Fix chart auto toggle to clearly split follow vs manual zoom.

On tail refresh, auto-on always snaps to latest candles while auto-off preserves the saved viewport with clamped range restore.

Co-authored-by: Cursor <cursoragent@cursor.com>

manual_trading_hub/static/chart.js

@@ -2026,12 +2026,6 @@
     return true;
   }
 
-  function isViewingChartTail(range, candleCount) {
-    if (!range || candleCount <= 0) return true;
-    const maxTo = candleCount - 1 + RIGHT_OFFSET_BARS;
-    return range.to >= maxTo - 24;
-  }
-
   function markChartRangeUserAdjusted() {
     chartRangeUserLocked = true;
     if (chartRangeLockTimer) clearTimeout(chartRangeLockTimer);
@@ -2041,14 +2035,37 @@
     }, 30000);
   }
 
+  function clampVisibleLogicalRange(range, candleCount) {
+    if (!range || candleCount <= 0) return null;
+    const maxTo = candleCount - 1 + RIGHT_OFFSET_BARS;
+    const from = Math.max(-2, Math.min(range.from, candleCount - 1));
+    const to = Math.max(0, Math.min(range.to, maxTo + 8));
+    if (to <= from) return null;
+    return { from: from, to: to };
+  }
+
   function restoreVisibleLogicalRange(range, candleCount) {
-    if (!chart || !range || !isVisibleRangeValidForCandles(range, candleCount)) return false;
+    const clamped = clampVisibleLogicalRange(range, candleCount);
+    if (!chart || !clamped || !isVisibleRangeValidForCandles(clamped, candleCount)) return false;
     suppressRangeUserLock = true;
-    chart.timeScale().setVisibleLogicalRange(range);
+    chart.timeScale().setVisibleLogicalRange(clamped);
     suppressRangeUserLock = false;
     return true;
   }
 
+  function applyPreservedVisibleRange(range, candleCount) {
+    if (!chart || !range || !candleCount) return;
+    function applyOnce() {
+      if (!chart || !lastCandles.length) return;
+      applyChartRightGap();
+      restoreVisibleLogicalRange(range, lastCandles.length);
+      updateVisibleRangeMarkers();
+    }
+    applyOnce();
+    requestAnimationFrame(applyOnce);
+    setTimeout(applyOnce, 0);
+  }
+
   function shouldLoadOlderOnRange(range) {
     if (!range || !lastCandles.length) return false;
     const n = lastCandles.length;
@@ -2229,11 +2246,9 @@
     if (!lastViewKey || vKey !== lastViewKey) return;
     const myToken = loadToken;
     const epochAtStart = chartViewEpoch;
-    const candleCountBefore = lastCandles.length;
+    const autoFollow = priceAutoScale;
     let savedRange = null;
     if (chart) savedRange = chart.timeScale().getVisibleLogicalRange();
-    const wasViewingTail =
-      !savedRange || isViewingChartTail(savedRange, candleCountBefore);
     try {
       const data = await fetchChartChunk({
         exchange_key: exKey,
@@ -2255,37 +2270,20 @@
           applyChartPriceFormat();
         }
       }
-      const autoFollow = priceAutoScale;
-      const shouldPreserve =
-        savedRange &&
-        isVisibleRangeValidForCandles(savedRange, candleCountBefore) &&
-        (!autoFollow || chartRangeUserLocked || !wasViewingTail);
       applyCandlesToChart(
         mergeCandles(lastCandles, alignCandlesToTick(data.candles), { prepend: false }),
         0,
         {
-          preserveRange: !!shouldPreserve,
+          preserveRange: false,
           skipAutoScale: !autoFollow,
         }
       );
       if (epochAtStart !== chartViewEpoch) return;
       const n = lastCandles.length;
-      const minorTailUpdate = Math.abs(n - candleCountBefore) <= CHART_TAIL_REFRESH_LIMIT + 5;
-      if (!autoFollow) {
-        if (savedRange && isVisibleRangeValidForCandles(savedRange, n)) {
-          restoreVisibleLogicalRange(savedRange, n);
-        }
-      } else if (wasViewingTail && !chartRangeUserLocked) {
-        restoreVisibleLogicalRange(tailVisibleLogicalRange(n), n);
-      } else if (shouldPreserve && minorTailUpdate) {
-        if (!restoreVisibleLogicalRange(savedRange, n) && !chartRangeUserLocked) {
-          restoreVisibleLogicalRange(tailVisibleLogicalRange(n), n);
-        }
-      } else if (!restoreVisibleLogicalRange(savedRange, n) && !chartRangeUserLocked) {
-        const curRange = chart && chart.timeScale().getVisibleLogicalRange();
-        if (!curRange || !isVisibleRangeValidForCandles(curRange, n)) {
-          restoreVisibleLogicalRange(tailVisibleLogicalRange(n), n);
-        }
+      if (autoFollow) {
+        applyDefaultVisibleRange();
+      } else if (savedRange) {
+        applyPreservedVisibleRange(savedRange, n);
       }
       scheduleRangeUiUpdate();
       if (posContext) {

manual_trading_hub/static/index.html

@@ -349,7 +349,7 @@
 
   <div id="toast"></div>
   <script src="https://unpkg.com/lightweight-charts@4.2.0/dist/lightweight-charts.standalone.production.js"></script>
-  <script src="/assets/chart.js?v=20260604-upnl-contracts"></script>
+  <script src="/assets/chart.js?v=20260608-auto-viewport"></script>
   <script src="/assets/archive.js?v=20260607-hub-archive-v6"></script>
   <script src="/assets/ai_review_render.js?v=2"></script>
   <script src="/assets/app.js?v=20260607-hub-archive-v1"></script>