diff --git a/api/app/Enums/FormBuilder/ApplyStatus.php b/api/app/Enums/FormBuilder/ApplyStatus.php
new file mode 100644
index 00000000..a6e28edb
--- /dev/null
+++ b/api/app/Enums/FormBuilder/ApplyStatus.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums\FormBuilder;
+
+/**
+ * RFC-WS-6 §3 (Q4) — apply-state of a FormSubmission's binding pipeline.
+ * Distinct from {@see \App\Models\FormBuilder\FormSubmission::$identity_match_status},
+ * which tracks identity resolution (RFC O1).
+ */
+enum ApplyStatus: string
+{
+    case PENDING = 'pending';
+    case COMPLETED = 'completed';
+    case PARTIAL = 'partial';
+    case FAILED = 'failed';
+
+    public function isTerminal(): bool
+    {
+        return $this !== self::PENDING;
+    }
+
+    public function isOpen(): bool
+    {
+        return $this !== self::COMPLETED;
+    }
+
+    public function label(): string
+    {
+        return match ($this) {
+            self::PENDING => 'Wachtrij',
+            self::COMPLETED => 'Voltooid',
+            self::PARTIAL => 'Gedeeltelijk mislukt',
+            self::FAILED => 'Mislukt',
+        };
+    }
+}
diff --git a/api/app/Enums/FormBuilder/BindingTargetType.php b/api/app/Enums/FormBuilder/BindingTargetType.php
new file mode 100644
index 00000000..9f50c3de
--- /dev/null
+++ b/api/app/Enums/FormBuilder/BindingTargetType.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums\FormBuilder;
+
+/**
+ * RFC-WS-6 §4 (V1) — storage shape of a binding-target attribute, as
+ * declared by {@see \App\FormBuilder\Bindings\BindingTypeRegistry}.
+ *
+ * Source of truth for whether a target accepts the `Append` merge
+ * strategy (only COLLECTION does — V1 rejects scalar-append).
+ */
+enum BindingTargetType: string
+{
+    case SCALAR = 'scalar';
+    case COLLECTION = 'collection';
+    case RELATION = 'relation';
+}
diff --git a/api/app/Enums/FormBuilder/DismissalReasonType.php b/api/app/Enums/FormBuilder/DismissalReasonType.php
new file mode 100644
index 00000000..634bbccd
--- /dev/null
+++ b/api/app/Enums/FormBuilder/DismissalReasonType.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums\FormBuilder;
+
+/**
+ * RFC-WS-6 §4 (V2) — typed reason for dismissing a
+ * {@see \App\Models\FormBuilder\FormSubmissionActionFailure}.
+ *
+ * `manually_resolved` is intentionally absent — Resolve and Dismiss are
+ * separate workflows (resolved_at + resolved_note vs. dismissed_at +
+ * dismissed_reason_type/note).
+ */
+enum DismissalReasonType: string
+{
+    case SCHEMA_DELETED = 'schema_deleted';
+    case TARGET_ENTITY_DELETED = 'target_entity_deleted';
+    case BINDING_REMOVED = 'binding_removed';
+    case DUPLICATE_SUBMISSION = 'duplicate_submission';
+    case DATA_QUALITY_ISSUE = 'data_quality_issue';
+    case OTHER = 'other';
+
+    public function requiresNote(): bool
+    {
+        return $this === self::OTHER;
+    }
+
+    public function label(): string
+    {
+        return match ($this) {
+            self::SCHEMA_DELETED => 'Formulier verwijderd',
+            self::TARGET_ENTITY_DELETED => 'Doel-entiteit verwijderd',
+            self::BINDING_REMOVED => 'Binding verwijderd',
+            self::DUPLICATE_SUBMISSION => 'Dubbele inzending',
+            self::DATA_QUALITY_ISSUE => 'Datakwaliteit-probleem',
+            self::OTHER => 'Anders',
+        };
+    }
+}
diff --git a/api/tests/Unit/Enums/FormBuilder/ApplyStatusTest.php b/api/tests/Unit/Enums/FormBuilder/ApplyStatusTest.php
new file mode 100644
index 00000000..9a7f3f1f
--- /dev/null
+++ b/api/tests/Unit/Enums/FormBuilder/ApplyStatusTest.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit\Enums\FormBuilder;
+
+use App\Enums\FormBuilder\ApplyStatus;
+use PHPUnit\Framework\TestCase;
+
+final class ApplyStatusTest extends TestCase
+{
+    public function test_has_four_cases_with_stable_values(): void
+    {
+        $values = array_map(fn (ApplyStatus $case) => $case->value, ApplyStatus::cases());
