diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2ad21e1..6dfaa89 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.2.1] - 2026-02-01
+
+- Fix MCP notifications handling
+
 ## [0.1.1] - 2026-02-01
 
 - Release fixes for publishing
diff --git a/bindings/python/pyproject.toml b/bindings/python/pyproject.toml
index eecc3cb..19f7cad 100644
--- a/bindings/python/pyproject.toml
+++ b/bindings/python/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "mermkit"
-version = "0.1.1"
+version = "0.2.1"
 description = "Python bindings for mermkit (Mermaid rendering toolkit)"
 readme = "README.md"
 requires-python = ">=3.8"
diff --git a/bindings/rust/Cargo.toml b/bindings/rust/Cargo.toml
index a99ab89..ae0ae6b 100644
--- a/bindings/rust/Cargo.toml
+++ b/bindings/rust/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "mermkit"
-version = "0.1.1"
+version = "0.2.1"
 edition = "2021"
 description = "Rust bindings for mermkit (Mermaid rendering toolkit)"
 license = "MIT"
diff --git a/package.json b/package.json
index 8274da3..8cc50a5 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "mermkit",
   "private": true,
-  "version": "0.1.1",
+  "version": "0.2.1",
   "repository": {
     "type": "git",
     "url": "https://github.com/MermaidKit/mermkit.git"
diff --git a/packages/adapters/package.json b/packages/adapters/package.json
index 4e8b9ba..e96cca3 100644
--- a/packages/adapters/package.json
+++ b/packages/adapters/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@mermkit/adapters",
-  "version": "0.1.1",
+  "version": "0.2.1",
   "repository": {
     "type": "git",
     "url": "https://github.com/MermaidKit/mermkit.git"
@@ -18,6 +18,6 @@
     "build": "tsc -b"
   },
   "dependencies": {
-    "@mermkit/core": "0.1.1"
+    "@mermkit/core": "0.2.1"
   }
 }
diff --git a/packages/cli/package.json b/packages/cli/package.json
index 1c95bd9..ebc11d8 100644
--- a/packages/cli/package.json
+++ b/packages/cli/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@mermkit/cli",
-  "version": "0.1.1",
+  "version": "0.2.1",
   "repository": {
     "type": "git",
     "url": "https://github.com/MermaidKit/mermkit.git"
@@ -19,8 +19,8 @@
     "build": "tsc -b"
   },
   "dependencies": {
-    "@mermkit/core": "0.1.1",
-    "@mermkit/render": "0.1.1",
-    "@mermkit/adapters": "0.1.1"
+    "@mermkit/core": "0.2.1",
+    "@mermkit/render": "0.2.1",
+    "@mermkit/adapters": "0.2.1"
   }
 }
diff --git a/packages/cli/src/cli.ts b/packages/cli/src/cli.ts
index 570de64..ed13d75 100644
--- a/packages/cli/src/cli.ts
+++ b/packages/cli/src/cli.ts
@@ -744,7 +744,7 @@ type JsonRpcRequest = {
 
 type JsonRpcResponse = {
   jsonrpc: "2.0";
-  id: string | number | null;
+  id: string | number;
   result?: unknown;
   error?: { code: number; message: string };
 };
@@ -753,6 +753,14 @@ function writeMcpResponse(response: JsonRpcResponse): void {
   stdout.write(`${JSON.stringify(response)}\n`);
 }
 
+function maybeWriteMcpResponse(
+  id: string | number | undefined,
+  response: Omit<JsonRpcResponse, "id">
+): void {
+  if (typeof id !== "string" && typeof id !== "number") return;
+  writeMcpResponse({ ...response, id });
+}
+
 function buildMcpToolDefinitions(): Array<{ name: string; description: string; inputSchema: Record<string, unknown> }> {
   return buildToolDefinitions().map((tool) => ({
     name: tool.name,
@@ -771,20 +779,14 @@ async function cmdMcp(): Promise<void> {
     try {
       request = JSON.parse(trimmed) as JsonRpcRequest;
     } catch (error) {
-      writeMcpResponse({
-        jsonrpc: "2.0",
-        id: null,
-        error: { code: -32700, message: `parse error: ${errorMessage(error)}` }
-      });
       continue;
     }
 
-    const id = request.id ?? null;
+    const id = request.id;
 
     if (request.method === "initialize") {
-      writeMcpResponse({
+      maybeWriteMcpResponse(id, {
         jsonrpc: "2.0",
-        id,
         result: {
           protocolVersion: "2024-11-05",
           capabilities: { tools: {} },
@@ -795,9 +797,8 @@ async function cmdMcp(): Promise<void> {
     }
 
     if (request.method === "tools/list") {
-      writeMcpResponse({
+      maybeWriteMcpResponse(id, {
         jsonrpc: "2.0",
-        id,
         result: { tools: buildMcpToolDefinitions() }
       });
       continue;
@@ -810,11 +811,10 @@ async function cmdMcp(): Promise<void> {
 
       try {
         const content = await executeMcpTool(toolName, toolInput);
-        writeMcpResponse({ jsonrpc: "2.0", id, result: { content } });
+        maybeWriteMcpResponse(id, { jsonrpc: "2.0", result: { content } });
       } catch (error) {
-        writeMcpResponse({
+        maybeWriteMcpResponse(id, {
           jsonrpc: "2.0",
-          id,
           result: {
             content: [{ type: "text", text: `error: ${errorMessage(error)}` }],
             isError: true
@@ -824,9 +824,8 @@ async function cmdMcp(): Promise<void> {
       continue;
     }
 
-    writeMcpResponse({
+    maybeWriteMcpResponse(id, {
       jsonrpc: "2.0",
-      id,
       error: { code: -32601, message: `method not found: ${request.method}` }
     });
   }
diff --git a/packages/core/package.json b/packages/core/package.json
index a7e75b5..741a458 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@mermkit/core",
-  "version": "0.1.1",
+  "version": "0.2.1",
   "repository": {
     "type": "git",
     "url": "https://github.com/MermaidKit/mermkit.git"
diff --git a/packages/render/package.json b/packages/render/package.json
index d0a6c61..b0c0e94 100644
--- a/packages/render/package.json
+++ b/packages/render/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@mermkit/render",
-  "version": "0.1.1",
+  "version": "0.2.1",
   "repository": {
     "type": "git",
     "url": "https://github.com/MermaidKit/mermkit.git"
@@ -18,7 +18,7 @@
     "build": "tsc -b"
   },
   "dependencies": {
-    "@mermkit/core": "0.1.1"
+    "@mermkit/core": "0.2.1"
   },
   "optionalDependencies": {
     "dompurify": "^3.1.5",