A small reference demo for separating UI stalls from network delays

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A small reference demo for separating UI stalls from network delays operates in show hn launch.

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I built a small reference demo that streams data in the browser, intentionally stalls the UI, and exports a structured trace you can compare across runs.This isn’t a benchmark or a product. I mostly built it to sanity-check my own understanding of a common problem: is this slowdown coming from the network or from the UI thread?What the demo does:Uses real SSE streaming (no simulated network behavior)Relies on real browser throttling (DevTools → Network → 3G)Intentionally blocks the main thread to create real UI stallsExports a plain JSON trace with strict event orderingHow to try it:Open the siteSet DevTools → Network → 3GClick Run All (Standard Test)Download the traceRun it again and compar

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Website: deterministic-stream-demo1.pages.dev