diff --git a/apps/api/src/services/serializers/project.ts b/apps/api/src/services/serializers/project.ts
index dd996fb..2fbe21a 100644
--- a/apps/api/src/services/serializers/project.ts
+++ b/apps/api/src/services/serializers/project.ts
@@ -76,6 +76,7 @@ export interface ProjectDetail {
   readonly featured: boolean;
   readonly createdAt: string;
   readonly updatedAt: string;
+  readonly deletedAt: string | null;
 }
 
 export interface HelpWantedRoleSummary {
@@ -243,5 +244,6 @@ export function serializeProjectDetail(
     featured: project.featured,
     createdAt: project.createdAt,
     updatedAt: project.updatedAt,
+    deletedAt: project.deletedAt ?? null,
   };
 }
diff --git a/apps/web/src/lib/api.ts b/apps/web/src/lib/api.ts
index aad8868..4a9c1d7 100644
--- a/apps/web/src/lib/api.ts
+++ b/apps/web/src/lib/api.ts
@@ -175,6 +175,7 @@ export interface ProjectDetail {
   readonly featured: boolean;
   readonly createdAt: string;
   readonly updatedAt: string;
+  readonly deletedAt: string | null;
 }
 
 export interface PersonListItem {
diff --git a/apps/web/src/screens/ProjectDetail.tsx b/apps/web/src/screens/ProjectDetail.tsx
index 2441aa6..2a4c5b9 100644
--- a/apps/web/src/screens/ProjectDetail.tsx
+++ b/apps/web/src/screens/ProjectDetail.tsx
@@ -136,6 +136,10 @@ export function ProjectDetail({ anchor }: ProjectDetailProps = {}) {
   const isSoleMaintainer = (myMembership?.isMaintainer ?? false) && maintainerCount === 1;
   const canJoin = isSignedIn && !isMember;
   const canLeave = isMember && !isSoleMaintainer;
+  // Only staff can see a soft-deleted project at all (non-staff get 404), so a
+  // non-null deletedAt here means the viewer is staff; gate anyway for clarity.
+  const isStaff = person?.accountLevel === 'staff' || person?.accountLevel === 'administrator';
+  const showDeletedBanner = project.deletedAt !== null && isStaff;
 
   const runMembership = async (fn: () => Promise<void>): Promise<void> => {
     setMemberBusy(true);
@@ -154,6 +158,24 @@ export function ProjectDetail({ anchor }: ProjectDetailProps = {}) {
 
   return (
     <div className="container mx-auto px-4 py-8">
+      {/* Soft-delete banner — staff only (project-detail.md) */}
+      {showDeletedBanner && (
+        <div
+          role="status"
+          className="mb-6 flex flex-wrap items-center justify-between gap-3 rounded-md border border-yellow-400 bg-yellow-50 px-4 py-3 text-sm text-yellow-900"
+        >
+          <span>This project is deleted — only staff can see it.</span>
+          <Button
+            size="sm"
+            variant="outline"
+            disabled={memberBusy}
+            onClick={() => void runMembership(() => api.projects.restore(slug).then(() => undefined))}
+          >
+            {memberBusy ? 'Restoring…' : 'Restore'}
+          </Button>
+        </div>
+      )}
+
       {/* Header */}
       <div className="mb-6">
         <div className="flex items-start justify-between gap-4 mb-3">
diff --git a/apps/web/tests/ProjectDetail.test.tsx b/apps/web/tests/ProjectDetail.test.tsx
index 5c2e654..baf4206 100644
--- a/apps/web/tests/ProjectDetail.test.tsx
+++ b/apps/web/tests/ProjectDetail.test.tsx
@@ -257,4 +257,23 @@ describe('ProjectDetail', () => {
     });
     expect(screen.queryByRole('button', { name: /join project/i })).not.toBeInTheDocument();
   });
+
+  it('shows the soft-delete banner + Restore for staff viewing a deleted project', async () => {
+    const deleted = { ...PROJECT, deletedAt: '2026-06-01T00:00:00Z' } as unknown as typeof PROJECT;
+    mockSignedIn(deleted, 'staff');
+    renderDetail();
+    await waitFor(() => {
+      expect(screen.getByText(/this project is deleted/i)).toBeInTheDocument();
+    });
+    expect(screen.getByRole('button', { name: /restore/i })).toBeInTheDocument();
+  });
+
+  it('does not show the soft-delete banner for an active project', async () => {
+    mockSignedIn({ ...PROJECT, deletedAt: null } as unknown as typeof PROJECT, 'staff');
+    renderDetail();
+    await waitFor(() => {
+      expect(screen.getByRole('heading', { name: 'Sample Project', level: 1 })).toBeInTheDocument();
+    });
+    expect(screen.queryByText(/this project is deleted/i)).not.toBeInTheDocument();
+  });
 });
diff --git a/specs/api/projects.md b/specs/api/projects.md
index f0ffb13..488607c 100644
--- a/specs/api/projects.md
+++ b/specs/api/projects.md
@@ -130,12 +130,15 @@ Fetches a single project by slug.
     "canDelete": false
   },
   "createdAt": "...",
-  "updatedAt": "..."
+  "updatedAt": "...",
+  "deletedAt": "..." | null
 }
 ```
 
 `permissions` is the *current caller's* permissions on this project — the frontend uses it to decide which actions to render. The server still enforces the same rules on each mutation endpoint.
 
+`deletedAt` is `null` for active projects. It is non-null only when a soft-deleted project is fetched by staff (non-staff get `404`), so the SPA can render the soft-delete banner with a Restore action.
+
 ### Errors
 
 - `404 not_found` — slug doesn't match (or is soft-deleted and caller can't see deleted).