Added support for empty mcpServer type, normalized "http" type (Claude Code) to "streamable-http". Added support for custom headers in config from file (mcpServers).

Author: BobDickinson

cli/src/cli.ts

@@ -49,6 +49,7 @@ type ServerConfig =
   | {
       type: "sse" | "streamable-http";
       url: string;
+      headers?: Record<string, string>;
       note?: string;
     };
 
@@ -111,6 +112,11 @@ async function runWeb(args: Args): Promise<void> {
     startArgs.push("--server-url", args.serverUrl);
   }
 
+  // Pass headers if specified (for SSE/streamable-http)
+  if (args.headers && Object.keys(args.headers).length > 0) {
+    startArgs.push("--headers", JSON.stringify(args.headers));
+  }
+
   // Pass cwd if specified (for stdio transport)
   if (args.cwd) {
     startArgs.push("--cwd", path.resolve(args.cwd));
@@ -244,7 +250,13 @@ function loadConfigFile(configPath: string, serverName: string): ServerConfig {
     }
 
     const serverConfig = parsedConfig.mcpServers[serverName];
-
+    if (serverConfig?.type === undefined) {
+      // Normalize missing type to "stdio" (backwards compatibility)
+      return { ...serverConfig, type: "stdio" };
+    } else if (serverConfig.type === "http") {
+      // Normalize "http" to "streamable-http" (some clients, like Claude Code, use http instead of streamable-http)
+      return { ...serverConfig, type: "streamable-http" };
+    }
     return serverConfig;
   } catch (err: unknown) {
     if (err instanceof SyntaxError) {
@@ -382,7 +394,6 @@ function parseArgs(): Args {
   // etc.)
   if (options.config && options.server) {
     const config = loadConfigFile(options.config, options.server);
-
     if (config.type === "stdio") {
       const cwd = options.cwd ?? config.cwd ?? path.resolve(process.cwd());
       return {
@@ -396,6 +407,10 @@ function parseArgs(): Args {
         cwd: path.resolve(cwd),
       };
     } else if (config.type === "sse" || config.type === "streamable-http") {
+      const headers = {
+        ...(config.headers || {}),
+        ...(options.header || {}),
+      };
       return {
         command: config.url,
         args: finalArgs,
@@ -404,32 +419,10 @@ function parseArgs(): Args {
         dev: options.dev || false,
         transport: config.type,
         serverUrl: config.url,
-        headers: options.header,
-      };
-    } else {
-      // Backwards compatibility: if no type field, assume stdio
-      const cwd =
-        options.cwd ??
-        (config as { cwd?: string }).cwd ??
-        path.resolve(process.cwd());
-      return {
-        command: (config as { command?: string }).command || "",
-        args: [
-          ...(((config as { args?: string[] }).args || []) as string[]),
-          ...finalArgs,
-        ],
-        envArgs: {
-          ...(((config as { env?: Record<string, string> }).env ||
-            {}) as Record<string, string>),
-          ...(options.e || {}),
-        },
-        cli: options.cli || false,
-        dev: options.dev || false,
-        transport: "stdio",
-        headers: options.header,
-        cwd: path.resolve(cwd),
+        headers: Object.keys(headers).length > 0 ? headers : undefined,
       };
     }
+    throw new Error(`Invalid server config: ${JSON.stringify(config)}`);
   }
 
   // Otherwise use command line arguments

core/mcp/remote/node/server.ts

@@ -186,6 +186,7 @@ function buildInitialConfigFromEnv(): {
   defaultArgs?: string[];
   defaultTransport?: string;
   defaultServerUrl?: string;
+  defaultHeaders?: Record<string, string>;
   defaultCwd?: string;
   defaultEnvironment: Record<string, string>;
 } {
@@ -238,6 +239,20 @@ function buildInitialConfigFromEnv(): {
     ...(process.env.MCP_INITIAL_SERVER_URL
       ? { defaultServerUrl: process.env.MCP_INITIAL_SERVER_URL }
       : {}),
+    ...(process.env.MCP_INITIAL_HEADERS
+      ? (() => {
+          try {
+            const parsed = JSON.parse(
+              process.env.MCP_INITIAL_HEADERS,
+            ) as Record<string, string>;
+            return Object.keys(parsed).length > 0
+              ? { defaultHeaders: parsed }
+              : {};
+          } catch {
+            return {};
+          }
+        })()
+      : {}),
     ...(process.env.MCP_INITIAL_CWD
       ? { defaultCwd: process.env.MCP_INITIAL_CWD }
       : {}),

