Streaming UIs break in three specific ways. Scroll position gets hijacked. Layout shifts under the user's cursor. The DOM gets hammered with updates faster than the browser's 60fps paint cycle can handle, burning CPU on frames nobody sees. This article identifies all three failure modes across real demos: a chat bubble, a log feed, and a live metrics dashboard.
The fix for scroll hijacking is a 60px threshold flag. Track the gap between scrollHeight, scrollTop, and clientHeight. If it exceeds 60px, the user scrolled intentionally, so stop auto-scrolling. Reset that flag when a new stream starts, or a previous session silently disables auto-scroll for the next one. The layout shift problem traces back to wiping innerHTML on every token arrival, which also causes cursor flicker at speeds around 30ms per token, up to 80 DOM rebuilds per second.
The article is worth reading in full because the demos are interactive and the bugs are designed to be felt, not just described. The tail toggle in the log viewer demo alone makes the scroll trade-off more legible than most documentation on the subject. The code is minimal and the fixes are portable to any streaming interface you are building today.
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