From 58d5221ca1453454341fe31777d5297def7cb6b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=A8=8B=E5=BA=8F=E5=91=98=E9=98=BF=E6=B1=9F=28Relakkes?=
 =?UTF-8?q?=29?= <relakkes@gmail.com>
Date: Fri, 12 Jun 2026 10:41:33 +0800
Subject: [PATCH] feat(activity): add plugin and skill usage insights

Add historical tool and skill aggregation to activity stats, compact the token summary, and show Codex-style activity insights with plugin/skill ranking.

Tested: bun test src/utils/__tests__/stats.test.ts
Tested: bun run check:persistence-upgrade
Tested: bun run check:desktop
Not-tested: bun run check:server (previous full run exposed unrelated conversations WebSocket timeouts; focused stats and persistence checks passed)
Confidence: medium
Scope-risk: moderate
---
 desktop/src/api/activityStats.ts            |  11 +-
 desktop/src/i18n/locales/en.ts              |  11 +
 desktop/src/i18n/locales/jp.ts              |  11 +
 desktop/src/i18n/locales/kr.ts              |  11 +
 desktop/src/i18n/locales/zh-TW.ts           |  11 +
 desktop/src/i18n/locales/zh.ts              |  11 +
 desktop/src/pages/ActivitySettings.test.tsx |  53 ++++-
 desktop/src/pages/ActivitySettings.tsx      | 232 +++++++++++++++++---
 desktop/src/theme/globals.css               |  16 +-
 desktop/src/theme/globals.test.ts           |  11 +-
 src/server/__tests__/settings.test.ts       |   2 +
 src/utils/__tests__/stats.test.ts           |  72 +++++-
 src/utils/stats.ts                          |  65 ++++++
 src/utils/statsCache.ts                     |  57 ++++-
 14 files changed, 502 insertions(+), 72 deletions(-)

diff --git a/desktop/src/api/activityStats.ts b/desktop/src/api/activityStats.ts
index bd7d274c..695799f3 100644
--- a/desktop/src/api/activityStats.ts
+++ b/desktop/src/api/activityStats.ts
@@ -29,6 +29,13 @@ export type SessionStats = {
   timestamp: string
 }
 
+export type ModelUsage = {
+  inputTokens?: number
+  outputTokens?: number
+  cacheReadInputTokens?: number
+  cacheCreationInputTokens?: number
+}
+
 export type ActivityStats = {
   totalSessions: number
   totalMessages: number
@@ -38,7 +45,9 @@ export type ActivityStats = {
   dailyActivity: DailyActivity[]
   dailyModelTokens: DailyModelTokens[]
   longestSession: SessionStats | null
-  modelUsage: Record<string, unknown>
+  modelUsage: Record<string, ModelUsage>
+  toolUsage: Record<string, number>
+  skillUsage: Record<string, number>
   firstSessionDate: string | null
   lastSessionDate: string | null
   peakActivityDay: string | null
diff --git a/desktop/src/i18n/locales/en.ts b/desktop/src/i18n/locales/en.ts
index dc73a734..0122b022 100644
--- a/desktop/src/i18n/locales/en.ts
+++ b/desktop/src/i18n/locales/en.ts
@@ -226,6 +226,8 @@ export const en = {
   'settings.activity.count.sessionOther': '{count} sessions',
   'settings.activity.count.dayOne': '{count} day',
   'settings.activity.count.dayOther': '{count} days',
+  'settings.activity.count.runOne': '{count} run',
+  'settings.activity.count.runOther': '{count} runs',
   'settings.activity.weekday.mon': 'Mon',
   'settings.activity.weekday.wed': 'Wed',
   'settings.activity.weekday.fri': 'Fri',
@@ -234,6 +236,15 @@ export const en = {
   'settings.activity.tokens': 'Tokens',
   'settings.activity.messages': 'Messages',
   'settings.activity.tools': 'Tools',
+  'settings.activity.activityInsights': 'Activity insights',
+  'settings.activity.activeRate': 'Active rate',
+  'settings.activity.mostUsedModel': 'Most used model',
+  'settings.activity.exploredSkills': 'Skills explored',
+  'settings.activity.totalSkillUses': 'Skill uses',
+  'settings.activity.totalToolCalls': 'Tool calls',
+  'settings.activity.totalSessions': 'Total sessions',
+  'settings.activity.mostUsedPluginsAndSkills': 'Most used plugins & skills',
+  'settings.activity.none': 'None',
   'settings.activity.less': 'Less',
   'settings.activity.more': 'More',
 
diff --git a/desktop/src/i18n/locales/jp.ts b/desktop/src/i18n/locales/jp.ts
index 4ac0d9d4..b0781967 100644
--- a/desktop/src/i18n/locales/jp.ts
+++ b/desktop/src/i18n/locales/jp.ts
@@ -228,6 +228,8 @@ export const jp: Record<TranslationKey, string> = {
   'settings.activity.count.sessionOther': '{count} セッション',
   'settings.activity.count.dayOne': '{count} 日',
   'settings.activity.count.dayOther': '{count} 日',
+  'settings.activity.count.runOne': '{count} 回実行',
+  'settings.activity.count.runOther': '{count} 回実行',
   'settings.activity.weekday.mon': '月',
   'settings.activity.weekday.wed': '水',
   'settings.activity.weekday.fri': '金',
@@ -236,6 +238,15 @@ export const jp: Record<TranslationKey, string> = {
   'settings.activity.tokens': 'トークン',
   'settings.activity.messages': 'メッセージ',
   'settings.activity.tools': 'ツール',
+  'settings.activity.activityInsights': 'アクティビティ分析',
+  'settings.activity.activeRate': 'アクティブ率',
+  'settings.activity.mostUsedModel': '最も使ったモデル',
+  'settings.activity.exploredSkills': '使用したスキル',
+  'settings.activity.totalSkillUses': 'スキル使用数',
+  'settings.activity.totalToolCalls': 'ツール呼び出し',
+  'settings.activity.totalSessions': 'セッション総数',
+  'settings.activity.mostUsedPluginsAndSkills': 'よく使うプラグイン/スキル',
+  'settings.activity.none': 'なし',
   'settings.activity.less': '少ない',
   'settings.activity.more': '多い',
 
