diff --git a/app/Http/Controllers/CustomFilterController.php b/app/Http/Controllers/CustomFilterController.php
index e42344638..39d8e6d96 100644
--- a/app/Http/Controllers/CustomFilterController.php
+++ b/app/Http/Controllers/CustomFilterController.php
@@ -145,6 +145,8 @@ class CustomFilterController extends Controller
                 ->toArray();
 
             if (! empty($existingKeywords)) {
+                DB::rollBack();
+
                 return response()->json([
                     'error' => 'Duplicate keywords found',
                     'message' => 'The following keywords already exist: '.implode(', ', $existingKeywords),
@@ -314,6 +316,8 @@ class CustomFilterController extends Controller
 
             $keywordIds = collect($validatedData['keywords_attributes'])->pluck('id')->filter()->toArray();
             if (count($keywordIds) && ! CustomFilterKeyword::whereCustomFilterId($filter->id)->whereIn('id', $keywordIds)->count()) {
+                DB::rollBack();
+
                 return response()->json([
                     'error' => 'Record not found',
                 ], 404);
@@ -336,6 +340,8 @@ class CustomFilterController extends Controller
                     ->toArray();
 
                 if (! empty($existingKeywords)) {
+                    DB::rollBack();
+
                     return response()->json([
                         'error' => 'Duplicate keywords found',
                         'message' => 'The following keywords already exist: '.implode(', ', $existingKeywords),
@@ -396,6 +402,8 @@ class CustomFilterController extends Controller
                             ->first();
 
                         if (! isset($keywordData['_destroy']) && $filter->keywords()->pluck('id')->search($keywordData['id']) === false) {
+                            DB::rollBack();
+
                             return response()->json([
                                 'error' => 'Duplicate keywords found',
                                 'message' => 'The following keywords already exist: '.$keywordData['keyword'],
@@ -427,6 +435,8 @@ class CustomFilterController extends Controller
                         $maxKeywordsPerFilter = CustomFilter::getMaxKeywordsPerFilter();
 
                         if ($existingKeywordCount >= $maxKeywordsPerFilter) {
+                            DB::rollBack();
+
                             return response()->json([
                                 'error' => 'Keyword limit exceeded',
                                 'message' => 'A filter can have a maximum of '.$maxKeywordsPerFilter.' keywords.',
diff --git a/tests/Feature/Api/CustomFilterTransactionTest.php b/tests/Feature/Api/CustomFilterTransactionTest.php
new file mode 100644
index 000000000..0b9db3351
--- /dev/null
+++ b/tests/Feature/Api/CustomFilterTransactionTest.php
@@ -0,0 +1,100 @@
+<?php
+
+use App\Models\CustomFilter;
+use App\Models\User;
+use Illuminate\Foundation\Testing\LazilyRefreshDatabase;
+use Illuminate\Support\Facades\Cache;
+use Illuminate\Support\Facades\DB;
+use Laravel\Passport\Passport;
+
+uses(LazilyRefreshDatabase::class);
+
+/*
+|--------------------------------------------------------------------------
+| Custom filter transaction hygiene
+|--------------------------------------------------------------------------
+|
+| store()/update() open a manual DB::beginTransaction() and return early
+| (duplicate keyword, keyword not found) without a matching commit or
+| rollback. That leaves the transaction open on the connection past the
+| end of the request. Assert the connection's transaction level is back
+| to where it started once the early-exit response is returned.
+|
+*/
+
+function resetCustomFilterTransactionTestLimitStatics(): void
+{
+    foreach (['maxCreatePerHour', 'maxUpdatesPerHour', 'maxFiltersPerUser', 'maxKeywordsPerFilter'] as $prop) {
+        $ref = new ReflectionProperty(CustomFilter::class, $prop);
+        $ref->setAccessible(true);
+        $ref->setValue(null, null);
+    }
+}
+
+beforeEach(function () {
+    Cache::flush();
+    config(['instance.custom_filters.max_create_per_hour' => 100]);
+    config(['instance.custom_filters.max_updates_per_hour' => 100]);
+    config(['instance.custom_filters.max_filters_per_user' => 100]);
+    config(['instance.custom_filters.max_keywords_per_filter' => 100]);
+    resetCustomFilterTransactionTestLimitStatics();
+});
+
+it('does not leave an open transaction when store() rejects a duplicate keyword', function () {
+    $user = User::factory()->create();
+    $user->refresh();
+    Passport::actingAs($user, ['read', 'write']);
+
+    $filter = CustomFilter::create([
+        'title' => 'existing',
+        'context' => ['home'],
+        'action' => CustomFilter::ACTION_WARN,
+        'profile_id' => $user->profile_id,
+    ]);
+    $filter->keywords()->create(['keyword' => 'alpha', 'whole_word' => true]);
+
+    $levelBefore = DB::transactionLevel();
+
+    $this->postJson('/api/v2/filters', [
+        'title' => 'new filter',
+        'context' => ['home'],
+        'filter_action' => 'warn',
+        'keywords_attributes' => [
+            ['keyword' => 'alpha', 'whole_word' => true],
+        ],
+    ])->assertStatus(422)->assertJson(['error' => 'Duplicate keywords found']);
+
+    expect(DB::transactionLevel())->toBe($levelBefore);
+});
+
+it('does not leave an open transaction when update() rejects a duplicate keyword', function () {
+    $user = User::factory()->create();
+    $user->refresh();
+    Passport::actingAs($user, ['read', 'write']);
+
+    $other = CustomFilter::create([
+        'title' => 'other',
+        'context' => ['home'],
+        'action' => CustomFilter::ACTION_WARN,
+        'profile_id' => $user->profile_id,
+    ]);
+    $other->keywords()->create(['keyword' => 'apple', 'whole_word' => true]);
+
+    $target = CustomFilter::create([
+        'title' => 'target',
+        'context' => ['home'],
+        'action' => CustomFilter::ACTION_WARN,
+        'profile_id' => $user->profile_id,
+    ]);
+    $target->keywords()->create(['keyword' => 'banana', 'whole_word' => true]);
+
+    $levelBefore = DB::transactionLevel();
+
+    $this->putJson('/api/v2/filters/'.$target->id, [
+        'keywords_attributes' => [
+            ['keyword' => 'apple', 'whole_word' => true],
+        ],
+    ])->assertStatus(422)->assertJson(['error' => 'Duplicate keywords found']);
+
+    expect(DB::transactionLevel())->toBe($levelBefore);
+});