Rewrote the application's error messages against a written tone standard after a refused sign‑in blamed the user for mistyping when the provider actually required an app‑specific password, and covered it with a test that names the provider.

Situation. A sign‑in against a major mail provider failed, and the application told the user their password was incorrect. It was not incorrect. That provider requires an application‑specific password for third‑party clients and rejects the account password regardless of how carefully it is typed. The message sent the user to retype something that could never work, and the actual instruction — go and generate a different kind of password — appeared nowhere.

Task. The error messages had to be rewritten against a written standard rather than patched one at a time, since this one was the visible instance of a habit running through all of them.

Action. The standard has three requirements: say what happened, never imply the user did something wrong when the cause is elsewhere, and give the next action when one exists. Applied across the error surface, most messages violated at least one — several were the underlying library’s error string passed through, which describes a condition to a programmer rather than a situation to a person. The provider case was rewritten to name the provider, state that it requires an app‑specific password for other clients, and say where to create one. The test is what stops it regressing, and it is deliberately specific: it drives a sign‑in failure against that provider and asserts the message contains the provider’s name and the phrase describing the required credential type. A test asserting only that some error appeared would pass on the original wrong message, so the assertion is on the content, which is the only part that was ever broken.

Result. The error surface follows a stated standard and the case that prompted it is covered by a test that fails on the old text. What remains unresolved is scale: the standard is enforced by review and by one test on one message, and the other providers with their own particular requirements have no equivalent test, so the class is documented rather than closed.