diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..3f759d74
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2026-08-01 - ISO 문자열 파싱 최적화
+**Learning:** 반복문 내에서 `new Date().getTime()`을 호출하면 불필요한 Date 객체 할당이 발생하여 성능 저하 및 메인 스레드 블로킹을 유발함. 특히 가상화 리스트(`react-window` 등) 렌더링 루프에서는 이런 계산을 외부로 빼거나, V8 엔진에서 빠른 `Date.parse()`를 사용하는 것이 유리함.
+**Action:** 앞으로는 성능이 중요한 렌더링 경로나 루프 내에서 날짜 파싱이 필요할 때 객체 할당을 피하기 위해 `Date.parse(string)`을 사용할 것. 또한 정적인 계산값(예: sessionStartedAt)은 상위 컴포넌트에서 `useMemo`로 처리하여 하위 컴포넌트에 원시 값으로 전달할 것.
\ No newline at end of file
diff --git a/packages/web/src/components/dashboard/event-list.tsx b/packages/web/src/components/dashboard/event-list.tsx
index a3e4406c..5452c797 100644
--- a/packages/web/src/components/dashboard/event-list.tsx
+++ b/packages/web/src/components/dashboard/event-list.tsx
@@ -39,9 +39,9 @@ type FlatRow =
 
 const ROW_HEIGHT = 36;
 
-function formatElapsed(timestamp: string, sessionStartedAt: string): string {
-  const t = new Date(timestamp).getTime();
-  const start = new Date(sessionStartedAt).getTime();
+function formatElapsed(timestamp: string, sessionStartedAtMs: number): string {
+  const t = Date.parse(timestamp);
+  const start = sessionStartedAtMs;
   if (Number.isNaN(t) || Number.isNaN(start)) return "";
   const diffSec = Math.max(0, Math.floor((t - start) / 1000));
   const h = Math.floor(diffSec / 3600);
@@ -123,7 +123,8 @@ function getSinglePreview(event: TimelineEvent): string {
     return normalized.slice(0, 80);
   }
   if (event.isSkillCall && event.skillName) return `Skill: ${event.skillName}`;
-  if (event.isAgentCall && event.agentType) return `Subagent: ${event.agentType}`;
+  if (event.isAgentCall && event.agentType)
+    return `Subagent: ${event.agentType}`;
   return event.toolName;
 }
 
@@ -207,7 +208,7 @@ function RowView({
 type RowProps = {
   rows: FlatRow[];
   selectedIdx: number;
-  sessionStartedAt: string;
+  sessionStartedAtMs: number;
   onSelect: (idx: number) => void;
   onToggleGroup: (firstIdx: number) => void;
 };
@@ -217,7 +218,7 @@ function Row({
   style,
   rows,
   selectedIdx,
-  sessionStartedAt,
+  sessionStartedAtMs,
   onSelect,
   onToggleGroup,
 }: RowComponentProps<RowProps>) {
@@ -230,7 +231,7 @@ function Row({
         <RowView
           label="Tool"
           preview={`${row.toolName} x${row.count}`}
-          time={formatElapsed(row.firstEvent.timestamp, sessionStartedAt)}
+          time={formatElapsed(row.firstEvent.timestamp, sessionStartedAtMs)}
           icon={getIcon(row.firstEvent)}
           isSelected={false}
           onClick={() => onToggleGroup(row.groupFirstIdx)}
@@ -241,18 +242,19 @@ function Row({
   }
 
   const label = row.labelOverride ?? getSingleLabel(row.event);
-  const preview = row.labelOverride === "Tool"
-    ? row.event.kind === "tool"
-      ? row.event.toolName
-      : getSinglePreview(row.event)
-    : getSinglePreview(row.event);
+  const preview =
+    row.labelOverride === "Tool"
+      ? row.event.kind === "tool"
+        ? row.event.toolName
+        : getSinglePreview(row.event)
+      : getSinglePreview(row.event);
 
   return (
     <div style={style} role="listitem">
       <RowView
         label={label}
         preview={preview}
-        time={formatElapsed(row.event.timestamp, sessionStartedAt)}
+        time={formatElapsed(row.event.timestamp, sessionStartedAtMs)}
         icon={getIcon(row.event)}
         isSelected={row.idx === selectedIdx}
         onClick={() => onSelect(row.idx)}
@@ -271,6 +273,11 @@ export function EventList({
   expandedGroups,
   onToggleGroup,
 }: EventListProps) {
+  const sessionStartedAtMs = useMemo(
+    () => Date.parse(sessionStartedAt),
+    [sessionStartedAt],
+  );
+
   const rows = useMemo(
     () => buildFlatRows(groups, expandedGroups, selectedIdx),
     [groups, expandedGroups, selectedIdx],
@@ -292,7 +299,7 @@ export function EventList({
       rowProps={{
         rows,
         selectedIdx,
-        sessionStartedAt,
+        sessionStartedAtMs,
         onSelect,
         onToggleGroup,
       }}
diff --git a/packages/web/src/components/dashboard/session-timeline-chart.tsx b/packages/web/src/components/dashboard/session-timeline-chart.tsx
index f5a7a32c..4ed9f6e9 100644
--- a/packages/web/src/components/dashboard/session-timeline-chart.tsx
+++ b/packages/web/src/components/dashboard/session-timeline-chart.tsx
@@ -1,6 +1,6 @@
-'use client'
+"use client";
 
