diff --git a/api/app/Models/FormBuilder/FormSubmission.php b/api/app/Models/FormBuilder/FormSubmission.php
index c2641ab5..e3ad9325 100644
--- a/api/app/Models/FormBuilder/FormSubmission.php
+++ b/api/app/Models/FormBuilder/FormSubmission.php
@@ -6,6 +6,8 @@ namespace App\Models\FormBuilder;
 
 use App\Enums\FormBuilder\FormSubmissionReviewStatus;
 use App\Enums\FormBuilder\FormSubmissionStatus;
+use App\Models\Event;
+use App\Models\Organisation;
 use App\Models\User;
 use Illuminate\Database\Eloquent\Concerns\HasUlids;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
@@ -27,6 +29,8 @@ final class FormSubmission extends Model
 
     protected $fillable = [
         'form_schema_id',
+        'organisation_id',
+        'event_id',
         'subject_type',
         'subject_id',
         'submitted_by_user_id',
@@ -77,6 +81,16 @@ final class FormSubmission extends Model
         return $this->belongsTo(FormSchema::class, 'form_schema_id');
     }
 
+    public function organisation(): BelongsTo
+    {
+        return $this->belongsTo(Organisation::class);
+    }
+
+    public function event(): BelongsTo
+    {
+        return $this->belongsTo(Event::class);
+    }
+
     public function subject(): MorphTo
     {
         return $this->morphTo();
diff --git a/api/app/Observers/FormBuilder/FormSubmissionObserver.php b/api/app/Observers/FormBuilder/FormSubmissionObserver.php
new file mode 100644
index 00000000..73795580
--- /dev/null
+++ b/api/app/Observers/FormBuilder/FormSubmissionObserver.php
@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Observers\FormBuilder;
+
+use App\Models\Event;
+use App\Models\FormBuilder\FormSubmission;
+use App\Models\Scopes\OrganisationScope;
+
+/**
+ * Populates the denormalized organisation_id and event_id columns on
+ * form_submissions per ARCH-CONSOLIDATION-ADDENDUM-2026-04-24.md Q2.
+ *
+ * organisation_id resolves from the parent schema (always present —
+ * form_schemas carries the tenant column directly). event_id resolves
+ * to the schema owner when owner_type === 'event'; otherwise it falls
+ * back to the active route's {event} parameter (for submissions created
+ * inside an events/{event}/... route, e.g. the portal flow). Purposes
+ * like user_profile or signature_contract that have neither an
+ * event-owned schema nor an event-scoped route produce event_id = null,
+ * which is valid per migration 2026_04_24_200000.
+ */
+final class FormSubmissionObserver
+{
+    public function creating(FormSubmission $submission): void
+    {
+        if ($submission->organisation_id === null) {
+            $submission->organisation_id = $this->resolveOrganisationId($submission);
+        }
+
+        if ($submission->event_id === null) {
+            $submission->event_id = $this->resolveEventId($submission);
+        }
+    }
+
+    private function resolveOrganisationId(FormSubmission $submission): ?string
+    {
+        if ($submission->form_schema_id === null) {
+            return null;
+        }
+
+        $schema = $submission->relationLoaded('schema')
+            ? $submission->getRelation('schema')
+            : \App\Models\FormBuilder\FormSchema::query()
+                ->withoutGlobalScope(OrganisationScope::class)
+                ->find($submission->form_schema_id);
+
+        return $schema?->organisation_id;
+    }
+
+    private function resolveEventId(FormSubmission $submission): ?string
+    {
+        $schema = $submission->relationLoaded('schema')
+            ? $submission->getRelation('schema')
+            : \App\Models\FormBuilder\FormSchema::query()
+                ->withoutGlobalScope(OrganisationScope::class)
+                ->find($submission->form_schema_id);
+
+        if ($schema !== null && $schema->owner_type === 'event' && $schema->owner_id !== null) {
+            return (string) $schema->owner_id;
+        }
+
+        // Fall back to the active route — portal + organizer flows that
+        // scope submissions by the current event via /events/{event}/...
+        $route = request()?->route();
+        if ($route === null) {
+            return null;
+        }
+
+        $eventParam = $route->parameter('event');
+        if ($eventParam instanceof Event) {
+            return (string) $eventParam->id;
+        }
+        if (is_string($eventParam) && $eventParam !== '') {
+            return $eventParam;
+        }
+
+        return null;
+    }
+}
diff --git a/api/app/Providers/AppServiceProvider.php b/api/app/Providers/AppServiceProvider.php
index 3189c6d0..192c3f50 100644
--- a/api/app/Providers/AppServiceProvider.php
+++ b/api/app/Providers/AppServiceProvider.php
@@ -48,6 +48,7 @@ use App\Models\VolunteerAvailability;
 use App\Events\FormBuilder\FormSubmissionSubmitted;
 use App\Listeners\FormBuilder\SyncTagPickerSelectionsOnSubmit;
 use App\Listeners\FormBuilder\TriggerPersonIdentityMatchOnFormSubmit;
+use App\Observers\FormBuilder\FormSubmissionObserver;
 use App\Observers\FormBuilder\FormValueObserver;
 use App\Observers\PersonObserver;
 use App\Observers\UserObserver;
@@ -91,6 +92,7 @@ class AppServiceProvider extends ServiceProvider
         Person::observe(PersonObserver::class);
         User::observe(UserObserver::class);
         FormValue::observe(FormValueObserver::class);
+        \App\Models\FormBuilder\FormSubmission::observe(FormSubmissionObserver::class);
 
