Persisting a cookie based session over node-http-proxy

I have a simple Express based Node.js web server that I'm using for development of a JavaScript application. I set up the server to use node-http-proxy to proxy API requests the application makes to a Jetty server that is running on a different domain and port. This setup has been working flawlessly until I started to run into problems with session management.

Upon authentication the application server returns a cookie with an auth token representing the server session. When I run the JS application off of my filesystem (file://) I can see that once client receives the cookie, it is sent in all the subsequent API requests. When I run the JS app on the node server and API calls are proxied through node-http-proxy (RoutingProxy) the request headers never include the cookie.

Is there something I need to handle manually to support this type of session persistence through the proxy? I've been digging through the node-http-proxy code but it is a little over my head because I am new to Node.

https://gist.github.com/2475547 or:

var express = require('express'),
    routingProxy = require('http-proxy').RoutingProxy(),
    app = express.createServer();

var apiVersion = 1.0,
    apiHost = my.host.com,
    apiPort = 8080;

function apiProxy(pattern, host, port) {
    return function(req, res, next) {
        if (req.url.match(pattern)) {
            routingProxy.proxyRequest(req, res, {host: host, port: port});
        } else {
            next();
        }
    }
}

app.configure(function () {
    // API proxy middleware
    app.use(apiProxy(new RegExp('\/' + apiVersion + '\/.*'), apiHost, apiPort));

    // Static content middleware
    app.use(express.methodOverride());
    app.use(express.bodyParser());
    app.use(express.static(__dirname));
    app.use(express.errorHandler({
        dumpExceptions: true, 
        showStack: true
    }));
    app.use(app.router);
});

app.listen(3000);