diff --git a/node_modules/c9/urls.js b/node_modules/c9/urls.js
new file mode 100644
index 00000000..d3dabbfa
--- /dev/null
+++ b/node_modules/c9/urls.js
@@ -0,0 +1,78 @@
+/**
+ * Base URL utilities for the Ajax.org Cloud IDE
+ * 
+ * Access via require("c9/urls").
+ *
+ * @copyright 2015, Ajax.org B.V.
+ */
+
+var plugin = module.exports = main;
+var assert = require("assert");
+ 
+plugin.consumes = ["error.logger"];
+plugin.provides = ["urls"];
+
+var errorLogger = mockErrorLogger;
+
+function main(options, imports, register) {
+    errorLogger = imports["error.logger"];
+    
+    register(null, {
+        urls: plugin
+    });
+}
+
+/**
+ * Get a desired base URL, given some context.
+ * 
+ * @param req                            The current request object or URL
+ * @param {String} sourceUrlPattern      The source URL pattern, e.g. https://ide.$DOMAIN
+ * @param {String} targetBaseUrlPattern  The target URL pattern, e.g. https://$DOMAIN
+ */
+plugin.getBaseUrl = function(req, sourceBaseUrlPattern, targetBaseUrlPattern) {
+    var sourceHost = req.host || req;
+    var sourceHostMatcher = sourceBaseUrlPattern
+        .replace(/^https?:\/\//, "")
+        .replace(/\/.*/, "")
+        .replace("$DOMAIN", "([^/]+)");
+    var hostMatch = sourceHost.match(sourceHostMatcher);
+    if (!hostMatch) {
+        errorLogger.log(new Error("Could not construct URL: request host "
+            + sourceHost + " should match " + sourceBaseUrlPattern));
+        return replaceDomain(targetBaseUrlPattern, "c9.io");
+    }
+    
+    return replaceDomain(targetBaseUrlPattern, hostMatch[1]);
+};
+
+plugin.replaceDomains = function(settings, domains) {
+    domains = Array.isArray(domains) ? domains : domains.split(",");
+    var primaryDomain = domains[0];
+    settings.domains = domains;
+    settings.primaryDomain = replaceDomain(settings.primaryDomain || "$DOMAIN", primaryDomain);
+    settings.primaryBaseUrl = replaceDomain(settings.primaryBaseUrl || "https://$DOMAIN", primaryDomain);
+    for (var s in settings) {
+        if (!settings[s])
+            continue;
+        if (settings[s].baseUrl)
+            settings[s].baseUrl = replaceDomain(settings[s].baseUrl, primaryDomain);
+        if (settings[s].primaryBaseUrl)
+            settings[s].primaryBaseUrl = replaceDomain(settings[s].primaryBaseUrl, primaryDomain);
+        if (settings[s].baseUrls) {
+            assert(settings[s].baseUrls.length === 1);
+            settings[s].baseUrls = domains.map(function(d) {
+                return replaceDomain(settings[s].baseUrls[0], d);
+            });
+        }
+    }
+};
+
+function replaceDomain(url, domain) {
+    return url.replace("$DOMAIN", domain);
+}
+
+function mockErrorLogger() {}
+mockErrorLogger.log = function(err) {
+    console.error(err.stack);
+};
+plugin.mockErrorLogger = mockErrorLogger;
diff --git a/node_modules/c9/urls_test.js b/node_modules/c9/urls_test.js
new file mode 100644
index 00000000..ed7dde66
--- /dev/null
+++ b/node_modules/c9/urls_test.js
@@ -0,0 +1,123 @@
+/*global describe it beforeEach afterEach*/
+"use strict";
+"use server";
+"use mocha";
+
+require("c9/inline-mocha")(module);
+if (typeof define === "undefined") {
+    require("amd-loader");
+    require("../../test/setup_paths");
+}
+
+var assert = require("assert");
+var urls = require("./urls");
+var url = require("url");
+var sinon = require("sinon");
+
+describe("urls", function() {
+    
+    this.timeout(15000);
+    
+    it("can do basic domain substitution in settings", function() {
+        var settings = {
+            domains: ["c9.io"],
+            preview: {
+                baseUrl: "https://preview.$DOMAIN"
+            },
+            ide: {
+                baseUrlPattern: "https://ide.$DOMAIN"
+            }
+        };
+        urls.replaceDomains(settings, "cloud9beta.com");
+        assert.equal(settings.primaryDomain, "cloud9beta.com");
+        assert.equal(settings.preview.baseUrl, "https://preview.cloud9beta.com");
+        assert.equal(settings.ide.baseUrlPattern, "https://ide.$DOMAIN");
+    });
+    
