feat: add command line option to enable HTTP proxy support

Author: phoval

README.md

@@ -135,6 +135,22 @@ To bypass authentication, or to emit custom headers on all requests to your remo
       ]
 ```
 
+* To enable an outbound HTTP(S) proxy for mcp-remote, add the `--enable-proxy` flag. When enabled, mcp-remote will use the proxy settings from common environment variables (for example `HTTP_PROXY`, `HTTPS_PROXY`, and `NO_PROXY`).
+
+Example:
+
+```json
+    "args": [
+      "mcp-remote",
+      "https://remote.mcp.server/sse",
+      "--enable-proxy"
+    ],
+    "env": {
+      "HTTPS_PROXY": "http://127.0.0.1:3128",
+      "NO_PROXY": "localhost,127.0.0.1"
+    }
+```
+
 * To ignore specific tools from the remote server, add the `--ignore-tool` flag. This will filter out tools matching the specified patterns from both `tools/list` responses and block `tools/call` requests. Supports wildcard patterns with `*`.
 
 ```json

src/lib/utils.ts

@@ -14,7 +14,7 @@ import fs from 'fs'
 import { readFile, rm } from 'fs/promises'
 import path from 'path'
 import { version as MCP_REMOTE_VERSION } from '../../package.json'
-import { fetch, setGlobalDispatcher, RequestInit, EnvHttpProxyAgent } from 'undici';
+import { fetch, setGlobalDispatcher, RequestInit, EnvHttpProxyAgent } from 'undici'
 
 // Global type declaration for typescript
 declare global {
@@ -33,9 +33,6 @@ const pid = process.pid
 // Global debug flag
 export let DEBUG = false
 
-// Use env proxy
-setGlobalDispatcher(new EnvHttpProxyAgent());
-
 // Helper function for timestamp formatting
 function getTimestamp(): string {
   const now = new Date()
@@ -646,6 +643,13 @@ export async function parseCommandLineArgs(args: string[], usage: string) {
     log('Debug mode enabled - detailed logs will be written to ~/.mcp-auth/')
   }
 
+  const enableProxy = args.includes('--enable-proxy')
+  if (enableProxy) {
+    // Use env proxy
+    setGlobalDispatcher(new EnvHttpProxyAgent())
+    log('HTTP proxy support enabled - using system HTTP_PROXY/HTTPS_PROXY environment variables')
+  }
+
   // Parse transport strategy
   let transportStrategy: TransportStrategy = 'http-first' // Default
   const transportIndex = args.indexOf('--transport')