diff --git a/desktop/src/i18n/locales/kr.ts b/desktop/src/i18n/locales/kr.ts
index e43721a7..0561056d 100644
--- a/desktop/src/i18n/locales/kr.ts
+++ b/desktop/src/i18n/locales/kr.ts
@@ -228,6 +228,8 @@ export const kr: Record<TranslationKey, string> = {
   'settings.activity.count.sessionOther': '{count} 세션',
   'settings.activity.count.dayOne': '{count}일',
   'settings.activity.count.dayOther': '{count}일',
+  'settings.activity.count.runOne': '{count}회 실행',
+  'settings.activity.count.runOther': '{count}회 실행',
   'settings.activity.weekday.mon': '월',
   'settings.activity.weekday.wed': '수',
   'settings.activity.weekday.fri': '금',
@@ -236,6 +238,15 @@ export const kr: Record<TranslationKey, string> = {
   'settings.activity.tokens': '토큰',
   'settings.activity.messages': '메시지',
   'settings.activity.tools': '도구',
+  'settings.activity.activityInsights': '활동 인사이트',
+  'settings.activity.activeRate': '활성 비율',
+  'settings.activity.mostUsedModel': '가장 많이 쓴 모델',
+  'settings.activity.exploredSkills': '사용한 스킬',
+  'settings.activity.totalSkillUses': '스킬 사용 수',
+  'settings.activity.totalToolCalls': '도구 호출',
+  'settings.activity.totalSessions': '총 세션',
+  'settings.activity.mostUsedPluginsAndSkills': '자주 쓰는 플러그인/스킬',
+  'settings.activity.none': '없음',
   'settings.activity.less': '적음',
   'settings.activity.more': '많음',
 
diff --git a/desktop/src/i18n/locales/zh-TW.ts b/desktop/src/i18n/locales/zh-TW.ts
index bf538026..9e9ab57d 100644
--- a/desktop/src/i18n/locales/zh-TW.ts
+++ b/desktop/src/i18n/locales/zh-TW.ts
@@ -228,6 +228,8 @@ export const zh: Record<TranslationKey, string> = {
   'settings.activity.count.sessionOther': '{count} 次會話',
   'settings.activity.count.dayOne': '{count} 天',
   'settings.activity.count.dayOther': '{count} 天',
+  'settings.activity.count.runOne': '{count} 次執行',
+  'settings.activity.count.runOther': '{count} 次執行',
   'settings.activity.weekday.mon': '週一',
   'settings.activity.weekday.wed': '週三',
   'settings.activity.weekday.fri': '週五',
@@ -236,6 +238,15 @@ export const zh: Record<TranslationKey, string> = {
   'settings.activity.tokens': 'Token',
   'settings.activity.messages': '訊息',
   'settings.activity.tools': '工具',
+  'settings.activity.activityInsights': '活動洞察',
+  'settings.activity.activeRate': '活躍率',
+  'settings.activity.mostUsedModel': '最常用模型',
+  'settings.activity.exploredSkills': '已使用的技能',
+  'settings.activity.totalSkillUses': '技能使用總數',
+  'settings.activity.totalToolCalls': '工具呼叫',
+  'settings.activity.totalSessions': '會話總數',
+  'settings.activity.mostUsedPluginsAndSkills': '最常用的外掛和技能',
+  'settings.activity.none': '暫無',
   'settings.activity.less': '少',
   'settings.activity.more': '多',
 
diff --git a/desktop/src/i18n/locales/zh.ts b/desktop/src/i18n/locales/zh.ts
index 479d7a35..bd06b081 100644
--- a/desktop/src/i18n/locales/zh.ts
+++ b/desktop/src/i18n/locales/zh.ts
@@ -228,6 +228,8 @@ export const zh: Record<TranslationKey, string> = {
   'settings.activity.count.sessionOther': '{count} 次会话',
   'settings.activity.count.dayOne': '{count} 天',
   'settings.activity.count.dayOther': '{count} 天',
+  'settings.activity.count.runOne': '{count} 次运行',
+  'settings.activity.count.runOther': '{count} 次运行',
   'settings.activity.weekday.mon': '周一',
   'settings.activity.weekday.wed': '周三',
   'settings.activity.weekday.fri': '周五',
@@ -236,6 +238,15 @@ export const zh: Record<TranslationKey, string> = {
   'settings.activity.tokens': 'Token',
   'settings.activity.messages': '消息',
   'settings.activity.tools': '工具',
+  'settings.activity.activityInsights': '活动洞察',
+  'settings.activity.activeRate': '活跃率',
+  'settings.activity.mostUsedModel': '最常用模型',
+  'settings.activity.exploredSkills': '已使用的技能',
+  'settings.activity.totalSkillUses': '技能使用总数',
+  'settings.activity.totalToolCalls': '工具调用',
+  'settings.activity.totalSessions': '会话总数',
+  'settings.activity.mostUsedPluginsAndSkills': '最常用的插件和技能',
+  'settings.activity.none': '暂无',
   'settings.activity.less': '少',
   'settings.activity.more': '多',
 
diff --git a/desktop/src/pages/ActivitySettings.test.tsx b/desktop/src/pages/ActivitySettings.test.tsx
index 62e34e87..f15edb4b 100644
--- a/desktop/src/pages/ActivitySettings.test.tsx
+++ b/desktop/src/pages/ActivitySettings.test.tsx
@@ -62,7 +62,28 @@ const activityResponse = {
     { date: '2026-05-09', tokensByModel: { 'claude-sonnet': 128_000 } },
   ],
   longestSession: null,
-  modelUsage: {},
+  modelUsage: {
+    'claude-sonnet': {
+      inputTokens: 1_900_000,
+      outputTokens: 700_000,
+      cacheReadInputTokens: 230_000,
+      cacheCreationInputTokens: 34_000,
+    },
+  },
+  toolUsage: {
+    Bash: 180,
+    Read: 160,
+    Skill: 40,
+    mcp__github__get_pull_request: 14,
+    mcp__chrome_devtools__new_page: 8,
+    mcp__figma__get_screenshot: 7,
+    mcp__linear__create_issue: 2,
+  },
+  skillUsage: {
+    'frontend-design': 24,
+    'git-commit-pr': 16,
+    'code-review': 11,
+  },
   firstSessionDate: '2025-06-01T10:00:00.000Z',
   lastSessionDate: '2026-05-09T11:00:00.000Z',
   peakActivityDay: '2026-04-20',
@@ -195,6 +216,27 @@ describe('ActivitySettings', () => {
     expect(screen.getByText('0m')).toBeInTheDocument()
     expect(screen.getByText('9 days')).toBeInTheDocument()
     expect(screen.getByText('18 days')).toBeInTheDocument()
+    expect(screen.getByText('Activity insights')).toBeInTheDocument()
+    expect(screen.getByText('Active rate')).toBeInTheDocument()
+    expect(screen.getByText('Most used model')).toBeInTheDocument()
+    expect(screen.getByText('Skills explored')).toBeInTheDocument()
+    expect(screen.getByText('Skill uses')).toBeInTheDocument()
+    expect(screen.getByText('Tool calls')).toBeInTheDocument()
+    expect(screen.getByText('Total sessions')).toBeInTheDocument()
+    expect(screen.getByText('Most used plugins & skills')).toBeInTheDocument()
+    expect(screen.getByText('Sonnet')).toBeInTheDocument()
+    expect(screen.getByText('$frontend-design')).toBeInTheDocument()
+    expect(screen.getByText('$git-commit-pr')).toBeInTheDocument()
+    expect(screen.getByText('$code-review')).toBeInTheDocument()
+    expect(screen.getByText('@github')).toBeInTheDocument()
+    expect(screen.getByText('@chrome-devtools')).toBeInTheDocument()
+    expect(screen.getByText('@figma')).toBeInTheDocument()
+    expect(screen.getByText('24 runs')).toBeInTheDocument()
+    expect(screen.getByText('14 runs')).toBeInTheDocument()
+    expect(screen.getByText('7 runs')).toBeInTheDocument()
+    expect(screen.queryByText('@linear')).not.toBeInTheDocument()
+    expect(screen.queryByText('Bash')).not.toBeInTheDocument()
+    expect(screen.queryByText('Read')).not.toBeInTheDocument()
     expect(screen.getAllByText('May').length).toBeGreaterThan(0)
     expect(screen.queryByText('5月')).not.toBeInTheDocument()
 
