diff --git a/src/__mocks__/service.mocks.js b/src/__mocks__/service.mocks.js
index ec36a5f..d9523df 100644
--- a/src/__mocks__/service.mocks.js
+++ b/src/__mocks__/service.mocks.js
@@ -48,3 +48,7 @@ export const mockCodexGlobals = {
   getPublicIp: vi.fn(),
   getTestnetSPRs: vi.fn(),
 };
+
+export const mockCodexApp = {
+  openCodexApp: vi.fn(),
+};
diff --git a/src/main.js b/src/main.js
index ef50b55..f12da02 100644
--- a/src/main.js
+++ b/src/main.js
@@ -20,7 +20,6 @@ import {
 import { runCodex, checkNodeStatus } from "./handlers/nodeHandlers.js";
 import { showInfoMessage } from "./utils/messages.js";
 import { ConfigService } from "./services/configService.js";
-import { openCodexApp } from "./services/codexApp.js";
 
 import { UiService } from "./services/uiService.js";
 import { FsService } from "./services/fsService.js";
@@ -36,6 +35,7 @@ import { ShellService } from "./services/shellService.js";
 import { OsService } from "./services/osService.js";
 import { ProcessControl } from "./handlers/processControl.js";
 import { CodexGlobals } from "./services/codexGlobals.js";
+import { CodexApp } from "./services/codexApp.js";
 
 async function showNavigationMenu() {
   console.log("\n");
@@ -104,6 +104,7 @@ export async function main() {
   const uiService = new UiService();
   const fsService = new FsService();
   const configService = new ConfigService(fsService);
+  const codexApp = new CodexApp(configService);
   const pathSelector = new PathSelector(uiService, new MenuLoop(), fsService);
   const numberSelector = new NumberSelector(uiService);
   const shellService = new ShellService();
@@ -142,6 +143,7 @@ export async function main() {
     configMenu,
     installer,
     processControl,
+    codexApp,
   );
 
   await mainMenu.show();
diff --git a/src/services/codexApp.js b/src/services/codexApp.js
index 838c1e8..a22f487 100644
--- a/src/services/codexApp.js
+++ b/src/services/codexApp.js
@@ -1,17 +1,22 @@
 import open from "open";
 
-export function openCodexApp(config) {
-  // TODO: Update this to the main URL when the PR for adding api-port query parameter support
-  // has been merged and deployed.
-  // See: https://github.com/codex-storage/codex-marketplace-ui/issues/92
+export class CodexApp {
+  constructor(configService) {
+    this.configService = configService;
+  }
 
-  const segments = [
-    "https://releases-v0-0-14.codex-marketplace-ui.pages.dev/",
-    "?",
-    `api-port=${config.ports.apiPort}`,
-  ];
+  openCodexApp = async () => {
+    // TODO: Update this to the main URL when the PR for adding api-port query parameter support
+    // has been merged and deployed.
+    // See: https://github.com/codex-storage/codex-marketplace-ui/issues/92
 
-  const url = segments.join("");
+    const segments = [
+      "https://releases-v0-0-14.codex-marketplace-ui.pages.dev/",
+      "?",
+      `api-port=${this.configService.get().ports.apiPort}`,
+    ];
 
-  open(url);
+    const url = segments.join("");
+    open(url);
+  };
 }
diff --git a/src/services/configService.js b/src/services/configService.js
index 91169a5..c899b98 100644
--- a/src/services/configService.js
+++ b/src/services/configService.js
@@ -6,6 +6,8 @@ import {
   getCodexLogsDefaultPath,
 } from "../utils/appData.js";
 
+import path from "path";
+
 const defaultConfig = {
   codexExe: "",
   // User-selected config options:
@@ -99,7 +101,7 @@ export class ConfigService {
 
     this.fs.writeFile(
       this.config.codexConfigFilePath,
-      `data-dir="${this.format(this.config.dataDir)}"${nl}` +
+      `data-dir="${this.format(this.toRelative(this.config.dataDir))}"${nl}` +
         `log-level="DEBUG"${nl}` +
         `log-file="${this.format(this.getLogFilePath())}"${nl}` +
         `storage-quota=${this.config.storageQuota}${nl}` +
@@ -115,4 +117,9 @@ export class ConfigService {
   format = (str) => {
     return str.replaceAll("\\", "/");
   };
+
+  toRelative = (str) => {
+    throw new Error("This code does not belong in this file. Move it.");
+    return path.relative(this.config.codexInstallPath, str);
+  };
 }
diff --git a/src/ui/mainMenu.js b/src/ui/mainMenu.js
index 0ae5703..dd52439 100644
--- a/src/ui/mainMenu.js
+++ b/src/ui/mainMenu.js
@@ -6,6 +6,7 @@ export class MainMenu {
     configMenu,
     installer,
     processControl,
+    codexApp,
   ) {
     this.ui = uiService;
     this.loop = menuLoop;
@@ -13,6 +14,7 @@ export class MainMenu {
     this.configMenu = configMenu;
     this.installer = installer;
     this.processControl = processControl;
+    this.codexApp = codexApp;
 
     this.loop.initialize(this.promptMainMenu);
   }
@@ -54,7 +56,7 @@ export class MainMenu {
     await this.ui.askMultipleChoice("Codex is running", [
       {
         label: "Open Codex app",
-        action: this.openCodexApp,
+        action: this.codexApp.openCodexApp,
       },
       {
         label: "Stop Codex",
@@ -67,10 +69,6 @@ export class MainMenu {
     ]);
   };
 
-  openCodexApp = async () => {
-    console.log("todo!");
-  };
-
   showNotRunningMenu = async () => {
     await this.ui.askMultipleChoice("Codex is not running", [
       {
diff --git a/src/ui/mainMenu.test.js b/src/ui/mainMenu.test.js
index c464c9e..e05d2b6 100644
--- a/src/ui/mainMenu.test.js
+++ b/src/ui/mainMenu.test.js
@@ -1,6 +1,6 @@
 import { describe, beforeEach, it, expect, vi } from "vitest";
 import { MainMenu } from "./mainMenu.js";
-import { mockUiService } from "../__mocks__/service.mocks.js";
+import { mockUiService, mockCodexApp } from "../__mocks__/service.mocks.js";
 import { mockInstallMenu, mockConfigMenu } from "../__mocks__/ui.mocks.js";
 import {
   mockInstaller,
@@ -21,6 +21,7 @@ describe("mainmenu", () => {
       mockConfigMenu,
       mockInstaller,
       mockProcessControl,
+      mockCodexApp,
     );
   });
 
@@ -113,7 +114,7 @@ describe("mainmenu", () => {
       expect(mockUiService.askMultipleChoice).toHaveBeenCalledWith(
         "Codex is running",
         [
-          { label: "Open Codex app", action: mainmenu.openCodexApp },
+          { label: "Open Codex app", action: mockCodexApp.openCodexApp },
           { label: "Stop Codex", action: mockProcessControl.stopCodexProcess },
           { label: "Exit", action: mockMenuLoop.stopLoop },
         ],