The status ticker that blacked out its own words
Superseded 2026-08-17. The compositor and texture-ceiling account below is a true record of what was found and fixed in August, and it no longer explains what the operator is seeing now — the track was re-measured this week at 2,018.7 CSS px, which is under the common 8,192-pixel texture ceiling at every plausible device pixel ratio. A second, separate cause is being worked. This entry stays up because deleting a superseded explanation is how a wrong idea survives.
What was wrong before this entry: the scrolling status line at the top of the site went black in patches while it moved, swallowing whole words.
Two mechanisms were found. A full-page noise overlay was set to a blend mode with nothing isolating it, so it blended against the root backdrop rather than the page, and it was compositing a black frame over any promoted layer beneath it. The ticker track was such a layer: it had been pinned as a permanently promoted compositor surface, and it measured 4,305 CSS pixels wide, which is 8,610 device pixels at a device pixel ratio of 2 — past the 8,192 limit that graphics stacks commonly impose on a single texture.
Four changes landed: the page body was given its own isolation context, the overlay was moved below the bar in stacking order, the promotion hint was removed from the track, and the bar itself was given an opaque background with paint containment. The track later regrew to 9,613 device pixels and the item set was halved, bringing it to 2,019 CSS pixels.
Then the measurement that retired the explanation. Re-measured on 17 August, the track is 2,018.7 CSS pixels — 4,037 device pixels at a ratio of 2, 6,056 at 3, 8,075 at 4. It is under the ceiling at every plausible ratio, so the texture account cannot be what the operator is still seeing on a phone. The geometry that can explain it is different and is being worked separately: the bar's edge fades are a fixed 20 pixels wide at every screen size, which is four per cent of a desktop window and twenty-six per cent of a 360-pixel phone.
The reason this entry is marked superseded rather than edited: the first explanation was reasoned from real measurements and it was still not the whole cause. Rewriting it in place would hide that, and the record's only value is that it does not.