+        sort($values);
+        $this->assertSame(['completed', 'failed', 'partial', 'pending'], $values);
+    }
+
+    public function test_is_terminal_truth_table(): void
+    {
+        $this->assertFalse(ApplyStatus::PENDING->isTerminal());
+        $this->assertTrue(ApplyStatus::COMPLETED->isTerminal());
+        $this->assertTrue(ApplyStatus::PARTIAL->isTerminal());
+        $this->assertTrue(ApplyStatus::FAILED->isTerminal());
+    }
+
+    public function test_is_open_truth_table(): void
+    {
+        $this->assertTrue(ApplyStatus::PENDING->isOpen());
+        $this->assertFalse(ApplyStatus::COMPLETED->isOpen());
+        $this->assertTrue(ApplyStatus::PARTIAL->isOpen());
+        $this->assertTrue(ApplyStatus::FAILED->isOpen());
+    }
+
+    public function test_label_returns_non_empty_dutch_string_for_each_case(): void
+    {
+        foreach (ApplyStatus::cases() as $case) {
+            $this->assertNotSame('', $case->label());
+        }
+    }
+}
diff --git a/api/tests/Unit/Enums/FormBuilder/BindingTargetTypeTest.php b/api/tests/Unit/Enums/FormBuilder/BindingTargetTypeTest.php
new file mode 100644
index 00000000..72f1d1ba
--- /dev/null
+++ b/api/tests/Unit/Enums/FormBuilder/BindingTargetTypeTest.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit\Enums\FormBuilder;
+
+use App\Enums\FormBuilder\BindingTargetType;
+use PHPUnit\Framework\TestCase;
+
+final class BindingTargetTypeTest extends TestCase
+{
+    public function test_has_three_cases_with_stable_values(): void
+    {
+        $values = array_map(fn (BindingTargetType $case) => $case->value, BindingTargetType::cases());
+        sort($values);
+        $this->assertSame(['collection', 'relation', 'scalar'], $values);
+    }
+
+    public function test_from_string_round_trip(): void
+    {
+        $this->assertSame(BindingTargetType::SCALAR, BindingTargetType::from('scalar'));
+        $this->assertSame(BindingTargetType::COLLECTION, BindingTargetType::from('collection'));
+        $this->assertSame(BindingTargetType::RELATION, BindingTargetType::from('relation'));
+    }
+}
diff --git a/api/tests/Unit/Enums/FormBuilder/DismissalReasonTypeTest.php b/api/tests/Unit/Enums/FormBuilder/DismissalReasonTypeTest.php
new file mode 100644
index 00000000..64e5e126
--- /dev/null
+++ b/api/tests/Unit/Enums/FormBuilder/DismissalReasonTypeTest.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit\Enums\FormBuilder;
+
+use App\Enums\FormBuilder\DismissalReasonType;
+use PHPUnit\Framework\TestCase;
+
+final class DismissalReasonTypeTest extends TestCase
+{
+    public function test_has_six_cases_with_stable_values(): void
+    {
+        $values = array_map(fn (DismissalReasonType $case) => $case->value, DismissalReasonType::cases());
+        sort($values);
+        $this->assertSame([
+            'binding_removed',
+            'data_quality_issue',
+            'duplicate_submission',
+            'other',
+            'schema_deleted',
+            'target_entity_deleted',
+        ], $values);
+    }
+
+    public function test_manually_resolved_is_intentionally_absent(): void
+    {
+        $values = array_map(fn (DismissalReasonType $case) => $case->value, DismissalReasonType::cases());
+        $this->assertNotContains('manually_resolved', $values);
+    }
+
+    public function test_requires_note_only_for_other(): void
+    {
+        $this->assertTrue(DismissalReasonType::OTHER->requiresNote());
+
+        foreach (DismissalReasonType::cases() as $case) {
+            if ($case === DismissalReasonType::OTHER) {
+                continue;
+            }
+            $this->assertFalse($case->requiresNote(), "{$case->value} must not require a note");
+        }
+    }
+
+    public function test_label_returns_non_empty_dutch_string_for_each_case(): void
+    {
+        foreach (DismissalReasonType::cases() as $case) {
+            $this->assertNotSame('', $case->label());
+        }
+    }
+}