diff --git a/app/Livewire/Pages/Bio/Edit.php b/app/Livewire/Pages/Bio/Edit.php
index 037fb83..f086e85 100644
--- a/app/Livewire/Pages/Bio/Edit.php
+++ b/app/Livewire/Pages/Bio/Edit.php
@@ -43,10 +43,30 @@ class Edit extends Component
     {
         $page = BioPage::findOrFail($this->pageId);
 
+        $newSlug = $state['slug'] ?? $page->slug;
+
+        $slugTaken = BioPage::where('workspace_id', $page->workspace_id)
+            ->where('slug', $newSlug)
+            ->where('id', '!=', $page->id)
+            ->whereNull('deleted_at')
+            ->exists();
+
+        if ($slugTaken) {
+            $this->dispatch('toast', message: 'Slug "' . $newSlug . '" ist bereits vergeben.', type: 'error');
+
+            return;
+        }
+
+        if (! preg_match('/^[a-zA-Z0-9_-]{1,64}$/', $newSlug)) {
+            $this->dispatch('toast', message: 'Slug: nur Buchstaben, Zahlen, - und _. Max 64 Zeichen.', type: 'error');
+
+            return;
+        }
+
         $displayName = $state['profile']['displayName'] ?? '';
 
         $page->update([
-            'slug'         => $state['slug'] ?? $page->slug,
+            'slug'         => $newSlug,
             'title'        => ['en' => $displayName, 'de' => $displayName],
             'is_published' => false,
             'theme'        => [
diff --git a/database/migrations/2026_05_17_600000_bio_pages_unique_workspace_slug.php b/database/migrations/2026_05_17_600000_bio_pages_unique_workspace_slug.php
new file mode 100644
index 0000000..68eb336
--- /dev/null
+++ b/database/migrations/2026_05_17_600000_bio_pages_unique_workspace_slug.php
@@ -0,0 +1,25 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('bio_pages', function (Blueprint $table) {
+            // Slug must be unique within a workspace regardless of subdomain_host.
+            // The old (subdomain_host, slug) unique allowed MySQL NULL bypass —
+            // two rows with NULL subdomain_host + same slug were not caught.
+            $table->unique(['workspace_id', 'slug'], 'bio_pages_workspace_slug_unique');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('bio_pages', function (Blueprint $table) {
+            $table->dropUnique('bio_pages_workspace_slug_unique');
+        });
+    }
+};