diff --git a/ui/src/components/app-sidebar-session-catalog-state.ts b/ui/src/components/app-sidebar-session-catalog-state.ts
new file mode 100644
index 000000000000..87df3f2ec67e
--- /dev/null
+++ b/ui/src/components/app-sidebar-session-catalog-state.ts
@@ -0,0 +1,79 @@
+import type {
+  SessionCatalog,
+  SessionCatalogHost,
+  SessionCatalogSession,
+} from "../../../packages/gateway-protocol/src/index.ts";
+import { GatewayRequestError } from "../api/gateway.ts";
+
+type SessionCatalogError = NonNullable<SessionCatalog["error"]>;
+
+export function sessionCatalogRequestError(error: unknown): SessionCatalogError {
+  return {
+    code: error instanceof GatewayRequestError ? error.gatewayCode : "UNAVAILABLE",
+    message: error instanceof Error ? error.message : String(error),
+  };
+}
+
+export function mergeCatalogSessionRows(
+  first: readonly SessionCatalogSession[],
+  second: readonly SessionCatalogSession[],
+): SessionCatalogSession[] {
+  const seen = new Set(first.map((session) => session.threadId));
+  return [...first, ...second.filter((session) => !seen.has(session.threadId))];
+}
+
+export function preserveExpandedCatalogHost(
+  freshHost: SessionCatalogHost,
+  previous: SessionCatalogHost | undefined,
+): SessionCatalogHost {
+  if (!previous) {
+    return freshHost;
+  }
+  const { sessions, nextCursor, ...previousDetails } = previous;
+  const { sessions: _freshSessions, nextCursor: _freshNextCursor, ...freshDetails } = freshHost;
+  return {
+    ...previousDetails,
+    ...freshDetails,
+    sessions,
+    ...(nextCursor !== undefined ? { nextCursor } : {}),
+  };
+}
+
+export function mergeSessionCatalogPage(params: {
+  current: SessionCatalog;
+  page: SessionCatalog;
+  cursors: Readonly<Record<string, string>>;
+}): { catalog: SessionCatalog; advancedHostIds: string[] } {
+  const pageHosts = new Map(params.page.hosts.map((host) => [host.hostId, host]));
+  const advancedHostIds: string[] = [];
+  const hosts = params.current.hosts.map((host) => {
+    const requestedCursor = params.cursors[host.hostId];
+    const pageHost = pageHosts.get(host.hostId);
+    if (requestedCursor === undefined || host.nextCursor !== requestedCursor || !pageHost) {
+      return host;
+    }
+    if (pageHost.error) {
+      return preserveExpandedCatalogHost(pageHost, host);
+    }
+    advancedHostIds.push(host.hostId);
+    const { nextCursor, sessions, error: _pageError, ...pageHostDetails } = pageHost;
+    const { nextCursor: _currentCursor, error: _currentError, ...currentHost } = host;
+    return {
+      ...currentHost,
+      ...pageHostDetails,
+      sessions: mergeCatalogSessionRows(host.sessions, sessions),
+      ...(nextCursor ? { nextCursor } : {}),
+    };
+  });
+  const { hosts: _currentHosts, error: _currentError, ...currentDetails } = params.current;
+  const { hosts: _pageHosts, error: pageError, ...pageDetails } = params.page;
+  return {
+    catalog: {
+      ...currentDetails,
+      ...pageDetails,
+      hosts,
+      ...(pageError ? { error: pageError } : {}),
+    },
+    advancedHostIds,
+  };
+}
diff --git a/ui/src/components/app-sidebar.test.ts b/ui/src/components/app-sidebar.test.ts
index da20bbb2d9c7..537fb05fea51 100644
--- a/ui/src/components/app-sidebar.test.ts
+++ b/ui/src/components/app-sidebar.test.ts
@@ -7,7 +7,7 @@ import type {
   SessionCatalog,
   SessionsCatalogListResult,
 } from "../../../packages/gateway-protocol/src/index.ts";
-import type { GatewayBrowserClient } from "../api/gateway.ts";
+import { GatewayRequestError, type GatewayBrowserClient } from "../api/gateway.ts";
 import type { AgentsListResult, SessionsListResult } from "../api/types.ts";
 import type { RouteId } from "../app-route-paths.ts";
 import {
@@ -1095,6 +1095,127 @@ describe("AppSidebar session catalog pagination", () => {
     }
   });
 
+  it("shows a rejected load-more request and clears it after a successful retry", async () => {
+    vi.useFakeTimers();
+    try {
+      const request = vi
+        .fn()
+        .mockResolvedValueOnce(catalogPage([{ threadId: "thread-1", name: "Newest" }], "page-2"))
+        .mockRejectedValueOnce(
+          new GatewayRequestError({ code: "UNAVAILABLE", message: "Second page unavailable" }),
+        )
+        .mockResolvedValueOnce(catalogPage([{ threadId: "thread-2", name: "Older" }]));
