diff --git a/src/shared/hooks/useShapeSet.ts b/src/shared/hooks/useShapeSet.ts
new file mode 100644
index 0000000..a08f622
--- /dev/null
+++ b/src/shared/hooks/useShapeSet.ts
@@ -0,0 +1,57 @@
+/**
+ * useShapeSet — `useShape` narrowed back down to "just the set".
+ *
+ * WHY THIS EXISTS. `@ng-org/orm` changed `useShape`'s contract between alpha.18
+ * and alpha.21: it used to RETURN the `DeepSignalSet`, and now returns a result
+ * object that carries it under `data`, alongside `isLoading`, `promise`,
+ * `subscription` and the paging controls. Every Festipod call site wants the set,
+ * so the whole adaptation lives HERE, in one place, rather than being spelled out
+ * at each `useShape(...)`.
+ *
+ * AND THE BUMP IS NOT OPTIONAL. `@ng-org/refine-providers` imports
+ * `RdfOrmSubscription` from `@ng-org/orm`; alpha.18 published that class under
+ * the name `OrmSubscription` and only alpha.21 exports `RdfOrmSubscription`. So
+ * using the providers requires alpha.21, which requires absorbing this break.
+ *
+ * WHILE LOADING, `data` is `undefined`. Callers get an empty set instead — and a
+ * set that REFUSES writes, which is what alpha.18 handed back for an undefined
+ * scope: *"an empty set is returned which errors if you try to make modifications
+ * on it"*. Accepting the write instead would drop it on the floor, silently, in
+ * exactly the window where a caller is most likely to try.
+ */
+
+import { useMemo } from 'react';
+import { useShape } from '@ng-org/orm/react';
+import type { ShapeType, BaseType } from '@ng-org/shex-orm';
+import type { DeepSignalSet } from '@ng-org/alien-deepsignals';
+
+/**
+ * `scope` is either a single store/document NURI (mono-store mode) or a
+ * `{ graphs }` set of document NURIs (multi-document mode — storeRegistry).
+ * `useShape` accepts both natively.
+ */
+export type ShapeScope = string | { graphs: string[] } | undefined;
+
+/** An empty set that names the problem instead of swallowing a write. */
+function notLoadedSet<T>(): DeepSignalSet<T> {
+  const refuse = (): never => {
+    throw new Error(
+      'useShapeSet: the shape subscription has not loaded yet — read it, do not write to it',
+    );
+  };
+  return Object.assign(new Set<T>(), { add: refuse, delete: refuse }) as unknown as DeepSignalSet<T>;
+}
+
+export function useShapeSet<NgT extends BaseType>(
+  shapeType: ShapeType<NgT>,
+  scope: ShapeScope,
+): DeepSignalSet<NgT> {
+  // Memoised so the placeholder keeps ONE identity for this hook instance: it
+  // lands in `useCallback` dependency arrays, and a fresh set on every render
+  // would rebuild every mutation callback for as long as the load takes.
+  const placeholder = useMemo(() => notLoadedSet<NgT>(), []);
+  const result = useShape(shapeType as never, scope as never) as unknown as {
+    data?: DeepSignalSet<NgT>;
+  };
+  return result?.data ?? placeholder;
+}
diff --git a/src/shared/hooks/useShapeWithDefaults.ts b/src/shared/hooks/useShapeWithDefaults.ts
index cf1667e..39b357b 100644
--- a/src/shared/hooks/useShapeWithDefaults.ts
+++ b/src/shared/hooks/useShapeWithDefaults.ts
@@ -8,9 +8,10 @@
  * Must only be called when NG is connected (inside NgDataProvider).
  */
 
-import { useShape } from '@ng-org/orm/react';
 import type { ShapeType, BaseType } from '@ng-org/shex-orm';
 import type { DeepSignalSet } from '@ng-org/alien-deepsignals';
+import { useShapeSet, type ShapeScope } from './useShapeSet';
+
 export interface ShapeWithDefaults<NgT extends BaseType, AppT> {
   /** Mapped items from NG store */
   items: AppT[];
@@ -18,12 +19,9 @@ export interface ShapeWithDefaults<NgT extends BaseType, AppT> {
   ngSet: DeepSignalSet<NgT>;
 }
 
