diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 34bb9ba5c..38e595462 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -402,13 +402,13 @@ importers:
     dependencies:
       '@modelcontextprotocol/sdk':
         specifier: '>=1.27.1'
-        version: 1.27.1(zod@3.25.76)
+        version: 1.27.1(zod@4.4.3)
       ws:
         specifier: ^8.18.0
         version: 8.18.3
       zod:
-        specifier: ^3.24.0
-        version: 3.25.76
+        specifier: ^4.4.3
+        version: 4.4.3
     devDependencies:
       '@types/node':
         specifier: ^22.14.0
@@ -6277,6 +6277,28 @@ snapshots:
     transitivePeerDependencies:
       - supports-color
 
+  '@modelcontextprotocol/sdk@1.27.1(zod@4.4.3)':
+    dependencies:
+      '@hono/node-server': 1.19.11(hono@4.12.8)
+      ajv: 8.18.0
+      ajv-formats: 3.0.1(ajv@8.18.0)
+      content-type: 1.0.5
+      cors: 2.8.6
+      cross-spawn: 7.0.6
+      eventsource: 3.0.7
+      eventsource-parser: 3.0.6
+      express: 5.2.1
+      express-rate-limit: 8.3.1(express@5.2.1)
+      hono: 4.12.8
+      jose: 6.1.3
+      json-schema-typed: 8.0.2
+      pkce-challenge: 5.0.1
+      raw-body: 3.0.2
+      zod: 4.4.3
+      zod-to-json-schema: 3.25.1(zod@4.4.3)
+    transitivePeerDependencies:
+      - supports-color
+
   '@napi-rs/wasm-runtime@1.1.4(@emnapi/core@1.10.0)(@emnapi/runtime@1.10.0)':
     dependencies:
       '@emnapi/core': 1.10.0
@@ -10742,6 +10764,10 @@ snapshots:
     dependencies:
       zod: 3.25.76
 
+  zod-to-json-schema@3.25.1(zod@4.4.3):
+    dependencies:
+      zod: 4.4.3
+
   zod@3.25.76: {}
 
   zod@4.4.3: {}
diff --git a/vmark-mcp-server/package.json b/vmark-mcp-server/package.json
index 49cc3cc88..fa135302c 100644
--- a/vmark-mcp-server/package.json
+++ b/vmark-mcp-server/package.json
@@ -32,7 +32,7 @@
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.27.1",
     "ws": "^8.18.0",
-    "zod": "^3.24.0"
+    "zod": "^4.4.3"
   },
   "devDependencies": {
     "@types/node": "^22.14.0",
diff --git a/vmark-mcp-server/src/cli.ts b/vmark-mcp-server/src/cli.ts
index b14fe7ab8..b62b02166 100644
--- a/vmark-mcp-server/src/cli.ts
+++ b/vmark-mcp-server/src/cli.ts
@@ -398,7 +398,8 @@ function jsonSchemaPropertyToZod(prop: JsonSchemaProperty): ZodTypeAny {
           }
           schema = z.object(shape);
         } else {
-          schema = z.record(z.unknown());
+          // zod 4 requires an explicit key type for z.record().
+          schema = z.record(z.string(), z.unknown());
         }
         break;
       default: