diff --git a/app/Livewire/Admin/Datacenters.php b/app/Livewire/Admin/Datacenters.php
index b91a6ac..7160efb 100644
--- a/app/Livewire/Admin/Datacenters.php
+++ b/app/Livewire/Admin/Datacenters.php
@@ -21,10 +21,14 @@ class Datacenters extends Component
 
     public function save(): void
     {
+        // Normalize before validating so the unique check matches how the row is
+        // stored — otherwise `FSN` passes the rule but the lowercased insert collides.
+        $this->code = strtolower(trim($this->code));
+
         $data = $this->validate();
 
         Datacenter::create([
-            'code' => strtolower($data['code']),
+            'code' => $data['code'],
             'name' => $data['name'],
             'location' => $data['location'] ?: null,
             'active' => true,
diff --git a/app/Models/Customer.php b/app/Models/Customer.php
index 1d9379c..1ae7df5 100644
--- a/app/Models/Customer.php
+++ b/app/Models/Customer.php
@@ -7,8 +7,10 @@ use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\UniqueConstraintViolationException;
 use Illuminate\Support\Facades\Hash;
 use Illuminate\Support\Str;
+use RuntimeException;
 
 class Customer extends Model
 {
@@ -32,20 +34,49 @@ class Customer extends Model
         return $this->hasMany(Instance::class);
     }
 
-    /** Find or create the portal login account for this customer and link it. */
+    /**
+     * Find or create the portal login account for this customer and link it.
+     * Race-safe against the unique email index, and never links an operator
+     * account — that would carry admin authorization into an impersonated
+     * "customer" session.
+     */
     public function ensureUser(): User
     {
         if ($this->user) {
             return $this->user;
         }
 
-        $user = User::query()->firstOrCreate(
-            ['email' => $this->email],
-            ['name' => $this->name, 'password' => Hash::make(Str::random(40)), 'is_admin' => false],
-        );
+        if (($existing = User::query()->where('email', $this->email)->first()) !== null) {
+            $this->assertNotAdmin($existing);
+            $this->update(['user_id' => $existing->id]);
+
+            return $existing;
+        }
+
+        try {
+            $user = User::query()->create([
+                'email' => $this->email,
+                'name' => $this->name,
+                'password' => Hash::make(Str::random(40)),
+                'is_admin' => false,
+            ]);
+        } catch (UniqueConstraintViolationException) {
+            // Concurrent first-time creation — re-fetch and link the winner.
+            $user = User::query()->where('email', $this->email)->firstOrFail();
+            $this->assertNotAdmin($user);
+        }
 
         $this->update(['user_id' => $user->id]);
 
         return $user->refresh();
     }
+
+    private function assertNotAdmin(User $user): void
+    {
+        if ($user->is_admin) {
+            throw new RuntimeException(
+                "Refusing to link admin account {$user->email} as a portal login for customer {$this->id}.",
+            );
+        }
+    }
 }
diff --git a/resources/views/layouts/portal-app.blade.php b/resources/views/layouts/portal-app.blade.php
index 271e87c..1d2d848 100644
--- a/resources/views/layouts/portal-app.blade.php
+++ b/resources/views/layouts/portal-app.blade.php
@@ -13,10 +13,13 @@
         {{-- Admin impersonation banner — visible on every portal page until the admin returns. --}}
         <div class="flex flex-wrap items-center justify-center gap-x-3 gap-y-1 border-b border-warning-border bg-warning-bg px-4 py-2 text-center text-sm font-medium text-ink">
             <span>{{ __('impersonate.banner', ['name' => auth()->user()->name]) }}</span>
-            <a href="{{ route('impersonate.leave') }}" class="inline-flex items-center gap-1 rounded-pill border border-warning-border px-3 py-0.5 font-semibold text-warning underline-offset-2 hover:underline">
-                <x-ui.icon name="log-out" class="size-4" />
-                {{ __('impersonate.leave') }}
-            </a>
+            <form method="POST" action="{{ route('impersonate.leave') }}" class="inline">
+                @csrf
+                <button type="submit" class="inline-flex items-center gap-1 rounded-pill border border-warning-border px-3 py-0.5 font-semibold text-warning underline-offset-2 hover:underline">
+                    <x-ui.icon name="log-out" class="size-4" />
+                    {{ __('impersonate.leave') }}
+                </button>
+            </form>
         </div>
     @endif
     <div class="flex min-h-screen lg:h-screen lg:overflow-hidden">
diff --git a/resources/views/livewire/admin/customers.blade.php b/resources/views/livewire/admin/customers.blade.php
index db749be..92fe163 100644
--- a/resources/views/livewire/admin/customers.blade.php
+++ b/resources/views/livewire/admin/customers.blade.php
@@ -28,11 +28,14 @@
                                 <td class="px-4 py-3 font-mono text-body">{{ $r['mrr'] }}</td>
                                 <td class="px-4 py-3"><x-ui.badge :status="$r['status']">{{ __('admin.status.'.$r['status']) }}</x-ui.badge></td>
                                 <td class="px-4 py-3 text-right">
-                                    <a href="{{ route('admin.impersonate', $r['uuid']) }}"
-                                       class="inline-flex items-center gap-1.5 rounded-md border border-line px-3 py-1.5 text-xs font-semibold text-body hover:border-accent-border hover:text-accent-text">
-                                        <x-ui.icon name="log-out" class="size-3.5" />
-                                        {{ __('admin.impersonate') }}
-                                    </a>
+                                    <form method="POST" action="{{ route('admin.impersonate', $r['uuid']) }}" class="inline">
+                                        @csrf
+                                        <button type="submit"
+                                                class="inline-flex items-center gap-1.5 rounded-md border border-line px-3 py-1.5 text-xs font-semibold text-body hover:border-accent-border hover:text-accent-text">
+                                            <x-ui.icon name="log-out" class="size-3.5" />
+                                            {{ __('admin.impersonate') }}
+                                        </button>
+                                    </form>
                                 </td>
                             </tr>
                         @empty
diff --git a/routes/web.php b/routes/web.php
index cdf3cda..ba9dce3 100644
--- a/routes/web.php
+++ b/routes/web.php
@@ -46,7 +46,8 @@ Route::middleware('auth')->group(function () {
     Route::get('/support', Support::class)->name('support');
 
