diff --git a/app/Http/Controllers/Settings/CategoryController.php b/app/Http/Controllers/Settings/CategoryController.php
index 8b92ea00..aa96248a 100644
--- a/app/Http/Controllers/Settings/CategoryController.php
+++ b/app/Http/Controllers/Settings/CategoryController.php
@@ -107,7 +107,8 @@ class CategoryController extends Controller
     {
         if (! str_contains($exception->getMessage(), 'categories_user_id_name_unique')
             && ! str_contains($exception->getMessage(), 'categories_user_id_name_active_unique')
-            && ! str_contains($exception->getMessage(), 'categories_user_id_parent_name_active_unique')) {
+            && ! str_contains($exception->getMessage(), 'categories_user_id_parent_name_active_unique')
+            && ! str_contains($exception->getMessage(), 'categories_space_id_parent_name_active_unique')) {
             throw $exception;
         }
 
diff --git a/database/migrations/2026_07_06_130000_rescope_unique_indexes_to_space.php b/database/migrations/2026_07_06_130000_rescope_unique_indexes_to_space.php
new file mode 100644
index 00000000..81f72a1a
--- /dev/null
+++ b/database/migrations/2026_07_06_130000_rescope_unique_indexes_to_space.php
@@ -0,0 +1,67 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Category, label and saved-filter names were unique per user. Now that a
+     * user can own several spaces (each seeded with the same default category
+     * names), those constraints must be per space instead — otherwise creating a
+     * second space collides with the first space's categories. Runs after the
+     * backfill, so space_id is already populated on every existing row.
+     *
+     * The old composite uniques also served as the index MySQL requires for the
+     * `user_id` foreign key, so we add a plain `user_id` index before dropping
+     * them (and drop it again on rollback once the composite is restored).
+     */
+    public function up(): void
+    {
+        Schema::table('categories', function (Blueprint $table) {
+            $table->index('user_id', 'categories_user_id_index');
+            $table->dropUnique('categories_user_id_parent_name_active_unique');
+            $table->unique(
+                ['space_id', 'parent_unique_marker', 'name', 'active_unique_marker'],
+                'categories_space_id_parent_name_active_unique',
+            );
+        });
+
+        Schema::table('labels', function (Blueprint $table) {
+            $table->index('user_id', 'labels_user_id_index');
+            $table->dropUnique('labels_user_id_name_deleted_at_unique');
+            $table->unique(['space_id', 'name', 'deleted_at'], 'labels_space_id_name_deleted_at_unique');
+        });
+
+        Schema::table('saved_filters', function (Blueprint $table) {
+            $table->index('user_id', 'saved_filters_user_id_index');
+            $table->dropUnique('saved_filters_user_id_name_unique');
+            $table->unique(['space_id', 'name'], 'saved_filters_space_id_name_unique');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('categories', function (Blueprint $table) {
+            $table->dropUnique('categories_space_id_parent_name_active_unique');
+            $table->unique(
+                ['user_id', 'parent_unique_marker', 'name', 'active_unique_marker'],
+                'categories_user_id_parent_name_active_unique',
+            );
+            $table->dropIndex('categories_user_id_index');
+        });
+
+        Schema::table('labels', function (Blueprint $table) {
+            $table->dropUnique('labels_space_id_name_deleted_at_unique');
+            $table->unique(['user_id', 'name', 'deleted_at'], 'labels_user_id_name_deleted_at_unique');
+            $table->dropIndex('labels_user_id_index');
+        });
+
+        Schema::table('saved_filters', function (Blueprint $table) {
+            $table->dropUnique('saved_filters_space_id_name_unique');
+            $table->unique(['user_id', 'name'], 'saved_filters_user_id_name_unique');
+            $table->dropIndex('saved_filters_user_id_index');
+        });
+    }
+};
diff --git a/tests/Feature/Spaces/SpaceManagementTest.php b/tests/Feature/Spaces/SpaceManagementTest.php
index b114d63f..b9749fd3 100644
--- a/tests/Feature/Spaces/SpaceManagementTest.php
+++ b/tests/Feature/Spaces/SpaceManagementTest.php
@@ -1,5 +1,6 @@
 <?php
 
+use App\Actions\CreateDefaultCategories;
 use App\Features\Spaces;
 use App\Models\Account;
 use App\Models\Category;
@@ -11,6 +12,11 @@ it('creates a space, seeds its categories and switches to it', function () {
     $user = User::factory()->onboarded()->create();
     Feature::for($user)->activate(Spaces::class);
 
+    // The personal space already carries the default categories (as it would
+    // after registration), so seeding the same names into a second space must
+    // NOT collide — category name uniqueness is per space, not per user.
+    app(CreateDefaultCategories::class)->handle($user, $user->personalSpace);
+
     $this->actingAs($user)->post('/settings/spaces', ['name' => 'Acme'])
         ->assertRedirect();
 
@@ -18,7 +24,8 @@ it('creates a space, seeds its categories and switches to it', function () {
 
     expect($space)->not->toBeNull()
         ->and($user->fresh()->current_space_id)->toBe($space->id)
-        ->and(Category::where('space_id', $space->id)->count())->toBeGreaterThan(0);
+        ->and(Category::where('space_id', $space->id)->count())->toBeGreaterThan(0)
+        ->and(Category::where('space_id', $user->personalSpace->id)->count())->toBeGreaterThan(0);
 });
 
 it('forbids creating a space without the spaces feature', function () {