diff --git a/.github/renovate/docker.json5 b/.github/renovate/docker.json5
index 652bd3c8..c88db7aa 100644
--- a/.github/renovate/docker.json5
+++ b/.github/renovate/docker.json5
@@ -1,16 +1,16 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "packageRules": [
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  packageRules: [
     {
-      "description": "Group Docker non-major and digest updates",
-      "matchManagers": ["dockerfile"],
+      description: 'Group Docker non-major and digest updates',
+      matchManagers: ['dockerfile'],
       // Node.jsのDockerイメージはnode.json5でまとめて管理するため、ここでは除外する。
-      "matchPackageNames": ["!node"],
-      "matchUpdateTypes": ["minor", "patch", "digest", "pinDigest"],
-      "groupName": "Docker non-major dependencies",
+      matchPackageNames: ['!node'],
+      matchUpdateTypes: ['minor', 'patch', 'digest', 'pinDigest'],
+      groupName: 'Docker non-major dependencies',
       // 現在は無効化中。将来再開する場合はtrueに変更する。
-      "automerge": false,
-      "automergeType": "pr",
+      automerge: false,
+      automergeType: 'pr',
     },
   ],
 }
diff --git a/.github/renovate/github-actions.json5 b/.github/renovate/github-actions.json5
index 4b29f0af..c6f84698 100644
--- a/.github/renovate/github-actions.json5
+++ b/.github/renovate/github-actions.json5
@@ -1,54 +1,54 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "customManagers": [
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  customManagers: [
     // 定期実行ワークフローで使用するRenovate本体（Dockerイメージのバージョンとダイジェスト）
     {
-      "customType": "regex",
-      "description": "Update the Renovate image used by the GitHub Action",
-      "managerFilePatterns": [".github/workflows/renovate.yaml"],
-      "matchStrings": [
-        "renovate-version: (?<currentValue>[^@\\s]+)@(?<currentDigest>sha256:[a-f0-9]+)",
+      customType: 'regex',
+      description: 'Update the Renovate image used by the GitHub Action',
+      managerFilePatterns: ['.github/workflows/renovate.yaml'],
+      matchStrings: [
+        'renovate-version: (?<currentValue>[^@\\s]+)@(?<currentDigest>sha256:[a-f0-9]+)',
       ],
-      "depNameTemplate": "ghcr.io/renovatebot/renovate",
-      "datasourceTemplate": "docker",
-      "versioningTemplate": "docker",
+      depNameTemplate: 'ghcr.io/renovatebot/renovate',
+      datasourceTemplate: 'docker',
+      versioningTemplate: 'docker',
     },
     // 設定検証ワークフローでnpx経由で使用するRenovate CLI（npmパッケージのバージョン）
     {
-      "customType": "regex",
-      "description": "Update the Renovate config validator",
-      "managerFilePatterns": [
-        ".github/workflows/renovate-config-validator-ci.yaml",
+      customType: 'regex',
+      description: 'Update the Renovate config validator',
+      managerFilePatterns: [
+        '.github/workflows/renovate-config-validator-ci.yaml',
       ],
-      "matchStrings": ["renovate@(?<currentValue>[^\\s]+)"],
-      "depNameTemplate": "renovate",
-      "datasourceTemplate": "npm",
+      matchStrings: ['renovate@(?<currentValue>[^\\s]+)'],
+      depNameTemplate: 'renovate',
+      datasourceTemplate: 'npm',
     },
   ],
-  "packageRules": [
+  packageRules: [
     {
-      "description": "Keep the Renovate runner and validator in one update",
-      "matchManagers": ["custom.regex"],
-      "matchPackageNames": ["ghcr.io/renovatebot/renovate", "renovate"],
-      "groupName": "Renovate",
+      description: 'Keep the Renovate runner and validator in one update',
+      matchManagers: ['custom.regex'],
+      matchPackageNames: ['ghcr.io/renovatebot/renovate', 'renovate'],
+      groupName: 'Renovate',
