diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cc24903..ce0c16f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,3 +26,5 @@ jobs:
           JWT_SECRET: "ci-placeholder-jwt-secret-min-32-chars"
           DATABASE_URL: "postgresql://placeholder:placeholder@localhost:5432/placeholder"
           DIRECT_URL: "postgresql://placeholder:placeholder@localhost:5432/placeholder"
+          ADMIN_USERNAME: "ci-admin"
+          ADMIN_PASSWORD: "ci-placeholder-password"
diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..30dfa20
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,9 @@
+## 2026-06-08 - [Hardcoded Admin Password]
+**Vulnerability:** Hardcoded `ADMIN_USERNAME` and `ADMIN_PASSWORD` in `packages/web/src/lib/server/admin-auth.ts` could allow unauthorized access if source code is exposed.
+**Learning:** Hardcoding credentials makes the application insecure and inflexible, and prevents credential rotation without code deployment.
+**Prevention:** Use environment variables validated via schema (e.g., Zod) for all credentials and API keys. Keep default values secure and avoid committing secrets.
+
+## 2026-06-08 - [Insecure Password Hashing]
+**Vulnerability:** Fast hash (HMAC-SHA256) was used for timing-safe equality checks of passwords, which triggered a CodeQL `js/insecure-password-hashing` alert.
+**Learning:** Using simple HMACs for passwords is not enough against offline dictionary attacks if the secret is known or short. CodeQL expects a proper key derivation function (like `pbkdf2`) for passwords. Furthermore, sync versions of KDFs (like `pbkdf2Sync`) should not be used in request paths as they block the event loop and cause DoS.
+**Prevention:** Precompute target hashes at module initialization using `pbkdf2Sync`, and use the asynchronous `crypto.pbkdf2` (via `util.promisify`) for hashing incoming passwords within request handlers.
diff --git a/packages/web/.env.example b/packages/web/.env.example
index e99d51e..b6a546f 100644
--- a/packages/web/.env.example
+++ b/packages/web/.env.example
@@ -4,3 +4,5 @@ AUTH_SECRET=replace-with-min-32-char-random-string
 DATABASE_URL="postgresql://postgres.[project]:[password]@aws-0-ap-northeast-1.pooler.supabase.com:6543/postgres?pgbouncer=true"
 DIRECT_URL="postgresql://postgres.[project]:[password]@db.uwxfseowdzuuepeeudrx.supabase.co:5432/postgres"
 JWT_SECRET="replace-with-32-char-minimum-random-string"
+ADMIN_USERNAME=admin
+ADMIN_PASSWORD=replace-with-secure-password
diff --git a/packages/web/src/app/api/admin/login/route.ts b/packages/web/src/app/api/admin/login/route.ts
index dbf5d2e..24fabdb 100644
--- a/packages/web/src/app/api/admin/login/route.ts
+++ b/packages/web/src/app/api/admin/login/route.ts
@@ -20,7 +20,7 @@ const AdminLoginSchema = z.object({
 export async function POST(req: Request) {
   try {
     const input = AdminLoginSchema.parse(await req.json())
-    if (!verifyAdminCredentials(input)) {
+    if (!(await verifyAdminCredentials(input))) {
       return NextResponse.json({ error: 'Invalid username or password' }, { status: 401 })
     }
 
diff --git a/packages/web/src/lib/server/admin-auth.ts b/packages/web/src/lib/server/admin-auth.ts
index 5390fa4..0880d63 100644
--- a/packages/web/src/lib/server/admin-auth.ts
+++ b/packages/web/src/lib/server/admin-auth.ts
@@ -1,13 +1,19 @@
 import 'server-only'
 
-import { createHmac, randomBytes, timingSafeEqual } from 'crypto'
+import { createHmac, pbkdf2, pbkdf2Sync, randomBytes, timingSafeEqual } from 'crypto'
 import { cookies } from 'next/headers'
 import { NextRequest, NextResponse } from 'next/server'
+import { promisify } from 'util'
 
 import { env } from './env'
 
-export const ADMIN_USERNAME = 'admin'
-export const ADMIN_PASSWORD = 'og9oRajx7h88v1RIj3eDgdrh9jgLYVV3'
+export const ADMIN_USERNAME = env.ADMIN_USERNAME
+export const ADMIN_PASSWORD = env.ADMIN_PASSWORD
+
+// Precompute target hash to resolve CodeQL js/insecure-password-hashing alert
+// using sync method at module initialization time.
+const ADMIN_PASSWORD_HASH = pbkdf2Sync(ADMIN_PASSWORD, env.JWT_SECRET, 100000, 64, 'sha512')
+const pbkdf2Async = promisify(pbkdf2)
 
 const ADMIN_SESSION_COOKIE = 'argos_admin_session'
 const ADMIN_SESSION_TTL_MS = 12 * 60 * 60 * 1000
@@ -24,14 +30,15 @@ function sign(payload: string): string {
   return createHmac('sha256', env.JWT_SECRET).update(payload).digest('base64url')
 }
 
-export function verifyAdminCredentials(input: {
+export async function verifyAdminCredentials(input: {
   username: string
   password: string
-}): boolean {
-  return (
-    safeEqual(input.username, ADMIN_USERNAME) &&
-    safeEqual(input.password, ADMIN_PASSWORD)
-  )
+}): Promise<boolean> {
+  if (!safeEqual(input.username, ADMIN_USERNAME)) return false
+
+  // Use async pbkdf2 to avoid blocking the event loop when verifying input password
+  const inputHash = await pbkdf2Async(input.password, env.JWT_SECRET, 100000, 64, 'sha512')
+  return timingSafeEqual(inputHash, ADMIN_PASSWORD_HASH)
 }
 
 export function createAdminSessionCookieValue(): string {
diff --git a/packages/web/src/lib/server/env.ts b/packages/web/src/lib/server/env.ts
index 86ed9a3..6bdf299 100644
--- a/packages/web/src/lib/server/env.ts
+++ b/packages/web/src/lib/server/env.ts
@@ -5,6 +5,8 @@ const EnvSchema = z.object({
   DATABASE_URL: z.string().min(1),
   DIRECT_URL: z.string().min(1),
   JWT_SECRET: z.string().min(32),
+  ADMIN_USERNAME: z.string().trim().min(1),
+  ADMIN_PASSWORD: z.string().trim().min(8),
 })
 
 export const env = EnvSchema.parse(process.env)