+    it("can do basic domain substitution in settings a list of domains", function() {
+        var settings = {
+            domains: ["c9.io"],
+            preview: {
+                baseUrl: "https://preview.$DOMAIN"
+            },
+            ide: {
+                baseUrlPattern: "https://ide.$DOMAIN"
+            }
+        };
+        urls.replaceDomains(settings, "cloud9beta.com,cs50.me");
+        assert.equal(settings.primaryDomain, "cloud9beta.com");
+        assert.deepEqual(settings.domains, ["cloud9beta.com", "cs50.me"]);
+        assert.equal(settings.preview.baseUrl, "https://preview.cloud9beta.com");
+        assert.equal(settings.ide.baseUrlPattern, "https://ide.$DOMAIN");
+    });
+    
+    it("behaves like an architect plugin", function(next) {
+        urls({}, { "error.logger": urls.mockErrorLogger }, function(err, result) {
+            assert(!err, err);
+            assert(result.urls.getBaseUrl);
+            next();
+        });
+    });
+    
+    it("can get the base url for a request", function() {
+        var mockRequest = {
+            host: "preview.c9.io"
+        };
+        var baseUrl = urls.getBaseUrl(mockRequest, "https://preview.$DOMAIN", "https://ide.$DOMAIN");
+        assert.equal(baseUrl, "https://ide.c9.io");
+    });
+    
+    it("can get the base url for a request with root domain source", function() {
+        var mockRequest = {
+            host: "c9.io"
+        };
+        var baseUrl = urls.getBaseUrl(mockRequest, "https://$DOMAIN", "https://ide.$DOMAIN");
+        assert.equal(baseUrl, "https://ide.c9.io");
+    });
+    
+    it("can get the base url for a request with root domain target", function() {
+        var mockRequest = {
+            host: "preview.cloud9beta.com"
+        };
+        var baseUrl = urls.getBaseUrl(mockRequest, "https://preview.$DOMAIN", "https://$DOMAIN");
+        assert.equal(baseUrl, "https://cloud9beta.com");
+    });
+    
+    it("gracefully copes with source domain mismatch", function() {
+        var mockRequest = {
+            host: "preview.cloud9beta.com"
+        };
+        urls.mockErrorLogger.log = sinon.spy();
+        var baseUrl = urls.getBaseUrl(mockRequest, "https://ide.$DOMAIN", "https://$DOMAIN");
+        assert.equal(baseUrl, "https://c9.io");
+        assert(urls.mockErrorLogger.log.called);
+    });
+    
+    it("can get the base url in dogfooding mode", function() {
+        var mockRequest = {
+            host: "newclient-lennartcl.c9.io"
+        };
+        var baseUrl = urls.getBaseUrl(mockRequest, "https://$DOMAIN", "https://ide.$DOMAIN");
+        assert.equal(baseUrl, "https://ide.newclient-lennartcl.c9.io");
+    });
+    
+    it("can get the base url in dogfooding mode (2)", function() {
+        var mockRequest = {
+            host: "preview.newclient-lennartcl.c9.io"
+        };
+        var baseUrl = urls.getBaseUrl(mockRequest, "https://preview.$DOMAIN", "https://ide.$DOMAIN");
+        assert.equal(baseUrl, "https://ide.newclient-lennartcl.c9.io");
+    });
+    
+    it("even works with URL objects", function() {
+        var input = url.parse("https://preview.newclient-lennartcl.c9.io");
+        var baseUrl = urls.getBaseUrl(input, "https://preview.$DOMAIN", "https://ide.$DOMAIN");
+        assert.equal(baseUrl, "https://ide.newclient-lennartcl.c9.io");
+    });
+    
+    it("even works with strings", function() {
+        var input = "https://preview.newclient-lennartcl.c9.io";
+        var baseUrl = urls.getBaseUrl(input, "https://preview.$DOMAIN", "https://ide.$DOMAIN");
+        assert.equal(baseUrl, "https://ide.newclient-lennartcl.c9.io");
+    });
+});
\ No newline at end of file
diff --git a/server.js b/server.js
index 52a7b2e8..6cb21bb1 100755
--- a/server.js
+++ b/server.js
@@ -11,7 +11,7 @@ var architect = require("architect");
 var optimist = require("optimist");
 var async = require("async");
 var os = require("os");
-var urls = require("./plugins/c9.core/urls");
+var urls = require("c9/urls");
 require("c9/setup_paths.js");
 
 if (process.version.match(/^v0/) && parseFloat(process.version.substr(3)) < 10) {