diff --git a/.github/workflows/ci-failure-notify.yml b/.github/workflows/ci-failure-notify.yml
new file mode 100644
index 0000000..4f40ba6
--- /dev/null
+++ b/.github/workflows/ci-failure-notify.yml
@@ -0,0 +1,90 @@
+name: CI Failure Slack Notify
+
+on:
+  workflow_run:
+    workflows:
+      - CI
+      - Playwright E2E Tests
+      - TruffleHog Secret Scan
+      - Lighthouse CI
+    types: [completed]
+    branches: [main]
+
+jobs:
+  notify-failure:
+    name: Notify Slack on failure
+    runs-on: ubuntu-latest
+    if: ${{ github.event.workflow_run.conclusion == 'failure' }}
+    steps:
+      - name: Send Slack notification
+        env:
+          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
+          SLACK_CHANNEL_ID: ${{ vars.SLACK_CHANNEL_ID }}
+          WORKFLOW_NAME: ${{ github.event.workflow_run.name }}
+          RUN_URL: ${{ github.event.workflow_run.html_url }}
+          ACTOR: ${{ github.event.workflow_run.actor.login }}
+          COMMIT_SHA: ${{ github.event.workflow_run.head_sha }}
+          SERVER_URL: ${{ github.server_url }}
+          REPOSITORY: ${{ github.repository }}
+        run: |
+          SHORT_SHA="${COMMIT_SHA:0:7}"
+          COMMIT_URL="${SERVER_URL}/${REPOSITORY}/commit/${COMMIT_SHA}"
+
+          PAYLOAD=$(jq -n \
+            --arg channel "$SLACK_CHANNEL_ID" \
+            --arg text "🚨 ${WORKFLOW_NAME} が main ブランチで失敗しました" \
+            --arg workflow "$WORKFLOW_NAME" \
+            --arg actor "$ACTOR" \
+            --arg commit_url "$COMMIT_URL" \
+            --arg short_sha "$SHORT_SHA" \
+            --arg run_url "$RUN_URL" \
+            '{
+              channel: $channel,
+              text: $text,
+              blocks: [
+                {
+                  type: "header",
+                  text: {
+                    type: "plain_text",
+                    text: "🚨 CI/CD 失敗通知（main ブランチ）",
+                    emoji: true
+                  }
+                },
+                {
+                  type: "section",
+                  fields: [
+                    { type: "mrkdwn", text: ("*ワークフロー:*\n" + $workflow) },
+                    { type: "mrkdwn", text: "*ブランチ:*\n`main`" },
+                    { type: "mrkdwn", text: ("*実行者:*\n" + $actor) },
+                    { type: "mrkdwn", text: ("*コミット:*\n<" + $commit_url + "|" + $short_sha + ">") }
+                  ]
+                },
+                {
+                  type: "actions",
+                  elements: [
+                    {
+                      type: "button",
+                      text: { type: "plain_text", text: "📋 ログを確認", emoji: true },
+                      url: $run_url,
+                      style: "danger"
+                    }
+                  ]
+                }
+              ]
+            }')
+
+          RESPONSE=$(curl -sf -X POST "https://slack.com/api/chat.postMessage" \
+            -H "Authorization: Bearer ${SLACK_BOT_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "$PAYLOAD") || true
+
+          if [ -z "$RESPONSE" ]; then
+            echo "::error::Slack API request failed (network error or empty response)"
+            exit 1
+          fi
+
+          if ! echo "$RESPONSE" | jq -e '.ok == true' > /dev/null; then
+            ERROR=$(echo "$RESPONSE" | jq -r '.error // "unknown_error"')
+            echo "::error::Slack API error: ${ERROR}"
+            exit 1
+          fi
diff --git a/.github/workflows/dependabot-automerge.yml b/.github/workflows/dependabot-automerge.yml
new file mode 100644
index 0000000..13d1853
--- /dev/null
+++ b/.github/workflows/dependabot-automerge.yml
@@ -0,0 +1,50 @@
+name: Dependabot自動マージ
+
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot-automerge:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+
+    steps:
+      - name: Dependabotメタデータ取得
+        id: metadata
+        uses: dependabot/fetch-metadata@21025c705c08248db411dc16f3619e6b5f9ea21a # v2
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+
+      - name: 更新タイプをチェック
+        id: check-update-type
+        run: |
+          # グループ化PRの場合、updated-dependencies-jsonから各依存関係の更新タイプを確認
+          DEPENDENCIES='${{ steps.metadata.outputs.updated-dependencies-json }}'
+          
+          # 依存関係が空の場合はスキップ
+          if [ -z "$DEPENDENCIES" ] || [ "$DEPENDENCIES" = "[]" ]; then
+            echo "can-automerge=false" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+          
+          # すべての依存関係がpatchまたはminorかチェック
+          CAN_MERGE=$(echo "$DEPENDENCIES" | jq -r '
+            if length == 0 then
