diff --git a/.codacy.yaml b/.codacy.yaml
new file mode 100644
index 00000000..9570fdeb
--- /dev/null
+++ b/.codacy.yaml
@@ -0,0 +1,16 @@
+---
+# Codacy configuration
+# https://docs.codacy.com/repositories-configure/codacy-configuration-file/
+#
+# 本プロジェクトのフロントエンドは ESLint + Prettier を採用しており、Biome は
+# 導入していない。Codacy がデフォルトで有効化している Biome 解析は二重解析と
+# なるだけでなく、`noReactSpecificProps` のようなルールが React プロジェクトの
+# `className` 属性を誤検知し、Quality Gate を恒常的に fail させる原因となる。
+#
+# Codacy の設定ファイルではツール自体の enable/disable は切り替えられない
+# (Code patterns UI 経由のみ) ため、Biome に対してすべてのファイルを
+# exclude_paths で除外することで実質的に無効化する。
+engines:
+  biome:
+    exclude_paths:
+      - '**'
diff --git a/frontend/src/pages/Channels.tsx b/frontend/src/pages/Channels.tsx
index cb31edc0..22339cef 100644
--- a/frontend/src/pages/Channels.tsx
+++ b/frontend/src/pages/Channels.tsx
@@ -162,7 +162,7 @@ export default function Channels() {
                     </div>
                     <button
                       onClick={() => handleDelete(ch.id)}
-                      className="p-2 text-red-600 hover:bg-red-50 rounded-md shrink-0"
+                      className="p-2 text-red-600 hover:bg-red-50 rounded-md shrink-0 focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-red-500 focus-visible:ring-offset-1 transition-colors"
                       title={`${ch.displayName} を削除`}
                       aria-label={`${ch.displayName} を削除`}
                     >
@@ -183,7 +183,7 @@ export default function Channels() {
                       <button
                         type="button"
                         onClick={() => handleCopy(ch.channelId, ch.id)}
-                        className="px-2 py-1.5 text-slate-700 hover:bg-slate-100 rounded-md flex items-center gap-1 text-xs border border-slate-300 shrink-0"
+                        className="px-2 py-1.5 text-slate-700 hover:bg-slate-100 rounded-md flex items-center gap-1 text-xs border border-slate-300 shrink-0 focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-1 transition-colors"
                         aria-label={`Webhook URL をコピー: ${webhookUrl}`}
                       >
                         {isCopied ? (
diff --git a/frontend/src/pages/Contact.tsx b/frontend/src/pages/Contact.tsx
index da27a111..040d10b4 100644
--- a/frontend/src/pages/Contact.tsx
+++ b/frontend/src/pages/Contact.tsx
@@ -134,7 +134,7 @@ export default function Contact() {
                   setBody('');
                   setUrl('');
                 }}
-                className="underline text-slate-700"
+                className="underline text-slate-700 focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-2 rounded-sm transition-colors"
               >
                 続けて問い合わせる
               </button>
diff --git a/frontend/src/pages/FaqArticle.tsx b/frontend/src/pages/FaqArticle.tsx
index b5746078..1b127d1c 100644
--- a/frontend/src/pages/FaqArticle.tsx
+++ b/frontend/src/pages/FaqArticle.tsx
@@ -161,7 +161,7 @@ function FaqArticleContent({ faq }: { faq: FaqArticleType }) {
                   aria-pressed={false}
                   aria-label="役に立った"
                   onClick={() => setFeedback('up')}
-                  className="inline-flex items-center gap-2 px-4 py-2 border border-slate-300 text-sm text-slate-700 rounded-md hover:bg-slate-50"
+                  className="inline-flex items-center gap-2 px-4 py-2 border border-slate-300 text-sm text-slate-700 rounded-md hover:bg-slate-50 focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-2 transition-colors"
                 >
                   <ThumbsUp size={ICON_SIZE.sm} />
                   役に立った
@@ -171,7 +171,7 @@ function FaqArticleContent({ faq }: { faq: FaqArticleType }) {
                   aria-pressed={false}
                   aria-label="役に立たなかった"
                   onClick={() => setFeedback('down')}
