June 28, 2026
Build later, fight now
The Cost Yagni Was Never About – By Kent Beck
Kent Beck says “stop building early” — and the comments instantly turned into a workplace food fight
TLDR: Kent Beck argues that “don’t build it yet” isn’t about being cheap — it’s about avoiding bad early decisions and delaying costs until they’re truly worth it. Commenters immediately split between “AI makes rewrites cheap now” and “working software has trust you can’t casually rebuild,” turning a design lesson into a mini civil war.
Software legend Kent Beck just revived one of coding’s most famous rules — YAGNI, short for “You Aren’t Gonna Need It,” which basically means: don’t build extra stuff before it’s actually needed. But Beck’s big twist is that this was never mainly about saving effort. His argument is spicier: building too early locks you into the wrong shape and makes you pay twice later, even if your guess was smart. In plain English, he’s saying the real danger isn’t laziness — it’s getting ahead of yourself.
And oh, the comment section did not sit quietly with that. One camp basically yelled, “Cute theory, but AI changed the math.” Their hot take: rewriting, testing, and even doing scary live changes are all getting cheaper, so maybe waiting isn’t the obvious winner anymore. Another crowd agreed with Beck on one very human point: software that already works has built-up trust, and ripping it apart can destroy that trust overnight. That turned the thread from philosophy class into a full-on custody battle over whether “working code” is a priceless asset or just tomorrow’s disposable draft.
Then came the drive-by chaos. One commenter flatly said Beck’s advice sounds useless for chip companies, where you must plan far ahead and can’t show customers half-finished work. Another accused the whole argument of collapsing unless prediction is actually hard — directly poking at Beck’s core claim. There weren’t many jokes, but the funniest running vibe was the accidental roast of AI itself: Beck says even the “genies” don’t get YAGNI, and the replies basically answered, “Neither do humans, apparently.”
Key Points
- •Kent Beck argues that YAGNI is about the timing of design decisions, not about avoiding design altogether.
- •The article says YAGNI is often misread as a rule for saving coding effort, a framing Beck rejects.
- •Beck defines the main cost of violating YAGNI as building speculative structure before the feature that needs it exists.
- •He identifies one cost as lost optionality: early structure can be wrong for future requirements and reduces flexibility even if the prediction is correct.
- •He identifies a second cost as net present value loss: building infrastructure early pulls cost forward and delays shipping revenue-generating features.