What’s one time YAGNI didn’t apply—and you were glad you built it early?

We all know the principle: You Ain’t Gonna Need It. Don’t build features, abstractions, or infrastructure “just in case” someone needs them later.

But I’m curious—what’s something you built early that technically violated YAGNI, but ended up being a great call?

Maybe it was:

• Laying the groundwork for internationalization before it was needed
• Designing the system with plug-and-play architecture in mind
• Adding logging or metrics hooks that paid off later
• Supporting time zones up front before anyone asked for them
• Setting up automated code formatting and CI on day one

I would love to hear what those “YAGNI exceptions” look like in your experience and which ones you now deliberately include when starting a new project.