diff --git a/app/Http/Controllers/Api/DatabasesController.php b/app/Http/Controllers/Api/DatabasesController.php
index 84486f6a9f..aa646abe32 100644
--- a/app/Http/Controllers/Api/DatabasesController.php
+++ b/app/Http/Controllers/Api/DatabasesController.php
@@ -3364,6 +3364,10 @@ class DatabasesController extends Controller
                 response: 409,
                 description: 'Another start, restart or import of this database is already in progress.',
             ),
+            new OA\Response(
+                response: 422,
+                description: 'The database cannot start yet, for example because a CA certificate is missing.',
+            ),
         ]
     )]
     public function action_deploy(Request $request)
@@ -3386,6 +3390,10 @@ class DatabasesController extends Controller
         if (str($database->status)->contains('running')) {
             return response()->json(['message' => 'Database is already running.'], 400);
         }
+        $prerequisiteError = StartDatabase::prerequisiteError($database);
+        if ($prerequisiteError !== null) {
+            return response()->json(['message' => $prerequisiteError], 422);
+        }
         $reservation = StartDatabase::reserveOperation($database);
         if ($reservation === null) {
             return response()->json(['message' => ResourceStartActivity::DATABASE_OPERATION_IN_PROGRESS_MESSAGE], 409);
@@ -3558,6 +3566,10 @@ class DatabasesController extends Controller
                 response: 409,
                 description: 'Another start, restart or import of this database is already in progress.',
             ),
+            new OA\Response(
+                response: 422,
+                description: 'The database cannot start yet, for example because a CA certificate is missing.',
+            ),
         ]
     )]
     public function action_restart(Request $request)
@@ -3577,6 +3589,10 @@ class DatabasesController extends Controller
 
         $this->authorize('manage', $database);
 
+        $prerequisiteError = StartDatabase::prerequisiteError($database);
+        if ($prerequisiteError !== null) {
+            return response()->json(['message' => $prerequisiteError], 422);
+        }
         $reservation = StartDatabase::reserveOperation($database);
         if ($reservation === null) {
             return response()->json(['message' => ResourceStartActivity::DATABASE_OPERATION_IN_PROGRESS_MESSAGE], 409);
diff --git a/app/Http/Controllers/Api/DeployController.php b/app/Http/Controllers/Api/DeployController.php
index b58a72d6ff..e5aac43b85 100644
--- a/app/Http/Controllers/Api/DeployController.php
+++ b/app/Http/Controllers/Api/DeployController.php
@@ -559,6 +559,11 @@ class DeployController extends Controller
                 } catch (AuthorizationException $e) {
                     return ['message' => 'Unauthorized to start this database.', 'deployment_uuid' => null];
                 }
+                $prerequisiteError = StartDatabase::prerequisiteError($resource);
+                if ($prerequisiteError !== null) {
+                    $message = $prerequisiteError;
+                    break;
+                }
                 $reservation = StartDatabase::reserveOperation($resource);
                 if ($reservation === null) {
                     $message = ResourceStartActivity::DATABASE_OPERATION_IN_PROGRESS_MESSAGE;
diff --git a/app/Livewire/Project/Database/Heading.php b/app/Livewire/Project/Database/Heading.php
index a7e8cfedd8..af6f7405e0 100644
--- a/app/Livewire/Project/Database/Heading.php
+++ b/app/Livewire/Project/Database/Heading.php
@@ -158,6 +158,7 @@ class Heading extends Component
                 return;
             }
             $this->auditDatabaseAction('ui.database.restarted');
+            $this->dispatch('info', 'Restarting database.');
             $this->markDeploymentRunning($activity);
             $this->js("window.dispatchEvent(new CustomEvent('startdatabase'))");
             $this->dispatch('activityMonitor', $activity->id, ServiceStatusChanged::class);
diff --git a/app/Mcp/Tools/Control.php b/app/Mcp/Tools/Control.php
index aca6b46564..65ec7ca4c1 100644
--- a/app/Mcp/Tools/Control.php
+++ b/app/Mcp/Tools/Control.php
@@ -141,6 +141,11 @@ class Control extends Tool
             return ['message' => 'Database is already running.'];
         }
 
