Problem

In Codespaces, creating an employee fails:

POST https://…-4200.app.github.dev:5300/employees net::ERR_ADDRESS_UNREACHABLE

Root cause

ApiConfigService built the API base URL as ${window.location.hostname}:5300. In Codespaces the client host is …-4200.app.github.dev, so this produced …-4200.app.github.dev:5300. Codespaces doesn't expose ports as :port on the same host — each forwarded port is a separate subdomain (…-5300.app.github.dev) served over 443. The host:5300 URL therefore resolves to nothing.

Fix

When the host ends with .app.github.dev, swap the port segment (-4200 → -5300) and use the default (443) port; keep ${hostname}:5300 for local development.

if (hostname.endsWith('.app.github.dev')) {
  const apiHost = hostname.replace(/-\d+\.app\.github\.dev$/, '-5300.app.github.dev');
  return `${protocol}//${apiHost}`;
}
return `${protocol}//${hostname}:5300`;

Verification

• ng build passes.
• Transform check: …-4200.app.github.dev → https://…-5300.app.github.dev; localhost → http://localhost:5300.
• The API port (5300) is already made public by .devcontainer/portSetup.sh, and the server enables permissive CORS.