@@ -239,13 +281,14 @@ describe('ActivitySettings', () => {
     expect(editButton.closest('div')).toHaveClass('group/activity-profile')
   })
 
-  it('uses a balanced responsive summary grid instead of the loose medium-width layout', async () => {
+  it('uses a compact summary strip instead of the loose card layout', async () => {
     render(<ActivitySettings />)
 
     await flushActivityLoad()
 
     const summaryPanel = screen.getByText('Total tokens').closest('section')
     expect(summaryPanel).toHaveClass('activity-summary-panel')
+    expect(summaryPanel).toHaveClass('max-w-[900px]')
 
     const summaryGrid = summaryPanel?.querySelector('.activity-summary-grid')
     expect(summaryGrid).not.toHaveClass('sm:grid-cols-2')
@@ -256,10 +299,11 @@ describe('ActivitySettings', () => {
     expect(primaryMetric).toHaveClass('activity-summary-metric-primary')
     expect(primaryMetric).not.toHaveClass('sm:col-span-2')
     expect(primaryMetric).not.toHaveClass('lg:col-span-1')
+    expect(primaryMetric).toHaveClass('text-center')
 
     const longestTaskValue = screen.getByText('0m')
     expect(longestTaskValue).toHaveClass('activity-summary-value')
-    expect(longestTaskValue).not.toHaveClass('truncate')
+    expect(longestTaskValue).toHaveClass('truncate')
     expect(longestTaskValue).not.toHaveClass('break-words')
   })
 
@@ -364,6 +408,8 @@ describe('ActivitySettings', () => {
       activeDays: 0,
       dailyActivity: [],
       dailyModelTokens: [],
+      toolUsage: {},
+      skillUsage: {},
       longestSession: {
         id: 'session-1',
         startedAt: '2026-05-09T08:00:00.000Z',
@@ -388,5 +434,6 @@ describe('ActivitySettings', () => {
     expect(screen.getByText('1 小时 30 分钟')).toBeInTheDocument()
     expect(screen.getByText('12 消息')).toBeInTheDocument()
     expect(screen.getByText('暂无本地用量')).toBeInTheDocument()
+    expect(screen.queryByText('活动洞察')).not.toBeInTheDocument()
   })
 })
diff --git a/desktop/src/pages/ActivitySettings.tsx b/desktop/src/pages/ActivitySettings.tsx
index 8f581c5a..bd473316 100644
--- a/desktop/src/pages/ActivitySettings.tsx
+++ b/desktop/src/pages/ActivitySettings.tsx
@@ -28,6 +28,19 @@ type SummaryMetric = {
   detail?: string
 }
 
+type InsightMetric = {
+  label: string
+  value: string
+  detail?: string
+}
+
+type PluginRankItem = {
+  id: string
+  label: string
+  count: number
+  kind: 'plugin' | 'skill'
+}
+
 type HeatmapMode = 'daily' | 'weekly' | 'cumulative'
 
 const WEEK_COUNT = 52
@@ -102,6 +115,18 @@ function formatTokens(tokens: number) {
   return `${tokens}`
 }
 
+function formatInteger(value: number, locale: Locale) {
+  return new Intl.NumberFormat(DATE_LOCALES[locale], { maximumFractionDigits: 0 }).format(value)
+}
+
+function formatPercent(numerator: number, denominator: number, locale: Locale) {
+  if (denominator <= 0) return '0%'
+  return new Intl.NumberFormat(DATE_LOCALES[locale], {
+    maximumFractionDigits: 0,
+    style: 'percent',
+  }).format(numerator / denominator)
+}
+
 function formatDayCount(value: number, t: ReturnType<typeof useTranslation>) {
   return t(value === 1 ? 'settings.activity.count.dayOne' : 'settings.activity.count.dayOther', { count: value })
 }
@@ -131,6 +156,67 @@ function formatMessageCount(value: number, t: ReturnType<typeof useTranslation>)
   return `${value} ${t('settings.activity.messages')}`
 }
 