-import React, { useMemo } from 'react'
+import React, { useMemo } from "react";
 import {
   ComposedChart,
   Bar,
@@ -10,83 +10,83 @@ import {
   Tooltip,
   ResponsiveContainer,
   TooltipProps,
-} from 'recharts'
-import { formatTokens, formatCost, formatRelativeTime } from '@/lib/format'
-import type { SessionTimelineUsage, SessionDetail } from '@argos/shared'
+} from "recharts";
+import { formatTokens, formatCost, formatRelativeTime } from "@/lib/format";
+import type { SessionTimelineUsage, SessionDetail } from "@argos/shared";
 
 interface SessionTimelineChartProps {
-  usageTimeline: SessionTimelineUsage[]
-  messages: SessionDetail['messages']
-  sessionStartedAt: string
+  usageTimeline: SessionTimelineUsage[];
+  messages: SessionDetail["messages"];
+  sessionStartedAt: string;
 }
 
 interface ToolCallPoint {
-  timestamp: string
-  toolName: string
-  parsedTimestamp: number
+  timestamp: string;
+  toolName: string;
+  parsedTimestamp: number;
 }
 
 interface ChartDataItem {
-  relativeTime: string
-  input: number
-  output: number
-  cost: number
-  model?: string | null
-  toolSummary: string
+  relativeTime: string;
+  input: number;
+  output: number;
+  cost: number;
+  model?: string | null;
+  toolSummary: string;
 }
 
 function getToolSummaryForIndex(
   index: number,
   usageTimeline: SessionTimelineUsage[],
-  toolCalls: ToolCallPoint[]
+  toolCalls: ToolCallPoint[],
 ): string {
-  if (toolCalls.length === 0) return ''
+  if (toolCalls.length === 0) return "";
 
-  const currentTimestamp = new Date(usageTimeline[index]!.timestamp).getTime()
+  const currentTimestamp = Date.parse(usageTimeline[index]!.timestamp);
   const prevTimestamp =
-    index > 0 ? new Date(usageTimeline[index - 1]!.timestamp).getTime() : 0
+    index > 0 ? Date.parse(usageTimeline[index - 1]!.timestamp) : 0;
 
   // 현재 usageTimeline timestamp 이전이면서, 이전 usageTimeline timestamp 이후의 tool events 찾기
   // 첫 번째 bar(index=0)는 prevTimestamp가 0이므로 해당 bar 이전의 모든 이벤트를 포함
   const relevantTools = toolCalls.filter((e) => {
-    const toolTimestamp = e.parsedTimestamp
-    return toolTimestamp <= currentTimestamp && toolTimestamp > prevTimestamp
-  })
+    const toolTimestamp = e.parsedTimestamp;
+    return toolTimestamp <= currentTimestamp && toolTimestamp > prevTimestamp;
+  });
 
-  if (relevantTools.length === 0) return ''
+  if (relevantTools.length === 0) return "";
 
   // 이름별로 카운트
-  const counts = new Map<string, number>()
+  const counts = new Map<string, number>();
   for (const tool of relevantTools) {
-    const name = tool.toolName || 'unknown'
-    counts.set(name, (counts.get(name) || 0) + 1)
+    const name = tool.toolName || "unknown";
+    counts.set(name, (counts.get(name) || 0) + 1);
   }
 
   // 배열로 변환하여 카운트 내림차순 정렬
-  const sorted = Array.from(counts.entries()).sort((a, b) => b[1] - a[1])
+  const sorted = Array.from(counts.entries()).sort((a, b) => b[1] - a[1]);
 
   // 최대 3개까지만 표시
-  const displayCount = Math.min(3, sorted.length)
+  const displayCount = Math.min(3, sorted.length);
   const displayItems = sorted.slice(0, displayCount).map(([name, count]) => {
-    return count > 1 ? `${name} x${count}` : name
-  })
+    return count > 1 ? `${name} x${count}` : name;
+  });
 
-  const remaining = sorted.length - displayCount
+  const remaining = sorted.length - displayCount;
   if (remaining > 0) {
-    return `${displayItems.join(', ')} +${remaining} more`
+    return `${displayItems.join(", ")} +${remaining} more`;
   }
 
