diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..0552480
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-24 - Optimize Prisma nested include iterations
+**Learning:** When calculating totals or metrics from large nested datasets (e.g., from Prisma `include` results), using multiple chained `.reduce()` calls causes multiple iterations over the same data, leading to unnecessary memory allocation and iteration overhead.
+**Action:** Replace multiple chained array iteration methods (like `.reduce()`, `.map()`, or `.filter()`) with a single `for...of` loop when aggregating multiple metrics from the same dataset to minimize iteration overhead.
diff --git a/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/[sessionId]/route.ts b/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/[sessionId]/route.ts
index 35486b8..fa43615 100644
--- a/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/[sessionId]/route.ts
+++ b/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/[sessionId]/route.ts
@@ -43,9 +43,15 @@ export async function GET(
       return forbiddenByRole(access.role, '본인 세션만 열람 가능')
     }
 
-    const totalInput = session.usageRecords.reduce((sum, r) => sum + r.inputTokens, 0)
-    const totalOutput = session.usageRecords.reduce((sum, r) => sum + r.outputTokens, 0)
-    const totalCost = session.usageRecords.reduce((sum, r) => sum + (r.estimatedCostUsd ?? 0), 0)
+    let totalInput = 0
+    let totalOutput = 0
+    let totalCost = 0
+
+    for (const r of session.usageRecords) {
+      totalInput += r.inputTokens
+      totalOutput += r.outputTokens
+      totalCost += r.estimatedCostUsd ?? 0
+    }
 
     const usageTimeline: SessionTimelineUsage[] = session.usageRecords.map((r) => ({
       timestamp: r.timestamp.toISOString(),
diff --git a/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/route.ts b/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/route.ts
index 25fbe70..7d6a4d4 100644
--- a/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/route.ts
+++ b/packages/web/src/app/api/orgs/[orgSlug]/dashboard/sessions/route.ts
@@ -33,14 +33,17 @@ const sessionInclude = {
 type SessionWithInclude = Prisma.ClaudeSessionGetPayload<{ include: typeof sessionInclude }>
 
 function getSessionTotals(session: SessionWithInclude) {
-  return {
-    inputTokens: session.usageRecords.reduce((sum, r) => sum + r.inputTokens, 0),
-    outputTokens: session.usageRecords.reduce((sum, r) => sum + r.outputTokens, 0),
-    estimatedCostUsd: session.usageRecords.reduce(
-      (sum, r) => sum + (r.estimatedCostUsd ?? 0),
-      0,
-    ),
+  let inputTokens = 0
+  let outputTokens = 0
+  let estimatedCostUsd = 0
+
+  for (const r of session.usageRecords) {
+    inputTokens += r.inputTokens
+    outputTokens += r.outputTokens
+    estimatedCostUsd += r.estimatedCostUsd ?? 0
   }
+
+  return { inputTokens, outputTokens, estimatedCostUsd }
 }
 
 function mapSessionItem(session: SessionWithInclude): SessionItem {
diff --git a/packages/web/src/lib/server/weekly-report.ts b/packages/web/src/lib/server/weekly-report.ts
index ace2f44..b18bb4c 100644
--- a/packages/web/src/lib/server/weekly-report.ts
+++ b/packages/web/src/lib/server/weekly-report.ts
@@ -446,17 +446,18 @@ export async function getWeeklyReport(
   }
 
   // Insights — delegation
-  const totalAgentCalls = thisWeekRollups.reduce(
-    (sum, r) => sum + Object.values(r.agentCounts).reduce((a, b) => a + b, 0),
-    0,
-  )
-  const totalSkillCalls = thisWeekRollups.reduce(
-    (sum, r) => sum + Object.values(r.skillCounts).reduce((a, b) => a + b, 0),
-    0,
-  )
+  let totalAgentCalls = 0
+  let totalSkillCalls = 0
   const distinctSkillsThisWeek = new Set<string>()
+
   for (const r of thisWeekRollups) {
-    for (const k of Object.keys(r.skillCounts)) distinctSkillsThisWeek.add(k)
+    for (const count of Object.values(r.agentCounts)) {
+      totalAgentCalls += count
+    }
+    for (const [skillName, count] of Object.entries(r.skillCounts)) {
+      totalSkillCalls += count
+      distinctSkillsThisWeek.add(skillName)
+    }
   }
 
   const insights: WeeklyInsights = {