+function formatRunCount(value: number, t: ReturnType<typeof useTranslation>) {
+  return t(value === 1 ? 'settings.activity.count.runOne' : 'settings.activity.count.runOther', { count: value })
+}
+
+function getModelTokenTotal(usage: ActivityStatsResponse['modelUsage'][string] | undefined) {
+  if (!usage) return 0
+  return (
+    (usage.inputTokens ?? 0) +
+    (usage.outputTokens ?? 0) +
+    (usage.cacheReadInputTokens ?? 0) +
+    (usage.cacheCreationInputTokens ?? 0)
+  )
+}
+
+function formatModelName(model: string) {
+  return model
+    .replace(/^claude-/i, '')
+    .replace(/-/g, ' ')
+    .replace(/\b\w/g, (char) => char.toUpperCase())
+}
+
+function getPluginNameFromToolName(toolName: string) {
+  if (!toolName.startsWith('mcp__')) return null
+  const parts = toolName.split('__').filter(Boolean)
+  const serverName = parts[1]
+  if (!serverName) return null
+  if (serverName === 'codex_apps' && parts[2]) return parts[2]
+  return serverName
+}
+
+function formatPluginName(pluginName: string) {
+  return pluginName.replace(/_/g, '-')
+}
+
+function buildPluginAndSkillRankItems(stats: ActivityStatsResponse | null) {
+  const skillItems = Object.entries(stats?.skillUsage ?? {}).map<PluginRankItem>(([skill, count]) => ({
+    id: `skill:${skill}`,
+    label: `$${skill}`,
+    count,
+    kind: 'skill',
+  }))
+
+  const pluginUsage = new Map<string, number>()
+  for (const [toolName, count] of Object.entries(stats?.toolUsage ?? {})) {
+    const pluginName = getPluginNameFromToolName(toolName)
+    if (!pluginName || count <= 0) continue
+    pluginUsage.set(pluginName, (pluginUsage.get(pluginName) || 0) + count)
+  }
+  const pluginItems = [...pluginUsage.entries()].map<PluginRankItem>(([pluginName, count]) => ({
+    id: `plugin:${pluginName}`,
+    label: `@${formatPluginName(pluginName)}`,
+    count,
+    kind: 'plugin',
+  }))
+
+  return [...skillItems, ...pluginItems]
+    .filter((item) => item.count > 0)
+    .sort((a, b) => b.count - a.count || a.label.localeCompare(b.label))
+    .slice(0, 6)
+}
+
 function withProfileDefaults(profile: Partial<DesktopProfilePreferences> | null | undefined): DesktopProfilePreferences {
   return { ...DEFAULT_PROFILE, ...profile }
 }
@@ -461,12 +547,31 @@ export function ActivitySettings() {
       sum + Object.values(day.tokensByModel).reduce((daySum, tokens) => daySum + tokens, 0)
     ), 0)
   }, [stats])
+  const totalToolCalls = useMemo(() => {
+    return (stats?.dailyActivity ?? []).reduce((sum, day) => sum + day.toolCallCount, 0)
+  }, [stats])
+  const totalSkillUses = useMemo(() => {
+    return Object.values(stats?.skillUsage ?? {}).reduce((sum, count) => sum + count, 0)
+  }, [stats])
+  const exploredSkillsCount = Object.keys(stats?.skillUsage ?? {}).length
+  const topModel = useMemo(() => {
+    return Object.entries(stats?.modelUsage ?? {}).reduce<{
+      model: string
+      tokens: number
+    } | null>((top, [model, usage]) => {
+      const tokens = getModelTokenTotal(usage)
+      if (tokens <= 0) return top
+      if (!top || tokens > top.tokens) return { model, tokens }
+      return top
+    }, null)
+  }, [stats])
   const peakTokens = useMemo(() => {
     return (stats?.dailyModelTokens ?? []).reduce((peak, day) => {
       const dayTotal = Object.values(day.tokensByModel).reduce((sum, tokens) => sum + tokens, 0)
       return Math.max(peak, dayTotal)
     }, 0)
   }, [stats])
+  const topPluginItems = useMemo(() => buildPluginAndSkillRankItems(stats), [stats])
   const metrics: SummaryMetric[] = [
     {
       label: t('settings.activity.totalTokens'),
@@ -494,6 +599,33 @@ export function ActivitySettings() {
       detail: formatSessionCount(last30Usage.sessions, t),
     },
   ]
+  const insightMetrics: InsightMetric[] = [
+    {
+      label: t('settings.activity.activeRate'),
+      value: formatPercent(stats?.activeDays ?? 0, stats?.totalDays ?? 0, locale),
+    },
+    {
+      label: t('settings.activity.mostUsedModel'),
+      value: topModel ? formatModelName(topModel.model) : t('settings.activity.none'),
+      detail: topModel ? `${formatTokens(topModel.tokens)} ${t('settings.activity.tokens')}` : undefined,
+    },
+    {
+      label: t('settings.activity.exploredSkills'),
+      value: formatInteger(exploredSkillsCount, locale),
+    },
+    {
+      label: t('settings.activity.totalSkillUses'),
+      value: formatInteger(totalSkillUses, locale),
+    },
+    {
+      label: t('settings.activity.totalToolCalls'),
+      value: formatInteger(totalToolCalls, locale),
+    },
+    {
+      label: t('settings.activity.totalSessions'),
+      value: formatInteger(stats?.totalSessions ?? 0, locale),
+    },
+  ]
   const avatarSrc = profile.avatarFile ? getProfileAvatarUrl(profile.avatarUpdatedAt) : DEFAULT_AVATAR_SRC
   const avatarClassName = profile.avatarFile
     ? 'h-full w-full object-cover'
@@ -565,9 +697,9 @@ export function ActivitySettings() {
   }
 
   return (
-    <div className="mx-auto w-full max-w-[1160px] min-w-0 pb-12">
-      <section className="relative flex min-h-[245px] flex-col items-center justify-start pt-6 text-center">
-        <div className="relative h-[88px] w-[88px] overflow-hidden rounded-full border border-[var(--color-border)] bg-[var(--color-surface-container-lowest)] shadow-[0_12px_34px_-24px_rgba(15,23,42,0.65)]">
+    <div className="mx-auto w-full max-w-[1060px] min-w-0 pb-12">
+      <section className="relative flex min-h-[176px] flex-col items-center justify-start pt-4 text-center">
+        <div className="relative h-16 w-16 overflow-hidden rounded-full border border-[var(--color-border)] bg-[var(--color-surface-container-lowest)] shadow-[0_10px_28px_-22px_rgba(15,23,42,0.6)]">
           <img
             src={avatarSrc}
             alt={`${profile.displayName} avatar`}
@@ -578,8 +710,8 @@ export function ActivitySettings() {
             }}
           />
         </div>
-        <div className="group/activity-profile mt-6 flex max-w-full items-center justify-center gap-2">
-          <h1 className="max-w-[min(720px,calc(100%-2.25rem))] truncate text-4xl font-semibold tracking-tight text-[var(--color-text-primary)] sm:text-[44px]">{profile.displayName}</h1>
+        <div className="group/activity-profile mt-4 flex max-w-full items-center justify-center gap-2">
+          <h1 className="max-w-[min(720px,calc(100%-2.25rem))] truncate text-[28px] font-semibold tracking-tight text-[var(--color-text-primary)] sm:text-[34px]">{profile.displayName}</h1>
           <button
             type="button"
             aria-label={t('settings.activity.editProfile')}
@@ -600,30 +732,30 @@ export function ActivitySettings() {
             href={profileSubtitleHref}
             target="_blank"
             rel="noreferrer"
-            className="mt-3 inline-flex max-w-full items-center justify-center gap-2 truncate text-lg text-[var(--color-text-tertiary)] transition-colors hover:text-[var(--color-text-primary)]"
+            className="mt-2 inline-flex max-w-full items-center justify-center gap-2 truncate text-base text-[var(--color-text-tertiary)] transition-colors hover:text-[var(--color-text-primary)]"
           >
             <span>{profile.subtitle}</span>
           </a>
         ) : (
-          <div className="mt-3 max-w-full truncate text-lg text-[var(--color-text-tertiary)]">{profile.subtitle}</div>
+          <div className="mt-2 max-w-full truncate text-base text-[var(--color-text-tertiary)]">{profile.subtitle}</div>
         )}
         {profileStatus && <div className="mt-3 text-xs text-[var(--color-success)]">{profileStatus}</div>}
         {profileError && !isEditingProfile && <div className="mt-3 text-xs text-[var(--color-error)]">{profileError}</div>}
       </section>
 
