capture_output=True,
+                        timeout=120,
+                        text=True,
+                        check=False,
+                    )
+                    
+                    if result.returncode == 0:
+                        major = _get_yarn_major_version(["yarn"])
+                        
+                        if major and major >= 4:
+                            if DEBUG:
+                                print(f"   ✓ Yarn {major}.x installed via 'yarn set version'")
+                            return True
+                except Exception as e:
+                    if DEBUG:
+                        print(f"   ⚠ 'yarn set version' failed: {e}")
             
             return False