arul28 · Oct 17, 2026 · Oct 17, 2026 · Oct 17, 2026
@@ -15,7 +15,7 @@ import { shallow } from "zustand/shallow";
 import { useShallow } from "zustand/react/shallow";
 
 import { AppShell } from "./AppShell";
-import { ACCOUNT_SETTINGS_ROUTE, resolveSettingsTab } from "../settings/settingsManifest";
+import { ACCOUNT_SETTINGS_ROUTE, isMachineScopedSettingsRoute, resolveSettingsTab } from "../settings/settingsManifest";
 import {
   InboundDeeplinkModal,
   type InboundDeeplinkDispatchOptions,
@@ -302,7 +302,9 @@ function serializeProjectRoute(location: ReturnType<typeof useLocation>): string
 
 function serializeStoredProjectRoute(location: ReturnType<typeof useLocation>): string | null {
   const route = serializeProjectRoute(location);
-  if (!route || location.pathname !== "/files") return route;
+  // A machine page is never the project's remembered route; the last project route stays.
+  if (!route || isMachineScopedSettingsRoute(route)) return null;
+  if (location.pathname !== "/files") return route;
   const params = new URLSearchParams(location.search ?? "");
   if (!params.has("externalPath") && !params.has("externalOpen")) return route;
   params.delete("externalPath");

@@ -10,6 +10,8 @@ import { isCssZoomedBrowserSurface } from "../../lib/webClientMode";
 import { TopBar } from "./TopBar";
 import { memoWithLatestHandlers } from "../../lib/stableIdentity";
 import { useProjectSidebarShortcuts } from "./projectSidebar/useProjectSidebarShortcuts";
+import { isSettingsRoute } from "./projectSidebar/settingsReturnRoute";
+import { isMachineScopedSettingsRoute } from "../settings/settingsManifest";
 import { useProjectTabShortcuts } from "./useProjectTabShortcuts";
 import { ProjectTransitionErrorAlert } from "./ProjectTransitionErrorAlert";
 import { TabBackground } from "../ui/TabBackground";
@@ -226,6 +228,7 @@ function serializeLocationRoute(location: ReturnType<typeof useLocation>): strin
   if (!allowedRoots.some((root) => pathname === root || pathname.startsWith(`${root}/`))) {
     return null;
   }
+  if (isMachineScopedSettingsRoute(route)) return null;
   return route;
 }
 
@@ -998,6 +1001,7 @@ export function AppShell({ children }: { children: React.ReactNode }) {
     projectRoot: currentProjectRoot,
     keybindings,
     navigate,
+    sidebarLocked: isSettingsRoute(location.pathname),
   });
 
   /** `⌃Tab` with nothing to cycle: open the palette on its project picker. */
@@ -1089,6 +1093,7 @@ export function AppShell({ children }: { children: React.ReactNode }) {
           musicRouteActive={isMusicRoute}
           accountRouteActive={isAccountRoute}
           settingsRouteActive={location.pathname === "/settings"}
+          projectSidebarLocked={isSettingsRoute(location.pathname)}
           onNavigate={(path, opts) => navigate(path, opts)}
           onOpenActivityPane={() => setActivityPaneOpen(true)}
         />

@@ -708,6 +708,7 @@ export function TopBar({
   accountRouteActive = false,
   hubRouteActive = false,
   settingsRouteActive = false,
+  projectSidebarLocked = false,
   onOpenActivityPane,
   onNavigate,
 }: {
@@ -720,6 +721,8 @@ export function TopBar({
   hubRouteActive?: boolean;
   /** The `#/settings` route is in front. Drives the standalone Settings tab. */
   settingsRouteActive?: boolean;
+  /** Settings is in front and holds the project sidebar open, so its toggle is disabled. */
+  projectSidebarLocked?: boolean;
   onNavigate?: (path: string, opts?: { replace?: boolean }) => void;
   /** Raises the shell's Activity pane over whatever tab is in front. */
   onOpenActivityPane?: () => void;
@@ -2051,7 +2054,9 @@ export function TopBar({
       <div aria-hidden className="pointer-events-none absolute inset-0 -z-10 overflow-hidden">
         <WorkToolPickerBackdrop theme={theme} field="window" />
       </div>
-      {projectSurfaceVisible ? <ProjectSidebarToggle shortcut={sidebarToggleShortcut} /> : null}
+      {projectSurfaceVisible ? (
+        <ProjectSidebarToggle shortcut={sidebarToggleShortcut} locked={projectSidebarLocked} />
+      ) : null}
 
