Fix command-line argument passing to pre-fill UI

When running the inspector with command-line arguments (e.g.,
`npx @modelcontextprotocol/inspector node build/index.js arg1 arg2`),
the command and arguments were not being properly passed through to
the UI for pre-filling.

Changes:
- cli.ts now passes command and args to start.js
- start.js uses --command for the command and --args for arguments
- Server parses the new --command parameter
- /config endpoint returns correct values for UI pre-filling

This ensures the UI correctly displays the command and arguments
passed on the command line instead of showing old localStorage values.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: felixweinberger

cli/src/cli.ts

@@ -66,8 +66,21 @@ async function runWebClient(args: Args): Promise<void> {
     abort.abort();
   });
 
+  // Build arguments to pass to start.js
+  const startArgs: string[] = [];
+
+  // Pass environment variables
+  for (const [key, value] of Object.entries(args.envArgs)) {
+    startArgs.push("-e", `${key}=${value}`);
+  }
+
+  // Pass command and args (using -- to separate them)
+  if (args.command) {
+    startArgs.push("--", args.command, ...args.args);
+  }
+
   try {
-    await spawnPromise("node", [inspectorClientPath], {
+    await spawnPromise("node", [inspectorClientPath, ...startArgs], {
       signal: abort.signal,
       echoOutput: true,
     });

client/bin/start.js

@@ -91,8 +91,10 @@ async function startProdServer(serverOptions) {
     "node",
     [
       inspectorServerPath,
-      ...(command ? [`--env`, command] : []),
-      ...(mcpServerArgs ? [`--args=${mcpServerArgs.join(" ")}`] : []),
+      ...(command ? [`--command`, command] : []),
+      ...(mcpServerArgs && mcpServerArgs.length > 0
+        ? [`--args`, mcpServerArgs.join(" ")]
+        : []),
     ],
     {
       env: {

server/src/index.ts

@@ -39,6 +39,7 @@ const { values } = parseArgs({
   options: {
     env: { type: "string", default: "" },
     args: { type: "string", default: "" },
+    command: { type: "string", default: "" },
   },
 });
 
@@ -520,7 +521,7 @@ app.get("/config", originValidationMiddleware, authMiddleware, (req, res) => {
   try {
     res.json({
       defaultEnvironment,
-      defaultCommand: values.env,
+      defaultCommand: values.command,
       defaultArgs: values.args,
     });
   } catch (error) {