diff --git a/frontend/src/pages/ProjectByIdPage.tsx b/frontend/src/pages/ProjectByIdPage.tsx
index 90a5f188..2c9b311e 100644
--- a/frontend/src/pages/ProjectByIdPage.tsx
+++ b/frontend/src/pages/ProjectByIdPage.tsx
@@ -3,6 +3,7 @@ import { useParams, useNavigate } from 'react-router-dom';
 import { getProjectById } from '../services/projectService';
 import { useSimulatorStore } from '../store/useSimulatorStore';
 import { useProjectStore } from '../store/useProjectStore';
+import { useLibraryManifestStore } from '../store/useLibraryManifestStore';
 import { useSEO } from '../utils/useSEO';
 import { EditorPage } from './EditorPage';
 import type { BoardInstance, BoardKind } from '../types/board';
@@ -56,6 +57,14 @@ export const ProjectByIdPage: React.FC = () => {
       .then((project) => {
         const payload = buildLoadPayload(project);
         loadProjectState(payload);
+        // P2.4 — restore the declared library manifest (compile scope), also
+        // clearing any stale example manifest from before this load.
+        try {
+          const libs = JSON.parse(project.libraries_json || '[]');
+          useLibraryManifestStore.getState().setLibraries(Array.isArray(libs) ? libs : null);
+        } catch {
+          useLibraryManifestStore.getState().setLibraries(null);
+        }
         setCurrentProject({
           id: project.id,
           slug: project.slug,
diff --git a/frontend/src/services/projectService.ts b/frontend/src/services/projectService.ts
index e9519545..f2fd33a8 100644
--- a/frontend/src/services/projectService.ts
+++ b/frontend/src/services/projectService.ts
@@ -42,6 +42,7 @@ export interface ProjectResponse {
   components_json: string;
   wires_json: string;
   boards_json: string; // serialized BoardInstance[]
+  libraries_json?: string; // P2.4 — declared library manifest (compile scope)
   owner_username: string;
   created_at: string;
   updated_at: string;
@@ -62,6 +63,7 @@ export interface ProjectSaveData {
   components_json: string;
   wires_json: string;
   boards_json?: string; // serialized BoardInstance[]
+  libraries_json?: string; // P2.4 — declared library manifest (compile scope)
 }
 
 export async function getMyProjects(): Promise<ProjectResponse[]> {
diff --git a/frontend/src/utils/projectPayload.ts b/frontend/src/utils/projectPayload.ts
index e253fc7a..674a930c 100644
--- a/frontend/src/utils/projectPayload.ts
+++ b/frontend/src/utils/projectPayload.ts
@@ -11,6 +11,7 @@ import type { BoardInstance } from '../types/board';
 import type { Wire } from '../types/wire';
 import { useEditorStore, chipFileGroupId } from '../store/useEditorStore';
 import { useSimulatorStore } from '../store/useSimulatorStore';
+import { useLibraryManifestStore } from '../store/useLibraryManifestStore';
 
 /**
  * Editor groups owned by programmable custom-chips on the canvas (those whose
@@ -107,6 +108,9 @@ export function buildSavePayload(meta: SnapshotInputs = {}): ProjectSaveData {
     components_json: JSON.stringify(sim.components),
     wires_json: JSON.stringify(sim.wires),
     boards_json: JSON.stringify(sim.boards.map(serialisableBoard)),
+    // P2.4 — persist the declared library manifest (compile scope) so reloading
+    // the project re-sends it. Empty when the project declares no libraries.
+    libraries_json: JSON.stringify(useLibraryManifestStore.getState().libraries ?? []),
   };
 }