diff --git a/src/handlers/accounts.ts b/src/handlers/accounts.ts
index 11451a0..e1b4fb2 100644
--- a/src/handlers/accounts.ts
+++ b/src/handlers/accounts.ts
@@ -754,7 +754,7 @@ export async function handleVerifyPassword(request: Request, env: Env, userId: s
 }
 
 // POST /api/accounts/api-key
-export async function handleGetApiKey(request: Request, env: Env, userId: string): Promise<Response>{
+export async function handleGetApiKey(request: Request, env: Env, userId: string): Promise<Response> {
   return apiKey(request, env, userId, false);
 }
 
@@ -763,7 +763,7 @@ export async function handleRotateApiKey(request: Request, env: Env, userId: str
   return apiKey(request, env, userId, true);
 }
 
-async function apiKey(request: Request, env: Env, userId: string,rotate: boolean): Promise<Response> {
+async function apiKey(request: Request, env: Env, userId: string, rotate: boolean): Promise<Response> {
   const storage = new StorageService(env.DB);
   const auth = new AuthService(env);
   const user = await storage.getUserById(userId);
@@ -786,28 +786,32 @@ async function apiKey(request: Request, env: Env, userId: string,rotate: boolean
   if (!currentHash) return errorResponse('masterPasswordHash is required', 400);
   const valid = await auth.verifyPassword(currentHash, user.masterPasswordHash, user.email);
   if (!valid) return errorResponse('Invalid password', 400);
-  
+
   if (rotate || user.apiKey === null) {
     // Upstream apikeys are 30-character random alphanumeric strings
     user.apiKey = randomStringAlphanum(LIMITS.auth.clientSecretLength);
+    if (rotate) {
+      user.securityStamp = generateUUID();
+      await storage.deleteRefreshTokensByUserId(user.id);
+    }
     user.updatedAt = new Date().toISOString();
     await storage.saveUser(user);
   }
 
-  return  jsonResponse({
+  return jsonResponse({
     apiKey: user.apiKey,
-    revisionDate: user.updatedAt, 
+    revisionDate: user.updatedAt,
     object: 'apiKey',
-  }); 
+  });
 }
 
 // Generate a random alphanumeric string of the given length using crypto.getRandomValues.
 function randomStringAlphanum(length: number): string {
-  const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
   const array = new Uint8Array(length);
   crypto.getRandomValues(array);
-  
-  let result = "";
+
+  let result = '';
   for (let i = 0; i < length; i++) {
     result += chars[array[i] % chars.length];
   }
diff --git a/src/handlers/identity.ts b/src/handlers/identity.ts
index ca8c49b..e8e1bf1 100644
--- a/src/handlers/identity.ts
+++ b/src/handlers/identity.ts
@@ -48,6 +48,18 @@ function parseCookieValue(request: Request, name: string): string | null {
   return null;
 }
 
+function constantTimeEquals(a: string, b: string): boolean {
+  const encA = new TextEncoder().encode(a);
+  const encB = new TextEncoder().encode(b);
+  if (encA.length !== encB.length) return false;
+
+  let diff = 0;
+  for (let i = 0; i < encA.length; i++) {
+    diff |= encA[i] ^ encB[i];
+  }
+  return diff === 0;
+}
+
 function buildRefreshCookie(request: Request, refreshToken: string, maxAgeSeconds: number): string {
   const isHttps = new URL(request.url).protocol === 'https:';
   const parts = [
@@ -395,8 +407,12 @@ export async function handleToken(request: Request, env: Env): Promise<Response>
       return identityErrorResponse('Account is disabled', 'invalid_grant', 400);
     }
 
+    if (!user.apiKey || !constantTimeEquals(clientSecret, user.apiKey)) {
+      await rateLimit.recordFailedLogin(loginIdentifier);
+      return identityErrorResponse('ClientId or clientSecret is incorrect. Try again', 'invalid_grant', 400);
+    }
 