       {/* Branding */}
       <img

@@ -0,0 +1,30 @@
+/* @vitest-environment jsdom */
+
+import { afterEach, describe, expect, it } from "vitest";
+import { readStoredProjectRoute, writeStoredProjectRoute } from "./projectRouteStorage";
+
+const BINDING_KEY = "local:/Users/arul/ADE";
+const STORAGE_KEY = `ade:project-route:${BINDING_KEY}`;
+
+describe("project route memory", () => {
+  afterEach(() => {
+    window.localStorage.clear();
+  });
+
+  it("never remembers a machine-scoped settings page, and restores a stale one to the default", () => {
+    writeStoredProjectRoute(BINDING_KEY, "/lanes");
+    writeStoredProjectRoute(BINDING_KEY, "/settings?tab=storage#diagnostics");
+    // `#diagnostics` names a This computer card, so it wins over `?tab=chat`.
+    writeStoredProjectRoute(BINDING_KEY, "/settings?tab=chat#diagnostics");
+    expect(window.localStorage.getItem(STORAGE_KEY)).toBe("/lanes");
+
+    // A project settings page is still remembered.
+    writeStoredProjectRoute(BINDING_KEY, "/settings?tab=secrets");
+    expect(window.localStorage.getItem(STORAGE_KEY)).toBe("/settings?tab=secrets");
+
+    // A value stored before machine pages were excluded restores to the default and is replaced.
+    window.localStorage.setItem(STORAGE_KEY, "/settings?tab=storage#diagnostics");
+    expect(readStoredProjectRoute(BINDING_KEY)).toBe("/work");
+    expect(window.localStorage.getItem(STORAGE_KEY)).toBe("/work");
+  });
+});
@@ -1,7 +1,11 @@
+import { isMachineScopedSettingsRoute } from "../settings/settingsManifest";
+
 /// Per-surface route memory: each open project tab remembers its last route
 /// under `ade:project-route:<bindingKey>` so tab switches replay where the
 /// user left off. Shared by ProjectTabHost (read/write on tab swaps) and
 /// TopBar (read when routing back to a project from the Chats machine tab).
+/// Machine-scoped settings pages (This computer) are never remembered: they
+/// describe one computer, not the project, so they are not a start page.
 const PROJECT_ROUTE_STORAGE_PREFIX = "ade:project-route:";
 const STORED_PROJECT_ROUTE_ROOTS = [
   "/lanes",
@@ -26,6 +30,11 @@ export function readStoredProjectRoute(bindingKey: string): string | null {
       writeStoredProjectRoute(bindingKey, "/work");
       return "/work";
     }
+    // Stored before machine pages were excluded: restore the default instead.
+    if (isMachineScopedSettingsRoute(value)) {
+      writeStoredProjectRoute(bindingKey, "/work");
+      return "/work";
+    }
     const pathname = value.split(/[?#]/, 1)[0] ?? "";
     const isSupported = STORED_PROJECT_ROUTE_ROOTS.some(
       (root) => pathname === root || pathname.startsWith(`${root}/`),
@@ -47,6 +56,8 @@ export function readStoredProjectSettingsRoute(bindingKey: string): string | nul
 }
 
 export function writeStoredProjectRoute(bindingKey: string, route: string): void {
+  // A machine page is not the project's start page, so the project keeps the one it had.
+  if (isMachineScopedSettingsRoute(route)) return;
   try {
     window.localStorage.setItem(projectRouteStorageKey(bindingKey), route);
   } catch {

