Revert "fix sse endpoint path preservation"

Author: bhosmer-ant

src/client/sse.test.ts

@@ -87,7 +87,7 @@ describe("SSEClientTransport", () => {
       await transport.send(message);
 
       // Verify the POST request maintains the custom path
-      expect(lastServerRequest.url).toBe("/custom/path/sse");
+      expect(lastServerRequest.url).toBe("/custom/path/messages");
     });
 
     it("handles multiple levels of custom paths", async () => {
@@ -107,7 +107,7 @@ describe("SSEClientTransport", () => {
       await transport.send(message);
 
       // Verify the POST request maintains the full custom path
-      expect(lastServerRequest.url).toBe("/api/v1/custom/deep/path/sse");
+      expect(lastServerRequest.url).toBe("/api/v1/custom/deep/path/messages");
     });
 
     it("maintains custom path for SSE connection", async () => {
@@ -130,7 +130,7 @@ describe("SSEClientTransport", () => {
       };
 
       await transport.send(message);
-      expect(lastServerRequest.url).toBe("/custom/path/sse");
+      expect(lastServerRequest.url).toBe("/custom/path/messages");
     });
 
     it("establishes SSE connection and receives endpoint", async () => {

src/client/sse.ts

@@ -147,7 +147,13 @@ export class SSEClientTransport implements Transport {
           this._endpoint = new URL(messageEvent.data, this._url);
 
           // If the original URL had a custom path, preserve it in the endpoint URL
-          this._endpoint.pathname = this._url.pathname;
+          const originalPath = this._url.pathname;
+          if (originalPath && originalPath !== '/' && originalPath !== '/sse') {
+            // Extract the base path from the original URL (everything before the /sse suffix)
+            const basePath = originalPath.replace(/\/sse$/, '');
+            // The endpoint should use the same base path but with /messages instead of /sse
+            this._endpoint.pathname = basePath + '/messages';
+          }
 
           if (this._endpoint.origin !== this._url.origin) {
             throw new Error(