         // ARCH §31.10 — FORM-02 TAG_PICKER sync listener.
         \Illuminate\Support\Facades\Event::listen(
diff --git a/api/database/factories/FormBuilder/FormSubmissionFactory.php b/api/database/factories/FormBuilder/FormSubmissionFactory.php
index 911a0478..4bc4b264 100644
--- a/api/database/factories/FormBuilder/FormSubmissionFactory.php
+++ b/api/database/factories/FormBuilder/FormSubmissionFactory.php
@@ -5,8 +5,10 @@ declare(strict_types=1);
 namespace Database\Factories\FormBuilder;
 
 use App\Enums\FormBuilder\FormSubmissionStatus;
+use App\Models\Event;
 use App\Models\FormBuilder\FormSchema;
 use App\Models\FormBuilder\FormSubmission;
+use App\Models\Organisation;
 use Illuminate\Database\Eloquent\Factories\Factory;
 
 /** @extends Factory<FormSubmission> */
@@ -40,4 +42,26 @@ final class FormSubmissionFactory extends Factory
     {
         return $this->state(fn () => ['is_test' => true]);
     }
+
+    /**
+     * Force a specific tenant. The observer would otherwise resolve it
+     * from the schema parent; this state lets tests override for edge
+     * cases (e.g. cross-org leakage scenarios in Commit 3).
+     */
+    public function forOrganisation(Organisation $organisation): static
+    {
+        return $this->state(fn () => ['organisation_id' => $organisation->id]);
+    }
+
+    /**
+     * Force a specific event + its organisation. Addendum Q2 contract:
+     * any submission tied to an event also has that event's org.
+     */
+    public function forEvent(Event $event): static
+    {
+        return $this->state(fn () => [
+            'event_id' => $event->id,
+            'organisation_id' => $event->organisation_id,
+        ]);
+    }
 }
diff --git a/api/database/migrations/2026_04_24_200000_add_denormalized_context_to_form_submissions.php b/api/database/migrations/2026_04_24_200000_add_denormalized_context_to_form_submissions.php
new file mode 100644
index 00000000..860443b5
--- /dev/null
+++ b/api/database/migrations/2026_04_24_200000_add_denormalized_context_to_form_submissions.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+// Addendum Q2 exception: form_submissions is the single rapportage-hot
+// table that earns denormalized organisation_id + event_id columns.
+// Every other form-builder child table resolves its tenant via FK-chain
+// through its parent (see OrganisationScope).
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('form_submissions', function (Blueprint $table): void {
+            // organisation_id is NOT NULL — every submission belongs to a
+            // tenant. Pre-launch: form_submissions is empty at migration
+            // time, so MySQL/SQLite accept NOT NULL without a default.
+            $table->foreignUlid('organisation_id')
+                ->after('form_schema_id')
+                ->constrained('organisations')
+                ->cascadeOnDelete();
+
+            // event_id is nullable — purposes like user_profile have no
+            // event. The observer resolves it from the schema owner
+            // (owner_type === 'event') or from the active route.
+            $table->foreignUlid('event_id')
+                ->nullable()
+                ->after('organisation_id')
+                ->constrained('events')
+                ->nullOnDelete();
+
+            $table->index(['organisation_id', 'status'], 'fs_org_status_idx');
+            $table->index(['event_id', 'status'], 'fs_event_status_idx');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('form_submissions', function (Blueprint $table): void {
+            $table->dropIndex('fs_org_status_idx');
+            $table->dropIndex('fs_event_status_idx');
+            $table->dropConstrainedForeignId('organisation_id');