+      const gateway = createGatewayHarness({ request } as unknown as GatewayBrowserClient);
+      gateway.publish({
+        hello: {
+          features: { methods: ["sessions.catalog.list"] },
+        } as ApplicationGatewaySnapshot["hello"],
+      });
+      const { sidebar } = await mountSidebar(
+        gateway.gateway,
+        createSessions("main", ["agent:main:main"]),
+      );
+      sidebar.connected = true;
+      await sidebar.updateComplete;
+      await vi.advanceTimersByTimeAsync(0);
+      await sidebar.updateComplete;
+
+      const section = () => sidebar.querySelector('[data-session-section="catalog:codex"]');
+      const loadMore = () =>
+        sidebar.querySelector<HTMLButtonElement>('[data-session-catalog-load-more="codex"]');
+      loadMore()?.click();
+      await vi.advanceTimersByTimeAsync(0);
+      await sidebar.updateComplete;
+
+      expect(section()?.querySelector('[data-session-catalog-error="codex"]')).not.toBeNull();
+      expect(
+        section()?.querySelector(".sidebar-session-group-toggle")?.getAttribute("aria-label"),
+      ).toContain("Second page unavailable");
+      expect(sidebar.sessionCatalogs[0]?.error?.code).toBe("UNAVAILABLE");
+      expect(sidebar.sessionCatalogs[0]?.hosts[0]?.nextCursor).toBe("page-2");
+      expect(loadMore()?.disabled).toBe(false);
+
+      loadMore()?.click();
+      await vi.advanceTimersByTimeAsync(0);
+      await sidebar.updateComplete;
+
+      expect(request).toHaveBeenNthCalledWith(3, "sessions.catalog.list", {
+        agentId: "main",
+        catalogId: "codex",
+        cursors: { "gateway:local": "page-2" },
+      });
+      expect(section()?.querySelector('[data-session-catalog-error="codex"]')).toBeNull();
+      expect(sidebar.textContent).toContain("Older");
+      expect(loadMore()).toBeNull();
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
+  it.each(["catalog", "host"] as const)(
+    "preserves the current page while exposing a structured %s load-more error",
+    async (errorOwner) => {
+      vi.useFakeTimers();
+      try {
+        const structuredError =
+          errorOwner === "catalog"
+            ? {
+                catalogs: [
+                  {
+                    id: "codex",
+                    label: "Codex",
+                    capabilities: { continueSession: true, archive: true },
+                    hosts: [],
+                    error: { code: "catalog_error", message: "Catalog page failed" },
+                  },
+                ],
+              }
+            : catalogErrorPage("Host page failed");
+        const request = vi
+          .fn()
+          .mockResolvedValueOnce(catalogPage([{ threadId: "thread-1", name: "Newest" }], "page-2"))
+          .mockResolvedValueOnce(structuredError)
+          .mockResolvedValueOnce(catalogPage([{ threadId: "thread-2", name: "Older" }]));
+        const gateway = createGatewayHarness({ request } as unknown as GatewayBrowserClient);
+        gateway.publish({
+          hello: {
+            features: { methods: ["sessions.catalog.list"] },
+          } as ApplicationGatewaySnapshot["hello"],
+        });
+        const { sidebar } = await mountSidebar(
+          gateway.gateway,
+          createSessions("main", ["agent:main:main"]),
+        );
+        sidebar.connected = true;
+        await sidebar.updateComplete;
+        await vi.advanceTimersByTimeAsync(0);
+        await sidebar.updateComplete;
+
+        const loadMore = () =>
+          sidebar.querySelector<HTMLButtonElement>('[data-session-catalog-load-more="codex"]');
+        loadMore()?.click();
+        await vi.advanceTimersByTimeAsync(0);
+        await sidebar.updateComplete;
+
+        const section = sidebar.querySelector('[data-session-section="catalog:codex"]');
+        expect(section?.querySelector('[data-session-catalog-error="codex"]')).not.toBeNull();
+        expect(
+          section?.querySelector(".sidebar-session-group-toggle")?.getAttribute("aria-label"),
+        ).toContain(errorOwner === "catalog" ? "Catalog page failed" : "Host page failed");
+        expect(sidebar.textContent).toContain("Newest");
+        expect(sidebar.sessionCatalogs[0]?.hosts[0]?.nextCursor).toBe("page-2");
+
+        loadMore()?.click();
+        await vi.advanceTimersByTimeAsync(0);
+        await sidebar.updateComplete;