+        $prerequisiteError = StartDatabase::prerequisiteError($database);
+        if ($prerequisiteError !== null) {
+            throw new \RuntimeException($prerequisiteError);
+        }
+
         $reservation = StartDatabase::reserveOperation($database);
         if ($reservation === null) {
             throw new \RuntimeException(ResourceStartActivity::DATABASE_OPERATION_IN_PROGRESS_MESSAGE);
diff --git a/resources/views/livewire/project/database/heading.blade.php b/resources/views/livewire/project/database/heading.blade.php
index abf58177c7..eec4add287 100644
--- a/resources/views/livewire/project/database/heading.blade.php
+++ b/resources/views/livewire/project/database/heading.blade.php
@@ -183,7 +183,7 @@
                     window.dispatchEvent(new CustomEvent('database-action-finished'));
                     return;
                 }
-                window.dispatchEvent(new CustomEvent('startdatabase'));
+                // start() opens the log dialog only when the start was queued.
                 try {
                     await $wire.$call('start');
                 } finally {
@@ -197,8 +197,7 @@
                     return;
                 }
                 window.dispatchEvent(new CustomEvent('database-busy'));
-                $wire.$dispatch('info', 'Restarting database.');
-                window.dispatchEvent(new CustomEvent('startdatabase'));
+                // restart() opens the log dialog only when the restart was queued.
                 try {
                     await $wire.$call('restart');
                 } finally {
diff --git a/tests/Feature/StartClickhouseVolumesTest.php b/tests/Feature/StartClickhouseVolumesTest.php
index faa13a0944..8193cdb95e 100644
--- a/tests/Feature/StartClickhouseVolumesTest.php
+++ b/tests/Feature/StartClickhouseVolumesTest.php
@@ -19,6 +19,7 @@ use App\Models\User;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Illuminate\Support\Facades\Process;
 use Illuminate\Support\Facades\Queue;
+use Illuminate\Support\Str;
 use Livewire\Livewire;
 use Spatie\Activitylog\Models\Activity;
 use Symfony\Component\Yaml\Yaml;
@@ -174,3 +175,43 @@ it('reads the data mount with sudo on a non-root server', function () {
     expect($database->fresh()->anonymousDataVolume())->toBe('3f1c0ffee')
         ->and(ranRemoteCommandContaining("sudo docker inspect --format '{{range .Mounts}}{{if eq .Destination \"/var/lib/clickhouse\"}}{{.Type}} {{.Name}}{{end}}{{end}}' '{$database->uuid}' 2>/dev/null || sudo true"))->toBeTrue();
 });
+
+it('rejects an API start or restart of a blocked database at once', function (string $method, string $path) {
+    $database = create_standalone_clickhouse($this->environment->id, $this->destination);
+    fakeClickhouseDataMount('3f1c0ffee');
+    $plainToken = Str::random(40);
+    $token = $this->owner->tokens()->create([
+        'name' => 'clickhouse-test',
+        'token' => hash('sha256', $plainToken),
+        'abilities' => ['*'],
+        'team_id' => $this->team->id,
+    ]);
+
+    $response = $this->withHeader('Authorization', 'Bearer '.$token->getKey().'|'.$plainToken)
+        ->json($method, str_replace('{uuid}', $database->uuid, $path));
+
+    $response->assertStatus(422);
+    expect($response->json('message'))->toContain('unnamed Docker volume 3f1c0ffee');
+    Queue::assertNothingPushed();
+})->with([
+    'start' => ['POST', '/api/v1/databases/{uuid}/start'],
+    'restart' => ['POST', '/api/v1/databases/{uuid}/restart'],
+]);
+
+it('reports a blocked database in the deploy API', function () {
+    $database = create_standalone_clickhouse($this->environment->id, $this->destination);
+    fakeClickhouseDataMount('3f1c0ffee');
+    $plainToken = Str::random(40);
+    $token = $this->owner->tokens()->create([
+        'name' => 'clickhouse-test',
+        'token' => hash('sha256', $plainToken),
+        'abilities' => ['*'],
+        'team_id' => $this->team->id,
+    ]);
+
+    $response = $this->withHeader('Authorization', 'Bearer '.$token->getKey().'|'.$plainToken)
+        ->postJson('/api/v1/deploy', ['uuid' => $database->uuid]);
+
+    expect($response->json('deployments.0.message'))->toContain('unnamed Docker volume 3f1c0ffee');
+    Queue::assertNothingPushed();
+});