Every team plans for the work it can see, then gets wrecked by the work it can't.

Something I've watched break plan after plan: teams fill the sprint to capacity with planned work, then act shocked when bugs, support fires, and "quick favors" blow it apart. But that unplanned work isn't a surprise. It shows up every single sprint. The only thing you don't know is which fire, not whether there'll be one.

So you've got a plan built on 100% of capacity going to planned work, in a world where it never once has. The gap gets paid for by people quietly working late, and by the roadmap slipping in a way nobody scheduled.

The teams I've seen handle it well treat unplanned work as a first-class citizen. They reserve capacity for it on purpose, based on what it actually ate last quarter, instead of pretending this sprint will be the clean one. It never is.

For people who run teams: how do you actually model the reserve for unplanned work? A fixed percentage? Gut feel? Do you protect it, or does it get eaten the moment planned work runs long?