diff --git a/apps/web/src/components/Sidebar.browser.test.tsx b/apps/web/src/components/Sidebar.browser.test.tsx
index c1cae81000123..ed24a60e0cd3f 100644
--- a/apps/web/src/components/Sidebar.browser.test.tsx
+++ b/apps/web/src/components/Sidebar.browser.test.tsx
@@ -16,7 +16,7 @@ import { makeThreadFixture } from "../test-fixtures";
 import { useHandleNewThread } from "../hooks/useHandleNewThread";
 import { __setClientSettingsForTests, getClientSettings } from "../hooks/useSettings";
 import { useThreadRouteTarget } from "../hooks/useThreadRouteTarget";
-import { useProjects, useQuietThreadShells } from "../state/entities";
+import { useProjects, useQuietThreadShells, useServerConfigs } from "../state/entities";
 import { useTerminalUiStateStore } from "../terminalUiStateStore";
 import type { Project } from "../types";
 import Sidebar from "./Sidebar";
@@ -112,6 +112,57 @@ describe("sidebar header new thread", () => {
   });
 });
 
+describe("sidebar settled shelf", () => {
+  // regression: #34291 changing the project filter collapsed an expanded Settled shelf back to 10
+  it("keeps its expanded length when the project filter changes", async () => {
+    using stack = new DisposableStack();
+    localStorage.setItem("t3code:sidebar:settled-expanded", "true");
+    stack.defer(() => localStorage.removeItem("t3code:sidebar:settled-expanded"));
+    const projectA = project("a");
+    const projectB = project("b");
+    const settled = (projectId: ProjectId, index: number) => ({
+      ...threadShell(projectId, index),
+      settledOverride: "settled" as const,
+    });
+    const threads = [
+      ...Array.from({ length: 14 }, (_, index) => settled(projectA.id, index)),
+      ...Array.from({ length: 2 }, (_, index) => settled(projectB.id, 14 + index)),
+    ];
+    vi.mocked(useProjects).mockReturnValue([projectA, projectB]);
+    vi.mocked(useQuietThreadShells).mockReturnValue(threads);
+    // Threads only count as settled once their environment's config has loaded.
+    vi.mocked(useServerConfigs).mockReturnValue(
+      new Map([[projectA.environmentId, { environment: { capabilities: {} } } as never]]),
+    );
+    vi.mocked(useThreadRouteTarget).mockReturnValue(null);
+    vi.mocked(useHandleNewThread).mockReturnValue({
+      activeDraftThread: null,
+      activeThread: null,
+      defaultProjectRef: { environmentId: projectA.environmentId, projectId: projectA.id },
+      defaultProjectFallbackReady: true,
+      handleNewThread: vi.fn().mockResolvedValue(null),
+      routeDraftId: null,
+      routeThreadRef: null,
+    });
+    await using screen = await render(
+      <SidebarProvider>
+        <Sidebar routeReveal={{ observedKey: null, pendingKey: null }} />
+      </SidebarProvider>,
+    );
+
+    await userEvent.click(screen.getByRole("button", { name: "Show 6 more" }));
+    await expect.element(screen.getByText("Thread 15").first()).toBeInTheDocument();
+
+    await userEvent.click(screen.getByRole("combobox", { name: "Filter threads by project" }));
+    await userEvent.click(screen.getByRole("option", { name: "a" }));
+    await expect.element(screen.getByRole("button", { name: "Settled14" })).toBeInTheDocument();
+    expect(
+      screen.getByRole("button", { name: /^Thread \d+, a$/ }).elements(),
+      "the Settled shelf fell back to its first page",
+    ).toHaveLength(14);
+  });
+});
+
 function threadShell(projectId: ProjectId, index: number): EnvironmentThreadShell {
   return makeThreadFixture({
     environmentId: EnvironmentId.make("local"),
diff --git a/apps/web/src/components/Sidebar.tsx b/apps/web/src/components/Sidebar.tsx
index 8fa58d8456f75..87e8ef18694b8 100644
--- a/apps/web/src/components/Sidebar.tsx
+++ b/apps/web/src/components/Sidebar.tsx
@@ -412,7 +412,6 @@ function routeThreadOnly(
 
 // Separate hooks cache maps independently of later Sidebar hooks and preserve dnd-kit inputs.
 function useSidebarThreads(input: {
-  readonly projectScopeKey: string | null;
   readonly scopedProjectKeys: ReadonlySet<string> | null;
   readonly serverConfigs: ReadonlyMap<EnvironmentId, EnvironmentServerConfig>;
   readonly connectedEnvironmentIds: readonly EnvironmentId[];
@@ -426,7 +425,6 @@ function useSidebarThreads(input: {
   readonly keepEmptyFolders: (group: SidebarProjectSnapshot) => boolean;
 }) {
   const {
-    projectScopeKey,
     scopedProjectKeys,
     serverConfigs,
     connectedEnvironmentIds,
@@ -465,15 +463,7 @@ function useSidebarThreads(input: {
   // Shared with the old per-project sidebar, so folders keep their open state.
   const projectExpandedById = useUiStateStore((store) => store.projectExpandedById);
   const setProjectExpanded = useUiStateStore((store) => store.setProjectExpanded);
-  const [settledTail, setSettledTail] = useState({
-    scopeKey: projectScopeKey,
-    count: SETTLED_TAIL_INITIAL_COUNT,
-  });
-  if (settledTail.scopeKey !== projectScopeKey) {
-    setSettledTail({ scopeKey: projectScopeKey, count: SETTLED_TAIL_INITIAL_COUNT });
-  }
-  const settledVisibleCount =
-    settledTail.scopeKey === projectScopeKey ? settledTail.count : SETTLED_TAIL_INITIAL_COUNT;
+  const [settledVisibleCount, setSettledVisibleCount] = useState(SETTLED_TAIL_INITIAL_COUNT);
 
   const partition = partitionSidebarThreads({
     threads,
@@ -575,11 +565,7 @@ function useSidebarThreads(input: {
     settledCount,
     olderSettledShelf,
     hiddenSettledCount: Math.max(0, settledCount - visibleSettledThreads.length),
-    showMoreSettled: () =>
-      setSettledTail((current) => ({
-        scopeKey: current.scopeKey,
-        count: current.count + SETTLED_TAIL_PAGE_COUNT,
-      })),
+    showMoreSettled: () => setSettledVisibleCount((count) => count + SETTLED_TAIL_PAGE_COUNT),
     settledShelfExpanded,
     toggleSettledShelf: () => setSettledShelfExpanded((value) => !value),
     snoozedShelfExpanded,
@@ -1138,7 +1124,6 @@ export default function Sidebar({ routeReveal }: { routeReveal: SidebarRouteReve
     findThread: (key) => threads.find((candidate) => threadShellKey(candidate) === key),
   });
   const projectScopeKeys = revealWidensScope ? [] : chosenProjectScopeKeys;
-  const projectScopeKey = projectScopeKeys.length === 0 ? null : projectScopeKeys.join("\n");
   const toggleProjectScopeKey = (key: string) =>
     setProjectScopeKeys(
       projectScopeKeys.includes(key)
@@ -1336,7 +1321,6 @@ export default function Sidebar({ routeReveal }: { routeReveal: SidebarRouteReve
     pinnedKeysById,
     activeKeysById,
   } = useSidebarThreads({
-    projectScopeKey,
     scopedProjectKeys,
     serverConfigs,
     connectedEnvironmentIds,