Diagnostic mode found in one hover what four local hypotheses could not.
coordinateToTime answers null over the right-hand price axis, over the
whitespace past the last bar, and anywhere outside the chart. snapPoint read
that as "the newest bar":
const fallbackT = point.t ?? this.bars[this.bars.length - 1]?.t ?? null;
so the indicator jumped to the live edge from wherever the cursor actually was —
hundreds of points away, on a bar the user was nowhere near. It matches the
screenshot exactly: the crosshair read 22:42 while the snap label read 22:58,
which was the last bar.
Two faults behind it. The tool's pointer listener is on window, so it processes
moves over the sidebar — a real sample reported x=1409 on a chart 1280 wide. And
a null time meant a default instead of no answer.
A pointer outside the plot now hides the indicator, and a null time resolves to
the bar nearest in pixels rather than the newest. An e2e test hovers a bar, the
price axis, the sidebar and back, asserting the indicator never sits at the live
edge from mid-chart and disappears once the cursor leaves.
Worth recording that device pixel ratio, viewport size, resize desynchronisation
and the chart scrolling under the gesture were each measured and ruled out
before this, none of which was the cause. With the browser on another machine,
instrumenting it should have come first.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Chris Amow
fa577bacb7