From 54d6929149387f197c4554115b9242f31e6dbe7c Mon Sep 17 00:00:00 2001
From: ihrpr <inna@anthropic.com>
Date: Tue, 15 Apr 2025 11:58:43 +0100
Subject: [PATCH] don't need to re-initialize when we reconnect a session

---
 src/client/index.ts          | 6 +++++-
 src/server/streamableHttp.ts | 5 ++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/client/index.ts b/src/client/index.ts
index 64ea62c4..a3edd0be 100644
--- a/src/client/index.ts
+++ b/src/client/index.ts
@@ -126,7 +126,11 @@ export class Client<
 
   override async connect(transport: Transport, options?: RequestOptions): Promise<void> {
     await super.connect(transport);
-
+    // When transport sessionId is already set this means we are trying to reconnect.
+    // In this case we don't need to initialize again.
+    if (transport.sessionId !== undefined) {
+      return;
+    }
     try {
       const result = await this.request(
         {
diff --git a/src/server/streamableHttp.ts b/src/server/streamableHttp.ts
index 012458f2..fed85ad9 100644
--- a/src/server/streamableHttp.ts
+++ b/src/server/streamableHttp.ts
@@ -331,11 +331,10 @@ export class StreamableHTTPServerTransport implements Transport {
       const isInitializationRequest = messages.some(
         msg => 'method' in msg && msg.method === 'initialize'
       );
-      const mcpSessionId = req.headers["mcp-session-id"] as string | undefined;
       if (isInitializationRequest) {
         // If it's a server with session management and the session ID is already set we should reject the request
         // to avoid re-initialization.
-        if (this._initialized && this.sessionId !== undefined && mcpSessionId !== this.sessionId) {
+        if (this._initialized) {
           res.writeHead(400).end(JSON.stringify({
             jsonrpc: "2.0",
             error: {
@@ -357,7 +356,7 @@ export class StreamableHTTPServerTransport implements Transport {
           }));
           return;
         }
-        this.sessionId = mcpSessionId ?? this.sessionIdGenerator();
+        this.sessionId = this.sessionIdGenerator();
         this._initialized = true;
 
       }