@@ -73,10 +73,10 @@ describe("ProjectSidebar footer", () => {
   });
 
   it("reopens the project's stored settings page", () => {
-    window.localStorage.setItem(`ade:project-route:local:${ROOT}`, "/settings?tab=appearance#theme");
+    window.localStorage.setItem(`ade:project-route:local:${ROOT}`, "/settings?tab=chat");
     renderSidebar("/work");
     fireEvent.click(screen.getByRole("button", { name: "Settings" }));
-    expect(screen.getByTestId("location").textContent).toBe("/settings?tab=appearance#theme");
+    expect(screen.getByTestId("location").textContent).toBe("/settings?tab=chat");
   });
 
   it("returns to where you were when the cog is clicked again", () => {
@@ -89,12 +89,12 @@ describe("ProjectSidebar footer", () => {
   });
 
   it("reopens the last settings section used in this session before the stored one", () => {
-    window.localStorage.setItem(`ade:project-route:local:${ROOT}`, "/settings?tab=appearance#theme");
-    renderSidebar("/settings?tab=providers");
+    window.localStorage.setItem(`ade:project-route:local:${ROOT}`, "/settings?tab=secrets");
+    renderSidebar("/settings?tab=chat");
     cleanup();
     renderSidebar("/lanes");
     fireEvent.click(screen.getByRole("button", { name: "Settings" }));
-    expect(screen.getByTestId("location").textContent).toBe("/settings?tab=providers");
+    expect(screen.getByTestId("location").textContent).toBe("/settings?tab=chat");
   });
 
   it("keeps the page under CTO selected and turns the footer into one Back button", () => {

@@ -33,7 +33,7 @@ export { projectSidebarTabForPath };
  */
 export function ProjectSidebar({ route, heldRoute = null }: { route: string; heldRoute?: string | null }) {
   const navigate = useNavigate();
-  const { width, hidden } = useProjectSidebarPrefs();
+  const { width, hidden: hiddenByPreference } = useProjectSidebarPrefs();
   const setSlotTarget = useProjectSidebarSlotTarget();
   // Select scalars only: the sidebar sits beside every tab page, and a wide
   // selector here would re-render it on every unrelated store write.
@@ -47,6 +47,9 @@ export function ProjectSidebar({ route, heldRoute = null }: { route: string; hel
   const activeTab = projectSidebarTabForPath(pathname);
   const heldTab = heldRoute ? projectSidebarTabForPath(heldRoute.split(/[?#]/, 1)[0] || "/work") : null;
   const settingsActive = pathname === "/settings" || pathname.startsWith("/settings/");
+  // Settings keeps the sidebar open. The saved preference is left alone, so
+  // leaving Settings restores the sidebar the way the user had it.
+  const hidden = hiddenByPreference && !settingsActive;
   const settingsVisible = !isWebClientMode() || WEB_CLIENT_TAB_PATHS.has("/settings");
   const routeKey = bindingKey ?? (projectRoot ? `local:${projectRoot}` : null);
   // The star pill is a desktop-only nudge, shown under the Work session list.