     },
     {
-      "description": "Automerge non-major Renovate updates",
-      "matchManagers": ["custom.regex"],
-      "matchPackageNames": ["ghcr.io/renovatebot/renovate", "renovate"],
-      "matchUpdateTypes": ["minor", "patch", "digest", "pinDigest"],
+      description: 'Automerge non-major Renovate updates',
+      matchManagers: ['custom.regex'],
+      matchPackageNames: ['ghcr.io/renovatebot/renovate', 'renovate'],
+      matchUpdateTypes: ['minor', 'patch', 'digest', 'pinDigest'],
       // 現在は無効化中。将来再開する場合はtrueに変更する。
-      "automerge": false,
-      "automergeType": "pr",
+      automerge: false,
+      automergeType: 'pr',
     },
     {
-      "description": "Group GitHub Actions non-major and digest updates",
-      "matchManagers": ["github-actions"],
-      "matchUpdateTypes": ["minor", "patch", "digest", "pinDigest"],
-      "groupName": "GitHub Actions non-major dependencies",
+      description: 'Group GitHub Actions non-major and digest updates',
+      matchManagers: ['github-actions'],
+      matchUpdateTypes: ['minor', 'patch', 'digest', 'pinDigest'],
+      groupName: 'GitHub Actions non-major dependencies',
       // 現在は無効化中。将来再開する場合はtrueに変更する。
-      "automerge": false,
-      "automergeType": "pr",
+      automerge: false,
+      automergeType: 'pr',
     },
   ],
 }
diff --git a/.github/renovate/labels.json5 b/.github/renovate/labels.json5
index fd3acdee..993478d8 100644
--- a/.github/renovate/labels.json5
+++ b/.github/renovate/labels.json5
@@ -1,34 +1,34 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "labels": ["dependencies"],
-  "packageRules": [
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  labels: ['dependencies'],
+  packageRules: [
     {
-      "matchUpdateTypes": ["major"],
-      "addLabels": ["type/major"],
+      matchUpdateTypes: ['major'],
+      addLabels: ['type/major'],
     },
     {
-      "matchUpdateTypes": ["minor"],
-      "addLabels": ["type/minor"],
+      matchUpdateTypes: ['minor'],
+      addLabels: ['type/minor'],
     },
     {
-      "matchUpdateTypes": ["patch"],
-      "addLabels": ["type/patch"],
+      matchUpdateTypes: ['patch'],
+      addLabels: ['type/patch'],
     },
     {
-      "matchDatasources": ["npm"],
-      "addLabels": ["renovate/npm"],
+      matchDatasources: ['npm'],
+      addLabels: ['renovate/npm'],
     },
     {
-      "matchDatasources": ["docker"],
-      "addLabels": ["renovate/docker"],
+      matchDatasources: ['docker'],
+      addLabels: ['renovate/docker'],
     },
     {
-      "matchManagers": ["github-actions"],
-      "addLabels": ["renovate/actions"],
+      matchManagers: ['github-actions'],
+      addLabels: ['renovate/actions'],
     },
     {
-      "matchManagers": ["nodenv"],
-      "addLabels": ["renovate/node"],
+      matchManagers: ['nodenv'],
+      addLabels: ['renovate/node'],
     },
   ],
 }
diff --git a/.github/renovate/node.json5 b/.github/renovate/node.json5
index 7a1dba68..af2b18e4 100644
--- a/.github/renovate/node.json5
+++ b/.github/renovate/node.json5
@@ -1,23 +1,23 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "extends": ["replacements:tsconfig-bases-node"],
-  "packageRules": [
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  extends: ['replacements:tsconfig-bases-node'],
+  packageRules: [
     {
-      "description": "Keep Node.js versions in one update",
+      description: 'Keep Node.js versions in one update',
       // Dockerfile、.node-version、package.jsonなど、以下のマネージャーが対応する
       // Node.jsの更新はここで一元的に管理する。
-      "matchManagers": ["dockerfile", "nodenv", "npm"],