+              false
+            else
+              all(.[]; .["update-type"] == "version-update:semver-patch" or .["update-type"] == "version-update:semver-minor")
+            end
+          ')
+          
+          echo "can-automerge=$CAN_MERGE" >> $GITHUB_OUTPUT
+          echo "依存関係の更新タイプ確認完了: can-automerge=$CAN_MERGE"
+
+      - name: minor/patchを自動マージ
+        if: steps.check-update-type.outputs.can-automerge == 'true'
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/devin-slack-trigger.yml b/.github/workflows/devin-slack-trigger.yml
new file mode 100644
index 0000000..c5aa5e8
--- /dev/null
+++ b/.github/workflows/devin-slack-trigger.yml
@@ -0,0 +1,84 @@
+name: Devin Slack Trigger
+
+on:
+  issues:
+    types: [labeled]
+
+permissions:
+  issues: write
+
+jobs:
+  trigger-devin:
+    name: Trigger Devin via Slack
+    runs-on: ${{ vars.RUNNER_LINUX || 'ubuntu-latest' }}
+    # Slack への通知トリガのみの小さなジョブなので短めに打ち切る
+    timeout-minutes: 10
+    if: github.event.label.name == 'devin'
+    concurrency:
+      group: devin-trigger-${{ github.event.issue.number }}
+      cancel-in-progress: false
+
+    steps:
+      - name: Check for duplicate trigger
+        id: duplicate-check
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            const comments = await github.paginate(
+              github.rest.issues.listComments,
+              {
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.payload.issue.number,
+              }
+            );
+            const alreadyTriggered = comments.some(c =>
+              c.body?.includes('<!-- devin-slack-triggered -->')
+            );
+            if (alreadyTriggered) {
+              core.notice('Devin session already triggered for this issue. Skipping.');
+            }
+            core.setOutput('skip', String(alreadyTriggered));
+
+      - name: Post message to Slack
+        if: steps.duplicate-check.outputs.skip == 'false'
+        id: slack-post
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        env:
+          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
+          SLACK_CHANNEL_ID: ${{ vars.SLACK_CHANNEL_ID }}
+          DEVIN_USER_ID: ${{ vars.SLACK_DEVIN_USER_ID }}
+        with:
+          script: |
+            const issue = context.payload.issue;
+
+            const message = `!swe\n[${issue.title}]\n<@${process.env.DEVIN_USER_ID}> Please handle this issue. First, create a plan and share it before implementing. Think in English, respond in Japanese.\n${issue.html_url}`;
+
+            const resp = await fetch('https://slack.com/api/chat.postMessage', {
+              method: 'POST',
+              headers: {
+                'Authorization': `Bearer ${process.env.SLACK_BOT_TOKEN}`,
+                'Content-Type': 'application/json; charset=utf-8',
+              },
+              body: JSON.stringify({
+                channel: process.env.SLACK_CHANNEL_ID,
+                text: message,
+              }),
+            });
+
+            const data = await resp.json();
+            if (!data.ok) {
+              core.setFailed(`Slack API error: ${data.error || 'unknown'}`);
+            }
+
+      - name: Post marker comment
+        if: success() && steps.duplicate-check.outputs.skip == 'false'
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.issue.number,
+              body: ':robot_face: Devin session triggered via Slack <!-- devin-slack-triggered -->',
+            });
diff --git a/.github/workflows/merge-quality-gate.yml b/.github/workflows/merge-quality-gate.yml
new file mode 100644
index 0000000..94b8f2f
--- /dev/null
+++ b/.github/workflows/merge-quality-gate.yml
@@ -0,0 +1,142 @@
+name: Merge Quality Gate
+
+on:
+  pull_request:
+    branches: [main]
+    types: [closed]
+
+jobs:
+  check-quality:
+    name: Post-merge quality check
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.merged == true
+    permissions:
+      contents: read
+      checks: read
+      pull-requests: read
+    steps:
+      - name: Check for unresolved quality issues
+        id: check
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # aligned
+        with:
+          script: |
+            const prNumber = context.payload.pull_request.number;
+
+            // PRコメントを取得してLighthouseスコアを確認
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: prNumber,
+            });
+
+            const issues = [];
+
+            // Lighthouseスコア確認
+            const lhComment = comments.find(c => c.body?.includes('<!-- lighthouse-ci -->'));
+            if (lhComment) {
+              // 🔴🟠のみマッチ（🟢=良好スコアは品質問題として検出しない）
