diff --git a/frontend/src/pages/CompanyDetail.tsx b/frontend/src/pages/CompanyDetail.tsx
index ec54a30..fa97ed3 100644
--- a/frontend/src/pages/CompanyDetail.tsx
+++ b/frontend/src/pages/CompanyDetail.tsx
@@ -1,5 +1,5 @@
 import { useParams, useNavigate, Link } from '@tanstack/react-router';
-import { useState } from 'react';
+import { useState, useEffect } from 'react';
 import {
   useCompany,
   useCompanySources,
@@ -750,6 +750,34 @@ function TrendHistoryChart({ trends, latestTrends, ticker, marketPrices, range90
 
   const hasPrice = chartData.some((pt) => pt.price != null);
 
+  // Compute market open/close vertical markers for intraday and 1d windows
+  const showMarketMarkers = selectedWindow === 'intraday' || selectedWindow === '1d';
+  const marketMarkers: { ts: number; label: string }[] = [];
+  if (showMarketMarkers && chartData.length > 0) {
+    const minTs = chartData[0].timestamp;
+    const maxTs = chartData[chartData.length - 1].timestamp;
+    // Walk each day in the range and compute 9:30 AM ET (open) and 4:00 PM ET (close)
+    const dayMs = 86400_000;
+    const startDay = new Date(minTs);
+    startDay.setUTCHours(0, 0, 0, 0);
+    for (let d = startDay.getTime(); d <= maxTs + dayMs; d += dayMs) {
+      const date = new Date(d);
+      const dow = date.getUTCDay();
+      if (dow === 0 || dow === 6) continue; // skip weekends
+      // ET offset: EDT = UTC-4, EST = UTC-5. Approximate with -4 (summer).
+      // 9:30 AM ET = 13:30 UTC (EDT)
+      const openTs = d + 13 * 3600_000 + 30 * 60_000;
+      // 4:00 PM ET = 20:00 UTC (EDT)
+      const closeTs = d + 20 * 3600_000;
+      if (openTs >= minTs && openTs <= maxTs) {
+        marketMarkers.push({ ts: openTs, label: 'Open' });
+      }
+      if (closeTs >= minTs && closeTs <= maxTs) {
+        marketMarkers.push({ ts: closeTs, label: 'Close' });
+      }
+    }
+  }
+
   // Available windows from the data (check both history and latest)
   const allTrends = [...(trends ?? []), ...(latestTrends ?? [])];
   const availableWindows = [...new Set(allTrends.filter((t) => t.entity_id === ticker).map((t) => t.window))];
@@ -761,6 +789,93 @@ function TrendHistoryChart({ trends, latestTrends, ticker, marketPrices, range90
     .sort((a, b) => new Date(b.generated_at).getTime() - new Date(a.generated_at).getTime());
   const latest = latestForWindow[0] ?? (filtered.length > 0 ? filtered[filtered.length - 1] : null);
 
+  const [fullscreen, setFullscreen] = useState(false);
+
+  // Close fullscreen on Escape key
+  useEffect(() => {
+    if (!fullscreen) return;
+    const handler = (e: KeyboardEvent) => { if (e.key === 'Escape') setFullscreen(false); };
+    window.addEventListener('keydown', handler);
+    return () => window.removeEventListener('keydown', handler);
+  }, [fullscreen]);
+
+  // Shared chart content — rendered at different sizes
+  const chartContent = (height: number) => (
+    <ResponsiveContainer width="100%" height={height}>
+      <LineChart data={chartData} margin={{ top: 5, right: 20, bottom: 40, left: 0 }}>
+        <CartesianGrid strokeDasharray="3 3" stroke="#334155" />
+        {marketMarkers.map((m, i) => (
+          <ReferenceLine
+            key={`market-${i}`}
+            x={m.ts}
+            stroke={m.label === 'Open' ? '#22c55e' : '#ef4444'}
+            strokeDasharray="4 4"
+            strokeWidth={1}
+            strokeOpacity={0.5}
+            label={{ value: m.label, position: 'top', fill: m.label === 'Open' ? '#22c55e' : '#ef4444', fontSize: 9 }}
+          />
+        ))}
+        <XAxis
+          dataKey="timestamp"
+          type="number"
+          domain={['dataMin', 'dataMax']}
+          scale="time"
+          tick={<ChartXTick />}
+          tickLine={{ stroke: '#475569' }}
+          tickCount={8}
+        />
+        <YAxis
+          yAxisId="left"
+          domain={[0, 100]}
+          tick={{ fill: '#94a3b8', fontSize: 11 }}
+          tickLine={{ stroke: '#475569' }}
+          tickFormatter={(v) => `${v}%`}
+        />
+        {hasPrice && (
+          <YAxis
+            yAxisId="right"
+            orientation="right"
+            tick={{ fill: '#e879f9', fontSize: 11 }}
