diff --git a/README.md b/README.md
index 2800cfb1d..862de363b 100644
--- a/README.md
+++ b/README.md
@@ -441,7 +441,7 @@ app.post('/mcp', async (req, res) => {
     // New initialization request
     transport = new StreamableHTTPServerTransport({
       sessionIdGenerator: () => randomUUID(),
-      onsessioninitialized: (sessionId) => {
+      onSessionInitialized: (sessionId) => {
         // Store the transport by session ID
         transports[sessionId] = transport;
       },
diff --git a/src/examples/server/jsonResponseStreamableHttp.ts b/src/examples/server/jsonResponseStreamableHttp.ts
index 02d8c2de0..f9feb0c15 100644
--- a/src/examples/server/jsonResponseStreamableHttp.ts
+++ b/src/examples/server/jsonResponseStreamableHttp.ts
@@ -99,7 +99,7 @@ app.post('/mcp', async (req: Request, res: Response) => {
       transport = new StreamableHTTPServerTransport({
         sessionIdGenerator: () => randomUUID(),
         enableJsonResponse: true, // Enable JSON response mode
-        onsessioninitialized: (sessionId) => {
+        onSessionInitialized: (sessionId) => {
           // Store the transport by session ID when session is initialized
           // This avoids race conditions where requests might come in before the session is stored
           console.log(`Session initialized with ID: ${sessionId}`);
diff --git a/src/examples/server/simpleStreamableHttp.ts b/src/examples/server/simpleStreamableHttp.ts
index fea0eec07..8e19abd9b 100644
--- a/src/examples/server/simpleStreamableHttp.ts
+++ b/src/examples/server/simpleStreamableHttp.ts
@@ -514,7 +514,7 @@ const mcpPostHandler = async (req: Request, res: Response) => {
       transport = new StreamableHTTPServerTransport({
         sessionIdGenerator: () => randomUUID(),
         eventStore, // Enable resumability
-        onsessioninitialized: (sessionId) => {
+        onSessionInitialized: (sessionId) => {
           // Store the transport by session ID when session is initialized
           // This avoids race conditions where requests might come in before the session is stored
           console.log(`Session initialized with ID: ${sessionId}`);
diff --git a/src/examples/server/sseAndStreamableHttpCompatibleServer.ts b/src/examples/server/sseAndStreamableHttpCompatibleServer.ts
index ded110a13..41c2b62b8 100644
--- a/src/examples/server/sseAndStreamableHttpCompatibleServer.ts
+++ b/src/examples/server/sseAndStreamableHttpCompatibleServer.ts
@@ -110,7 +110,7 @@ app.all('/mcp', async (req: Request, res: Response) => {
       transport = new StreamableHTTPServerTransport({
         sessionIdGenerator: () => randomUUID(),
         eventStore, // Enable resumability
-        onsessioninitialized: (sessionId) => {
+        onSessionInitialized: (sessionId) => {
           // Store the transport by session ID when session is initialized
           console.log(`StreamableHTTP session initialized with ID: ${sessionId}`);
           transports[sessionId] = transport;
diff --git a/src/examples/server/standaloneSseWithGetStreamableHttp.ts b/src/examples/server/standaloneSseWithGetStreamableHttp.ts
index 8c8c3baaa..3f7498271 100644
--- a/src/examples/server/standaloneSseWithGetStreamableHttp.ts
+++ b/src/examples/server/standaloneSseWithGetStreamableHttp.ts
@@ -52,7 +52,7 @@ app.post('/mcp', async (req: Request, res: Response) => {
       // New initialization request
       transport = new StreamableHTTPServerTransport({
         sessionIdGenerator: () => randomUUID(),
-        onsessioninitialized: (sessionId) => {
+        onSessionInitialized: (sessionId) => {
           // Store the transport by session ID when session is initialized
           // This avoids race conditions where requests might come in before the session is stored
           console.log(`Session initialized with ID: ${sessionId}`);
@@ -63,7 +63,7 @@ app.post('/mcp', async (req: Request, res: Response) => {
       // Connect the transport to the MCP server
       await server.connect(transport);
 
-      // Handle the request - the onsessioninitialized callback will store the transport
+      // Handle the request - the onSessionInitialized callback will store the transport
       await transport.handleRequest(req, res, req.body);
       return; // Already handled
     } else {
diff --git a/src/server/streamableHttp.ts b/src/server/streamableHttp.ts
index 022d1a474..3682ccf0c 100644
--- a/src/server/streamableHttp.ts
+++ b/src/server/streamableHttp.ts
@@ -47,7 +47,7 @@ export interface StreamableHTTPServerTransportOptions {
    * and need to keep track of them.
    * @param sessionId The generated session ID
    */
-  onsessioninitialized?: (sessionId: string) => void;
+  onSessionInitialized?: (sessionId: string) => void;
 
   /**
    * If true, the server will return JSON responses instead of starting an SSE stream.
@@ -126,7 +126,7 @@ export class StreamableHTTPServerTransport implements Transport {
   private _enableJsonResponse: boolean = false;
   private _standaloneSseStreamId: string = '_GET_stream';
   private _eventStore?: EventStore;
-  private _onsessioninitialized?: (sessionId: string) => void;
+  private _onSessionInitialized?: (sessionId: string) => void;
   private _allowedHosts?: string[];
   private _allowedOrigins?: string[];
   private _enableDnsRebindingProtection: boolean;
@@ -140,7 +140,7 @@ export class StreamableHTTPServerTransport implements Transport {
     this.sessionIdGenerator = options.sessionIdGenerator;
     this._enableJsonResponse = options.enableJsonResponse ?? false;
     this._eventStore = options.eventStore;
-    this._onsessioninitialized = options.onsessioninitialized;
+    this._onSessionInitialized = options.onSessionInitialized;
     this._allowedHosts = options.allowedHosts;
     this._allowedOrigins = options.allowedOrigins;
     this._enableDnsRebindingProtection = options.enableDnsRebindingProtection ?? false;
@@ -443,10 +443,10 @@ export class StreamableHTTPServerTransport implements Transport {
         this.sessionId = this.sessionIdGenerator?.();
         this._initialized = true;
 
-        // If we have a session ID and an onsessioninitialized handler, call it immediately
+        // If we have a session ID and an onSessionInitialized handler, call it immediately
         // This is needed in cases where the server needs to keep track of multiple sessions
-        if (this.sessionId && this._onsessioninitialized) {
-          this._onsessioninitialized(this.sessionId);
+        if (this.sessionId && this._onSessionInitialized) {
+          this._onSessionInitialized(this.sessionId);
         }
 
       }