     // Return from an admin impersonation session (accessible as the customer user).
-    Route::get('/impersonate/leave', [ImpersonationController::class, 'leave'])->name('impersonate.leave');
+    // POST so Laravel's CSRF middleware protects the identity change.
+    Route::post('/impersonate/leave', [ImpersonationController::class, 'leave'])->name('impersonate.leave');
 });
 
 // Admin / operator console — dark theme, gated to is_admin users (R1/R2, R13).
@@ -58,7 +59,8 @@ Route::middleware(['auth', 'admin'])->prefix('admin')->name('admin.')->group(fun
     Route::get('/hosts/create', Admin\HostCreate::class)->name('hosts.create');
     Route::get('/hosts/{host}', Admin\HostDetail::class)->name('hosts.show');
     Route::get('/datacenters', Admin\Datacenters::class)->name('datacenters');
-    Route::get('/impersonate/{customer}', [ImpersonationController::class, 'start'])->name('impersonate');
+    // POST so the identity change is CSRF-protected (a GET could be forced cross-site).
+    Route::post('/impersonate/{customer}', [ImpersonationController::class, 'start'])->name('impersonate');
     Route::get('/provisioning', Admin\Provisioning::class)->name('provisioning');
     Route::get('/revenue', Admin\Revenue::class)->name('revenue');
 });
diff --git a/tests/Feature/ImpersonationTest.php b/tests/Feature/ImpersonationTest.php
index 7423219..3ec8758 100644
--- a/tests/Feature/ImpersonationTest.php
+++ b/tests/Feature/ImpersonationTest.php
@@ -10,7 +10,7 @@ it('lets an admin impersonate a customer and returns to the admin session', func
     $customer = Customer::factory()->create(['email' => 'c@imp.test', 'name' => 'Imp Kunde']);
 
     $this->actingAs($admin)
-        ->get(route('admin.impersonate', $customer->uuid))
+        ->post(route('admin.impersonate', $customer->uuid))
         ->assertRedirect(route('dashboard'));
 
     $customer->refresh();
@@ -19,7 +19,7 @@ it('lets an admin impersonate a customer and returns to the admin session', func
         ->and(session('impersonator_id'))->toBe($admin->id);
 
     // Return to the admin session.
-    $this->get(route('impersonate.leave'))->assertRedirect(route('admin.overview'));
+    $this->post(route('impersonate.leave'))->assertRedirect(route('admin.overview'));
 
     expect(auth()->id())->toBe($admin->id)
         ->and(session()->has('impersonator_id'))->toBeFalse();
@@ -33,17 +33,25 @@ it('reuses an existing portal user with the same email', function () {
     expect($customer->fresh()->user_id)->toBe($existing->id);
 });
 
+it('refuses to link an admin account as a portal login', function () {
+    $adminUser = User::factory()->create(['email' => 'ops@imp.test', 'is_admin' => true]);
+    $customer = Customer::factory()->create(['email' => 'ops@imp.test']);
+
+    expect(fn () => $customer->ensureUser())->toThrow(RuntimeException::class);
+    expect($customer->fresh()->user_id)->toBeNull();
+});
+
 it('forbids a non-admin from impersonating', function () {
     $user = User::factory()->create(['is_admin' => false]);
     $customer = Customer::factory()->create();
 
     $this->actingAs($user)
-        ->get(route('admin.impersonate', $customer->uuid))
+        ->post(route('admin.impersonate', $customer->uuid))
         ->assertForbidden();
 });
 
 it('gates impersonation start to authenticated users', function () {
     $customer = Customer::factory()->create();
 
-    $this->get(route('admin.impersonate', $customer->uuid))->assertRedirect('/login');
+    $this->post(route('admin.impersonate', $customer->uuid))->assertRedirect('/login');
 });