+            $table->dropConstrainedForeignId('event_id');
+        });
+    }
+};
diff --git a/api/tests/Feature/FormBuilder/FormSubmissionObserverTest.php b/api/tests/Feature/FormBuilder/FormSubmissionObserverTest.php
new file mode 100644
index 00000000..38cc57a3
--- /dev/null
+++ b/api/tests/Feature/FormBuilder/FormSubmissionObserverTest.php
@@ -0,0 +1,166 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Feature\FormBuilder;
+
+use App\Models\Event;
+use App\Models\FormBuilder\FormSchema;
+use App\Models\FormBuilder\FormSubmission;
+use App\Models\Organisation;
+use App\Models\User;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Route;
+use Tests\TestCase;
+
+/**
+ * WS-4 Commit 2 coverage — addendum Q2 denormalization observer.
+ *
+ * Guarantees that every form_submissions row carries correct
+ * organisation_id (always) and event_id (when resolvable from schema
+ * owner or active route).
+ */
+final class FormSubmissionObserverTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function test_organisation_id_resolves_from_schema(): void
+    {
+        $organisation = Organisation::factory()->create();
+        $schema = FormSchema::factory()->for($organisation)->create();
+
+        $submission = FormSubmission::factory()->for($schema, 'schema')->create();
+
+        $this->assertSame(
+            $organisation->id,
+            $submission->organisation_id,
+            'Observer must denormalize organisation_id from schema parent'
+        );
+    }
+
+    public function test_event_id_resolves_from_event_owned_schema(): void
+    {
+        $organisation = Organisation::factory()->create();
+        $event = Event::factory()->for($organisation)->create();
+        $schema = FormSchema::factory()->for($organisation)->create([
+            'owner_type' => 'event',
+            'owner_id' => $event->id,
+        ]);
+
+        $submission = FormSubmission::factory()->for($schema, 'schema')->create();
+
+        $this->assertSame(
+            $event->id,
+            $submission->event_id,
+            'Observer must resolve event_id from schema.owner_id when owner_type = event'
+        );
+    }
+
+    public function test_event_id_is_null_when_schema_has_no_event_owner_and_no_route(): void
+    {
+        $organisation = Organisation::factory()->create();
+        $schema = FormSchema::factory()->for($organisation)->create([
+            'owner_type' => 'organisation',
+            'owner_id' => $organisation->id,
+        ]);
+
+        $submission = FormSubmission::factory()->for($schema, 'schema')->create();
+
+        $this->assertNull(
+            $submission->event_id,
+            'Non-event-owned schema outside an event route yields event_id = null'
+        );
+        $this->assertSame($organisation->id, $submission->organisation_id);
+    }
+
+    public function test_event_id_resolves_from_active_route_when_schema_has_no_event_owner(): void
+    {
+        $organisation = Organisation::factory()->create();
+        $event = Event::factory()->for($organisation)->create();
+        $schema = FormSchema::factory()->for($organisation)->create([
+            'owner_type' => 'organisation',
+            'owner_id' => $organisation->id,
+        ]);
+
+        // Simulate a request bound to /events/{event}/... by firing the
+        // observer inside a controller invocation with the route
+        // parameter populated.
+        Route::get(
+            '/_test/events/{event}/submissions',
+            function (Event $event) use ($schema): array {
+                $submission = new FormSubmission();
+                $submission->form_schema_id = $schema->id;
+                $submission->status = 'draft';