+              const perfMatch = lhComment.body.match(/Performance\s*\|\s*(?:🔴|🟠)\s*(\d+)/);
+              if (perfMatch) {
+                const perfScore = parseInt(perfMatch[1]);
+                issues.push({
+                  type: 'lighthouse',
+                  message: `Lighthouse Performance: ${perfScore}/100`,
+                  score: perfScore,
+                });
+              }
+            }
+
+            // protect-main警告が残っていないか確認
+            const protectComment = comments.find(c => c.body?.includes('<!-- protect-main-bot -->'));
+            if (protectComment) {
+              issues.push({
+                type: 'protect-main',
+                message: 'mainブランチ保護ポリシー警告が未解消',
+              });
+            }
+
+            // チェック結果を出力
+            if (issues.length > 0) {
+              core.setOutput('has_issues', 'true');
+              core.setOutput('issues', JSON.stringify(issues));
+              core.info(`未解消の品質問題: ${issues.length}件`);
+            } else {
+              core.setOutput('has_issues', 'false');
+              core.info('品質問題なし');
+            }
+
+      - name: Notify Slack if unresolved issues
+        if: steps.check.outputs.has_issues == 'true'
+        env:
+          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
+          SLACK_CHANNEL_ID: ${{ vars.SLACK_CHANNEL_ID }}
+          ISSUES_JSON: ${{ steps.check.outputs.issues }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          PR_TITLE: ${{ github.event.pull_request.title }}
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          ACTOR: ${{ github.event.pull_request.merged_by.login }}
+        run: |
+          ISSUE_LIST=$(echo "$ISSUES_JSON" | jq -r '[.[] | "• " + .message] | join("\n")')
+
+          PAYLOAD=$(jq -n \
+            --arg channel "$SLACK_CHANNEL_ID" \
+            --arg text "⚠️ 品質問題が未解消のままマージされました: #${PR_NUMBER}" \
+            --arg pr_url "$PR_URL" \
+            --arg pr_number "$PR_NUMBER" \
+            --arg pr_title "$PR_TITLE" \
+            --arg actor "$ACTOR" \
+            --arg issues "$ISSUE_LIST" \
+            '{
+              channel: $channel,
+              text: $text,
+              blocks: [
+                {
+                  type: "header",
+                  text: {
+                    type: "plain_text",
+                    text: "⚠️ 品質問題未解消マージ通知",
+                    emoji: true
+                  }
+                },
+                {
+                  type: "section",
+                  fields: [
+                    { type: "mrkdwn", text: ("*PR:*\n<" + $pr_url + "|#" + $pr_number + " " + $pr_title + ">") },
+                    { type: "mrkdwn", text: ("*マージ実行者:*\n" + $actor) }
+                  ]
+                },
+                {
+                  type: "section",
+                  text: {
+                    type: "mrkdwn",
+                    text: ("*未解消の問題:*\n" + $issues)
+                  }
+                },
+                {
+                  type: "actions",
+                  elements: [
+                    {
+                      type: "button",
+                      text: { type: "plain_text", text: "📋 PRを確認", emoji: true },
+                      url: $pr_url
+                    }
+                  ]
+                }
+              ]
+            }')
+
+          RESPONSE=$(curl -sf -X POST "https://slack.com/api/chat.postMessage" \
+            -H "Authorization: Bearer ${SLACK_BOT_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "$PAYLOAD") || true
+
+          if [ -z "$RESPONSE" ]; then
+            echo "::error::Slack API request failed (network error or empty response)"
+            exit 1
+          fi
+
+          if ! echo "$RESPONSE" | jq -e '.ok == true' > /dev/null; then
+            ERROR=$(echo "$RESPONSE" | jq -r '.error // "unknown_error"')
+            echo "::error::Slack API error: ${ERROR}"
+            exit 1
+          fi
diff --git a/.github/workflows/trufflehog.yml b/.github/workflows/trufflehog.yml
new file mode 100644
index 0000000..a305bac
--- /dev/null
+++ b/.github/workflows/trufflehog.yml
@@ -0,0 +1,25 @@
+name: TruffleHog Secret Scan
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+  security-events: write
+
+jobs:
+  trufflehog:
+    name: Secret Scan
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6
+        with:
+          fetch-depth: 0
+
+      - name: TruffleHog OSS
+        uses: trufflesecurity/trufflehog@702bbefa350895c57f0e303eeb2855a1c637908f # v3.92.2
+        with:
+          extra_args: --only-verified