diff --git a/infra/keycloak/check_realms.py b/infra/keycloak/check_realms.py
index e338d29..4cb0965 100644
--- a/infra/keycloak/check_realms.py
+++ b/infra/keycloak/check_realms.py
@@ -1,19 +1,25 @@
 #!/usr/bin/env python3
 """Smoke-check the Keycloak realms: each realm's OIDC login works (password grant)
-and returns its expected identifying claim. Stdlib only. Exits non-zero on failure.
+and returns its expected identifying claim. The medewerker realm additionally enforces
+MFA (S-15c), so its login must be refused without a TOTP code. Stdlib only.
+Exits non-zero on failure.
 """
-import base64, json, sys, urllib.error, urllib.parse, urllib.request
+import base64, hashlib, hmac, json, struct, sys, time, urllib.error, urllib.parse, urllib.request
 
 BASE = "http://localhost:8180"
 CLIENT = "big-portal"
 PWD = "test123"
 
-# realm, user, claim ("__roles__" => check realm_access.roles), expected-contains
+# Fixture TOTP secret seeded into every medewerker in infra/keycloak/realms/medewerker-realm.json.
+# Keycloak HMACs the raw secret bytes, so no base32 decoding is involved.
+OTP_SECRET = b"BIGMEDEWERKEROTPSEED"
+
+# realm, user, claim ("__roles__" => check realm_access.roles), expected-contains, mfa-enforced
 CHECKS = [
-    ("digid", "jan-burger", "bsn", "123456782"),
-    ("eherkenning", "acme-ondernemer", "kvk", "12345678"),
-    ("eidas", "pierre-dupont", "eidas_id", "FR/NL"),
-    ("medewerker", "merel-behandelaar", "__roles__", "behandelaar"),
+    ("digid", "jan-burger", "bsn", "123456782", False),
+    ("eherkenning", "acme-ondernemer", "kvk", "12345678", False),
+    ("eidas", "pierre-dupont", "eidas_id", "FR/NL", False),
+    ("medewerker", "merel-behandelaar", "__roles__", "behandelaar", True),
 ]
 
 
@@ -23,10 +29,17 @@ def decode(jwt):
     return json.loads(base64.urlsafe_b64decode(p))
 
 
-def grant(realm, user):
+def totp(secret=OTP_SECRET, period=30, digits=6):
+    """RFC 6238 code: HMAC-SHA1 over the 30-second counter, dynamically truncated."""
+    mac = hmac.new(secret, struct.pack(">Q", int(time.time()) // period), hashlib.sha1).digest()
+    o = mac[-1] & 0x0F
+    return str((struct.unpack(">I", mac[o:o + 4])[0] & 0x7FFFFFFF) % 10 ** digits).zfill(digits)
+
+
+def grant(realm, user, **extra):
     data = urllib.parse.urlencode({
         "grant_type": "password", "client_id": CLIENT,
-        "username": user, "password": PWD, "scope": "openid",
+        "username": user, "password": PWD, "scope": "openid", **extra,
     }).encode()
     req = urllib.request.Request(
         f"{BASE}/realms/{realm}/protocol/openid-connect/token", data=data,
@@ -35,11 +48,27 @@ def grant(realm, user):
         return json.loads(r.read())
 
 
+def second_factor_refused(realm, user):
+    """The password alone must not yield a token on an MFA-enforced realm."""
+    try:
+        grant(realm, user)
+    except urllib.error.HTTPError as e:
+        return e.code in (400, 401)
+    return False
+
+
 def main():
     ok = True
-    for realm, user, claim, expect in CHECKS:
+    for realm, user, claim, expect, mfa in CHECKS:
+        extra = {}
+        if mfa:
+            refused = second_factor_refused(realm, user)
+            ok = ok and refused
+            print(f"{realm:12} {user:18} password-only login refused "
+                  f"[{'OK' if refused else 'MFA NOT ENFORCED'}]")
+            extra = {"totp": totp()}
         try:
-            at = decode(grant(realm, user)["access_token"])
+            at = decode(grant(realm, user, **extra)["access_token"])
             if claim == "__roles__":
                 val = at.get("realm_access", {}).get("roles", [])
                 good = expect in val
diff --git a/tests/e2e/catalogus.spec.ts b/tests/e2e/catalogus.spec.ts
index d7876c5..bb6e85f 100644
--- a/tests/e2e/catalogus.spec.ts
+++ b/tests/e2e/catalogus.spec.ts
@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test';
+import { loginMedewerker } from './medewerker-login';
 
 // S-15a walking skeleton: a beheerder logs in to the beheer portal (medewerker realm) and sees the
 // read-only ZTC catalogus. The verify stack seeds and publishes the BIG-REGISTRATIE zaaktype (the
@@ -7,10 +8,9 @@ import { expect, test } from '@playwright/test';
 test('a beheerder sees the published zaaktypen in the catalogus', async ({ page }) => {
   await page.goto('http://beheer/');
 
