Fix transport type propagation from CLI to web client

- Add --transport and --server-url support to client/bin/start.js
- Pass transport configuration through server to client via /config endpoint
- Update client App.tsx to use defaultTransport and defaultServerUrl from server
- Ensure SSE and HTTP transport configs work properly from CLI

Author: felixweinberger

client/bin/start.js

@@ -28,8 +28,15 @@ function getClientUrl(port, authDisabled, sessionToken, serverPort) {
 }
 
 async function startDevServer(serverOptions) {
-  const { SERVER_PORT, CLIENT_PORT, sessionToken, envVars, abort } =
-    serverOptions;
+  const {
+    SERVER_PORT,
+    CLIENT_PORT,
+    sessionToken,
+    envVars,
+    abort,
+    transport,
+    serverUrl,
+  } = serverOptions;
   const serverCommand = "npx";
   const serverArgs = ["tsx", "watch", "--clear-screen=false", "src/index.ts"];
   const isWindows = process.platform === "win32";
@@ -42,6 +49,8 @@ async function startDevServer(serverOptions) {
       CLIENT_PORT,
       MCP_PROXY_AUTH_TOKEN: sessionToken,
       MCP_ENV_VARS: JSON.stringify(envVars),
+      ...(transport ? { MCP_TRANSPORT: transport } : {}),
+      ...(serverUrl ? { MCP_SERVER_URL: serverUrl } : {}),
     },
     signal: abort.signal,
     echoOutput: true,
@@ -78,6 +87,8 @@ async function startProdServer(serverOptions) {
     abort,
     command,
     mcpServerArgs,
+    transport,
+    serverUrl,
   } = serverOptions;
   const inspectorServerPath = resolve(
     __dirname,
@@ -95,6 +106,8 @@ async function startProdServer(serverOptions) {
       ...(mcpServerArgs && mcpServerArgs.length > 0
         ? [`--args=${mcpServerArgs.join(" ")}`]
         : []),
+      ...(transport ? [`--transport=${transport}`] : []),
+      ...(serverUrl ? [`--server-url=${serverUrl}`] : []),
     ],
     {
       env: {
@@ -208,6 +221,8 @@ async function main() {
   let command = null;
   let parsingFlags = true;
   let isDev = false;
+  let transport = null;
+  let serverUrl = null;
 
   for (let i = 0; i < args.length; i++) {
     const arg = args[i];
@@ -222,6 +237,16 @@ async function main() {
       continue;
     }
 
+    if (parsingFlags && arg === "--transport" && i + 1 < args.length) {
+      transport = args[++i];
+      continue;
+    }
+
+    if (parsingFlags && arg === "--server-url" && i + 1 < args.length) {
+      serverUrl = args[++i];
+      continue;
+    }
+
     if (parsingFlags && arg === "-e" && i + 1 < args.length) {
       const envVar = args[++i];
       const equalsIndex = envVar.indexOf("=");
@@ -273,6 +298,8 @@ async function main() {
       abort,
       command,
       mcpServerArgs,
+      transport,
+      serverUrl,
     };
 
     const result = isDev

client/src/App.tsx

@@ -455,6 +455,14 @@ const App = () => {
         if (data.defaultArgs) {
           setArgs(data.defaultArgs);
         }
+        if (data.defaultTransport) {
+          setTransportType(
+            data.defaultTransport as "stdio" | "sse" | "streamable-http",
+          );
+        }
+        if (data.defaultServerUrl) {
+          setSseUrl(data.defaultServerUrl);
+        }
       })
       .catch((error) =>
         console.error("Error fetching default environment:", error),

server/src/index.ts

@@ -40,6 +40,8 @@ const { values } = parseArgs({
     env: { type: "string", default: "" },
     args: { type: "string", default: "" },
     command: { type: "string", default: "" },
+    transport: { type: "string", default: "" },
+    "server-url": { type: "string", default: "" },
   },
 });
 
@@ -523,6 +525,8 @@ app.get("/config", originValidationMiddleware, authMiddleware, (req, res) => {
       defaultEnvironment,
       defaultCommand: values.command,
       defaultArgs: values.args,
+      defaultTransport: values.transport,
+      defaultServerUrl: values["server-url"],
     });
   } catch (error) {
     console.error("Error in /config route:", error);