diff --git a/backend/server.js b/backend/server.js
index 14c4cac9..5048b4a1 100644
--- a/backend/server.js
+++ b/backend/server.js
@@ -568,13 +568,20 @@ app.use('/api/admin/photo-export', require('./src/routes/adminPhotoExport'));
 app.use('/api/admin/css-templates', require('./src/routes/adminCssTemplates'));
 app.use('/api/admin/events', require('./src/routes/adminEventRename'));
 app.use('/api/admin/users', require('./src/routes/adminUsers'));
-// Customer portal (#354). When the `customerPortal` feature flag is
-// OFF, both the admin-facing /api/admin/customers/* surface AND the
-// customer-facing /api/customer/* surface return 410 Gone — turning
-// the toggle off in Settings → Features cleanly kills the feature
-// everywhere, not just in the UI. The frontend RequireFeature guard
-// + AdminSidebar visibility still apply for navigation, but a stale
-// tab or third-party API client can't bypass the gate.
+// Customer portal (#354). The customerPortal feature flag is enforced
+// in TWO places:
+//   1. Frontend: RequireFeature guards + AdminSidebar visibility
+//      (handles navigation cleanly when an admin is using the app).
+//   2. Backend: the requireCustomerPortalEnabled middleware below.
+//      Belt-and-braces — a stale tab, a saved bookmark, or any
+//      third-party API client trying to hit /api/customer/* or
+//      /api/admin/customers/* gets a 410 Gone the moment the toggle
+//      is flipped off. Includes /api/customer/auth/login: flag off
+//      = nobody can log in until the admin re-enables, including
+//      already-issued customers (their sessions still have valid
+//      JWTs but every API call returns 410 → frontend boots them
+//      out). PR #458 deliberate departure from the prior design
+//      that left login alive when the rest of the surface was off.
 const {
   requireCustomerPortalEnabled,
   requireCustomerPortalEnabledAdmin,
diff --git a/backend/src/routes/customerAuth.js b/backend/src/routes/customerAuth.js
index 2f459177..87eb7b4b 100644
--- a/backend/src/routes/customerAuth.js
+++ b/backend/src/routes/customerAuth.js
@@ -48,12 +48,15 @@ const TOKEN_TTL_SECONDS = 24 * 60 * 60; // mirrors admin tokens
 
 // ---- login -------------------------------------------------------------
 
-// The customerPortal feature flag deliberately does NOT gate this route.
-// Flipping the master toggle off in Settings → Features hides the admin
-// UI surface (sidebar entry, /admin/customers page) but does not revoke
-// access for customers who already accepted an invitation. To lock out
-// existing customers, deactivate their accounts individually
-// (customer_accounts.is_active = false) — which IS enforced below.
+// Flag-gate note: this route IS now gated by the customerPortal feature
+// flag via the requireCustomerPortalEnabled middleware mounted in
+// server.js (`app.use('/api/customer/auth', requireCustomerPortalEnabled, …)`).
+// When the admin flips the toggle off in Settings → Features, every
+// customer-side endpoint — including login — returns 410. The previous
+// design left login reachable while the rest of the surface was gated;
+// that was confusing and asymmetric. Single source of truth wins.
+// To lock out a specific customer without disabling the feature for
+// everyone, deactivate the account (customer_accounts.is_active = false).
 router.post('/login', [
   body('email').isEmail().normalizeEmail().withMessage('Valid email is required'),
   body('password').isString().notEmpty(),