+            tickLine={{ stroke: '#475569' }}
+            tickFormatter={(v) => `$${v}`}
+            domain={[
+              range90d.low != null ? Math.floor(range90d.low * 0.97) : 'dataMin - 2',
+              range90d.high != null ? Math.ceil(range90d.high * 1.03) : 'dataMax + 2',
+            ]}
+          />
+        )}
+        <Tooltip content={TrendTooltip} />
+        <Legend wrapperStyle={{ color: '#94a3b8', fontSize: 12 }} />
+        {hasPrice && range90d.high != null && (
+          <ReferenceLine
+            yAxisId="right"
+            y={range90d.high}
+            stroke="#22c55e"
+            strokeDasharray="6 3"
+            strokeWidth={1.5}
+            label={{ value: `90d High $${range90d.high.toFixed(2)}`, position: 'insideTopRight', fill: '#22c55e', fontSize: 10 }}
+          />
+        )}
+        {hasPrice && range90d.low != null && (
+          <ReferenceLine
+            yAxisId="right"
+            y={range90d.low}
+            stroke="#ef4444"
+            strokeDasharray="6 3"
+            strokeWidth={1.5}
+            label={{ value: `90d Low $${range90d.low.toFixed(2)}`, position: 'insideBottomRight', fill: '#ef4444', fontSize: 10 }}
+          />
+        )}
+        <Line yAxisId="left" type="monotone" dataKey="strength" name="Trend Strength" stroke="#3b82f6" strokeWidth={2} dot={{ r: 3, fill: '#3b82f6' }} activeDot={{ r: 5 }} />
+        <Line yAxisId="left" type="monotone" dataKey="confidence" name="Confidence" stroke="#10b981" strokeWidth={2} dot={{ r: 3, fill: '#10b981' }} activeDot={{ r: 5 }} />
+        <Line yAxisId="left" type="monotone" dataKey="contradiction" name="Contradiction" stroke="#f59e0b" strokeWidth={1.5} strokeDasharray="5 5" dot={{ r: 2, fill: '#f59e0b' }} />
+        {hasPrice && (
+          <Line yAxisId="right" type="monotone" dataKey="price" name="Price" stroke="#e879f9" strokeWidth={2} dot={{ r: 3, fill: '#e879f9' }} activeDot={{ r: 5 }} connectNulls />
+        )}
+      </LineChart>
+    </ResponsiveContainer>
+  );
+
   return (
     <div className="space-y-4">
       {/* Window selector */}
@@ -789,110 +904,47 @@ function TrendHistoryChart({ trends, latestTrends, ticker, marketPrices, range90
         <>
           {/* Trend Strength & Confidence Chart */}
           <Card>
-            <h2 className="mb-3 text-sm font-medium text-gray-400">
-              Trend Strength & Confidence — {ticker} / {selectedWindow}
-            </h2>
-            <ResponsiveContainer width="100%" height={280}>
-              <LineChart data={chartData} margin={{ top: 5, right: 20, bottom: 40, left: 0 }}>
-                <CartesianGrid strokeDasharray="3 3" stroke="#334155" />
-                <XAxis
-                  dataKey="timestamp"
-                  type="number"
-                  domain={['dataMin', 'dataMax']}
-                  scale="time"
-                  tick={<ChartXTick />}
-                  tickLine={{ stroke: '#475569' }}
-                  tickCount={8}
-                />
-                <YAxis
-                  yAxisId="left"
-                  domain={[0, 100]}
-                  tick={{ fill: '#94a3b8', fontSize: 11 }}
-                  tickLine={{ stroke: '#475569' }}
-                  tickFormatter={(v) => `${v}%`}
-                />
-                {hasPrice && (
-                  <YAxis
-                    yAxisId="right"
-                    orientation="right"
-                    tick={{ fill: '#e879f9', fontSize: 11 }}
-                    tickLine={{ stroke: '#475569' }}
-                    tickFormatter={(v) => `$${v}`}
-                    domain={[
-                      range90d.low != null ? Math.floor(range90d.low * 0.97) : 'dataMin - 2',
-                      range90d.high != null ? Math.ceil(range90d.high * 1.03) : 'dataMax + 2',
-                    ]}
-                  />
-                )}
-                <Tooltip content={TrendTooltip} />
-                <Legend wrapperStyle={{ color: '#94a3b8', fontSize: 12 }} />
-                {hasPrice && range90d.high != null && (
-                  <ReferenceLine
-                    yAxisId="right"
-                    y={range90d.high}
-                    stroke="#22c55e"