-/**
- * `scope` is either a single store/document NURI (mono-store mode) or a
- * `{ graphs }` set of document NURIs (multi-document mode — storeRegistry).
- * `useShape` accepts both natively.
- */
-export type ShapeScope = string | { graphs: string[] } | undefined;
+// `ShapeScope` now belongs to useShapeSet (the module that talks to the ORM);
+// it is re-exported here so the existing importers stay unchanged.
+export type { ShapeScope };
 
 export function useShapeWithDefaults<NgT extends BaseType, AppT>(
   shapeType: ShapeType<NgT>,
@@ -34,7 +32,8 @@ export function useShapeWithDefaults<NgT extends BaseType, AppT>(
 ): ShapeWithDefaults<NgT, AppT> {
   // Mono-store: a single store NURI opens the repo in the verifier (enables
   // writes). Multi-document: a { graphs } scope subscribes to several docs.
-  const ngSet = useShape(shapeType, storeNuri as any) as DeepSignalSet<NgT>;
+  // `useShapeSet` is what unwraps the ORM's result object — see that module.
+  const ngSet = useShapeSet(shapeType, storeNuri);
   const usingDefaults = !shapesReady;
   const items = usingDefaults ? defaults : [...ngSet].map(item => mapFromNg(item as unknown as NgT));
 
diff --git a/src/shared/test-harness/harness-ng.tsx b/src/shared/test-harness/harness-ng.tsx
index cef00f2..eda48b3 100644
--- a/src/shared/test-harness/harness-ng.tsx
+++ b/src/shared/test-harness/harness-ng.tsx
@@ -12,7 +12,7 @@ import { createRoot } from 'react-dom/client';
 import { NextGraphProvider, useNextGraph } from '../context/NextGraphContext';
 import { RefineProvider } from '../refine/RefineProvider';
 import { FestipodDataProvider, useFestipodData } from '../context/FestipodDataContext';
-import { useShape } from '@ng-org/orm/react';
+import { useShapeSet } from '../hooks/useShapeSet';
 import { ng } from '@ng-org/web';
 import type { DeepSignalSet } from '@ng-org/alien-deepsignals';
 import {
@@ -67,9 +67,9 @@ function ConnectedHarness() {
 
   // Use private store NURI as scope (opens the repo for reads AND writes)
   const privateNuri = ngCtx.session && `did:ng:${ngCtx.session.private_store_id}`;
-  const events = useShape(FpEventShapeType, privateNuri) as DeepSignalSet<FpEvent>;
-  const users = useShape(FpUserProfileShapeType, privateNuri) as DeepSignalSet<FpUserProfile>;
-  const participations = useShape(FpParticipationShapeType, privateNuri) as DeepSignalSet<FpParticipation>;
+  const events = useShapeSet(FpEventShapeType, privateNuri);
+  const users = useShapeSet(FpUserProfileShapeType, privateNuri);
+  const participations = useShapeSet(FpParticipationShapeType, privateNuri);
 
   const [bridgeReady, setBridgeReady] = useState(false);
   // Stopgap multi-store validation: a doc created on demand via doc_create,
@@ -239,7 +239,7 @@ function ConnectedHarness() {
 // ============================================================================
 
 function FanoutProbe({ graphs }: { graphs: string[] }) {
-  const set = useShape(FpEventShapeType, { graphs } as any) as DeepSignalSet<FpEvent>;
+  const set = useShapeSet(FpEventShapeType, { graphs });
   useEffect(() => {
     (window as any).__fanout = {
       ready: true,
@@ -266,7 +266,7 @@ function FanoutProbe({ graphs }: { graphs: string[] }) {
 // ============================================================================
 
 function SmokeProbe({ docNuri }: { docNuri: string }) {
-  const set = useShape(FpParticipationShapeType, { graphs: [docNuri] } as any) as DeepSignalSet<FpParticipation>;
+  const set = useShapeSet(FpParticipationShapeType, { graphs: [docNuri] });
   useEffect(() => {
     (window as any).__smoke = {
       ready: true,