A chart should morph, not cut
When you change the date range, the old line should become the new line in front of you. A hard cut makes you re-read the axes every time; a morph lets you keep your place.
Change the window on most dashboards — seven days to ninety — and the chart is replaced. The old line vanishes, a new one appears, and your eye has to start over: find the axis, find the peak, rebuild the shape you were holding in your head a second ago.
That re-read is small, and it happens every single time, and it is why people stop changing the range and just look at whatever loaded first.
The line should redraw
Halvard tweens between states instead of swapping them. Every point on the line moves to its new value, so a seven-day view becomes a ninety-day view as a continuous motion. You watch the same curve stretch and settle rather than blink out and back. Because the two states share a shape, you keep your place — the peak you were looking at is still the peak, now at a new scale.
It is the same idea as a good transition anywhere: motion carries meaning that a cut throws away. Here the meaning is this is the same metric, seen over a longer window, and a morph says that where a hard cut says nothing.
When not to morph
Morphing between two genuinely unrelated series is a lie — it implies a relationship that is not there. So the console only morphs within a metric, across its windows and segments, never between one metric and another. Switching from revenue to latency is a cut, on purpose, because they are not the same shape and should not pretend to be.