Message List

Short version: the list has two modes. 1. Following — the viewport is held at the bottom, so every new token stays visible. 2. Taken over — you scrolled up, so the list stops moving and shows a “jump to latest” button instead. The hard part is telling those two apart, because growing content and a real scroll look almost identical from the outside.

Appending text does not change scrollTop — it changes scrollHeight, so your distance to the bottom grows without you touching anything. Implementations that treat “distance to bottom > 0” or “a scroll event fired” as “the reader took over” switch themselves off on the first chunk.

Compare the reported position with the position you last wrote yourself. While following, the list pins the viewport to the floor and remembers that value. A scroll event that reports a position above it can only have come from a human — wheel, touch, scrollbar, keyboard, find-in-page. Growth alone can never produce one.

Short version: the list has two modes. 1. Following — the viewport is held at the bottom, so every new token stays visible. 2. Taken over — you scrolled up, so the list stops moving and shows a “jump to latest” button instead. The hard part is telling those two apart, because growing content and a real scroll look almost identical from the outside.

Appending text does not change scrollTop — it changes scrollHeight, so your distance to the bottom grows without you touching anything. Implementations that treat “distance to bottom > 0” or “a scroll event fired” as “the reader took over” switch themselves off on the first chunk.

Compare the reported position with the position you last wrote yourself. While following, the list pins the viewport to the floor and remembers that value. A scroll event that reports a position above it can only have come from a human — wheel, touch, scrollbar, keyboard, find-in-page. Growth alone can never produce one.

https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollTop?utm_source=zyeon-ui&utm_medium=transcript&utm_campaign=scroll-follow-and-takeover-reference-2026

The message you are looking at is used as an anchor: its offset inside the scrollable content is recorded before the page lands and re-measured after. Whatever that offset grew by is added straight to scrollTop, so twenty messages can appear above you and the line you were reading does not move.

Only the slice you can see stays in the DOM; everything else collapses into two spacer boxes whose heights come from measured — not guessed — message heights wherever a measurement exists.

Turn 990 — answer for step 9.

Turn 992 — answer for step 2.

Turn 994 — answer for step 4.

Turn 996 — answer for step 6.

Turn 998 — answer for step 8. Heights deliberately vary between turns so the windowing has to measure rather than assume: this reply runs onto a second and probably a third line in a narrow transcript.