-                    strokeDasharray="6 3"
-                    strokeWidth={1.5}
-                    label={{ value: `90d High $${range90d.high.toFixed(2)}`, position: 'insideTopRight', fill: '#22c55e', fontSize: 10 }}
-                  />
-                )}
-                {hasPrice && range90d.low != null && (
-                  <ReferenceLine
-                    yAxisId="right"
-                    y={range90d.low}
-                    stroke="#ef4444"
-                    strokeDasharray="6 3"
-                    strokeWidth={1.5}
-                    label={{ value: `90d Low $${range90d.low.toFixed(2)}`, position: 'insideBottomRight', fill: '#ef4444', fontSize: 10 }}
-                  />
-                )}
-                <Line
-                  yAxisId="left"
-                  type="monotone"
-                  dataKey="strength"
-                  name="Trend Strength"
-                  stroke="#3b82f6"
-                  strokeWidth={2}
-                  dot={{ r: 3, fill: '#3b82f6' }}
-                  activeDot={{ r: 5 }}
-                />
-                <Line
-                  yAxisId="left"
-                  type="monotone"
-                  dataKey="confidence"
-                  name="Confidence"
-                  stroke="#10b981"
-                  strokeWidth={2}
-                  dot={{ r: 3, fill: '#10b981' }}
-                  activeDot={{ r: 5 }}
-                />
-                <Line
-                  yAxisId="left"
-                  type="monotone"
-                  dataKey="contradiction"
-                  name="Contradiction"
-                  stroke="#f59e0b"
-                  strokeWidth={1.5}
-                  strokeDasharray="5 5"
-                  dot={{ r: 2, fill: '#f59e0b' }}
-                />
-                {hasPrice && (
-                  <Line
-                    yAxisId="right"
-                    type="monotone"
-                    dataKey="price"
-                    name="Price"
-                    stroke="#e879f9"
-                    strokeWidth={2}
-                    dot={{ r: 3, fill: '#e879f9' }}
-                    activeDot={{ r: 5 }}
-                    connectNulls
-                  />
-                )}
-              </LineChart>
-            </ResponsiveContainer>
+            <div className="mb-3 flex items-center justify-between">
+              <h2 className="text-sm font-medium text-gray-400">
+                Trend Strength & Confidence — {ticker} / {selectedWindow}
+              </h2>
+              <button
+                onClick={() => setFullscreen(true)}
+                className="rounded-md border border-surface-700 px-2 py-1 text-xs text-gray-400 hover:bg-surface-800 hover:text-gray-200"
+                title="Expand chart"
+              >
+                ⛶ Expand
+              </button>
+            </div>
+            {chartContent(280)}
           </Card>
 
+          {/* Fullscreen overlay */}
+          {fullscreen && (
+            <div
+              className="fixed inset-0 z-50 flex flex-col bg-surface-950/95 p-6"
+              onClick={(e) => { if (e.target === e.currentTarget) setFullscreen(false); }}
+              role="dialog"
+              aria-label="Expanded chart"
+            >
+              <div className="mb-4 flex items-center justify-between">
+                <h2 className="text-lg font-medium text-gray-200">
+                  Trend Strength & Confidence — {ticker} / {selectedWindow}
+                </h2>
+                <button
+                  onClick={() => setFullscreen(false)}
+                  className="rounded-md border border-surface-700 px-3 py-1.5 text-sm text-gray-400 hover:bg-surface-800 hover:text-gray-200"
+                >
+                  ✕ Close
+                </button>
+              </div>
+              <div className="flex-1 min-h-0">
+                {chartContent(Math.max(400, window.innerHeight - 160))}
+              </div>
+            </div>
+          )}
+
+          {/* Direction Timeline */}
           {/* Direction Timeline */}
           <Card>
             <h2 className="mb-3 text-sm font-medium text-gray-400">