+        expect(sidebar.querySelector('[data-session-catalog-error="codex"]')).toBeNull();
+        expect(sidebar.textContent).toContain("Older");
+      } finally {
+        vi.useRealTimers();
+      }
+    },
+  );
+
   it("appends host pages and keeps them through the next poll refresh", async () => {
     vi.useFakeTimers();
     try {
diff --git a/ui/src/components/app-sidebar.ts b/ui/src/components/app-sidebar.ts
index c7819afa35a4..f92da695fefc 100644
--- a/ui/src/components/app-sidebar.ts
+++ b/ui/src/components/app-sidebar.ts
@@ -4,8 +4,6 @@ import { property, state } from "lit/decorators.js";
 import { keyed } from "lit/directives/keyed.js";
 import type {
   SessionCatalog,
-  SessionCatalogHost,
-  SessionCatalogSession,
   SessionsCatalogListResult,
 } from "../../../packages/gateway-protocol/src/index.ts";
 import type { GatewayBrowserClient } from "../api/gateway.ts";
@@ -96,6 +94,12 @@ import {
   sidebarMoreMenuHoldsActiveRoute,
   sidebarPluginTabs,
 } from "./app-sidebar-nav-menus.ts";
+import {
+  mergeCatalogSessionRows,
+  mergeSessionCatalogPage,
+  preserveExpandedCatalogHost,
+  sessionCatalogRequestError,
+} from "./app-sidebar-session-catalog-state.ts";
 import {
   adoptedCatalogSessionKeys,
   bindAdoptedCatalogSession,
@@ -234,31 +238,6 @@ function sessionCatalogHostKey(catalogId: string, hostId: string): string {
   return `${catalogId}\u0000${hostId}`;
 }
 
-function mergeCatalogSessionRows(
-  first: readonly SessionCatalogSession[],
-  second: readonly SessionCatalogSession[],
-): SessionCatalogSession[] {
-  const seen = new Set(first.map((session) => session.threadId));
-  return [...first, ...second.filter((session) => !seen.has(session.threadId))];
-}
-
-function preserveExpandedCatalogHost(
-  freshHost: SessionCatalogHost,
-  previous: SessionCatalogHost | undefined,
-): SessionCatalogHost {
-  if (!previous) {
-    return freshHost;
-  }
-  const { sessions, nextCursor, ...previousDetails } = previous;
-  const { sessions: _freshSessions, nextCursor: _freshNextCursor, ...freshDetails } = freshHost;
-  return {
-    ...previousDetails,
-    ...freshDetails,
-    sessions,
-    ...(nextCursor !== undefined ? { nextCursor } : {}),
-  };
-}
-
 class AppSidebar extends OpenClawLightDomContentsElement {
   @property({ attribute: false }) basePath = "";
   @property({ attribute: false }) activeRouteId?: NavigationRouteId;
@@ -658,49 +637,37 @@ class AppSidebar extends OpenClawLightDomContentsElement {
       if (!page) {
         return;
       }
-      const pageHosts = new Map(page.hosts.map((host) => [host.hostId, host]));
-      const requestedHosts = new Set(Object.keys(cursors));
-      let updated = false;
-      const catalogs = this.sessionCatalogs.map((currentCatalog) => {
-        if (currentCatalog.id !== catalogId) {
-          return currentCatalog;
-        }
-        return {
-          ...currentCatalog,
-          hosts: currentCatalog.hosts.map((host) => {
-            const pageHost = pageHosts.get(host.hostId);
-            if (
-              !requestedHosts.has(host.hostId) ||
-              host.nextCursor !== cursors[host.hostId] ||
-              !pageHost ||
-              pageHost.error
-            ) {
-              return host;
-            }
-            updated = true;
-            const key = sessionCatalogHostKey(catalogId, host.hostId);
-            this.sessionCatalogPageDepths.set(
-              key,
-              (this.sessionCatalogPageDepths.get(key) ?? 0) + 1,
-            );
-            const { nextCursor, sessions, ...pageHostDetails } = pageHost;
-            const { nextCursor: _currentCursor, ...currentHost } = host;
-            return {
-              ...currentHost,
-              ...pageHostDetails,
-              sessions: mergeCatalogSessionRows(host.sessions, sessions),
-              ...(nextCursor ? { nextCursor } : {}),
-            };
-          }),
-        };
-      });
-      if (updated) {
-        this.sessionCatalogs = catalogs;
-        this.sessionCatalogRevisions.set(catalogId, revision + 1);
-        this.sessionCatalogRevision += 1;
+      const current = this.sessionCatalogs.find((candidate) => candidate.id === catalogId);
+      if (!current) {
+        return;
       }
-    } catch {
-      // Keep the current cursor so the user can retry the same page.