-     // Persist device only after successful password + (optional) 2FA verification.
+    // Persist device only after successful client credential verification.
     const deviceSession =
       deviceInfo.deviceIdentifier
         ? { identifier: deviceInfo.deviceIdentifier, sessionStamp: generateUUID() }
@@ -423,7 +439,7 @@ export async function handleToken(request: Request, env: Env): Promise<Response>
       access_token: accessToken,
       expires_in: LIMITS.auth.accessTokenTtlSeconds,
       token_type: 'Bearer',
-      ...(shouldUseWebSession(request) ? { web_session: true } : { refresh_token: refreshToken } ),
+      ...(shouldUseWebSession(request) ? { web_session: true } : { refresh_token: refreshToken }),
       Key: user.key,
       PrivateKey: user.privateKey,
       AccountKeys: accountKeys,
@@ -643,10 +659,10 @@ export async function handleRevocation(request: Request, env: Env): Promise<Resp
 }
 
 export function checkClientCredentialsParam(clientId: string, clientSecret: string, scope: string): boolean {
-  if (scope !== "api") {
+  if (scope !== 'api') {
     return false;
   }
-  if (!clientId.startsWith("user.")) {
+  if (!clientId.startsWith('user.')) {
     return false;
   }
   if (!clientSecret) {
diff --git a/src/router-authenticated.ts b/src/router-authenticated.ts
index 8b777a2..bb1e8c3 100644
--- a/src/router-authenticated.ts
+++ b/src/router-authenticated.ts
@@ -121,11 +121,11 @@ export async function handleAuthenticatedRoute(
     return handleSetVerifyDevices(request, env, userId);
   }
 
-  if (path === '/api/accounts/api_key' && method === 'POST') {
+  if ((path === '/api/accounts/api-key' || path === '/api/accounts/api_key') && method === 'POST') {
     return handleGetApiKey(request, env, userId);
   }
 
-  if (path === '/api/accounts/rotate_api_key' && method === 'POST') {
+  if ((path === '/api/accounts/rotate-api-key' || path === '/api/accounts/rotate_api_key') && method === 'POST') {
     return handleRotateApiKey(request, env, userId);
   }
 
diff --git a/src/services/storage-user-repo.ts b/src/services/storage-user-repo.ts
index 1bad39c..fdb3ab0 100644
--- a/src/services/storage-user-repo.ts
+++ b/src/services/storage-user-repo.ts
@@ -105,7 +105,7 @@ export async function createFirstUser(db: D1Database, safeBind: SafeBind, user:
   const email = user.email.toLowerCase();
   const stmt = db.prepare(
     'INSERT INTO users(id, email, name, master_password_hint, master_password_hash, key, private_key, public_key, kdf_type, kdf_iterations, kdf_memory, kdf_parallelism, security_stamp, role, status, verify_devices, totp_secret, totp_recovery_code, api_key, created_at, updated_at) ' +
-    'SELECT ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?' +
+    'SELECT ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ? ' +
     'WHERE NOT EXISTS (SELECT 1 FROM users LIMIT 1)'
   );
   const result = await safeBind(
diff --git a/webapp/src/components/SettingsPage.tsx b/webapp/src/components/SettingsPage.tsx
index da49ebb..b669e57 100644
--- a/webapp/src/components/SettingsPage.tsx
+++ b/webapp/src/components/SettingsPage.tsx
@@ -294,21 +294,58 @@ export default function SettingsPage(props: SettingsPageProps) {
       <ConfirmDialog
         open={apiKeyDialogOpen}
         title={t('txt_api_key')}
-        message=""
+        message={t('txt_api_key_dialog_intro')}
         hideCancel
         confirmText={t('txt_close')}
         onConfirm={() => setApiKeyDialogOpen(false)}
         onCancel={() => setApiKeyDialogOpen(false)}
       >
-        <div className="stack" style={{ gap: 8, marginTop: 4 }}>
+        <div
+          style={{
+            border: '1px solid color-mix(in srgb, var(--danger) 24%, transparent)',
+            background: 'color-mix(in srgb, var(--danger) 7%, var(--surface))',
+            borderRadius: 8,
+            padding: 14,
+            marginTop: 12,
+            marginBottom: 14,
+          }}
+        >
+          <div style={{ fontWeight: 800, color: 'var(--danger)', marginBottom: 8 }}>{t('txt_warning')}</div>
+          <div style={{ color: 'var(--text)', lineHeight: 1.55 }}>{t('txt_api_key_warning_body')}</div>
+        </div>
+
+        <div
+          style={{
+            border: '1px solid color-mix(in srgb, var(--primary) 25%, transparent)',
+            background: 'color-mix(in srgb, var(--primary) 7%, var(--surface))',
+            borderRadius: 8,
+            padding: 14,
+            marginBottom: 10,
+          }}
+        >
+          <div style={{ display: 'flex', alignItems: 'center', gap: 8, fontWeight: 800, color: 'var(--primary)', marginBottom: 10 }}>
+            <KeyRound size={15} />
+            <span>{t('txt_oauth_client_credentials')}</span>
+          </div>
           {([
             [t('txt_client_id'), `user.${props.profile.id}`],
             [t('txt_client_secret'), apiKey],
             [t('txt_scope'), 'api'],
+            [t('txt_grant_type'), 'client_credentials'],
           ] as [string, string][]).map(([label, value]) => (
             <label key={label} className="field">
               <span>{label}</span>
-              <input className="input" readOnly value={value} onFocus={(e) => (e.currentTarget as HTMLInputElement).select()} />
+              <div style={{ display: 'grid', gridTemplateColumns: 'minmax(0, 1fr) auto', gap: 8 }}>
+                <input className="input" readOnly value={value} onFocus={(e) => (e.currentTarget as HTMLInputElement).select()} />
+                <button
+                  type="button"
+                  className="btn btn-secondary small"
+                  onClick={() => void copyTextToClipboard(value, { successMessage: t('txt_copied') })}
+                >
+                  <Clipboard size={14} className="btn-icon" />
+                  {t('txt_copy')}
+                </button>
+              </div>
             </label>
           ))}
         </div>
diff --git a/webapp/src/lib/api/auth.ts b/webapp/src/lib/api/auth.ts
index b6a0ad7..2d8ebce 100644
--- a/webapp/src/lib/api/auth.ts
+++ b/webapp/src/lib/api/auth.ts
@@ -596,7 +596,7 @@ export async function deleteAllAuthorizedDevices(authedFetch: AuthedFetch): Prom
 }
 