web/bin/start.js

@@ -21,6 +21,7 @@ async function startDevClient(clientOptions) {
     mcpServerArgs,
     transport,
     serverUrl,
+    headers,
     envVars,
     cwd,
     abort,
@@ -43,6 +44,9 @@ async function startDevClient(clientOptions) {
       : {}),
     ...(transport ? { MCP_INITIAL_TRANSPORT: transport } : {}),
     ...(serverUrl ? { MCP_INITIAL_SERVER_URL: serverUrl } : {}),
+    ...(headers && Object.keys(headers).length > 0
+      ? { MCP_INITIAL_HEADERS: JSON.stringify(headers) }
+      : {}),
     ...(envVars && Object.keys(envVars).length > 0
       ? { MCP_ENV_VARS: JSON.stringify(envVars) }
       : {}),
@@ -102,6 +106,7 @@ async function startProdClient(clientOptions) {
     mcpServerArgs,
     transport,
     serverUrl,
+    headers,
     envVars,
     cwd,
   } = clientOptions;
@@ -123,6 +128,9 @@ async function startProdClient(clientOptions) {
         : {}),
       ...(transport ? { MCP_INITIAL_TRANSPORT: transport } : {}),
       ...(serverUrl ? { MCP_INITIAL_SERVER_URL: serverUrl } : {}),
+      ...(headers && Object.keys(headers).length > 0
+        ? { MCP_INITIAL_HEADERS: JSON.stringify(headers) }
+        : {}),
       ...(envVars && Object.keys(envVars).length > 0
         ? { MCP_ENV_VARS: JSON.stringify(envVars) }
         : {}),
@@ -143,6 +151,7 @@ async function main() {
   let isDev = false;
   let transport = null;
   let serverUrl = null;
+  let headers = null;
   let cwd = null;
 
   for (let i = 0; i < args.length; i++) {
@@ -174,6 +183,15 @@ async function main() {
       continue;
     }
 
+    if (arg === "--headers" && i + 1 < args.length) {
+      try {
+        headers = JSON.parse(args[++i]);
+      } catch {
+        // Ignore invalid JSON
+      }
+      continue;
+    }
+
     if (arg === "--cwd" && i + 1 < args.length) {
       cwd = args[++i];
       continue;
@@ -210,6 +228,13 @@ async function main() {
   if (!transport && process.env.MCP_INITIAL_TRANSPORT) {
     transport = process.env.MCP_INITIAL_TRANSPORT;
   }
+  if (!headers && process.env.MCP_INITIAL_HEADERS) {
+    try {
+      headers = JSON.parse(process.env.MCP_INITIAL_HEADERS);
+    } catch {
+      // Ignore invalid JSON
+    }
+  }
   if (!cwd && process.env.MCP_INITIAL_CWD) {
     cwd = process.env.MCP_INITIAL_CWD;
   }
@@ -254,6 +279,7 @@ async function main() {
         mcpServerArgs,
         transport,
         serverUrl,
+        headers,
         envVars,
         cwd,
         abort,
@@ -274,6 +300,7 @@ async function main() {
         mcpServerArgs,
         transport,
         serverUrl,
+        headers,
         envVars,
         cwd,
         abort,

web/src/App.tsx

@@ -96,6 +96,7 @@ import ElicitationTab, {
 import {
   CustomHeaders,
   migrateFromLegacyAuth,
+  recordToHeaders,
 } from "./lib/types/customHeaders";
 import MetadataTab from "./components/MetadataTab";
 import TokenLoginScreen from "./components/TokenLoginScreen";
@@ -333,6 +334,7 @@ const App = () => {
     setSseUrl,
     setSandboxUrl,
     setCwd,
+    setCustomHeaders,
   });
   applyConfigRef.current = {
     setConfigFetchStatus,
@@ -345,6 +347,7 @@ const App = () => {
     setSseUrl,
     setSandboxUrl,
     setCwd,
+    setCustomHeaders,
   };
 
   // Helper to check if we can create InspectorClient (without actually creating it)
@@ -954,6 +957,15 @@ const App = () => {
           apply.setTransportType(transport || "stdio");
           apply.setSseUrl((data.defaultServerUrl as string) ?? "");
           apply.setCwd((data.defaultCwd as string) ?? "");
+          if (
+            data.defaultHeaders &&
+            typeof data.defaultHeaders === "object" &&
+            !Array.isArray(data.defaultHeaders)
+          ) {
+            apply.setCustomHeaders(
+              recordToHeaders(data.defaultHeaders as Record<string, string>),
+            );
+          }
         }
         apply.setSandboxUrl(
           typeof data.sandboxUrl === "string" ? data.sandboxUrl : undefined,