-      <section className="activity-summary-panel mx-auto mt-8 overflow-hidden rounded-[18px] border border-[var(--color-border)] bg-[var(--color-border)] p-px shadow-[0_18px_45px_-38px_rgba(15,23,42,0.65)]">
+      <section className="activity-summary-panel mx-auto mt-7 w-full max-w-[900px] overflow-hidden rounded-2xl border border-[var(--color-border)] bg-[var(--color-border)] p-px shadow-[0_12px_34px_-32px_rgba(15,23,42,0.55)]">
         {isLoading ? (
           <div className="activity-summary-grid grid gap-px">
             {Array.from({ length: 5 }).map((_, index) => (
               <div
                 key={index}
-                className={`activity-summary-metric min-h-[112px] animate-pulse bg-[var(--color-surface)] px-5 py-4 ${
+                className={`activity-summary-metric min-h-[76px] animate-pulse bg-[var(--color-surface)] px-4 py-3 ${
                   index === 0 ? 'activity-summary-metric-primary' : ''
                 }`}
               >
-                <div className="h-3 w-20 rounded bg-[var(--color-surface-container)]" />
-                <div className="mt-6 h-7 w-24 rounded bg-[var(--color-surface-container)]" />
-                <div className="mt-3 h-3 w-16 rounded bg-[var(--color-surface-container)]" />
+                <div className="mx-auto h-5 w-16 rounded bg-[var(--color-surface-container)]" />
+                <div className="mx-auto mt-2 h-3 w-20 rounded bg-[var(--color-surface-container)]" />
+                <div className="mx-auto mt-2 h-2.5 w-14 rounded bg-[var(--color-surface-container)]" />
               </div>
             ))}
           </div>
@@ -634,31 +766,21 @@ export function ActivitySettings() {
               return (
                 <div
                   key={metric.label}
-                  className={`activity-summary-metric min-w-0 bg-[var(--color-surface-container-lowest)] px-5 py-4 text-left opacity-0 shadow-[inset_0_1px_0_rgba(255,255,255,0.48)] [animation:activity-reveal_420ms_cubic-bezier(0.16,1,0.3,1)_forwards] ${
+                  className={`activity-summary-metric min-w-0 bg-[var(--color-surface-container-lowest)] px-4 py-3 text-center opacity-0 shadow-[inset_0_1px_0_rgba(255,255,255,0.48)] [animation:activity-reveal_420ms_cubic-bezier(0.16,1,0.3,1)_forwards] ${
                     isPrimary ? 'activity-summary-metric-primary' : ''
                   }`}
                   style={{ animationDelay: `${index * 45}ms` }}
                 >
-                  <div className="flex min-h-[104px] flex-col justify-between gap-4">
-                    <div className="flex min-w-0 items-center gap-2">
-                      <span
-                        className={`h-1.5 w-1.5 shrink-0 rounded-full ${
-                          isPrimary ? 'bg-[var(--color-primary)]' : 'bg-[var(--color-text-tertiary)] opacity-45'
-                        }`}
-                        aria-hidden="true"
-                      />
-                      <div className="min-w-0 truncate text-[13px] font-semibold text-[var(--color-text-secondary)]">
-                        {metric.label}
-                      </div>
+                  <div className="flex min-h-[68px] flex-col items-center justify-center gap-1.5">
+                    <div className={`activity-summary-value max-w-full truncate font-semibold leading-none tracking-tight text-[var(--color-text-primary)] tabular-nums ${
+                      isPrimary ? 'text-[23px]' : 'text-[22px]'
+                    }`}>
+                      {metric.value}
                     </div>
-                    <div className="min-w-0">
-                      <div className={`activity-summary-value max-w-full font-semibold leading-[1.08] tracking-tight text-[var(--color-text-primary)] tabular-nums ${
-                        isPrimary ? 'text-[32px] lg:text-[26px]' : 'text-[28px] lg:text-[26px]'
-                      }`}>
-                        {metric.value}
-                      </div>
-                      {metric.detail && <div className="mt-2 truncate text-sm text-[var(--color-text-tertiary)]">{metric.detail}</div>}
+                    <div className="min-w-0 truncate text-[13px] font-medium leading-tight text-[var(--color-text-secondary)]">
+                      {metric.label}
                     </div>
+                    {metric.detail && <div className="max-w-full truncate text-[11px] leading-tight text-[var(--color-text-tertiary)]">{metric.detail}</div>}
                   </div>
                 </div>
               )
@@ -776,8 +898,8 @@ export function ActivitySettings() {
         document.body,
       )}
 
-      <div className="mt-16">
-        <div className="mb-5 flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
+      <div className="mt-10">
+        <div className="mb-4 flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
           <div>
             <h2 className="text-xl font-semibold text-[var(--color-text-primary)]">{t('settings.activity.tokenActivity')}</h2>
           </div>
@@ -833,7 +955,7 @@ export function ActivitySettings() {
             <div ref={heatmapMeasureRef} className="min-w-0 pb-2">
               <div className="relative" style={{ width: heatmapWidth, maxWidth: '100%' }}>
                 <div
-                  className="mb-4 grid h-5 text-[11px] leading-none text-[var(--color-text-tertiary)]"
+                  className="mb-3 grid h-5 text-[11px] leading-none text-[var(--color-text-tertiary)]"
                   style={{
                     marginLeft: HEAT_LABEL_WIDTH,
                     gridTemplateColumns: `repeat(${WEEK_COUNT}, ${heatCellSize}px)`,
@@ -931,6 +1053,48 @@ export function ActivitySettings() {
           </>
         )}
       </div>
+
+      {!isLoading && !error && hasUsage && (
+        <div className={`mt-12 grid gap-10 ${
+          topPluginItems.length > 0 ? 'lg:grid-cols-[minmax(0,0.9fr)_minmax(0,1fr)]' : 'lg:max-w-[520px]'
+        }`}>
+          <section className="min-w-0">
+            <h2 className="text-lg font-semibold text-[var(--color-text-primary)]">{t('settings.activity.activityInsights')}</h2>
+            <dl className="mt-5 grid gap-3">
+              {insightMetrics.map((metric) => (
+                <div key={metric.label} className="grid grid-cols-[minmax(0,1fr)_auto] items-baseline gap-5">
+                  <dt className="min-w-0 truncate text-sm font-medium text-[var(--color-text-tertiary)]">{metric.label}</dt>
+                  <dd className="min-w-0 text-right text-sm font-semibold text-[var(--color-text-primary)]">
+                    <span className="tabular-nums">{metric.value}</span>
+                    {metric.detail && (
+                      <span className="ml-2 text-xs font-medium text-[var(--color-text-tertiary)]">{metric.detail}</span>
+                    )}
+                  </dd>
+                </div>
+              ))}
+            </dl>
+          </section>
+
+          {topPluginItems.length > 0 && (
+            <section className="min-w-0">
+              <h2 className="text-lg font-semibold text-[var(--color-text-primary)]">{t('settings.activity.mostUsedPluginsAndSkills')}</h2>
+              <div className="mt-5 grid gap-3">
+                {topPluginItems.map((item) => (
+                  <div key={item.id} className="grid grid-cols-[auto_minmax(0,1fr)_auto] items-center gap-3">
+                    <span className="flex h-7 w-7 items-center justify-center rounded-md border border-[var(--color-border)] bg-[var(--color-surface-container-lowest)] text-[var(--color-text-tertiary)]">
+                      <span className="material-symbols-outlined text-[16px]" aria-hidden="true">
+                        {item.kind === 'skill' ? 'extension' : 'hub'}
+                      </span>
+                    </span>
+                    <span className="min-w-0 truncate text-sm font-medium text-[var(--color-text-primary)]">{item.label}</span>
+                    <span className="text-sm text-[var(--color-text-tertiary)] tabular-nums">{formatRunCount(item.count, t)}</span>
+                  </div>
+                ))}
+              </div>
+            </section>
+          )}
+        </div>
+      )}
     </div>
   )
 }
diff --git a/desktop/src/theme/globals.css b/desktop/src/theme/globals.css
index 53fc18ff..6e7edaa4 100644
--- a/desktop/src/theme/globals.css
+++ b/desktop/src/theme/globals.css
@@ -1301,23 +1301,9 @@ button, input, textarea, select, a, [role="button"] {
   .activity-summary-grid {
     grid-template-columns: repeat(2, minmax(0, 1fr));
   }
-
-  .activity-summary-metric-primary {
-    grid-column: span 2;
-  }
 }
 
