diff --git a/package-lock.json b/package-lock.json
index f1cab87..958920c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -16,7 +16,7 @@
         "express": "^5.2.1",
         "html-to-md": "^0.8.8",
         "yargs": "^17.7.2",
-        "zod": "^3.25.76"
+        "zod": "^4.0.0"
       },
       "bin": {
         "doc-mcp-server": "build/index.js"
@@ -1790,6 +1790,16 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@modelcontextprotocol/inspector-client/node_modules/zod": {
+      "version": "3.25.76",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
+      "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+      "dev": true,
+      "license": "MIT",
+      "funding": {
+        "url": "https://github.com/sponsors/colinhacks"
+      }
+    },
     "node_modules/@modelcontextprotocol/inspector-server": {
       "version": "0.17.5",
       "resolved": "https://registry.npmjs.org/@modelcontextprotocol/inspector-server/-/inspector-server-0.17.5.tgz",
@@ -1809,6 +1819,26 @@
         "mcp-inspector-server": "build/index.js"
       }
     },
+    "node_modules/@modelcontextprotocol/inspector-server/node_modules/zod": {
+      "version": "3.25.76",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
+      "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+      "dev": true,
+      "license": "MIT",
+      "funding": {
+        "url": "https://github.com/sponsors/colinhacks"
+      }
+    },
+    "node_modules/@modelcontextprotocol/inspector/node_modules/zod": {
+      "version": "3.25.76",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
+      "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+      "dev": true,
+      "license": "MIT",
+      "funding": {
+        "url": "https://github.com/sponsors/colinhacks"
+      }
+    },
     "node_modules/@modelcontextprotocol/sdk": {
       "version": "1.24.3",
       "resolved": "https://registry.npmjs.org/@modelcontextprotocol/sdk/-/sdk-1.24.3.tgz",
@@ -12167,9 +12197,9 @@
       }
     },
     "node_modules/zod": {
-      "version": "3.25.76",
-      "resolved": "https://registry.npmmirror.com/zod/-/zod-3.25.76.tgz",
-      "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+      "version": "4.2.1",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-4.2.1.tgz",
+      "integrity": "sha512-0wZ1IRqGGhMP76gLqz8EyfBXKk0J2qo2+H3fi4mcUP/KtTocoX08nmIAHl1Z2kJIZbZee8KOpBCSNPRgauucjw==",
       "license": "MIT",
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
diff --git a/package.json b/package.json
index 6a5b5ed..2fd68a9 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,7 @@
     "express": "^5.2.1",
     "html-to-md": "^0.8.8",
     "yargs": "^17.7.2",
-    "zod": "^3.25.76"
+    "zod": "^4.0.0"
   },
   "devDependencies": {
     "@biomejs/biome": "2.3.7",