diff --git a/web/src/api/queries.ts b/web/src/api/queries.ts
index ad3aeb6..b777b8a 100644
--- a/web/src/api/queries.ts
+++ b/web/src/api/queries.ts
@@ -199,3 +199,32 @@ export function useDeleteObject() {
     onSuccess: () => qc.invalidateQueries({ queryKey: ["objects"] }),
   });
 }
+
+type Visibility = "draft" | "internal" | "public";
+
+/** Error carrying the HTTP status so callers can branch 422-gate vs 409-illegal. */
+export class VisibilityError extends Error {
+  constructor(public status: number) {
+    super(`visibility change failed (${status})`);
+    this.name = "VisibilityError";
+  }
+}
+
+export function useSetVisibility() {
+  const qc = useQueryClient();
+
+  return useMutation({
+    mutationFn: async ({ id, visibility }: { id: string; visibility: Visibility }) => {
+      const { response } = await api.POST("/api/admin/objects/{id}/visibility", {
+        params: { path: { id } },
+        body: { visibility },
+      });
+
+      if (response.status !== 204) throw new VisibilityError(response.status);
+    },
+    onSuccess: (_result, { id }) => {
+      void qc.invalidateQueries({ queryKey: ["object", id] });
+      void qc.invalidateQueries({ queryKey: ["objects"] });
+    },
+  });
+}
diff --git a/web/src/api/queries.visibility.test.tsx b/web/src/api/queries.visibility.test.tsx
new file mode 100644
index 0000000..35fa42d
--- /dev/null
+++ b/web/src/api/queries.visibility.test.tsx
@@ -0,0 +1,38 @@
+import { describe, expect, test } from "vitest";
+import { renderHook } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { http, HttpResponse } from "msw";
+import type { ReactNode } from "react";
+
+import { server } from "../test/server";
+import { useSetVisibility } from "./queries";
+
+function wrapper({ children }: { children: ReactNode }) {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  return <QueryClientProvider client={qc}>{children}</QueryClientProvider>;
+}
+
+describe("useSetVisibility", () => {
+  test("POSTs the target visibility and resolves on 204", async () => {
+    let body: unknown;
+    server.use(
+      http.post("/api/admin/objects/:id/visibility", async ({ request }) => {
+        body = await request.json();
+        return new HttpResponse(null, { status: 204 });
+      }),
+    );
+    const { result } = renderHook(() => useSetVisibility(), { wrapper });
+    await result.current.mutateAsync({ id: "o1", visibility: "internal" });
+    expect((body as { visibility: string }).visibility).toBe("internal");
+  });
+
+  test("throws a status-carrying error on 422 (publish gate)", async () => {
+    server.use(
+      http.post("/api/admin/objects/:id/visibility", () => new HttpResponse(null, { status: 422 })),
+    );
+    const { result } = renderHook(() => useSetVisibility(), { wrapper });
+    await expect(
+      result.current.mutateAsync({ id: "o1", visibility: "public" }),
+    ).rejects.toMatchObject({ status: 422 });
+  });
+});
diff --git a/web/src/objects/transitions.test.ts b/web/src/objects/transitions.test.ts
new file mode 100644
index 0000000..e7d3fd2
--- /dev/null
+++ b/web/src/objects/transitions.test.ts
@@ -0,0 +1,13 @@
+import { expect, test } from "vitest";
+
+import { adjacentTransitions } from "./transitions";
+
+test("draft can only go forward to internal", () => {
+  expect(adjacentTransitions("draft")).toEqual({ forward: "internal" });
+});
+test("internal can go forward to public and back to draft", () => {
+  expect(adjacentTransitions("internal")).toEqual({ forward: "public", back: "draft" });
+});
+test("public can only go back to internal", () => {
+  expect(adjacentTransitions("public")).toEqual({ back: "internal" });
+});
diff --git a/web/src/objects/transitions.ts b/web/src/objects/transitions.ts
new file mode 100644
index 0000000..8e88c20
--- /dev/null
+++ b/web/src/objects/transitions.ts
@@ -0,0 +1,14 @@
+export type Visibility = "draft" | "internal" | "public";
+
+/** The legal one-step visibility moves from `v`, per the backend state machine
+ *  (Draft<->Internal, Internal<->Public; no skipping). */
+export function adjacentTransitions(v: Visibility): { forward?: Visibility; back?: Visibility } {
+  switch (v) {
+    case "draft":
+      return { forward: "internal" };
+    case "internal":
+      return { forward: "public", back: "draft" };
+    case "public":
+      return { back: "internal" };
+  }
+}
diff --git a/web/src/test/handlers.ts b/web/src/test/handlers.ts
index 2531d0b..dce24de 100644
--- a/web/src/test/handlers.ts
+++ b/web/src/test/handlers.ts
@@ -38,4 +38,6 @@ export const handlers = [
   http.post("/api/admin/login", () => new HttpResponse(null, { status: 204 })),
 
   http.post("/api/admin/logout", () => new HttpResponse(null, { status: 204 })),
+
+  http.post("/api/admin/objects/:id/visibility", () => new HttpResponse(null, { status: 204 })),
 ];