-  // The beheer portal redirects to the Keycloak medewerker realm login (same realm as behandel).
-  await page.locator('#username').fill('bram-beheerder');
-  await page.locator('#password').fill('test123');
-  await page.locator('#kc-login').click();
+  // The beheer portal redirects to the Keycloak medewerker realm login (same realm as behandel),
+  // which enforces MFA: password, then a TOTP code.
+  await loginMedewerker(page, 'bram-beheerder');
 
   await expect(page.getByRole('heading', { name: /Catalogus/i })).toBeVisible();
 
diff --git a/tests/e2e/default-fill.spec.ts b/tests/e2e/default-fill.spec.ts
index 8ff8d03..637fe57 100644
--- a/tests/e2e/default-fill.spec.ts
+++ b/tests/e2e/default-fill.spec.ts
@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test';
+import { loginMedewerker } from './medewerker-login';
 
 // S-15b: a beheerder edits the ACL default-fill in the beheer portal and gets a saved confirmation.
 // Runs against the shared verify stack; it edits + saves (the ACL store is in-memory, ADR-0026) and
@@ -6,10 +7,8 @@ import { expect, test } from '@playwright/test';
 test('a beheerder edits and saves the default-fill', async ({ page }) => {
   await page.goto('http://beheer/');
 
-  // Keycloak medewerker-realm login (same realm as behandel).
-  await page.locator('#username').fill('bram-beheerder');
-  await page.locator('#password').fill('test123');
-  await page.locator('#kc-login').click();
+  // Keycloak medewerker-realm login (same realm as behandel) — password + enforced TOTP.
+  await loginMedewerker(page, 'bram-beheerder');
 
   await expect(page.getByRole('heading', { name: /Catalogus/i })).toBeVisible();
 
diff --git a/tests/e2e/medewerker-login.ts b/tests/e2e/medewerker-login.ts
new file mode 100644
index 0000000..93bd879
--- /dev/null
+++ b/tests/e2e/medewerker-login.ts
@@ -0,0 +1,27 @@
+import { createHmac } from 'node:crypto';
+import type { Page } from '@playwright/test';
+
+// The medewerker realm enforces MFA (S-15c), so a staff login is two steps: password, then a TOTP
+// code. The realm export seeds every medewerker with this fixture secret — Keycloak HMACs the raw
+// secret bytes — so the e2e can compute a valid code instead of enrolling an authenticator.
+const OTP_SECRET = 'BIGMEDEWERKEROTPSEED';
+
+// RFC 6238 TOTP: HMAC-SHA1 over the 30-second counter, dynamically truncated to 6 digits.
+export function totp(secret = OTP_SECRET, at = Date.now()): string {
+  const counter = Buffer.alloc(8);
+  counter.writeBigUInt64BE(BigInt(Math.floor(at / 1000 / 30)));
+  const mac = createHmac('sha1', secret).update(counter).digest();
+  const offset = mac[mac.length - 1] & 0x0f;
+  return String((mac.readUInt32BE(offset) & 0x7fffffff) % 1_000_000).padStart(6, '0');
+}
+
+export async function loginMedewerker(page: Page, username: string): Promise<void> {
+  await page.locator('#username').fill(username);
+  await page.locator('#password').fill('test123');
+  await page.locator('#kc-login').click();
+
+  // Keycloak's conditional-OTP step. Its lookAheadWindow accepts the neighbouring counters, so a
+  // code computed just before a 30-second boundary still validates — no retry needed.
+  await page.locator('#otp').fill(totp());
+  await page.locator('#kc-login').click();
+}
diff --git a/tests/e2e/registration.spec.ts b/tests/e2e/registration.spec.ts
index 27167e5..a7a9c0e 100644
--- a/tests/e2e/registration.spec.ts
+++ b/tests/e2e/registration.spec.ts
@@ -1,4 +1,5 @@
 import { expect, request, test } from '@playwright/test';
+import { loginMedewerker } from './medewerker-login';
 
 // Walking-skeleton happy path (S-08d + S-09 + S-09b + S-12 + S-10a + S-19b-2): a zorgprofessional
 // logs in via mock DigiD and submits through the self-service portal → BFF → domain; the entry
@@ -76,9 +77,8 @@ test('DigiD submit → public INGEDIEND → documenten → behandelaar goedkeurt
   // — the S-12 flow that replaces the temporary admin endpoint. The staff tab switches to the
   // medewerker realm (a different Keycloak realm than the citizen's digid session).
   await staff.goto('http://behandel/');
-  await staff.locator('#username').fill('merel-behandelaar');
-  await staff.locator('#password').fill('test123');
-  await staff.locator('#kc-login').click();
+  // That realm enforces MFA (S-15c), so the behandelaar logs in with password + TOTP.
+  await loginMedewerker(staff, 'merel-behandelaar');
 
   await expect(staff.getByRole('heading', { name: /Werkbak/i })).toBeVisible();