-                  className="inline-flex items-center gap-2 px-4 py-2 border border-slate-300 text-sm text-slate-700 rounded-md hover:bg-slate-50"
+                  className="inline-flex items-center gap-2 px-4 py-2 border border-slate-300 text-sm text-slate-700 rounded-md hover:bg-slate-50 focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-2 transition-colors"
                 >
                   <ThumbsDown size={ICON_SIZE.sm} />
                   役に立たなかった
diff --git a/frontend/src/pages/FormEdit.tsx b/frontend/src/pages/FormEdit.tsx
index 9a91d039..651c0f96 100644
--- a/frontend/src/pages/FormEdit.tsx
+++ b/frontend/src/pages/FormEdit.tsx
@@ -303,7 +303,7 @@ export default function FormEdit() {
         {!isNew && (
           <button
             onClick={handleDelete}
-            className="p-2 text-red-600 hover:bg-red-50 rounded-md"
+            className="p-2 text-red-600 hover:bg-red-50 rounded-md focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-red-500 focus-visible:ring-offset-1 transition-colors"
             title="フォームを削除"
             aria-label="フォームを削除"
           >
@@ -398,7 +398,7 @@ export default function FormEdit() {
                 tabIndex={tab === 'visual' ? 0 : -1}
                 onClick={() => switchTab('visual')}
                 onKeyDown={handleTabKeyDown}
-                className={`px-3 py-1 text-xs rounded ${
+                className={`px-3 py-1 text-xs rounded focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-1 transition-colors ${
                   tab === 'visual'
                     ? 'bg-white text-slate-900 shadow-sm'
                     : 'text-slate-600'
@@ -417,7 +417,7 @@ export default function FormEdit() {
                 tabIndex={tab === 'json' ? 0 : -1}
                 onClick={() => switchTab('json')}
                 onKeyDown={handleTabKeyDown}
-                className={`px-3 py-1 text-xs rounded ${
+                className={`px-3 py-1 text-xs rounded focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-1 transition-colors ${
                   tab === 'json'
                     ? 'bg-white text-slate-900 shadow-sm'
                     : 'text-slate-600'
diff --git a/frontend/src/pages/Submissions.tsx b/frontend/src/pages/Submissions.tsx
index ee06b3dc..4be1361a 100644
--- a/frontend/src/pages/Submissions.tsx
+++ b/frontend/src/pages/Submissions.tsx
@@ -127,7 +127,7 @@ export default function Submissions() {
           <button
             onClick={handleDownload}
             disabled={!exportFormId || downloading}
-            className="inline-flex items-center gap-2 px-4 py-2 bg-slate-900 text-white text-sm rounded-md disabled:opacity-50"
+            className="inline-flex items-center gap-2 px-4 py-2 bg-slate-900 text-white text-sm rounded-md disabled:opacity-50 focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-2 transition-colors"
           >
             <Download size={ICON_SIZE.sm} />
             {downloading ? 'ダウンロード中…' : 'CSVダウンロード'}
diff --git a/frontend/src/pages/admin/AdminContactDetail.tsx b/frontend/src/pages/admin/AdminContactDetail.tsx
index bb430d60..c430d5fb 100644
--- a/frontend/src/pages/admin/AdminContactDetail.tsx
+++ b/frontend/src/pages/admin/AdminContactDetail.tsx
@@ -133,7 +133,7 @@ export default function AdminContactDetail() {
               key={s}
               onClick={() => changeStatus(s)}
               disabled={updating || detail.status === s}
-              className={`px-3 py-1.5 rounded-md text-sm border ${
+              className={`px-3 py-1.5 rounded-md text-sm border focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-slate-900 focus-visible:ring-offset-2 transition-colors ${
                 detail.status === s
                   ? 'bg-slate-900 text-white border-slate-900'
                   : 'bg-white text-slate-700 border-slate-300 hover:bg-slate-50'