+                $submission->is_test = false;
+                $submission->save();
+
+                return ['id' => $submission->id, 'event_id' => $submission->event_id];
+            }
+        );
+
+        $response = $this->getJson("/_test/events/{$event->id}/submissions");
+        $response->assertOk();
+
+        $this->assertSame(
+            $event->id,
+            $response->json('event_id'),
+            'Route {event} parameter resolves event_id when schema has no event owner'
+        );
+    }
+
+    public function test_organisation_id_is_populated_on_every_create_path(): void
+    {
+        $organisation = Organisation::factory()->create();
+        $schema = FormSchema::factory()->for($organisation)->create();
+
+        // Direct factory
+        $s1 = FormSubmission::factory()->for($schema, 'schema')->create();
+        // Direct new() + save()
+        $s2 = new FormSubmission();
+        $s2->form_schema_id = $schema->id;
+        $s2->status = 'draft';
+        $s2->is_test = false;
+        $s2->save();
+        // Model::create()
+        $s3 = FormSubmission::create([
+            'form_schema_id' => $schema->id,
+            'status' => 'draft',
+            'is_test' => false,
+        ]);
+
+        foreach ([$s1, $s2, $s3] as $submission) {
+            $this->assertSame(
+                $organisation->id,
+                $submission->organisation_id,
+                'organisation_id must never be NULL — resolved on every create path'
+            );
+        }
+    }
+
+    public function test_denormalized_indexes_exist(): void
+    {
+        // Indexes named in the migration — addendum Q2 rapportage-hot.
+        $indexNames = collect(DB::select(
+            "SELECT name FROM sqlite_master WHERE type='index' AND tbl_name='form_submissions'"
+        ))->pluck('name')->toArray();
+
+        $this->assertContains('fs_org_status_idx', $indexNames);
+        $this->assertContains('fs_event_status_idx', $indexNames);
+    }
+
+    public function test_organisation_and_event_belongs_to_relationships_resolve(): void
+    {
+        $organisation = Organisation::factory()->create();
+        $event = Event::factory()->for($organisation)->create();
+        $schema = FormSchema::factory()->for($organisation)->create([
+            'owner_type' => 'event',
+            'owner_id' => $event->id,
+        ]);
+
+        $submission = FormSubmission::factory()->for($schema, 'schema')->create();
+
+        $this->assertTrue($submission->organisation->is($organisation));
+        $this->assertTrue($submission->event->is($event));
+    }
+}
diff --git a/dev-docs/ARCH-FORM-BUILDER.md b/dev-docs/ARCH-FORM-BUILDER.md
index f319e2b0..c54d71bf 100644
--- a/dev-docs/ARCH-FORM-BUILDER.md
+++ b/dev-docs/ARCH-FORM-BUILDER.md
@@ -666,6 +666,8 @@ submissions of the same schema. Enforcement:
 |---|---|---|
 | `id` | ULID | PK |
 | `form_schema_id` | ULID FK | → form_schemas |
+| `organisation_id` | ULID FK | → organisations, cascade delete. **Denormalized per ARCH-CONSOLIDATION-ADDENDUM-2026-04-24 Q2** — the single rapportage-hot exception. Populated by `FormSubmissionObserver::creating` from the schema parent. |
+| `event_id` | ULID FK nullable | → events, null on delete. Denormalized per addendum Q2. Observer resolves from `form_schemas.owner_id` when `owner_type = event`; else from the active route's `{event}` parameter. Null for purposes without an event context (`user_profile`, `signature_contract`). |
 | `subject_type` | string nullable | polymorph |
 | `subject_id` | ULID nullable | polymorph target |
 | `submitted_by_user_id` | ULID FK nullable | Authenticated submitter |
@@ -694,7 +696,7 @@ submissions of the same schema. Enforcement:
 