-      "matchPackageNames": ["node", "@types/node", "@tsconfig/node**"],
-      "groupName": "Node.js",
-      "rangeStrategy": "bump",
+      matchManagers: ['dockerfile', 'nodenv', 'npm'],
+      matchPackageNames: ['node', '@types/node', '@tsconfig/node**'],
+      groupName: 'Node.js',
+      rangeStrategy: 'bump',
     },
     {
-      "description": "Automerge non-major Node.js updates",
-      "matchManagers": ["dockerfile", "nodenv", "npm"],
-      "matchPackageNames": ["node", "@types/node", "@tsconfig/node**"],
-      "matchUpdateTypes": ["minor", "patch", "digest", "pinDigest"],
-      "automerge": false,
-      "automergeType": "pr",
+      description: 'Automerge non-major Node.js updates',
+      matchManagers: ['dockerfile', 'nodenv', 'npm'],
+      matchPackageNames: ['node', '@types/node', '@tsconfig/node**'],
+      matchUpdateTypes: ['minor', 'patch', 'digest', 'pinDigest'],
+      automerge: false,
+      automergeType: 'pr',
     },
   ],
 }
diff --git a/.github/renovate/npm.json5 b/.github/renovate/npm.json5
index 8672aefa..e969b3d8 100644
--- a/.github/renovate/npm.json5
+++ b/.github/renovate/npm.json5
@@ -1,16 +1,16 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "packageRules": [
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  packageRules: [
     {
-      "description": "Group npm minor and patch updates",
-      "matchManagers": ["npm"],
+      description: 'Group npm minor and patch updates',
+      matchManagers: ['npm'],
       // Node.js関連パッケージはnode.json5でまとめて管理するため、ここでは除外する。
-      "matchPackageNames": ["!node", "!@types/node", "!@tsconfig/node**"],
-      "matchUpdateTypes": ["minor", "patch"],
-      "groupName": "npm minor and patch dependencies",
+      matchPackageNames: ['!node', '!@types/node', '!@tsconfig/node**'],
+      matchUpdateTypes: ['minor', 'patch'],
+      groupName: 'npm minor and patch dependencies',
       // 現在は無効化中。将来再開する場合はtrueに変更する。
-      "automerge": false,
-      "automergeType": "pr",
+      automerge: false,
+      automergeType: 'pr',
     },
   ],
 }
diff --git a/.github/workflows/quality.yaml b/.github/workflows/quality.yaml
new file mode 100644
index 00000000..5c9b7f8b
--- /dev/null
+++ b/.github/workflows/quality.yaml
@@ -0,0 +1,42 @@
+name: Lint and Format
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+jobs:
+  lint-and-format:
+    name: Lint and Format
+    runs-on: ubuntu-24.04
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          persist-credentials: false
+      - name: Setup pnpm
+        uses: pnpm/action-setup@8912a9102ac27614460f54aedde9e1e7f9aec20d # v6.0.5
+      - name: Setup Node.js
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
+        with:
+          node-version-file: .node-version
+          cache: pnpm
+          cache-dependency-path: pnpm-lock.yaml
+      - name: Restore ESLint cache
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: .eslintcache
+          key: eslint-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml', 'eslint.config.js') }}-${{ github.sha }}
+          restore-keys: |
+            eslint-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml', 'eslint.config.js') }}-
+      - name: Install dependencies
+        run: pnpm ci
+      - name: Run ESLint
+        run: pnpm lint:check
+      - name: Check Prettier formatting
+        run: pnpm format:check
diff --git a/.github/workflows/renovate.yaml b/.github/workflows/renovate.yaml
index 275ea026..104e680e 100644
--- a/.github/workflows/renovate.yaml
+++ b/.github/workflows/renovate.yaml
@@ -2,11 +2,11 @@ name: Renovate
 