+      const merged = mergeSessionCatalogPage({ current, page, cursors });
+      for (const hostId of merged.advancedHostIds) {
+        const key = sessionCatalogHostKey(catalogId, hostId);
+        this.sessionCatalogPageDepths.set(key, (this.sessionCatalogPageDepths.get(key) ?? 0) + 1);
+      }
+      this.sessionCatalogs = this.sessionCatalogs.map((candidate) =>
+        candidate.id === catalogId ? merged.catalog : candidate,
+      );
+      this.sessionCatalogRevisions.set(catalogId, revision + 1);
+      this.sessionCatalogRevision += 1;
+    } catch (error) {
+      if (
+        generation !== this.sessionCatalogGeneration ||
+        revision !== (this.sessionCatalogRevisions.get(catalogId) ?? 0) ||
+        client !== this.gatewayClient
+      ) {
+        return;
+      }
+      // Preserve rows and cursors: the visible error explains that retrying
+      // Load More will request the same page rather than advancing past it.
+      this.sessionCatalogs = this.sessionCatalogs.map((candidate) =>
+        candidate.id === catalogId
+          ? { ...candidate, error: sessionCatalogRequestError(error) }
+          : candidate,
+      );
+      this.sessionCatalogRevisions.set(catalogId, revision + 1);
+      this.sessionCatalogRevision += 1;
     } finally {
       if (generation === this.sessionCatalogGeneration) {
         const loading = new Set(this.loadingMoreSessionCatalogIds);
diff --git a/ui/src/e2e/codex-sessions.e2e.test.ts b/ui/src/e2e/codex-sessions.e2e.test.ts
index bae01ee70703..feafeb530e39 100644
--- a/ui/src/e2e/codex-sessions.e2e.test.ts
+++ b/ui/src/e2e/codex-sessions.e2e.test.ts
@@ -79,6 +79,75 @@ suite("Codex native session catalog", () => {
     await page.close();
   });
 
+  it("shows a catalog Load More rejection without losing the retry cursor", async () => {
+    const page = await browser.newPage();
+    const pageErrors: string[] = [];
+    page.on("pageerror", (error) => pageErrors.push(error.message));
+    const gateway = await installMockGateway(page, {
+      featureMethods: ["chat.metadata", "chat.startup", "sessions.catalog.list"],
+      methodResponses: {
+        "sessions.catalog.list": {
+          catalogs: [
+            {
+              id: "codex",
+              label: "Codex",
+              capabilities: { continueSession: true, archive: true },
+              hosts: [
+                {
+                  hostId: "gateway:codex",
+                  label: "Local Codex",
+                  kind: "gateway",
+                  connected: true,
+                  sessions: [
+                    {
+                      threadId: "thread-1",
+                      name: "Newest session",
+                      status: "idle",
+                      archived: false,
+                      canContinue: true,
+                      canArchive: true,
+                    },
+                  ],
+                  nextCursor: "page-2",
+                },
+              ],
+            },
+          ],
+        },
+      },
+    });
+
+    try {
+      await page.goto(`${server.baseUrl}chat`);
+      await expect
+        .poll(async () => (await gateway.getRequests("sessions.catalog.list")).length)
+        .toBe(1);
+      const loadMore = page.locator('[data-session-catalog-load-more="codex"]');
+      await loadMore.waitFor({ state: "visible" });
+      await gateway.deferNext("sessions.catalog.list");
+      await loadMore.click();
+      await expect
+        .poll(async () => (await gateway.getRequests("sessions.catalog.list")).length)
+        .toBe(2);
+      await gateway.rejectDeferred("sessions.catalog.list", {
+        code: "UNAVAILABLE",
+        message: "Second catalog page unavailable",
+      });
+
+      const section = page.locator('[data-session-section="catalog:codex"]');
+      await section.locator('[data-session-catalog-error="codex"]').waitFor({ state: "visible" });
+      await expect
+        .poll(() => section.locator(".sidebar-session-group-toggle").getAttribute("aria-label"))
+        .toContain("Second catalog page unavailable");
+      await expect.poll(() => loadMore.getAttribute("aria-busy")).toBe("false");
+      expect(await loadMore.isEnabled()).toBe(true);
+      expect(await page.getByText("Newest session", { exact: true }).count()).toBe(1);
+      expect(pageErrors).toEqual([]);
+    } finally {
+      await page.close();
+    }
+  });
+
   it("adopts from the native chat composer, navigates, and auto-sends", async () => {
     const page = await browser.newPage();
     const gateway = await installMockGateway(page, {