diff --git a/api/database/migrations/2026_05_08_000001_add_failure_response_code_to_form_submissions.php b/api/database/migrations/2026_05_08_000001_add_failure_response_code_to_form_submissions.php
new file mode 100644
index 00000000..239f3480
--- /dev/null
+++ b/api/database/migrations/2026_05_08_000001_add_failure_response_code_to_form_submissions.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+/**
+ * Per RFC-WS-6 §Q3 v1.3 addition 2 + ARCH-BINDINGS §7.1 v1.2.
+ *
+ * Mirrors the FormBindingApplicatorException subclass classification onto
+ * a denormalised string column for response-shape rendering. Values:
+ *   - schema_config_error  (HTTP 422)
+ *   - temporary_error      (HTTP 503)
+ *   - data_integrity_error (HTTP 422)
+ *   - unknown_error        (HTTP 500)
+ *
+ * Read by the response renderer when apply_status='failed' to surface
+ * contextual user-facing error copy. The exception subclass on the
+ * action-failures row is the canonical source; this column is the
+ * response-shape driver. Both reference the same submission.id ULID.
+ *
+ * NULL when apply_status is not 'failed' (per the lifecycle:
+ * pending/completed/partial → no failure to classify).
+ */
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('form_submissions', function (Blueprint $table): void {
+            $table->string('failure_response_code', 40)
+                ->nullable()
+                ->after('apply_status');
+
+            $table->index('failure_response_code', 'fs_failure_response_code_idx');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('form_submissions', function (Blueprint $table): void {
+            $table->dropIndex('fs_failure_response_code_idx');
+            $table->dropColumn('failure_response_code');
+        });
+    }
+};
diff --git a/api/database/schema/mysql-schema.sql b/api/database/schema/mysql-schema.sql
index 190c5959..8daf9e65 100644
--- a/api/database/schema/mysql-schema.sql
+++ b/api/database/schema/mysql-schema.sql
@@ -761,6 +761,7 @@ CREATE TABLE `form_submissions` (
   `anonymised_at` timestamp NULL DEFAULT NULL,
   `identity_match_status` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL,
   `apply_status` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL,
+  `failure_response_code` varchar(40) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
   `apply_completed_at` timestamp NULL DEFAULT NULL,
   `search_index` mediumtext CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci,
   `created_at` timestamp NULL DEFAULT NULL,
@@ -778,6 +779,7 @@ CREATE TABLE `form_submissions` (
   KEY `fs_event_status_idx` (`event_id`,`status`),
   KEY `fs_schema_apply_status_idx` (`form_schema_id`,`apply_status`),
   KEY `fs_org_apply_status_idx` (`organisation_id`,`apply_status`),
+  KEY `fs_failure_response_code_idx` (`failure_response_code`),
   FULLTEXT KEY `fs_search_index_fulltext` (`search_index`),
   CONSTRAINT `form_submissions_event_id_foreign` FOREIGN KEY (`event_id`) REFERENCES `events` (`id`) ON DELETE SET NULL,
   CONSTRAINT `form_submissions_form_schema_id_foreign` FOREIGN KEY (`form_schema_id`) REFERENCES `form_schemas` (`id`) ON DELETE CASCADE,
@@ -1773,3 +1775,4 @@ INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (123,'2026_04_28_10
 INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (124,'2026_04_28_140000_add_kvk_number_to_companies_table',2);
 INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (125,'2026_04_28_180000_create_form_submission_action_failure_retry_attempts_table',2);
 INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (126,'2026_04_28_181000_add_exception_trace_to_form_submission_action_failures',2);
+INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (127,'2026_05_08_000001_add_failure_response_code_to_form_submissions',3);