fix(ui): preserve upstream sidebar and selection behavior

packages/ui/src/components/chat/MarkdownRendererImpl.performance.test.tsx

@@ -445,6 +445,52 @@ describe('MarkdownRenderer DOM mount performance contract', () => {
     clearDetachedMarkdownDomCache();
   });
 
+  test('does not detach Markdown DOM that intersects the active selection', async () => {
+    clearDetachedMarkdownDomCache();
+    const content = 'selected content';
+    const host = document.createElement('div');
+    document.body.replaceChildren(host);
+    const root = createRoot(host);
+    await act(async () => {
+      root.render(
+        <MarkdownRenderer
+          content={content}
+          messageId="message-selected"
+          part={{
+            id: 'part-selected',
+            sessionID: 'session-selected',
+            messageID: 'message-selected',
+            type: 'text',
+            text: content,
+            time: { start: 0, end: 1 },
+          }}
+          isAnimated={false}
+          enableFileReferences={false}
+        />,
+      );
+      await waitForSettledEffects();
+    });
+    const markdown = host.querySelector<HTMLElement>('[data-markdown-content]');
+    if (!markdown) throw new Error('Expected mounted Markdown content');
+    const originalGetSelection = window.getSelection;
+    Object.defineProperty(window, 'getSelection', {
+      configurable: true,
+      value: () => ({
+        rangeCount: 1,
+        isCollapsed: false,
+        getRangeAt: () => ({ intersectsNode: (node: Node) => node === markdown }),
+      }),
+    });
+
+    try {
+      await act(async () => root.unmount());
+      expect(detachedMarkdownDomCacheStats().entries).toBe(0);
+    } finally {
+      Object.defineProperty(window, 'getSelection', { configurable: true, value: originalGetSelection });
+      clearDetachedMarkdownDomCache();
+    }
+  });
+
   test('defers and batches Mermaid controller initialization after Markdown mount', async () => {
     const mounted = await mountFixture(fixtureWorkload.rendererCount);
     const critical = mounted.counts;

packages/ui/src/components/chat/MarkdownRendererImpl.tsx

@@ -843,6 +843,8 @@ const useMorphdomMarkdown = ({
       if (target.childNodes.length === 0 || shouldRefreshMermaidViewers(target)) return;
       if (Array.from(target.children).some((block) => !block.hasAttribute('data-md-id'))) return;
       if (target.querySelector('[data-md-copy-pending]')) return;
+      const selection = window.getSelection();
+      if (selection?.rangeCount && !selection.isCollapsed && selection.getRangeAt(0).intersectsNode(target)) return;
       const openMenu = target.querySelector<HTMLElement>('[data-md-menu]:not(.hidden)');
       const copiedButton = Array.from(target.querySelectorAll<HTMLButtonElement>('[data-md-action]'))
         .some((button) => button.getAttribute('title') === mountedDom.copiedLabel);

packages/ui/src/components/session/sidebar/projects/SessionGroupSection.test.ts

@@ -55,4 +55,14 @@ describe('selectFolderIdsForProjection', () => {
     expect([...selectFolderIdsForProjection(folders, { archivedBucket: true, searchQuery: 'matching' })])
       .toEqual(['root', 'child']);
   });
+
+  test('keeps a fuzzy folder match and its ancestor', () => {
+    const folders = [
+      { id: 'root', name: 'Root', parentId: null, nodeCount: 0 },
+      { id: 'child', name: 'Release Notes', parentId: 'root', nodeCount: 0 },
+    ];
+
+    expect([...selectFolderIdsForProjection(folders, { archivedBucket: false, searchQuery: 'release-notes' })])
+      .toEqual(['root', 'child']);
+  });
 });

packages/ui/src/components/session/sidebar/sessions/sessionNodeItemUtils.ts

@@ -1,4 +1,5 @@
 import { getRuntimeKey } from '@/lib/runtime-switch';
+import { matchesRankQuery } from '@/lib/search/fuzzySearch';
 import { normalizePath } from '@/lib/pathNormalization';
 import { resolveGlobalSessionDirectory } from '@/stores/useGlobalSessionsStore';
 import { getPinnedSessionKey } from '@/stores/useSessionPinnedStore';
@@ -227,7 +228,7 @@ export const selectFolderIdsForProjection = (
       keep = (childIdsByParentId.get(folderId) ?? []).some(shouldKeep);
     } else {
       if (!keep && !options.searchQuery) keep = true;
-      if (!keep && (entry.nodeCount > 0 || entry.name.toLowerCase().includes(options.searchQuery))) keep = true;
+      if (!keep && (entry.nodeCount > 0 || matchesRankQuery([entry.name], options.searchQuery))) keep = true;
       if (!keep) keep = (childIdsByParentId.get(folderId) ?? []).some(shouldKeep);
     }