diff --git a/dev.sh b/dev.sh
index 3088327..b91221b 100755
--- a/dev.sh
+++ b/dev.sh
@@ -21,13 +21,14 @@ if [ "$SSL" = "true" ]; then
   fi
 
   NG_SERVE="cd toju-app && npx ng serve --host=0.0.0.0 --ssl --ssl-cert=../.certs/localhost.crt --ssl-key=../.certs/localhost.key"
-  WAIT_URL="https://localhost:4200"
-  HEALTH_URL="https://localhost:3001/api/health"
+  # Use 127.0.0.1 so wait-on does not hit a stale HTTP listener on localhost (::1).
+  WAIT_URL="https://127.0.0.1:4200"
+  HEALTH_URL="https://127.0.0.1:3001/api/health"
   export NODE_TLS_REJECT_UNAUTHORIZED=0
 else
   NG_SERVE="cd toju-app && npx ng serve --host=0.0.0.0"
-  WAIT_URL="http://localhost:4200"
-  HEALTH_URL="http://localhost:3001/api/health"
+  WAIT_URL="http://127.0.0.1:4200"
+  HEALTH_URL="http://127.0.0.1:3001/api/health"
 fi
 
 exec npx concurrently --kill-others \
diff --git a/electron/window/create-window.ts b/electron/window/create-window.ts
index 7471dcf..1270f2d 100644
--- a/electron/window/create-window.ts
+++ b/electron/window/create-window.ts
@@ -11,6 +11,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import { DESKTOP_APP_DISPLAY_NAME } from '../app/desktop-branding.rules';
 import { readDesktopSettings } from '../desktop-settings';
+import { resolveDevelopmentClientUrl } from './dev-client-url.rules';
 
 let mainWindow: BrowserWindow | null = null;
 let tray: Tray | null = null;
@@ -277,11 +278,7 @@ export async function createWindow(): Promise<void> {
   }
 
   if (process.env['NODE_ENV'] === 'development') {
-    const devUrl = process.env['SSL'] === 'true'
-      ? 'https://localhost:4200'
-      : 'http://localhost:4200';
-
-    await mainWindow.loadURL(devUrl);
+    await mainWindow.loadURL(resolveDevelopmentClientUrl(process.env['SSL'] === 'true'));
 
     if (process.env['DEBUG_DEVTOOLS'] === '1') {
       mainWindow.webContents.openDevTools();
diff --git a/electron/window/dev-client-url.rules.spec.ts b/electron/window/dev-client-url.rules.spec.ts
new file mode 100644
index 0000000..991d180
--- /dev/null
+++ b/electron/window/dev-client-url.rules.spec.ts
@@ -0,0 +1,26 @@
+import {
+  describe,
+  expect,
+  it
+} from 'vitest';
+
+import {
+  DEV_CLIENT_HOST,
+  DEV_CLIENT_PORT,
+  resolveDevelopmentClientUrl
+} from './dev-client-url.rules';
+
+describe('dev-client-url.rules', () => {
+  it('targets loopback IPv4 so dev wait-on avoids stale localhost IPv6 listeners', () => {
+    expect(DEV_CLIENT_HOST).toBe('127.0.0.1');
+    expect(DEV_CLIENT_PORT).toBe(4200);
+  });
+
+  it('builds the HTTP dev client URL', () => {
+    expect(resolveDevelopmentClientUrl(false)).toBe('http://127.0.0.1:4200');
+  });
+
+  it('builds the HTTPS dev client URL', () => {
+    expect(resolveDevelopmentClientUrl(true)).toBe('https://127.0.0.1:4200');
+  });
+});
diff --git a/electron/window/dev-client-url.rules.ts b/electron/window/dev-client-url.rules.ts
new file mode 100644
index 0000000..fe8621e
--- /dev/null
+++ b/electron/window/dev-client-url.rules.ts
@@ -0,0 +1,8 @@
+export const DEV_CLIENT_HOST = '127.0.0.1';
+export const DEV_CLIENT_PORT = 4200;
+
+export function resolveDevelopmentClientUrl(sslEnabled: boolean): string {
+  const scheme = sslEnabled ? 'https' : 'http';
+
+  return `${scheme}://${DEV_CLIENT_HOST}:${DEV_CLIENT_PORT}`;
+}
diff --git a/package.json b/package.json
index ac2a396..417872b 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,7 @@
     "server:start": "cd server && npm start",
     "server:dev": "cd server && npm run dev",
     "electron": "npm run build && npm run build:electron && node tools/launch-electron.js . --no-sandbox --disable-dev-shm-usage",
-    "electron:dev": "concurrently \"npm run start\" \"wait-on http://localhost:4200 && npm run build:electron && cross-env NODE_ENV=development node tools/launch-electron.js . --no-sandbox --disable-dev-shm-usage\"",
+    "electron:dev": "concurrently \"npm run start\" \"wait-on http://127.0.0.1:4200 && npm run build:electron && cross-env NODE_ENV=development node tools/launch-electron.js . --no-sandbox --disable-dev-shm-usage\"",
     "electron:full": "./dev.sh",
     "electron:full:build": "npm run build:all && concurrently --kill-others \"cd server && npm start\" \"cross-env NODE_ENV=production node tools/launch-electron.js . --no-sandbox --disable-dev-shm-usage\"",
     "migration:generate": "typeorm migration:generate electron/migrations/Auto -d dist/electron/data-source.js",