-@container (min-width: 620px) {
-  .activity-summary-grid {
-    grid-template-columns: repeat(3, minmax(0, 1fr));
-  }
-
-  .activity-summary-metric-primary {
-    grid-column: span 2;
-  }
-}
-
-@container (min-width: 860px) {
+@container (min-width: 560px) {
   .activity-summary-grid {
     grid-template-columns: repeat(5, minmax(0, 1fr));
   }
diff --git a/desktop/src/theme/globals.test.ts b/desktop/src/theme/globals.test.ts
index 79a4a8c7..eaec2c18 100644
--- a/desktop/src/theme/globals.test.ts
+++ b/desktop/src/theme/globals.test.ts
@@ -89,18 +89,15 @@ describe('desktop theme tokens', () => {
     expect(css).toContain('box-shadow: var(--shadow-activity-cell-hover);')
   })
 
-  it('uses container queries for the activity summary grid', () => {
+  it('uses container queries for the compact activity summary strip', () => {
     const activitySummaryCss = getCssBetween('.activity-summary-panel {', '.activity-heat-cell {')
-    const mediumStart = activitySummaryCss.indexOf('@container (min-width: 620px)')
-    const wideStart = activitySummaryCss.indexOf('@container (min-width: 860px)')
-    const mediumSummaryCss = activitySummaryCss.slice(mediumStart, wideStart)
 
     expect(activitySummaryCss).toContain('container-type: inline-size;')
     expect(activitySummaryCss).toContain('@container (min-width: 360px)')
-    expect(activitySummaryCss).toContain('@container (min-width: 620px)')
-    expect(activitySummaryCss).toContain('@container (min-width: 860px)')
+    expect(activitySummaryCss).toContain('@container (min-width: 560px)')
     expect(activitySummaryCss).toContain('grid-template-columns: repeat(5, minmax(0, 1fr));')
-    expect(mediumSummaryCss).toContain('grid-column: span 2;')
+    expect(activitySummaryCss).toContain('grid-column: auto;')
+    expect(activitySummaryCss).not.toContain('grid-column: span 2;')
   })
 
   it('avoids color-mix in the startup-critical UI zoom shell chrome for Safari 15 WebView support', () => {
diff --git a/src/server/__tests__/settings.test.ts b/src/server/__tests__/settings.test.ts
index d789db3a..e6c05adc 100644
--- a/src/server/__tests__/settings.test.ts
+++ b/src/server/__tests__/settings.test.ts
@@ -982,6 +982,8 @@ describe('Activity Stats API', () => {
     const body = await res.json()
     expect(body.range).toBe('all')
     expect(body.stats.totalSessions).toBe(0)
+    expect(body.stats.toolUsage).toEqual({})
+    expect(body.stats.skillUsage).toEqual({})
     expect(new Date(body.generatedAt).toString()).not.toBe('Invalid Date')
   })
 
diff --git a/src/utils/__tests__/stats.test.ts b/src/utils/__tests__/stats.test.ts
index 7fd49bad..d2fffea1 100644
--- a/src/utils/__tests__/stats.test.ts
+++ b/src/utils/__tests__/stats.test.ts
@@ -41,7 +41,12 @@ function assistantEntry(
     cache_read_input_tokens?: number
     cache_creation_input_tokens?: number
   },
-  options: { model?: string; isSidechain?: boolean; parentUuid?: string } = {},
+  options: {
+    model?: string
+    isSidechain?: boolean
+    parentUuid?: string
+    content?: unknown[]
+  } = {},
 ) {
   return {
     type: 'assistant',
@@ -52,7 +57,7 @@ function assistantEntry(
     message: {
       role: 'assistant',
       model: options.model ?? 'claude-test',
-      content: [],
+      content: options.content ?? [],
       usage,
     },
   }
@@ -189,6 +194,59 @@ describe('activity stats token accounting', () => {
     expect(totalForDate(stats.dailyModelTokens, today)).toBe(34)
   })
 
+  it('tracks tool and skill usage from main and subagent transcripts', async () => {
+    const today = dateKey(0)
+
+    await writeJsonl(projectFile('tool-session'), [
+      userEntry('tool-user', at(today, '10:00:00')),
+      assistantEntry(
+        'tool-assistant',
+        at(today, '10:01:00'),
+        { input_tokens: 1, output_tokens: 1 },
+        {
+          parentUuid: 'tool-user',
+          content: [
+            { type: 'tool_use', id: 'tool-1', name: 'Bash', input: { command: 'pwd' } },
+            { type: 'tool_use', id: 'tool-2', name: 'Skill', input: { skill: 'frontend-design' } },
+            { type: 'tool_use', id: 'tool-3', name: 'mcp__figma__get_screenshot', input: {} },
+            { type: 'tool_use', id: 'tool-4', name: 'Skill', input: { skill: 42 } },
+          ],
+        },
+      ),
+    ])
+    await writeJsonl(subagentFile('tool-session', '001'), [
+      userEntry('agent-user', at(today, '10:02:00'), true),
+      assistantEntry(
+        'agent-assistant',
+        at(today, '10:03:00'),
+        { input_tokens: 2, output_tokens: 2 },
+        {
+          isSidechain: true,
+          parentUuid: 'agent-user',
+          content: [
+            { type: 'tool_use', id: 'tool-5', name: 'Skill', input: { skill: 'frontend-design' } },
+          ],
+        },
+      ),
+    ])
+
+    const stats = await aggregateClaudeCodeStatsForRange('all')
+
+    expect(stats.totalSessions).toBe(1)
+    expect(stats.dailyActivity.find(day => day.date === today)).toMatchObject({
+      sessionCount: 1,
+      toolCallCount: 5,
+    })
+    expect(stats.toolUsage).toMatchObject({
+      Bash: 1,
+      Skill: 3,
+      mcp__figma__get_screenshot: 1,
+    })
+    expect(stats.skillUsage).toEqual({
+      'frontend-design': 2,
+    })
+  })
+
   it('keeps resumed old sessions in range token totals with active daily session counts', async () => {
     const oldDate = dateKey(-50)
     const inRangeDate = dateKey(-1)
@@ -233,16 +291,18 @@ describe('activity stats token accounting', () => {
     expect(totalForDate(stats.dailyModelTokens, future)).toBe(0)
   })
 
