diff --git a/src/handlers/accounts.ts b/src/handlers/accounts.ts
index dd78d1c..9512609 100644
--- a/src/handlers/accounts.ts
+++ b/src/handlers/accounts.ts
@@ -6,6 +6,7 @@ import { auditRequestMetadata, writeAuditEvent, safeWriteAuditEvent } from '../s
 import { jsonResponse, errorResponse } from '../utils/response';
 import { generateUUID } from '../utils/uuid';
 import { LIMITS } from '../config/limits';
+import { hashApiKey } from '../utils/api-key';
 import { isTotpEnabled, verifyTotpToken } from '../utils/totp';
 import { createRecoveryCode, recoveryCodeEquals } from '../utils/recovery-code';
 import { buildAccountKeys } from '../utils/user-decryption';
@@ -1194,29 +1195,28 @@ async function apiKey(request: Request, env: Env, userId: string, rotate: boolea
   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);
-    AuthService.invalidateUserCache(user.id);
-    await writeAuditEvent(storage, {
-      actorUserId: user.id,
-      action: rotate ? 'account.api_key.rotate' : 'account.api_key.create',
-      category: 'security',
-      level: rotate ? 'security' : 'info',
-      targetType: 'user',
-      targetId: user.id,
-      metadata: auditRequestMetadata(request),
-    });
+  // Only the fresh secret is returned once; the database stores a hash.
+  const plainApiKey = randomStringAlphanum(LIMITS.auth.clientSecretLength);
+  user.apiKey = await hashApiKey(plainApiKey);
+  if (rotate) {
+    user.securityStamp = generateUUID();
+    await storage.deleteRefreshTokensByUserId(user.id);
   }
+  user.updatedAt = new Date().toISOString();
+  await storage.saveUser(user);
+  AuthService.invalidateUserCache(user.id);
+  await writeAuditEvent(storage, {
+    actorUserId: user.id,
+    action: rotate ? 'account.api_key.rotate' : 'account.api_key.create',
+    category: 'security',
+    level: rotate ? 'security' : 'info',
+    targetType: 'user',
+    targetId: user.id,
+    metadata: auditRequestMetadata(request),
+  });
 
   return jsonResponse({
-    apiKey: user.apiKey,
+    apiKey: plainApiKey,
     revisionDate: user.updatedAt,
     object: 'apiKey',
   });
diff --git a/src/handlers/identity.ts b/src/handlers/identity.ts
index 00baa80..9c8a547 100644
--- a/src/handlers/identity.ts
+++ b/src/handlers/identity.ts
@@ -22,6 +22,7 @@ import {
 } from './account-passkeys';
 import { isAuthRequestExpired } from '../services/storage-auth-request-repo';
 import { createPasskeyUserVerificationToken } from '../utils/user-verification-token';
+import { constantTimeEquals, verifyApiKey } from '../utils/api-key';
 
 const TWO_FACTOR_REMEMBER_TTL_MS = 30 * 24 * 60 * 60 * 1000;
 const TWO_FACTOR_PROVIDER_AUTHENTICATOR = 0;
@@ -106,18 +107,6 @@ 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 readBodyValue(body: Record<string, string>, names: string[]): string | undefined {
   for (const name of names) {
     const value = body[name];
@@ -688,7 +677,7 @@ 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)) {
+    if (!user.apiKey || !(await verifyApiKey(clientSecret, user.apiKey))) {
       await rateLimit.recordFailedLogin(loginIdentifier);
       await safeWriteAuditEvent(env, {
         actorUserId: user.id,
diff --git a/src/utils/api-key.ts b/src/utils/api-key.ts
new file mode 100644
index 0000000..8c03cbb
--- /dev/null
+++ b/src/utils/api-key.ts
@@ -0,0 +1,36 @@
+const API_KEY_HASH_PREFIX = 'sha256:';
+
+export 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 toHex(bytes: ArrayBuffer): string {
+  return [...new Uint8Array(bytes)]
+    .map((byte) => byte.toString(16).padStart(2, '0'))
+    .join('');
+}
+
+export function isStoredApiKeyHash(value: string | null | undefined): boolean {
+  return String(value || '').startsWith(API_KEY_HASH_PREFIX);
+}
+
+export async function hashApiKey(apiKey: string): Promise<string> {
+  const digest = await crypto.subtle.digest('SHA-256', new TextEncoder().encode(apiKey));
+  return `${API_KEY_HASH_PREFIX}${toHex(digest)}`;
+}
+
+export async function verifyApiKey(apiKey: string, storedApiKey: string | null | undefined): Promise<boolean> {
+  const stored = String(storedApiKey || '').trim();
+  if (!isStoredApiKeyHash(stored)) return false;
+
+  const hashed = await hashApiKey(apiKey);
+  return constantTimeEquals(hashed, stored);
+}