Every new feature breaks three old ones. We untangle why.

“A one-line change in the UI breaks something in billing.”

Usually means state or logic is shared across concerns that shouldn't touch — a component doing data-fetching, business logic, and rendering all in one file, so nothing about it is safe to change in isolation.

“New engineers need weeks before they can ship anything.”

Not a skill problem. If the system has no clear boundaries, there's no smaller thing to learn first — you have to understand the whole tangle before touching any of it.

“The same logic is copy-pasted in four different places, slightly differently each time.”

A common byproduct of prompt-by-prompt AI generation: each request solves its own problem without checking whether the solution already exists elsewhere in the codebase.

“Nobody wants to refactor because nobody's sure what'll break.”

Without tests or clear boundaries, refactoring is a bet, not an improvement. Teams rationally stop trying and pile new code on top instead.

“A single file is thousands of lines and does five unrelated things.”

The 'god file' pattern — everything lives here because it was easier to add one more thing than to figure out where it actually belongs.

“Estimates for 'simple' features keep being wrong by 3x or more.”

A reliable signal that the actual cost isn't the feature, it's the unplanned side effects rippling through code with no boundaries around it.