Replaying real-time telemetry through a live rendering pipeline, without touching the components

I have a set of React components that render live telemetry: an attitude indicator, a moving map, tapes and gauges, a scrolling event log. They take a data source, subscribe to it, and paint whatever numbers arrive. That works for a live feed. The obvious next thing you want is replay: load a recorded session, scrub a timeline, watch the same instruments play it back. The naive version of this is a trap, and it took me a wrong turn to see why. My first instinct was that replay is a data problem, load the samples, push them into the components in order, done. It compiled, it ran, and the charts were empty. Not broken, not erroring. Empty. The instruments that show a single current value worked fine. The time-series charts sat blank while correct data flowed into them. That empty chart is the whole story of this post, because the reason it's empty is the reason replay is more interesting than it looks. The components are watching a clock you forgot about Here's the data source interface these components consume. It's small on purpose: interface TelemetryValue { timestamp : number ; // wall-clock, unix ms value : number ; channel ?: string ; } interface AltaraDataSource { subscribe ( callback : ( value : TelemetryValue ) => void ): () => void ; getHistory (): TelemetryValue []; readonly status : ConnectionStatus ; destroy (): void ; } A live source stamps each sample with Date.now() as it arrives. A time-series chart, reasonably, assumes that's what timestamps mean: it anchors its x-axis to Date.now() and draws a moving window of the last few seconds, discarding anything older than windowMs because that's off the left edge of the view. Now replay a session recorded an hour ago. Every sample carries its original timestamp, an hour in the past. The chart buffers them correctly, then asks "is this within the last few seconds of now?", the answer is no for every single sample, and it draws nothing. The data is all there. It's just an hour to the left of the visible window,