diff --git a/src/Admin/OpenAI/AssistantAdmin.php b/src/Admin/OpenAI/AssistantAdmin.php
index a1d28181bdf..6ec0e6db902 100644
--- a/src/Admin/OpenAI/AssistantAdmin.php
+++ b/src/Admin/OpenAI/AssistantAdmin.php
@@ -25,6 +25,8 @@ protected function configureFormFields(FormMapper $form): void
                 ])
                 ->add('openAiId', TextType::class, [
                     'label' => 'ID OpenAI',
+                    'help_html' => true,
+                    'help' => 'ID commençant par <b>asst_</b>',
                 ])
             ->end()
         ;
diff --git a/src/Entity/OpenAI/Assistant.php b/src/Entity/OpenAI/Assistant.php
index 0fd3347c541..5727ec96d48 100644
--- a/src/Entity/OpenAI/Assistant.php
+++ b/src/Entity/OpenAI/Assistant.php
@@ -6,6 +6,7 @@
 use App\Entity\EntityIdentityTrait;
 use App\Entity\EntityTimestampableTrait;
 use App\OpenAI\Model\AssistantInterface;
+use App\Validator\OpenAI\ValidAssistantId;
 use Doctrine\ORM\Mapping as ORM;
 use Ramsey\Uuid\Uuid;
 use Ramsey\Uuid\UuidInterface;
@@ -35,6 +36,7 @@ class Assistant implements AssistantInterface
      * @ORM\Column(unique=true)
      *
      * @Assert\NotBlank
+     * @ValidAssistantId
      */
     public ?string $openAiId = null;
 
diff --git a/src/OpenAI/Client/Client.php b/src/OpenAI/Client/Client.php
index 3613387df45..240924b73cb 100755
--- a/src/OpenAI/Client/Client.php
+++ b/src/OpenAI/Client/Client.php
@@ -6,6 +6,9 @@
 use App\OpenAI\Enum\MessageRoleEnum;
 use App\OpenAI\Enum\RunStatusEnum;
 use OpenAI\Client as OpenAIClient;
+use OpenAI\Exceptions\ErrorException;
+use OpenAI\Exceptions\TransporterException;
+use OpenAI\Exceptions\UnserializableResponse;
 
 class Client implements ClientInterface
 {
@@ -16,6 +19,17 @@ public function __construct(string $openAIApiKey)
         $this->openAI = \OpenAI::client($openAIApiKey);
     }
 
+    public function hasAssistant(string $assistantId): bool
+    {
+        try {
+            $this->openAI->assistants()->retrieve($assistantId);
+
+            return true;
+        } catch (ErrorException|UnserializableResponse|TransporterException $e) {
+            return false;
+        }
+    }
+
     public function createThread(): string
     {
         $threadResponse = $this->openAI->threads()->create([]);
diff --git a/src/OpenAI/Client/ClientInterface.php b/src/OpenAI/Client/ClientInterface.php
index fa4a92218d3..ee5e2934a64 100755
--- a/src/OpenAI/Client/ClientInterface.php
+++ b/src/OpenAI/Client/ClientInterface.php
@@ -7,6 +7,8 @@
 
 interface ClientInterface
 {
+    public function hasAssistant(string $assistantId): bool;
+
     public function createThread(): string;
 
     public function createUserMessage(string $threadId, string $content): string;
diff --git a/src/Validator/OpenAI/ValidAssistantId.php b/src/Validator/OpenAI/ValidAssistantId.php
new file mode 100644
index 00000000000..a3d9c1c1e4a
--- /dev/null
+++ b/src/Validator/OpenAI/ValidAssistantId.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace App\Validator\OpenAI;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * @Annotation
+ * @Target({"PROPERTY", "METHOD", "ANNOTATION"})
+ */
+class ValidAssistantId extends Constraint
+{
+    public string $errorMessage = 'admin.openai.assistant.not_valid';
+}
diff --git a/src/Validator/OpenAI/ValidAssistantIdValidator.php b/src/Validator/OpenAI/ValidAssistantIdValidator.php
new file mode 100644
index 00000000000..70b9cf39edf
--- /dev/null
+++ b/src/Validator/OpenAI/ValidAssistantIdValidator.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace App\Validator\OpenAI;
+
+use App\OpenAI\Client\ClientInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
+use Symfony\Component\Validator\Exception\UnexpectedValueException;
+
+class ValidAssistantIdValidator extends ConstraintValidator
+{
+    public function __construct(private readonly ClientInterface $client)
+    {
+    }
+
+    public function validate($value, Constraint $constraint)
+    {
+        if (!$constraint instanceof ValidAssistantId) {
+            throw new UnexpectedTypeException($constraint, ValidAssistantId::class);
+        }
+
+        if (null === $value) {
+            return;
+        }
+
+        if (!\is_string($value)) {
+            throw new UnexpectedValueException($value, 'string');
+        }
+
+        if (!$this->client->hasAssistant($value)) {
+            $this->context
+                ->buildViolation($constraint->errorMessage)
+                ->setParameter('{{ value }}', $value)
+                ->addViolation()
+            ;
+        }
+    }
+}
diff --git a/tests/OpenAI/Client/Client.php b/tests/OpenAI/Client/Client.php
index 7c5678e2524..9aa50a7b326 100644
--- a/tests/OpenAI/Client/Client.php
+++ b/tests/OpenAI/Client/Client.php
@@ -20,6 +20,11 @@ public function __construct()
         $this->faker = Factory::create('fr_FR');
     }
 
+    public function hasAssistant(string $assistantId): bool
+    {
+        return str_starts_with($assistantId, 'asst_');
+    }
+
     public function createThread(): string
     {
         return uniqid('thread_');
diff --git a/translations/validators.fr.yml b/translations/validators.fr.yml
index 44944bcdd16..aa62cc21603 100644
--- a/translations/validators.fr.yml
+++ b/translations/validators.fr.yml
@@ -620,3 +620,5 @@ admin.adherent.renaissance.membership_type.invalid_choice: Ce type d'adhésion n
 
 admin.membership.cotisation_amount_choice.not_blank: Veuillez spécifier un montant de cotisation.
 admin.membership.cotisation_amount_choice.invalid_choice: Ce montant de cotisation est invalide.
+
+admin.openai.assistant.not_valid: Impossible de récupérer les données de l'assistant "{{ value }}".