From c011a11b485ac35a378ee682472bceb7b67f82fa Mon Sep 17 00:00:00 2001
From: nexxo <nexxo@clupilot.local>
Date: Sat, 25 Jul 2026 14:47:04 +0200
Subject: [PATCH] fix(portal): atomic seat-limit (row lock) +
 billing-day-anchored cancellation date

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 app/Livewire/ConfirmCancelPackage.php | 11 +++++---
 app/Livewire/Users.php                | 39 ++++++++++++++++++---------
 2 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/app/Livewire/ConfirmCancelPackage.php b/app/Livewire/ConfirmCancelPackage.php
index 82cd8d9..d79f27f 100644
--- a/app/Livewire/ConfirmCancelPackage.php
+++ b/app/Livewire/ConfirmCancelPackage.php
@@ -50,12 +50,15 @@ class ConfirmCancelPackage extends ModalComponent
     private function currentPeriodEnd(Instance $instance): \Illuminate\Support\Carbon
     {
         $start = $instance->order?->created_at ?? $instance->created_at ?? now();
-        $end = $start->copy();
-        while ($end->lessThanOrEqualTo(now())) {
-            $end->addMonthNoOverflow();
+
+        // Always add from the immutable start so the billing-day anchor is kept
+        // (chaining addMonth would drift a Jan-31 start to Feb-28 → Mar-28).
+        $months = 1;
+        while ($start->copy()->addMonthsNoOverflow($months)->lessThanOrEqualTo(now())) {
+            $months++;
         }
 
-        return $end;
+        return $start->copy()->addMonthsNoOverflow($months);
     }
 
     private function customer(): ?Customer
diff --git a/app/Livewire/Users.php b/app/Livewire/Users.php
index 456a864..00c0590 100644
--- a/app/Livewire/Users.php
+++ b/app/Livewire/Users.php
@@ -4,6 +4,7 @@ namespace App\Livewire;
 
 use App\Models\Customer;
 use App\Models\Seat;
+use Illuminate\Support\Facades\DB;
 use Livewire\Attributes\Layout;
 use Livewire\Attributes\Validate;
 use Livewire\Component;
@@ -44,28 +45,40 @@ class Users extends Component
 
         $data = $this->validate();
 
-        // Seat-limit guard against the plan allowance.
-        if ($this->usedSeats($customer) >= $this->seatLimit($customer)) {
+        // Serialize the limit check with the insert so two concurrent invites for
+        // the last free seat can't both pass (lock the customer row).
+        $result = DB::transaction(function () use ($customer, $data) {
+            $locked = Customer::query()->whereKey($customer->id)->lockForUpdate()->first();
+
+            if ($locked->seats()->where('email', $data['inviteEmail'])->exists()) {
+                return 'duplicate';
+            }
+            if ($this->usedSeats($locked) >= $this->seatLimit($locked)) {
+                return 'limit';
+            }
+
+            $locked->seats()->create([
+                'email' => $data['inviteEmail'],
+                'name' => $data['inviteName'] ?: null,
+                'role' => $data['inviteRole'],
+                'status' => 'invited',
+                'invited_at' => now(),
+            ]);
+
+            return 'ok';
+        });
+
+        if ($result === 'limit') {
             $this->addError('inviteEmail', __('users.limit_reached'));
 
             return;
         }
-
-        // One seat per email per customer.
-        if ($customer->seats()->where('email', $data['inviteEmail'])->exists()) {
+        if ($result === 'duplicate') {
             $this->addError('inviteEmail', __('users.duplicate'));
 
             return;
         }
 
-        $customer->seats()->create([
-            'email' => $data['inviteEmail'],
-            'name' => $data['inviteName'] ?: null,
-            'role' => $data['inviteRole'],
-            'status' => 'invited',
-            'invited_at' => now(),
-        ]);
-
         $this->reset('inviteEmail', 'inviteName', 'inviteRole');
         $this->inviteRole = 'member';
         $this->dispatch('notify', message: __('users.invited'));