[A7med7x7]

Problem

Opening Relaunch faded into a soft blur, then the background snapped to a darker, much more saturated look in a single frame.

Cause: the blurred wallpaper was only requested when the window opened, and rendered in the background. For animated (aerial) wallpapers that means decoding a video frame, which takes a moment. Until it arrived, the system blur of whatever was behind the window showed. Then the wallpaper replaced it with no animation, and with a 1.15× saturation boost on top.

Launchpad didn't do this. It faded in one blurred, dimmed copy of the desktop picture and never swapped backgrounds mid-animation.

Fix

• Render the blurred wallpaper ahead of time: at launch, on Space and display changes, and when the wallpaper store changes. A normal ⌥Space open finds it ready.
• On a cold start, wait up to 0.25 s for it before fading in. If it's still late, cross-fade it in instead of swapping it.
• Use the system blur only as a fallback, when the wallpaper can't be read.
• Drop the saturation boost. Keep a slight dim.

Measured

Screen recordings at 60 fps, average of a background patch beside the grid:

	Before	After (warm, normal ⌥Space)	After (cold start)
Path	desktop → system blur → jump to wallpaper	desktop → wallpaper	desktop → wallpaper (cross-faded)
Largest one-frame brightness change	0.113 → 0.028	0.027	0.052 (first frame of the fade)
Largest one-frame saturation change	0.05 → 0.94	0.18	0.18
Frames for the background transition	1 (the snap)	12	13