fix(admin): enforce hosts.datacenter FK (restrictOnDelete) — no deactivation side-effect

The DB now refuses to orphan a host; datacenter delete pre-checks for a friendly
message and catches the constraint as the race backstop.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Livewire/Admin/ConfirmDeleteDatacenter.php

@@ -4,7 +4,7 @@ namespace App\Livewire\Admin;
 
 use App\Models\Datacenter;
 use App\Models\Host;
-use Illuminate\Support\Facades\DB;
+use Illuminate\Database\QueryException;
 use LivewireUI\Modal\ModalComponent;
 
 /**
@@ -30,24 +30,23 @@ class ConfirmDeleteDatacenter extends ModalComponent
 
     public function delete()
     {
-        // Serialize the guard with the delete: lock the datacenter row and
-        // re-check host membership inside the same transaction so a host created
-        // concurrently can't be orphaned (hosts.datacenter is a bare code).
-        DB::transaction(function () {
-            $dc = Datacenter::query()->where('uuid', $this->uuid)->lockForUpdate()->first();
-            if ($dc === null) {
-                return;
-            }
-            // Deactivate first so HostCreate's `exists:…,active,1` rule blocks any
-            // new host for this code while we finish deleting.
-            $dc->update(['active' => false]);
+        $dc = Datacenter::query()->where('uuid', $this->uuid)->first();
+        if ($dc === null) {
+            return $this->redirectRoute('admin.datacenters', navigate: true);
+        }
 
-            if (Host::query()->where('datacenter', $dc->code)->exists()) {
-                return; // still has hosts — leave it (deactivated)
-            }
+        // The hosts.datacenter → datacenters.code foreign key (restrictOnDelete)
+        // is the source of truth: the DB refuses to orphan a host. We pre-check
+        // for a friendly message and catch the constraint as the race backstop.
+        if (Host::query()->where('datacenter', $dc->code)->exists()) {
+            return $this->redirectRoute('admin.datacenters', navigate: true);
+        }
 
+        try {
             $dc->delete();
-        });
+        } catch (QueryException) {
+            // A host was created for this code concurrently — leave it intact.
+        }
 
         return $this->redirectRoute('admin.datacenters', navigate: true);
     }

database/migrations/2026_07_25_090008_add_datacenter_fk_to_hosts.php

@@ -0,0 +1,43 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+/**
+ * Enforce hosts.datacenter → datacenters.code at the database level so a
+ * datacenter with hosts can never be deleted (restrictOnDelete), closing the
+ * check-then-delete race in the admin console. All existing host codes were
+ * backfilled into datacenters by 2026_07_25_090001.
+ */
+return new class extends Migration
+{
+    public function up(): void
+    {
+        // Safety net: ensure every referenced code exists before adding the FK.
+        $now = now();
+        $missing = DB::table('hosts')
+            ->whereNotNull('datacenter')
+            ->whereNotIn('datacenter', fn ($q) => $q->from('datacenters')->select('code'))
+            ->distinct()->pluck('datacenter');
+        foreach ($missing as $code) {
+            DB::table('datacenters')->insert([
+                'uuid' => (string) \Illuminate\Support\Str::uuid(),
+                'code' => $code, 'name' => \Illuminate\Support\Str::upper($code),
+                'active' => true, 'created_at' => $now, 'updated_at' => $now,
+            ]);
+        }
+
+        Schema::table('hosts', function (Blueprint $table) {
+            $table->foreign('datacenter')->references('code')->on('datacenters')->restrictOnDelete();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('hosts', function (Blueprint $table) {
+            $table->dropForeign(['datacenter']);
+        });
+    }
+};