Draw volume, which travelled the whole pipeline unseen

Volume is parsed from both Schwab services, aggregated into every timeframe,
stored and broadcast in every bar payload — and nothing ever drew it.

An overlay histogram on its own hidden scale, confined to the bottom fifth and
tinted by each bar's direction. An overlay rather than a second pane, and
deliberately not on the price scale: volumes are five figures against
four-figure prices, so sharing a scale would flatten the candles into a line.
Verified in a browser that the price scales are untouched — the same price still
maps to the identical coordinate through both.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/IMPLEMENTATION_PLAN.md

@@ -1380,3 +1380,39 @@ trendline 147 points away.
 One limit worth knowing: tick *placement* is still computed on UTC days, so the
 day-change divider sits at 00:00 UTC rather than local midnight, labelled with
 the local date. The labels are right; the divider is in the UTC place.
+
+### 2026-08-10 (afternoon) — update rate, the left scale, and volume
+
+**Schwab conflates Level 1 to one update per second.** Chasing "still slow in
+market hours" ended at a hard ceiling rather than a bug. In regular hours the
+gaps between updates are whole multiples of 1.005s — 2.01, 3.02, 4.03 — which
+only happens if the source emits on a one-second cadence and some seconds carry
+no trade. `SCHWAB_TICK_SECONDS` was the limiter at 1.0 and is now 0.25, where it
+no longer binds. **One update per second is the source's ceiling.** Anything
+faster would mean inventing prices between trades, which a chart must not do.
+
+Two real losses were found on the way and fixed:
+
+- Higher timeframes only moved once a minute, because tick bars are 1m and the
+  socket filters by subscriber timeframe. `Runtime.provisional_higher` now
+  combines the aggregator's committed state with the live minute — without
+  mutating it, since the aggregator accumulates volume and would double count.
+- Trades carrying only a trade stamp and a moved `TOTAL_VOLUME` — no
+  `LAST_PRICE`, no `LAST_SIZE` — were skipped. 66 → 74 updates per 90s.
+
+**Daily context moved to the left price scale.** The right had prior-day levels,
+session VWAP and five daily MAs competing with the live price and hand-drawn
+intraday levels. The trap: a price scale takes its range from the series on it,
+so moving levels across draws them against a different range and puts them at
+the wrong height. A transparent candlestick mirror on the left scale feeds it
+exactly the right scale's input; verified as a zero-pixel delta between the two.
+Hand-drawn levels stay right, which is the space being cleared. `priceScaleId`
+is fixed at series creation, so it is passed at construction and kept out of the
+options reapplied afterwards.
+
+**Volume is finally drawn.** It travelled the entire pipeline — parsed from both
+Schwab services, aggregated, stored, broadcast in every bar — and nothing
+rendered it. Now an overlay histogram on its own hidden scale in the bottom
+fifth. An overlay rather than a pane, and emphatically not the price scale:
+volumes are five figures against four-figure prices, and sharing a scale would
+flatten the candles to a line.

static/chart.js

@@ -100,6 +100,20 @@ class ConfluenceChart {
       wickUpColor: 'transparent', wickDownColor: 'transparent',
       lastValueVisible: false, priceLineVisible: false,
     });
+    // Volume as an overlay on its own hidden scale, confined to the bottom
+    // fifth. An overlay rather than a pane so it cannot alter the price scale:
+    // volumes are five figures and prices four, and sharing a scale would
+    // flatten the candles into a line.
+    this.volume = this.chart.addSeries(LightweightCharts.HistogramSeries, {
+      priceScaleId: 'volume',
+      priceFormat: { type: 'volume' },
+      lastValueVisible: false,
+      priceLineVisible: false,
+    });
+    this.chart.priceScale('volume').applyOptions({
+      scaleMargins: { top: 0.82, bottom: 0 },
+      visible: false,
+    });
     this.resizeObserver = new ResizeObserver(() => {
       this.chart.applyOptions({ width: el.clientWidth, height: el.clientHeight });
       requestAnimationFrame(() => this.renderAnchorHandles());
@@ -186,6 +200,7 @@ class ConfluenceChart {
     const candleData = bars.map(this.toCandle);
     this.candles.setData(candleData);
     this.leftMirror.setData(candleData);
+    this.volume.setData(bars.map(ConfluenceChart.toVolume));
     // Anchored by time, not by logical index. A logical index addresses the
     // chart's *shared* scale — the union of every series' time points — not
     // this array. The daily MAs land straight after with hundreds of points
@@ -214,6 +229,7 @@ class ConfluenceChart {
     if (last && bar.t < last.t) return;
     this.candles.update(this.toCandle(bar));
     this.leftMirror.update(this.toCandle(bar));
+    this.volume.update(ConfluenceChart.toVolume(bar));
     if (this.bars.length && this.bars[this.bars.length - 1].t === bar.t) this.bars[this.bars.length - 1] = bar;
     else this.bars.push(bar);
     this.renderAnchorHandles();
@@ -724,6 +740,15 @@ class ConfluenceChart {
     if (this.onLineEnd) this.onLineEnd({ ...level });
   }
 
+  // Tinted by the bar's own direction, muted so the candles stay the subject.
+  static toVolume(bar) {
+    return {
+      time: bar.t,
+      value: bar.v,
+      color: bar.c >= bar.o ? 'rgba(39,130,92,.38)' : 'rgba(189,69,69,.38)',
+    };
+  }
+
   toCandle(bar) {
     return { time: bar.t, open: bar.o, high: bar.h, low: bar.l, close: bar.c };
   }