@@ -6,28 +6,44 @@ import { toggleProjectSidebarHidden, useProjectSidebarHidden } from "./projectSi
 /**
  * The top bar's sidebar toggle. It lives in its own component so only this
  * button, not the whole top bar, re-renders while the sidebar is resized.
+ *
+ * `locked` is set on Settings, which holds the sidebar open, so the toggle is
+ * disabled there. A collapsed sidebar shows the toggle in the accent colour with
+ * a dot, so it is easy to find.
  */
-export function ProjectSidebarToggle({ shortcut }: { shortcut: string | null }) {
+export function ProjectSidebarToggle({ shortcut, locked = false }: { shortcut: string | null; locked?: boolean }) {
   const hidden = useProjectSidebarHidden();
+  const collapsed = hidden && !locked;
+  const description = locked
+    ? "Settings keeps the sidebar open."
+    : collapsed
+      ? "Show the project sidebar."
+      : "Hide the project sidebar.";
   return (
     <SmartTooltip
       content={{
         label: "Toggle sidebar",
-        description: hidden ? "Show the project sidebar." : "Hide the project sidebar.",
-        shortcut: shortcut ?? undefined,
+        description,
+        // The shortcut does nothing on Settings, so the hint is not offered there.
+        shortcut: locked ? undefined : shortcut ?? undefined,
       }}
       wrapperStyle={{ WebkitAppRegion: "no-drag" } as React.CSSProperties}
     >
       <button
         type="button"
-        className="ade-shell-control inline-flex h-[24px] w-[24px] shrink-0 items-center justify-center"
+        className="ade-shell-control relative inline-flex h-[24px] w-[24px] shrink-0 items-center justify-center aria-disabled:cursor-not-allowed aria-disabled:opacity-40"
         data-variant="ghost"
+        data-collapsed={collapsed ? "true" : undefined}
         aria-label="Toggle sidebar"
-        aria-pressed={!hidden}
-        onClick={toggleProjectSidebarHidden}
+        aria-pressed={!collapsed}
+        aria-disabled={locked || undefined}
+        onClick={locked ? undefined : toggleProjectSidebarHidden}
         style={{ WebkitAppRegion: "no-drag" } as React.CSSProperties}
       >
         <SidebarSimple size={16} weight="regular" />
+        {collapsed ? (
+          <span aria-hidden className="absolute right-[3px] top-[3px] h-1.5 w-1.5 rounded-full bg-accent" />
+        ) : null}
       </button>
     </SmartTooltip>
   );

@@ -1,7 +1,11 @@
+import { isMachineScopedSettingsRoute } from "../../settings/settingsManifest";
+
 /**
  * Settings is a place you visit and leave. For each project this remembers
  * where you were before Settings (so the cog and the back button can return
  * you there) and the last Settings section you used (so the cog reopens it).
+ * A machine-scoped section (This computer) is not remembered: the cog opens
+ * Settings' default page instead.
  *
  * The project sidebar records every route it sees. Memory only: a restart
  * returns to Work, which is also where the app opens.
@@ -30,8 +34,11 @@ function isOverlayRoute(route: string): boolean {
 /** Records the route on screen for a project. */
 export function rememberProjectRoute(projectKey: string | null, route: string): void {
   if (!projectKey || !route || isOverlayRoute(route)) return;
-  if (isSettingsRoute(route)) settingsRouteByProject.set(projectKey, route);
-  else returnRouteByProject.set(projectKey, route);
+  if (isSettingsRoute(route)) {
+    if (!isMachineScopedSettingsRoute(route)) settingsRouteByProject.set(projectKey, route);
+  } else {
+    returnRouteByProject.set(projectKey, route);
+  }
 }
 
 /** Where to go when you leave Settings. */

@@ -30,14 +30,17 @@ function keystrokeIsClaimed(target: EventTarget | null): boolean {
  * shows or hides it. They follow the command palette's rule and work while a
  * text field has focus, but a handler that already used the chord (bold in the
  * PR markdown editor) wins because it calls `preventDefault` first.
+ * `sidebarLocked` is set on Settings, which keeps the sidebar open, so Mod+B
+ * is left alone there.
  */
 export function useProjectSidebarShortcuts(args: {
   enabled: boolean;
   projectRoot: string | null;
   keybindings: KeybindingsSnapshot | null;
   navigate: (path: string) => void;
+  sidebarLocked?: boolean;
 }): void {
-  const { enabled, projectRoot, keybindings, navigate } = args;
+  const { enabled, projectRoot, keybindings, navigate, sidebarLocked = false } = args;
 