-  it('invalidates pre-v5 stats caches because daily activity accounting changed', async () => {
+  it('invalidates pre-v6 stats caches because cached aggregates lack tool usage', async () => {
     await mkdir(tmpConfigDir, { recursive: true })
     await writeFile(
       join(tmpConfigDir, 'stats-cache.json'),
       JSON.stringify({
-        version: 3,
+        version: 5,
         lastComputedDate: dateKey(-1),
         dailyActivity: [{ date: dateKey(-1), messageCount: 1, sessionCount: 1, toolCallCount: 0 }],
         dailyModelTokens: [{ date: dateKey(-1), tokensByModel: { stale: 1 } }],
         modelUsage: {},
+        toolUsage: { stale: 1 },
+        skillUsage: { stale: 1 },
         totalSessions: 1,
         totalMessages: 1,
         longestSession: null,
@@ -255,8 +315,10 @@ describe('activity stats token accounting', () => {
 
     const cache = await loadStatsCache()
 
-    expect(STATS_CACHE_VERSION).toBe(5)
+    expect(STATS_CACHE_VERSION).toBe(6)
     expect(cache.dailyModelTokens).toEqual([])
+    expect(cache.toolUsage).toEqual({})
+    expect(cache.skillUsage).toEqual({})
     expect(cache.totalSessions).toBe(0)
   })
 })
diff --git a/src/utils/stats.ts b/src/utils/stats.ts
index f5ee0ed6..a89a4678 100644
--- a/src/utils/stats.ts
+++ b/src/utils/stats.ts
@@ -50,6 +50,10 @@ export type SessionStats = {
   timestamp: string
 }
 
+export type ToolUsageMap = { [toolName: string]: number }
+
+export type SkillUsageMap = { [skillName: string]: number }
+
 export type ClaudeCodeStats = {
   // Activity overview
   totalSessions: number
@@ -72,6 +76,10 @@ export type ClaudeCodeStats = {
   // Model usage aggregated
   modelUsage: { [modelName: string]: ModelUsage }
 
+  // Tool and skill usage aggregated from assistant tool_use blocks
+  toolUsage: ToolUsageMap
+  skillUsage: SkillUsageMap
+
   // Time stats
   firstSessionDate: string | null
   lastSessionDate: string | null
@@ -93,6 +101,8 @@ type ProcessedStats = {
   dailyActivity: DailyActivity[]
   dailyModelTokens: DailyModelTokens[]
   modelUsage: { [modelName: string]: ModelUsage }
+  toolUsage: ToolUsageMap
+  skillUsage: SkillUsageMap
   sessionStats: SessionStats[]
   hourCounts: { [hour: number]: number }
   totalMessages: number
@@ -126,6 +136,38 @@ function getTotalUsageTokens(usage: UsageLike): number {
   )
 }
 
+function incrementUsageCount(counts: Map<string, number>, name: string) {
+  const normalizedName = name.trim()
+  if (!normalizedName) return
+  counts.set(normalizedName, (counts.get(normalizedName) || 0) + 1)
+}
+
+function mergeUsageCounts(
+  ...sources: Array<Record<string, number> | undefined>
+): Record<string, number> {
+  const merged: Record<string, number> = {}
+  for (const source of sources) {
+    for (const [name, count] of Object.entries(source ?? {})) {
+      if (typeof count !== 'number' || count <= 0) continue
+      merged[name] = (merged[name] || 0) + count
+    }
+  }
+  return merged
+}
+
+function getSkillNameFromToolInput(toolName: string, input: unknown) {
+  if (toolName !== 'Skill') return null
+  if (
+    typeof input === 'object' &&
+    input !== null &&
+    'skill' in input &&
+    typeof (input as { skill: unknown }).skill === 'string'
+  ) {
+    return (input as { skill: string }).skill
+  }
+  return null
+}
+
 function isDateInRange(
   date: string,
   fromDate?: string,
@@ -163,6 +205,8 @@ async function processSessionFiles(
   let totalMessages = 0
   let totalSpeculationTimeSavedMs = 0
   const modelUsageAgg: { [modelName: string]: ModelUsage } = {}
+  const toolUsageMap = new Map<string, number>()
+  const skillUsageMap = new Map<string, number>()
   const shotDistributionMap = feature('SHOT_STATS')
     ? new Map<number, number>()
     : undefined
@@ -340,6 +384,16 @@ async function processSessionFiles(
             for (const block of content) {
               if (block.type === 'tool_use') {
                 getDailyActivity(messageDateKey).toolCallCount++
+                if (typeof block.name === 'string') {
+                  incrementUsageCount(toolUsageMap, block.name)
+                  const skillName = getSkillNameFromToolInput(
+                    block.name,
+                    block.input,
+                  )
+                  if (skillName) {
+                    incrementUsageCount(skillUsageMap, skillName)
+                  }
+                }
               }
             }
           }
@@ -404,6 +458,8 @@ async function processSessionFiles(
       .map(([date, tokensByModel]) => ({ date, tokensByModel }))
       .sort((a, b) => a.date.localeCompare(b.date)),
     modelUsage: modelUsageAgg,
+    toolUsage: Object.fromEntries(toolUsageMap),
+    skillUsage: Object.fromEntries(skillUsageMap),
     sessionStats: sessions,
     hourCounts: Object.fromEntries(hourCounts),
     totalMessages,
@@ -555,6 +611,9 @@ function cacheToStats(
     }
   }
 