-  return displayItems.join(', ')
+  return displayItems.join(", ");
 }
 
 function CustomTooltip({
   active,
   payload,
 }: TooltipProps<number, string> & { chartData?: ChartDataItem[] }) {
-  if (!active || !payload || payload.length === 0) return null
+  if (!active || !payload || payload.length === 0) return null;
 
-  const data = payload[0]?.payload as ChartDataItem | undefined
-  if (!data) return null
+  const data = payload[0]?.payload as ChartDataItem | undefined;
+  if (!data) return null;
 
   return (
     <div className="rounded-lg border border-border bg-popover text-popover-foreground shadow-lg p-3">
@@ -95,16 +95,22 @@ function CustomTooltip({
         <div className="flex items-center gap-2">
           <span className="h-2.5 w-2.5 rounded-full bg-chart-1" />
           <span className="text-muted-foreground">Input Tokens:</span>
-          <span className="font-medium tabular-nums">{formatTokens(data.input)}</span>
+          <span className="font-medium tabular-nums">
+            {formatTokens(data.input)}
+          </span>
         </div>
         <div className="flex items-center gap-2">
           <span className="h-2.5 w-2.5 rounded-full bg-chart-2" />
           <span className="text-muted-foreground">Output Tokens:</span>
-          <span className="font-medium tabular-nums">{formatTokens(data.output)}</span>
+          <span className="font-medium tabular-nums">
+            {formatTokens(data.output)}
+          </span>
         </div>
         <div className="pt-1 mt-1 border-t border-border">
           <span className="text-muted-foreground">Cost:</span>
-          <span className="font-medium ml-2 tabular-nums">{formatCost(data.cost)}</span>
+          <span className="font-medium ml-2 tabular-nums">
+            {formatCost(data.cost)}
+          </span>
         </div>
         {data.model && (
           <div>
@@ -120,7 +126,7 @@ function CustomTooltip({
         )}
       </div>
     </div>
-  )
+  );
 }
 
 export function SessionTimelineChart({
@@ -132,13 +138,13 @@ export function SessionTimelineChart({
   // 리렌더링 시마다 발생하는 불필요한 연산을 방지함. (배열 생성 오버헤드 감소)
   const toolCalls: ToolCallPoint[] = useMemo(() => {
     return messages
-      .filter((m) => m.role === 'TOOL')
+      .filter((m) => m.role === "TOOL")
       .map((m) => ({
         timestamp: m.timestamp,
-        toolName: m.toolName ?? 'unknown',
-        parsedTimestamp: new Date(m.timestamp).getTime(),
-      }))
-  }, [messages])
+        toolName: m.toolName ?? "unknown",
+        parsedTimestamp: Date.parse(m.timestamp),
+      }));
+  }, [messages]);
 
   // ⚡ Bolt: usageTimeline 배열을 순회하며 차트 데이터를 생성하는 비용이 높은 작업을
   // useMemo로 최적화하여 데이터 변경이 없을 때 캐시된 결과를 재사용함.
@@ -151,13 +157,15 @@ export function SessionTimelineChart({
       cost: u.estimatedCostUsd,
       model: u.model,
       toolSummary: getToolSummaryForIndex(idx, usageTimeline, toolCalls),
-    }))
-  }, [usageTimeline, sessionStartedAt, toolCalls])
+    }));
+  }, [usageTimeline, sessionStartedAt, toolCalls]);
 
   if (usageTimeline.length === 0) {
     return (
-      <p className="text-center text-muted-foreground py-8">No timeline data available</p>
-    )
+      <p className="text-center text-muted-foreground py-8">
+        No timeline data available
+      </p>
+    );
   }
 
   return (
@@ -169,16 +177,19 @@ export function SessionTimelineChart({
           stroke="var(--color-muted-foreground)"
           tickLine={false}
           axisLine={false}
-          style={{ fontSize: '11px' }}
+          style={{ fontSize: "11px" }}
         />
         <YAxis
           tickFormatter={formatTokens}
           stroke="var(--color-muted-foreground)"
           tickLine={false}
           axisLine={false}
-          style={{ fontSize: '11px' }}
+          style={{ fontSize: "11px" }}
+        />
+        <Tooltip
+          content={<CustomTooltip />}
+          cursor={{ fill: "var(--color-muted)", opacity: 0.4 }}
         />
-        <Tooltip content={<CustomTooltip />} cursor={{ fill: 'var(--color-muted)', opacity: 0.4 }} />
         <Bar
           dataKey="input"
           stackId="tokens"
@@ -193,5 +204,5 @@ export function SessionTimelineChart({
         />
       </ComposedChart>
     </ResponsiveContainer>
-  )
+  );
 }