cypress "cy.visit() failed trying to load" only in CI: baseUrl vs CI service hostname

TL;DR

Locally your app answers on your machine's loopback address, but in CI it usually runs as a service under a different hostname that your hardcoded baseUrl cannot reach. Set baseUrl from an environment variable the CI job provides, add a wait step so Cypress never visits before the server is listening, and the failure disappears.

cypress "cy.visit() failed trying to load" only in CI: baseUrl vs CI service hostname

Steps

1. Open your Cypress config and read the current baseUrl. Then check what hostname the app actually binds to in CI (a service name, an internal host, or a dynamic port), from the CI job definition or the service logs. Expected: you can state both values and see they do not match.
2. Make baseUrl configurable: read it from an environment variable with a local fallback, so CI injects its own hostname and local runs keep working unchanged. Expected: the config no longer hardcodes one hostname.
3. Set that variable in the CI job to the hostname the app service actually listens on. Expected: the variable is visible in the CI job environment.
4. Add a wait step before Cypress starts (a wait-on style check against the app URL) so the visit never races the server boot. Expected: Cypress starts only after the server answers.
5. Add a one-line smoke check in the pipeline that fetches the app URL before Cypress runs. Expected: the smoke check passes, then cy.visit() loads the page.

Use this when

• cy.visit() fails in CI but works on your machine
• The app runs as a CI service with its own hostname or port
• The error is a connection failure, not a rendered error page

Not for this skill when

• The page loads but shows the wrong content (that is an app or data problem)
• The app itself crashes on boot in CI (fix the boot, not the URL)
• The failure happens locally too (the baseUrl is wrong everywhere)

Variant phrasings

• cypress cy.visit failed trying to load in CI pipeline
• cypress baseUrl not working in CI
• cypress cannot reach app server in CI

Why it happens

baseUrl is usually written once, on a developer machine where the app listens on the loopback address. CI runs the app as a separate service with its own hostname and often a different port, and it may still be booting when Cypress starts. The hardcoded local URL then points at nothing, and cy.visit() reports that it failed trying to load.

Edge cases

• If the CI hostname includes a dynamic port, have the server write its bound address to a file or env var the Cypress job can read, rather than guessing the port.
• HTTPS in CI with a self-signed cert fails the visit for a different reason; that needs the cert trusted, not a baseUrl change.
• When the app and Cypress run in the same container, the service hostname may not resolve there; use the container-local address for that layout.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_jK1bRxHfWJ30YLm3gSThTQ