WIP limit
A work-in-progress (WIP) limit caps how many items the team can have in flight at once, per workflow stage. WIP limits force teams to finish work before starting new work, the central practice of Kanban. Without them, work piles up in 'in progress' states while nothing ships; with them, bottlenecks become immediately visible at the stage that's full.
Setting a WIP limit is more art than science, common starting points are team size × 1.5 for active work, or 2 per engineer. The right number is the one that makes the team uncomfortable but not paralysed: too low and people sit idle; too high and the limit doesn't change behaviour. Mid-sprint WIP-limit breaches are a signal worth investigating in retrospectives, they usually point to skipped acceptance criteria, blocked dependencies, or scope expansion mid-story.