From a64f429349c3cd3ea10cfc3e761ff6acb41e38f8 Mon Sep 17 00:00:00 2001
From: you <you@example.com>
Date: Thu, 19 Mar 2026 07:07:26 +0000
Subject: [PATCH] Fix VCR scrubber rubber-band: hold dragPct during async fetch

Root cause traced: mouseup sets VCR.dragging=false and starts async
fetch. Between fetch start and response (~50-200ms), the 30s interval
fires updateTimelinePlayhead() which found no matching branch for
REPLAY+old playhead, defaulting to x=cw (right edge snap).

Fix: dragPct now takes priority over buffer-based position during
REPLAY/PAUSED modes. Cleared only when fetch completes and replay
actually starts with real buffer data.
---
 public/live.js | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/public/live.js b/public/live.js
index 47a0936f..041a0503 100644
--- a/public/live.js
+++ b/public/live.js
@@ -346,14 +346,14 @@
     // Redraw sparkline (cheap, avoids double-buffer complexity)
     // Just draw playhead line on top — clear only the line area
     let x;
-    if (VCR.mode === 'LIVE' || VCR.playhead < 0) {
+    if (VCR.mode === 'LIVE') {
       x = cw; // rightmost = now
+    } else if (VCR.dragPct != null && (VCR.mode === 'REPLAY' || VCR.mode === 'PAUSED')) {
+      // After scrub: hold at drag position until replay tick updates it
+      x = VCR.dragPct * cw;
     } else if (VCR.playhead >= 0 && VCR.playhead < VCR.buffer.length) {
       const playTs = VCR.buffer[VCR.playhead].ts;
       x = ((playTs - startTs) / scopeMs) * cw;
-    } else if (VCR.mode === 'PAUSED' && VCR.dragPct != null) {
-      // After scrub, hold at last drag position
-      x = VCR.dragPct * cw;
     } else {
       x = cw;
     }
@@ -618,6 +618,7 @@
           VCR.playhead = closest;
           // Only replay ~50 packets from scrub point, not entire buffer to end
           VCR.scrubEnd = Math.min(closest + 50, VCR.buffer.length);
+          VCR.dragPct = null; // let replay tick drive playhead now
           startReplay();
         })
         .catch(() => {});