   const bindings = useMemo(() => {
     const tabs = visibleProjectSidebarTabs(PROJECT_SIDEBAR_TABS).flatMap((tab) =>
@@ -59,6 +62,7 @@ export function useProjectSidebarShortcuts(args: {
       if (event.defaultPrevented || event.isComposing) return;
       if (keystrokeIsClaimed(event.target)) return;
       if (eventMatchesBinding(event, bindings.toggle)) {
+        if (sidebarLocked) return;
         event.preventDefault();
         if (!event.repeat) toggleProjectSidebarHidden();
         return;
@@ -71,5 +75,5 @@ export function useProjectSidebarShortcuts(args: {
     };
     window.addEventListener("keydown", onKeyDown);
     return () => window.removeEventListener("keydown", onKeyDown);
-  }, [bindings, enabled, navigate, projectRoot]);
+  }, [bindings, enabled, navigate, projectRoot, sidebarLocked]);
 }
@@ -1431,6 +1431,35 @@ export function resolveSettingsHash(hash: string | null | undefined): SettingEnt
   return aliased ? (ENTRIES_BY_ID.get(aliased) ?? null) : null;
 }
 
+/**
+ * The tab a `/settings` route opens on, resolved the way `SettingsPage`
+ * resolves it: a `#hash` names one card and wins over `?tab=`, and a missing or
+ * unknown tab opens on `DEFAULT_SETTINGS_TAB`.
+ */
+export function settingsTabForRoute(route: string): SettingsTabId {
+  const url = new URL(route, "http://settings.invalid");
+  let hash = url.hash;
+  try {
+    hash = decodeURIComponent(hash);
+  } catch {
+    // A malformed escape is literal text, as it is on the settings page.
+  }
+  const linked = resolveSettingsHash(hash);
+  if (linked) return linked.tab;
+  return resolveSettingsTab(url.searchParams.get("tab")) ?? DEFAULT_SETTINGS_TAB;
+}
+
+/**
+ * Whether a route is a machine-scoped settings page: one of the This computer
+ * pages (General, Diagnostics, Providers and the rest). Those describe one
+ * computer, so a project must never remember one as its place to return to.
+ */
+export function isMachineScopedSettingsRoute(route: string): boolean {
+  const pathname = route.split(/[?#]/, 1)[0] ?? "";
+  if (pathname !== "/settings" && !pathname.startsWith("/settings/")) return false;
+  return isMachineSettingsTab(settingsTabForRoute(route));
+}
+
 /** The route a palette entry or deeplink should navigate to. */
 /**
  * The scope for one card's anchor, or null when the anchor is not a manifest

@@ -282,6 +282,12 @@ h6 {
   box-shadow: inset 0 0 0 1px var(--shell-control-focus-ring);
 }
 
+/* A collapsed project sidebar: its toggle takes the accent, and the dot the
+   toggle renders marks it (see ProjectSidebarToggle). */
+.ade-shell-control[data-collapsed="true"] {
+  color: var(--color-accent);
+}
+
 .ade-shell-control-kbd {
   color: var(--shell-control-kbd-fg);
   background: var(--shell-control-kbd-bg);

@@ -2052,6 +2052,21 @@ the new-project screen.
 `DEFAULT_SETTINGS_TAB` names where Settings opens. It used to be `tabs[0]`, so
 reordering the sidebar silently moved the landing page.
 
+### Settings holds the project sidebar open
+
+On any Settings page the project sidebar is shown: its toggle is disabled (the
+tooltip says why) and Mod+B does nothing. The saved show/hide preference is not
+changed, so leaving Settings restores the sidebar the way you had it. While the
+sidebar is collapsed, its toggle is drawn in the accent colour with a dot.
+
+A Machines page (General, Appearance, Apple devices, Providers, Lanes,
+Integrations, Diagnostics, Archive) describes one computer, so a project never
+remembers one as its start page. The project returns to its last page that is
+not a Machines page, and a stored Machines page from before this rule restores
+to Work. The cog reopens the project's last Account or Project section, or
+Settings' default page. `isMachineScopedSettingsRoute` in `settingsManifest.ts`
+decides which routes count.
+
 The pages themselves:
 
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