 on:
   push:
-    branches: ["main"]
+    branches: ['main']
 
   schedule:
     # Every day at 5 a.m. JST
-    - cron: "0 20 * * *"
+    - cron: '0 20 * * *'
 
   workflow_dispatch:
     inputs:
@@ -37,7 +37,7 @@ jobs:
         with:
           app-id: ${{ secrets.RENOVATE_APP_ID }}
           private-key: ${{ secrets.RENOVATE_APP_PRIVATE_KEY }}
-          repositories: "rucQ-UI"
+          repositories: 'rucQ-UI'
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           persist-credentials: false
diff --git a/.gitignore b/.gitignore
index df94c542..a7765301 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,6 +30,8 @@ coverage
 
 *.tsbuildinfo
 
+.eslintcache
+
 .env.local
 .env.*.local
 
diff --git a/.prettierignore b/.prettierignore
new file mode 100644
index 00000000..4d44ccc3
--- /dev/null
+++ b/.prettierignore
@@ -0,0 +1,3 @@
+*.md
+pnpm-lock.yaml
+public/mockServiceWorker.js
diff --git a/package.json b/package.json
index 5bf6f569..1a174413 100644
--- a/package.json
+++ b/package.json
@@ -14,8 +14,10 @@
     "preview:prod": "vite preview --mode production",
     "build-only": "vite build",
     "type-check": "vue-tsc --build",
-    "lint": "eslint . --fix",
-    "format": "prettier --write src/",
+    "lint": "eslint . --cache --cache-strategy content --cache-location .eslintcache --fix",
+    "lint:check": "eslint . --cache --cache-strategy content --cache-location .eslintcache --max-warnings=0",
+    "format": "prettier --write .",
+    "format:check": "prettier --check .",
     "generate:api": "openapi-typescript https://raw.githubusercontent.com/traPtitech/rucQ/main/openapi.yaml -o src/api/schema.d.ts && pnpm format"
   },
   "packageManager": "pnpm@11.5.0",
diff --git a/src/components/information/QuestionGroupPanel.vue b/src/components/information/QuestionGroupPanel.vue
index 57a4f7eb..84232e55 100644
--- a/src/components/information/QuestionGroupPanel.vue
+++ b/src/components/information/QuestionGroupPanel.vue
@@ -141,7 +141,7 @@ const allChecked = computed(() => {
   let result = true
   for (const question of props.questionGroup.questions) {
     const answer = answersMap[question.id]
-    if (!answer || answer.value === undefined || answer.value === null) {
+    if (answer?.value === undefined) {
       result = false // multiple の [], free_text の '' は falsy だが回答済みとみなす
       break
     }
diff --git a/src/components/layout/HeaderButton.vue b/src/components/layout/HeaderButton.vue
index 8c436278..f06df281 100644
--- a/src/components/layout/HeaderButton.vue
+++ b/src/components/layout/HeaderButton.vue
@@ -36,13 +36,7 @@ const campIconUrl = computed(() => {
 <template>
   <v-app-bar v-if="xs" elevation="2" color="white" density="comfortable" :class="$style.appBar">
     <template #prepend>
-      <img
-        :src="campIconUrl"
-        alt="rucQ Icon"
-        width="44"
-        height="44"
-        :class="$style.icon"
-      />
+      <img :src="campIconUrl" alt="rucQ Icon" width="44" height="44" :class="$style.icon" />
     </template>
     <v-app-bar-title :class="isArchived ? $style.archivedTitle : 'text-primary'">
       <span :class="$style.routeTitle">{{ route.name }} </span>
diff --git a/src/components/markdown/MarkdownPreview.vue b/src/components/markdown/MarkdownPreview.vue
index 704216a1..74276ff5 100644
--- a/src/components/markdown/MarkdownPreview.vue
+++ b/src/components/markdown/MarkdownPreview.vue
@@ -71,7 +71,7 @@ watch(
     headingElements.forEach((heading) => {
       const level = parseInt(heading.tagName.charAt(1))
       const id = `heading-${idCounter++}`
-      const text = heading.textContent ?? ''
+      const text = heading.textContent
 
       heading.setAttribute('id', id)
       headingInfos.push({ id, level, text })
diff --git a/src/components/rollcall/rollCallStream.ts b/src/components/rollcall/rollCallStream.ts
index 49aea35d..9043e649 100644
--- a/src/components/rollcall/rollCallStream.ts
+++ b/src/components/rollcall/rollCallStream.ts
@@ -64,7 +64,7 @@ export function useRollCallStream(rollcall: Ref<RollCall | undefined>, userId: s
         const idx = reactions.value.findIndex((r) => r.userId === ev.userId)
         const entry = { id: ev.id, userId: ev.userId, content: ev.content }
         if (idx >= 0) reactions.value[idx] = entry
-        else reactions.value.push(entry as RollCallReaction)
+        else reactions.value.push(entry)
         break
       }
       case 'updated': {
@@ -74,7 +74,7 @@ export function useRollCallStream(rollcall: Ref<RollCall | undefined>, userId: s
             id: ev.id,
             userId: ev.userId,
             content: ev.content,
-          } as RollCallReaction
+          }
         break
       }
       case 'deleted': {
@@ -105,7 +105,7 @@ export function useRollCallStream(rollcall: Ref<RollCall | undefined>, userId: s
   const chooseOption = async (content: string) => {
     if (!rollcall.value) return
     if (!rollcall.value.subjects.includes(userId)) return
-    if (myReaction.value && myReaction.value.content === content) return
+    if (myReaction.value?.content === content) return
     if (inFlight.value) return // いずれかの操作中は他の操作を禁止
 
     try {
diff --git a/src/store.ts b/src/store.ts
index e3621e64..b4d73294 100644
--- a/src/store.ts
+++ b/src/store.ts
@@ -152,7 +152,7 @@ export const useCampStore = defineStore('camp', () => {
 
   const isOperable = (camp: Camp) => {
     // 最新の合宿かつ登録済みで、かつ終了していない場合のみ操作可能
-    if (!latestCamp.value || latestCamp.value.id !== camp.id) return false
+    if (latestCamp.value?.id !== camp.id) return false
     return hasRegisteredLatest.value && !timeStore.isCampEnded(camp)
   }
 
