diff --git a/packages/ui/src/stores/DOCUMENTATION.md b/packages/ui/src/stores/DOCUMENTATION.md
index 6f893f51..c765dded 100644
--- a/packages/ui/src/stores/DOCUMENTATION.md
+++ b/packages/ui/src/stores/DOCUMENTATION.md
@@ -42,6 +42,10 @@ refresh attempt per opening, so a failed first load cannot create a retry loop.
 
 ### UI state stores
 
+Sidebar visibility and its persisted width are independent. Opening or closing
+the sidebar never writes a width; only resizing changes the saved choice.
+The initial width is separate from the component's minimum resize width.
+
 `useCommitSelectionStore.ts` shares the selected commit between desktop/mobile
 Changes and walkthrough. Choices are session-only and keyed by runtime, directory, and
 checked-out branch, with at most 100 remembered choices. The picker history
diff --git a/packages/ui/src/stores/useUIStore.sidebar.test.ts b/packages/ui/src/stores/useUIStore.sidebar.test.ts
new file mode 100644
index 00000000..726dd34a
--- /dev/null
+++ b/packages/ui/src/stores/useUIStore.sidebar.test.ts
@@ -0,0 +1,52 @@
+import { afterEach, expect, test } from 'bun:test';
+import { useUIStore } from './useUIStore';
+
+const originalOptions = useUIStore.persist.getOptions();
+const originalState = useUIStore.getState();
+
+afterEach(() => {
+  useUIStore.persist.setOptions(originalOptions);
+  useUIStore.setState(originalState, true);
+});
+
+test('the initial sidebar width is independent of its resize minimum', () => {
+  expect(useUIStore.getInitialState().sidebarWidth).toBe(280);
+});
+
+for (const width of [168, 280, 360]) {
+  test(`reopening a persisted ${width}px sidebar preserves its width`, async () => {
+    useUIStore.persist.setOptions({ storage: {
+      getItem: () => ({ version: originalOptions.version, state: { sidebarWidth: width, isSidebarOpen: true } }),
+      setItem: () => undefined,
+      removeItem: () => undefined,
+    } });
+    useUIStore.setState(useUIStore.getInitialState(), true);
+    await useUIStore.persist.rehydrate();
+
+    const actions = useUIStore.getState();
+    actions.toggleSidebar();
+    expect(useUIStore.getState().isSidebarOpen).toBe(false);
+    expect(useUIStore.getState().sidebarWidth).toBe(width);
+    actions.toggleSidebar();
+    expect(useUIStore.getState().isSidebarOpen).toBe(true);
+    expect(useUIStore.getState().sidebarWidth).toBe(width);
+
+    actions.setSidebarOpen(false);
+    actions.setSidebarOpen(true);
+    expect(useUIStore.getState().sidebarWidth).toBe(width);
+    const openState = useUIStore.getState();
+    actions.setSidebarOpen(true);
+    expect(useUIStore.getState()).toBe(openState);
+  });
+}
+
+test('a manual resize stays authoritative across repeated visibility changes', () => {
+  useUIStore.setState(useUIStore.getInitialState(), true);
+  const actions = useUIStore.getState();
+  actions.setSidebarWidth(420);
+  actions.setSidebarOpen(false);
+  actions.setSidebarOpen(true);
+  actions.toggleSidebar();
+  actions.toggleSidebar();
+  expect(useUIStore.getState().sidebarWidth).toBe(420);
+});
diff --git a/packages/ui/src/stores/useUIStore.ts b/packages/ui/src/stores/useUIStore.ts
index e2af3cd4..cbf9de35 100644
--- a/packages/ui/src/stores/useUIStore.ts
+++ b/packages/ui/src/stores/useUIStore.ts
@@ -217,7 +217,7 @@ const CONTEXT_PANEL_MAX_WIDTH = 1400;
 /** Per surface, not per panel: see clampContextPanelTabs. */
 const CONTEXT_PANEL_MAX_TABS = 12;
 const CONTEXT_PANEL_MAX_LABEL_LENGTH = 120;
-const LEFT_SIDEBAR_MIN_WIDTH = 168;
+const LEFT_SIDEBAR_DEFAULT_WIDTH = 280;
 /** Separates browser tabs opened in the same millisecond. */
 let browserTabSequence = 0;
 
@@ -762,7 +762,6 @@ interface UIStore {
   multiRunLauncherPrefillPrompt: string;
   isSidebarOpen: boolean;
   sidebarWidth: number;
-  hasManuallyResizedLeftSidebar: boolean;
   contextPanelByDirectory: Record<string, ContextPanelDirectoryState>;
   contextRailOrder: string[];
   /** Surface ids the user hid from the context rail; stored as the hidden set
@@ -1184,8 +1183,7 @@ export const useUIStore = create<UIStore>()(
         isMultiRunLauncherOpen: false,
         multiRunLauncherPrefillPrompt: '',
         isSidebarOpen: true,
-        sidebarWidth: LEFT_SIDEBAR_MIN_WIDTH,
-        hasManuallyResizedLeftSidebar: false,
+        sidebarWidth: LEFT_SIDEBAR_DEFAULT_WIDTH,
         contextPanelByDirectory: {},
         contextRailOrder: [],
         contextRailHiddenSurfaces: [],
@@ -1347,45 +1345,15 @@ export const useUIStore = create<UIStore>()(
         },
 
         toggleSidebar: () => {
-          set((state) => {
-            const newOpen = !state.isSidebarOpen;
-
-            if (newOpen && !state.hasManuallyResizedLeftSidebar) {
-              return {
-                isSidebarOpen: newOpen,
-                sidebarWidth: LEFT_SIDEBAR_MIN_WIDTH,
-              };
-            }
-            return { isSidebarOpen: newOpen };
-          });
+          set((state) => ({ isSidebarOpen: !state.isSidebarOpen }));
         },
 
         setSidebarOpen: (open) => {
-          set((state) => {
-            if (state.isSidebarOpen === open) {
-              if (!open) {
-                return state;
-              }
-              if (!state.hasManuallyResizedLeftSidebar && state.sidebarWidth !== LEFT_SIDEBAR_MIN_WIDTH) {
-                return {
-                  isSidebarOpen: open,
-                  sidebarWidth: LEFT_SIDEBAR_MIN_WIDTH,
-                };
-              }
-              return state;
-            }
-            if (open && !state.hasManuallyResizedLeftSidebar) {
-              return {
-                isSidebarOpen: open,
-                sidebarWidth: LEFT_SIDEBAR_MIN_WIDTH,
-              };
-            }
-            return { isSidebarOpen: open };
-          });
+          set((state) => state.isSidebarOpen === open ? state : { isSidebarOpen: open });
         },
 
         setSidebarWidth: (width) => {
-          set({ sidebarWidth: width, hasManuallyResizedLeftSidebar: true });
+          set({ sidebarWidth: width });
         },
 
         setContextRailOrder: (order) => {