diff --git a/api/app/Http/Controllers/Api/V1/Portal/EngagementPortalController.php b/api/app/Http/Controllers/Api/V1/Portal/EngagementPortalController.php
index 2ce4471a..d8d9683a 100644
--- a/api/app/Http/Controllers/Api/V1/Portal/EngagementPortalController.php
+++ b/api/app/Http/Controllers/Api/V1/Portal/EngagementPortalController.php
@@ -257,16 +257,13 @@ final class EngagementPortalController extends Controller
         // Pass event_id via the context bag — the schema is org-owned (not
         // event-owned) and this route has no {event} parameter for the
         // FormSubmissionObserver fallback. ARCH-FORM-BUILDER §17.3 footnote.
-        // idempotency_key column is varchar(30); a SHA-1 hex digest fits in
-        // 28 chars and uniquely keys "one draft per (schema, engagement)".
-        $key = 'aa-'.substr(hash('sha1', (string) $resolved->engagement->id), 0, 27);
-
+        // idempotency_key column is varchar(30); 'aa:' + 26-char ULID fits.
         return $this->submissionService->createDraft(
             schema: $schema,
             subject: $resolved->subject,
             submitter: null,
             context: [
-                'idempotency_key' => $key,
+                'idempotency_key' => 'aa:'.$resolved->engagement->id,
                 'event_id' => $resolved->eventId,
             ],
         );
diff --git a/api/app/Observers/OrganisationObserver.php b/api/app/Observers/OrganisationObserver.php
index ad7f9397..2aeb1f25 100644
--- a/api/app/Observers/OrganisationObserver.php
+++ b/api/app/Observers/OrganisationObserver.php
@@ -18,15 +18,18 @@ use App\Models\Organisation;
  * The default seeder is idempotent — if the org already owns an
  * artist_advance schema, the call is a no-op. Safe to re-run.
  *
- * Skipped during automated tests so existing FormSchema-counting
- * tests aren't perturbed; tests that need the auto-seed call
- * `ArtistAdvanceDefault::seedFor()` explicitly.
+ * Gated by `config('artist_advance.bootstrap_on_org_create')`. The
+ * config defaults to true (production behaviour); phpunit.xml flips
+ * it to false so existing FormSchema-counting tests aren't perturbed.
+ * Tests that need the auto-seed call `ArtistAdvanceDefault::seedFor()`
+ * explicitly. Tracked for removal by BACKLOG entry
+ * `TECH-OBSERVER-TEST-CONVERGENCE`.
  */
 final class OrganisationObserver
 {
     public function created(Organisation $organisation): void
     {
-        if (app()->runningUnitTests()) {
+        if (! (bool) config('artist_advance.bootstrap_on_org_create', true)) {
             return;
         }
 
diff --git a/api/config/artist_advance.php b/api/config/artist_advance.php
new file mode 100644
index 00000000..09c14b53
--- /dev/null
+++ b/api/config/artist_advance.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+return [
+    /*
+    |---------------------------------------------------------------------
+    | Bootstrap on organisation create
+    |---------------------------------------------------------------------
+    |
+    | When true (production default), OrganisationObserver provisions a
+    | default artist_advance FormSchema for every newly-created
+    | Organisation per RFC-TIMETABLE v0.2 D15. When false, the observer
+    | no-ops and tests opt in to the seeder explicitly via
+    | `ArtistAdvanceDefault::seedFor()`.
+    |
+    | Tracked for removal by BACKLOG: TECH-OBSERVER-TEST-CONVERGENCE —
+    | once existing FormSchema-counting tests are updated to expect the
+    | auto-bootstrapped schema, this flag goes away (productiegedrag =
+    | testgedrag, geen branching).
+    |
+    */
+
+    'bootstrap_on_org_create' => env('ARTIST_ADVANCE_BOOTSTRAP_ON_ORG_CREATE', true),
+];
diff --git a/api/phpunit.xml b/api/phpunit.xml
index 4337eea0..5b822fcd 100644
--- a/api/phpunit.xml
+++ b/api/phpunit.xml
@@ -35,6 +35,7 @@
         <env name="PULSE_ENABLED" value="false"/>
         <env name="TELESCOPE_ENABLED" value="false"/>
         <env name="NIGHTWATCH_ENABLED" value="false"/>
+        <env name="ARTIST_ADVANCE_BOOTSTRAP_ON_ORG_CREATE" value="false"/>
         <ini name="memory_limit" value="512M"/>
     </php>
 </phpunit>