+  const toolUsage = mergeUsageCounts(cache.toolUsage, todayStats?.toolUsage)
+  const skillUsage = mergeUsageCounts(cache.skillUsage, todayStats?.skillUsage)
+
   // Merge hour counts
   const hourCountsMap = new Map<number, number>()
   for (const [hour, count] of Object.entries(cache.hourCounts)) {
@@ -647,6 +706,8 @@ function cacheToStats(
     dailyModelTokens,
     longestSession,
     modelUsage,
+    toolUsage,
+    skillUsage,
     firstSessionDate,
     lastSessionDate,
     peakActivityDay,
@@ -868,6 +929,8 @@ function processedStatsToClaudeCodeStats(
     dailyModelTokens: dailyModelTokensSorted,
     longestSession,
     modelUsage: stats.modelUsage,
+    toolUsage: stats.toolUsage,
+    skillUsage: stats.skillUsage,
     firstSessionDate,
     lastSessionDate,
     peakActivityDay,
@@ -1101,6 +1164,8 @@ function getEmptyStats(): ClaudeCodeStats {
     dailyModelTokens: [],
     longestSession: null,
     modelUsage: {},
+    toolUsage: {},
+    skillUsage: {},
     firstSessionDate: null,
     lastSessionDate: null,
     peakActivityDay: null,
diff --git a/src/utils/statsCache.ts b/src/utils/statsCache.ts
index 4bafe631..bf6f4303 100644
--- a/src/utils/statsCache.ts
+++ b/src/utils/statsCache.ts
@@ -9,10 +9,16 @@ import { errorMessage } from './errors.js'
 import { getFsImplementation } from './fsOperations.js'
 import { logError } from './log.js'
 import { jsonParse, jsonStringify } from './slowOperations.js'
-import type { DailyActivity, DailyModelTokens, SessionStats } from './stats.js'
+import type {
+  DailyActivity,
+  DailyModelTokens,
+  SessionStats,
+  SkillUsageMap,
+  ToolUsageMap,
+} from './stats.js'
 
-export const STATS_CACHE_VERSION = 5
-const MIN_MIGRATABLE_VERSION = 5
+export const STATS_CACHE_VERSION = 6
+const MIN_MIGRATABLE_VERSION = 6
 const STATS_CACHE_FILENAME = 'stats-cache.json'
 
 /**
@@ -60,6 +66,9 @@ export type PersistedStatsCache = {
   dailyModelTokens: DailyModelTokens[]
   // Model usage aggregated (bounded by number of models)
   modelUsage: { [modelName: string]: ModelUsage }
+  // Tool and skill usage aggregated from assistant tool_use blocks
+  toolUsage: ToolUsageMap
+  skillUsage: SkillUsageMap
   // Session aggregates (replaces unbounded sessionStats array)
   totalSessions: number
   totalMessages: number
@@ -85,6 +94,8 @@ function getEmptyCache(): PersistedStatsCache {
     dailyActivity: [],
     dailyModelTokens: [],
     modelUsage: {},
+    toolUsage: {},
+    skillUsage: {},
     totalSessions: 0,
     totalMessages: 0,
     longestSession: null,
@@ -99,10 +110,10 @@ function getEmptyCache(): PersistedStatsCache {
  * Migrate an older cache to the current schema.
  * Returns null if the version is unknown or too old to migrate.
  *
- * Daily activity accounting changed in v5 to count per-day active parent
- * sessions from message timestamps instead of session-start dates. Older
- * caches are intentionally rejected so the next aggregation recomputes daily
- * session counts and token buckets with the same date semantics.
+ * Daily activity accounting changed in v5, and v6 added historical tool/skill
+ * usage. Older caches are intentionally rejected so the next aggregation
+ * recomputes fields that cannot be reconstructed from aggregate-only cache
+ * files without undercounting.
  */
 function migrateStatsCache(
   parsed: Partial<PersistedStatsCache> & { version: number },
@@ -117,6 +128,10 @@ function migrateStatsCache(
   if (
     !Array.isArray(parsed.dailyActivity) ||
     !Array.isArray(parsed.dailyModelTokens) ||
+    typeof parsed.toolUsage !== 'object' ||
+    parsed.toolUsage === null ||
+    typeof parsed.skillUsage !== 'object' ||
+    parsed.skillUsage === null ||
     typeof parsed.totalSessions !== 'number' ||
     typeof parsed.totalMessages !== 'number'
   ) {
@@ -128,6 +143,8 @@ function migrateStatsCache(
     dailyActivity: parsed.dailyActivity,
     dailyModelTokens: parsed.dailyModelTokens,
     modelUsage: parsed.modelUsage ?? {},
+    toolUsage: parsed.toolUsage,
+    skillUsage: parsed.skillUsage,
     totalSessions: parsed.totalSessions,
     totalMessages: parsed.totalMessages,
     longestSession: parsed.longestSession ?? null,
@@ -182,6 +199,10 @@ export async function loadStatsCache(): Promise<PersistedStatsCache> {
     if (
       !Array.isArray(parsed.dailyActivity) ||
       !Array.isArray(parsed.dailyModelTokens) ||
+      typeof parsed.toolUsage !== 'object' ||
+      parsed.toolUsage === null ||
+      typeof parsed.skillUsage !== 'object' ||
+      parsed.skillUsage === null ||
       typeof parsed.totalSessions !== 'number' ||
       typeof parsed.totalMessages !== 'number'
     ) {
@@ -263,6 +284,8 @@ export function mergeCacheWithNewStats(
     dailyActivity: DailyActivity[]
     dailyModelTokens: DailyModelTokens[]
     modelUsage: { [modelName: string]: ModelUsage }
+    toolUsage: ToolUsageMap
+    skillUsage: SkillUsageMap
     sessionStats: SessionStats[]
     hourCounts: { [hour: number]: number }
     totalSpeculationTimeSavedMs: number
@@ -270,6 +293,18 @@ export function mergeCacheWithNewStats(
   },
   newLastComputedDate: string,
 ): PersistedStatsCache {
+  const mergeUsageCounts = (
+    existingCounts: Record<string, number>,
+    nextCounts: Record<string, number>,
+  ) => {
+    const merged = { ...existingCounts }
+    for (const [name, count] of Object.entries(nextCounts)) {
+      if (typeof count !== 'number' || count <= 0) continue
+      merged[name] = (merged[name] || 0) + count
+    }
+    return merged
+  }
+
   // Merge daily activity - combine by date
   const dailyActivityMap = new Map<string, DailyActivity>()
   for (const day of existingCache.dailyActivity) {
@@ -331,6 +366,12 @@ export function mergeCacheWithNewStats(
     }
   }
 
+  const toolUsage = mergeUsageCounts(existingCache.toolUsage, newStats.toolUsage)
+  const skillUsage = mergeUsageCounts(
+    existingCache.skillUsage,
+    newStats.skillUsage,
+  )
+
   // Merge hour counts
   const hourCounts = { ...existingCache.hourCounts }
   for (const [hour, count] of Object.entries(newStats.hourCounts)) {
@@ -371,6 +412,8 @@ export function mergeCacheWithNewStats(
       .map(([date, tokensByModel]) => ({ date, tokensByModel }))
       .sort((a, b) => a.date.localeCompare(b.date)),
     modelUsage,
+    toolUsage,
+    skillUsage,
     totalSessions,
     totalMessages,
     longestSession,