Add --host parameter

Author: max-stytch

README.md

@@ -104,6 +104,17 @@ To bypass authentication, or to emit custom headers on all requests to your remo
       ]
 ```
 
+* To change which host `mcp-remote` registers as the OAuth callback URL (by default `127.0.0.1`), add the `--host` flag.
+
+```json
+      "args": [
+        "mcp-remote",
+        "https://remote.mcp.server/sse",
+        "--host",
+        "localhost"
+      ]
+```
+
 * To allow HTTP connections in trusted private networks, add the `--allow-http` flag. Note: This should only be used in secure private networks where traffic cannot be intercepted.
 
 ```json

src/client.ts

@@ -32,6 +32,7 @@ async function runClient(
   callbackPort: number,
   headers: Record<string, string>,
   transportStrategy: TransportStrategy = 'http-first',
+  host: string,
 ) {
   // Set up event emitter for auth flow
   const events = new EventEmitter()
@@ -46,6 +47,7 @@ async function runClient(
   const authProvider = new NodeOAuthClientProvider({
     serverUrl,
     callbackPort,
+    host,
     clientName: 'MCP CLI Client',
   })
 
@@ -152,8 +154,8 @@ async function runClient(
 
 // Parse command-line arguments and run the client
 parseCommandLineArgs(process.argv.slice(2), 'Usage: npx tsx client.ts <https://server-url> [callback-port]')
-  .then(({ serverUrl, callbackPort, headers, transportStrategy }) => {
-    return runClient(serverUrl, callbackPort, headers, transportStrategy)
+  .then(({ serverUrl, callbackPort, headers, transportStrategy, host }) => {
+    return runClient(serverUrl, callbackPort, headers, transportStrategy, host)
   })
   .catch((error) => {
     console.error('Fatal error:', error)

src/lib/node-oauth-client-provider.ts

@@ -36,7 +36,7 @@ export class NodeOAuthClientProvider implements OAuthClientProvider {
   }
 
   get redirectUrl(): string {
-    return `http://localhost:${this.options.callbackPort}${this.callbackPath}`
+    return `http://${this.options.host}:${this.options.callbackPort}${this.callbackPath}`;
   }
 
   get clientMetadata() {

src/lib/types.ts

@@ -8,6 +8,8 @@ export interface OAuthProviderOptions {
   serverUrl: string
   /** Port for the OAuth callback server */
   callbackPort: number
+  /** Desired hostname for the OAuth callback server */
+  host: string
   /** Path for the OAuth callback endpoint */
   callbackPath?: string
   /** Directory to store OAuth credentials */

src/lib/utils.ts

@@ -361,7 +361,7 @@ async function findExistingClientPort(serverUrlHash: string): Promise<number | u
     return undefined
   }
 
-  const localhostRedirectUri = clientInfo.redirect_uris.map((uri) => new URL(uri)).find(({ hostname }) => hostname === 'localhost')
+  const localhostRedirectUri = clientInfo.redirect_uris.map((uri) => new URL(uri)).find(({ hostname }) => hostname === 'localhost' || hostname === '127.0.0.1')
   if (!localhostRedirectUri) {
     throw new Error('Cannot find localhost callback URI from existing client information')
   }
@@ -449,6 +449,14 @@ export async function parseCommandLineArgs(args: string[], usage: string) {
     }
   }
 
+  // Parse host
+  let host = '127.0.0.1' // Default
+  const hostIndex = args.indexOf('--host')
+  if (hostIndex !== -1 && hostIndex < args.length - 1) {
+    host = args[hostIndex + 1]
+    log(`Using callback hostname: ${host}`)
+  }
+
   if (!serverUrl) {
     log(usage)
     process.exit(1)
@@ -505,7 +513,7 @@ export async function parseCommandLineArgs(args: string[], usage: string) {
     })
   }
 
-  return { serverUrl, callbackPort, headers, transportStrategy }
+  return { serverUrl, callbackPort, headers, transportStrategy, host }
 }
 
 /**

src/proxy.ts

@@ -32,6 +32,7 @@ async function runProxy(
   callbackPort: number,
   headers: Record<string, string>,
   transportStrategy: TransportStrategy = 'http-first',
+  host: string,
 ) {
   // Set up event emitter for auth flow
   const events = new EventEmitter()
@@ -46,6 +47,7 @@ async function runProxy(
   const authProvider = new NodeOAuthClientProvider({
     serverUrl,
     callbackPort,
+    host,
     clientName: 'MCP CLI Proxy',
   })
 
@@ -136,8 +138,8 @@ to the CA certificate file. If using claude_desktop_config.json, this might look
 
 // Parse command-line arguments and run the proxy
 parseCommandLineArgs(process.argv.slice(2), 'Usage: npx tsx proxy.ts <https://server-url> [callback-port]')
-  .then(({ serverUrl, callbackPort, headers, transportStrategy }) => {
-    return runProxy(serverUrl, callbackPort, headers, transportStrategy)
+  .then(({ serverUrl, callbackPort, headers, transportStrategy, host }) => {
+    return runProxy(serverUrl, callbackPort, headers, transportStrategy, host)
   })
   .catch((error) => {
     log('Fatal error:', error)