 export async function getApiKey(authedFetch: AuthedFetch, masterPasswordHash: string): Promise<string> {
-  const resp = await authedFetch('/api/accounts/api_key', {
+  const resp = await authedFetch('/api/accounts/api-key', {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ masterPasswordHash }),
@@ -610,7 +610,7 @@ export async function getApiKey(authedFetch: AuthedFetch, masterPasswordHash: st
 }
 
 export async function rotateApiKey(authedFetch: AuthedFetch, masterPasswordHash: string): Promise<string> {
-  const resp = await authedFetch('/api/accounts/rotate_api_key', {
+  const resp = await authedFetch('/api/accounts/rotate-api-key', {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ masterPasswordHash }),
diff --git a/webapp/src/lib/i18n.ts b/webapp/src/lib/i18n.ts
index f237e1c..439a25f 100644
--- a/webapp/src/lib/i18n.ts
+++ b/webapp/src/lib/i18n.ts
@@ -609,9 +609,13 @@ const messages: Record<Locale, Record<string, string>> = {
     txt_api_key_rotated: "API key rotated",
     txt_rotate_api_key_confirm: "Rotate API key? The current key will stop working immediately.",
     txt_api_key_is_empty: "API key is empty",
+    txt_api_key_dialog_intro: "Your API key can be used to authenticate with the Bitwarden CLI.",
+    txt_api_key_warning_body: "Your API key is an alternative authentication mechanism. Keep it secret.",
+    txt_oauth_client_credentials: "OAuth 2.0 Client Credentials",
     txt_client_id: "client_id",
     txt_client_secret: "client_secret",
     txt_scope: "scope",
+    txt_grant_type: "grant_type",
     txt_refresh: "Refresh",
     txt_refresh_in_seconds_s: "Refresh in {seconds}s",
     txt_regenerate: "Regenerate",
@@ -1382,9 +1386,13 @@ const zhCNOverrides: Record<string, string> = {
   txt_api_key_rotated: 'API 密钥已轮换',
   txt_rotate_api_key_confirm: '轮换 API 密钥？当前密钥将立即失效。',
   txt_api_key_is_empty: 'API 密钥为空',
+  txt_api_key_dialog_intro: '您的 API 密钥可用于在 Bitwarden CLI 中进行身份验证。',
+  txt_api_key_warning_body: '您的 API 密钥是一种替代身份验证机制。请严格保密。',
+  txt_oauth_client_credentials: 'OAuth 2.0 客户端凭据',
   txt_client_id: 'client_id',
   txt_client_secret: 'client_secret',
   txt_scope: 'scope',
+  txt_grant_type: 'grant_type',
   txt_refresh_in_seconds_s: '{seconds} 秒后刷新',
   txt_registration_succeeded_please_sign_in: '注册成功，请登录',
   txt_remove_device: '移除设备',