 **Relations:** belongsTo form_schema, hasMany form_values, hasMany form_submission_section_statuses, hasMany form_submission_delegations, belongsTo submittedBy / reviewedBy (User), morphsTo subject
 
-**Indexes:** `(form_schema_id, status)`, `(subject_type, subject_id)`, `(submitted_by_user_id)`, `(form_schema_id, review_status)` partial where not null, `FULLTEXT(search_index)` (MySQL)
+**Indexes:** `(form_schema_id, status)`, `(organisation_id, status)` (addendum Q2 — dashboards + CSV exports aggregate by tenant + status), `(event_id, status)` (addendum Q2 — event-scoped reporting), `(subject_type, subject_id)`, `(submitted_by_user_id)`, `(form_schema_id, review_status)` partial where not null, `FULLTEXT(search_index)` (MySQL)
 
 **Unique:** `(form_schema_id, idempotency_key)` partial where not null
 
diff --git a/dev-docs/SCHEMA.md b/dev-docs/SCHEMA.md
index 9f4b0ebc..a1990e12 100644
--- a/dev-docs/SCHEMA.md
+++ b/dev-docs/SCHEMA.md
@@ -2033,6 +2033,8 @@ that aggregates the user's submitted, non-test `form_submissions`.
 | ------------------------------------- | ------------------ | ---------------------------------------------------------------------------- |
 | `id`                                  | ULID               | PK                                                                           |
 | `form_schema_id`                      | ULID FK            | → form_schemas, cascade delete                                               |
+| `organisation_id`                     | ULID FK            | → organisations, cascade delete. Denormalized per addendum Q2 — this is the **only** form-builder child that carries a direct tenant column; every other child resolves tenant via FK-chain through its parent. Populated by `FormSubmissionObserver` from the schema parent. |
+| `event_id`                            | ULID FK nullable   | → events, null on delete. Denormalized per addendum Q2. Observer resolves from `form_schemas.owner_id` when `owner_type = event`; otherwise from the active route's `{event}` parameter. Null for purposes like `user_profile` / `signature_contract`. |
 | `subject_type`                        | string(50) null    | polymorph                                                                    |
 | `subject_id`                          | ULID nullable      | polymorph target                                                             |
 | `submitted_by_user_id`                | ULID FK nullable   | → users, null on delete                                                      |
@@ -2062,11 +2064,22 @@ that aggregates the user's submitted, non-test `form_submissions`.
 | `created_at`, `updated_at`            | timestamps         |                                                                              |
 | `deleted_at`                          | timestamp nullable | Soft delete                                                                  |
 
-**Relations:** `belongsTo` schema, submittedBy / reviewedBy (User); `morphsTo` subject; `hasMany` values, section statuses, delegations  
-**Indexes:** `(form_schema_id, status)`, `(subject_type, subject_id)`, `(submitted_by_user_id)`, `(form_schema_id, review_status)`, **UNIQUE** `(form_schema_id, idempotency_key)` (v2.1; replaced the non-unique composite index from v2.0), `(form_schema_id, identity_match_status)` (v2.1), `FULLTEXT(search_index)` (MySQL/InnoDB — best-effort, skipped gracefully on SQLite)  
+**Relations:** `belongsTo` schema, organisation, event, submittedBy / reviewedBy (User); `morphsTo` subject; `hasMany` values, section statuses, delegations  
+**Indexes:** `(form_schema_id, status)`, `(organisation_id, status)` (v2.2 — addendum Q2), `(event_id, status)` (v2.2 — addendum Q2), `(subject_type, subject_id)`, `(submitted_by_user_id)`, `(form_schema_id, review_status)`, **UNIQUE** `(form_schema_id, idempotency_key)` (v2.1; replaced the non-unique composite index from v2.0), `(form_schema_id, identity_match_status)` (v2.1), `FULLTEXT(search_index)` (MySQL/InnoDB — best-effort, skipped gracefully on SQLite)  
 **Events fired:** `FormSubmissionCreated`, `FormSubmissionDraftUpdated`, `FormSubmissionSubmitted`, `FormSubmissionReviewed`, `FormSubmissionSectionSubmitted`, `FormSubmissionSectionReviewed`, `FormSubmissionAnonymised`, `FormSubmissionArchived`, `FormSubmissionDeleted`  
 **Soft delete:** yes
 
+> **Denormalization rationale (addendum Q2):** `form_submissions` is the
+> single rapportage-hot table that earns a denormalized `organisation_id`
+> (and `event_id`). Aggregerende queries over duizenden rijen — dashboards,
+> CSV-exports, counts — run directly against these columns instead of
+> joining through `form_schemas`. Every other form-builder child table
+> (`form_schema_sections`, `form_fields`, `form_values`, `form_value_options`,
+> `form_submission_section_statuses`, `form_submission_delegations`,
+> `form_schema_webhooks`, `form_webhook_deliveries`) resolves its tenant
+> via the FK-chain strategy added to `OrganisationScope` in the same
+> addendum.
+
 ---
 
 ### `form_submission_section_statuses`