diff --git a/src/views/ActivityView.vue b/src/views/ActivityView.vue
index 7a2a5cdf..b040708c 100644
--- a/src/views/ActivityView.vue
+++ b/src/views/ActivityView.vue
@@ -81,58 +81,58 @@ const dailyActivities = computed(() => {
     <!-- Content -->
     <div v-else class="pa-4" :class="$style.container">
       <template v-for="day in dailyActivities" :key="day.date.toISOString()">
-      <h3 class="mb-2 mt-4" :class="$style.dayHeader">
-        {{ getDayStringNoPad(day.date) }}
-      </h3>
-      <div class="d-flex flex-column ga-3">
-        <template v-for="activity in day.activities" :key="`${activity.id}-${activity.time}`">
-          <activity-layout
-            v-if="activity.type === 'room_created'"
-            :type="activity.type"
-            :date="new Date(activity.time)"
-          >
-            <template #default="{ color }">
-              <span :class="`text-${color}`"> 部屋情報が公開されました </span>
-            </template>
-          </activity-layout>
-          <activity-layout
-            v-if="activity.type === 'payment_created'"
-            :type="activity.type"
-            :date="new Date(activity.time)"
-          >
-            <template #default="{ color }">
-              <span :class="`text-${color}`">
-                {{ activity.amount.toLocaleString() }} 円の支払いが作成されました
-              </span>
-            </template>
-          </activity-layout>
-          <activity-layout
-            v-if="activity.type === 'payment_amount_changed'"
-            :type="activity.type"
-            :date="new Date(activity.time)"
-          >
-            <template #default="{ color }">
-              <span :class="`text-${color}`">
-                支払い金額が {{ activity.amount.toLocaleString() }} 円に変更されました
-              </span>
-            </template>
-          </activity-layout>
-          <activity-layout
-            v-if="activity.type === 'payment_paid_changed'"
-            :type="activity.type"
-            :date="new Date(activity.time)"
-          >
-            <template #default="{ color }">
-              <span :class="`text-${color}`">
-                合宿係が {{ activity.amount.toLocaleString() }} 円の振込を確認しました
-              </span>
-            </template>
-          </activity-layout>
-          <roll-call-activity v-if="activity.type === 'roll_call_created'" :activity="activity" />
-          <question-activity v-if="activity.type === 'question_created'" :activity="activity" />
-        </template>
-      </div>
-    </template>
+        <h3 class="mb-2 mt-4" :class="$style.dayHeader">
+          {{ getDayStringNoPad(day.date) }}
+        </h3>
+        <div class="d-flex flex-column ga-3">
+          <template v-for="activity in day.activities" :key="`${activity.id}-${activity.time}`">
+            <activity-layout
+              v-if="activity.type === 'room_created'"
+              :type="activity.type"
+              :date="new Date(activity.time)"
+            >
+              <template #default="{ color }">
+                <span :class="`text-${color}`"> 部屋情報が公開されました </span>
+              </template>
+            </activity-layout>
+            <activity-layout
+              v-if="activity.type === 'payment_created'"
+              :type="activity.type"
+              :date="new Date(activity.time)"
+            >
+              <template #default="{ color }">
+                <span :class="`text-${color}`">
+                  {{ activity.amount.toLocaleString() }} 円の支払いが作成されました
+                </span>
+              </template>
+            </activity-layout>
+            <activity-layout
+              v-if="activity.type === 'payment_amount_changed'"
+              :type="activity.type"
+              :date="new Date(activity.time)"
+            >
+              <template #default="{ color }">
+                <span :class="`text-${color}`">
+                  支払い金額が {{ activity.amount.toLocaleString() }} 円に変更されました
+                </span>
+              </template>
+            </activity-layout>
+            <activity-layout
+              v-if="activity.type === 'payment_paid_changed'"
+              :type="activity.type"
+              :date="new Date(activity.time)"
+            >
+              <template #default="{ color }">
+                <span :class="`text-${color}`">
+                  合宿係が {{ activity.amount.toLocaleString() }} 円の振込を確認しました
+                </span>
+              </template>
+            </activity-layout>
+            <roll-call-activity v-if="activity.type === 'roll_call_created'" :activity="activity" />
+            <question-activity v-if="activity.type === 'question_created'" :activity="activity" />
+          </template>
+        </div>
+      </template>
     </div>
   </div>
 </template>