leaving a folder closes what was open in it

A pane shows a file from the folder you were in. Walking into another folder kept
it open, so the listing said one place and the pane said another — and the URL
carried a `?view=` that no longer belonged to its own pathname.

Navigating now drops the overlay params. Only those: anything else in the query is
left alone, because `useGlobalQueryString` puts real state there and a wholesale
reset takes it with it.

── The actual fix is that the list has an owner now ──

Which params belong to the overlay was a private array inside
`useFileViewerPanels`, so every other site that touched the query worked from
memory. That is exactly how `onCloseViewer` came to wipe the folder along with the
pane, and it is the thing TODO.md flagged as the reason a fifth handler would get
it wrong the same way.

`VIEWER_PARAMS` and `withoutViewerParams` now live in `files-route.ts` — a leaf
with no imports, so the hook and the browser can both depend on it without
depending on each other. Three readers, one list.

Writing this caught a fourth site immediately: `setViewerParams` had been
REPLACING the whole search since the folder left the query string, so opening a
file would have discarded global UI state. It clears the overlay and keeps the
rest, like everything else now does.

3 more tests, including that every key is covered rather than the obvious two.

tsgo clean, frontend builds, 840 pass / 7 fail — +3 new, same 7.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/workspaces/officerdev/src/apps/FileBrowser/FileBrowserApp/files-route.test.ts

@@ -6,6 +6,8 @@ import {
   folderHref,
   relativeToFolder,
   resolveInFolder,
+  VIEWER_PARAMS,
+  withoutViewerParams,
 } from './files-route';
 
 // The folder is in the URL path now, so every character a filesystem allows has to survive a round trip
@@ -150,3 +152,26 @@ describe('view param, relative to the folder in the path', () => {
     expect(resolveInFolder('/docs', '')).toBe('');
   });
 });
+
+describe('withoutViewerParams', () => {
+  test('drops the overlay, keeps everything else', () => {
+    // The "everything else" is the point: useGlobalQueryString puts arbitrary state in the URL, and a
+    // wholesale reset to '' would take it with it — which is the bug that sent people home on close.
+    const out = new URLSearchParams(withoutViewerParams('view=a.md&ephemeral=b.mp3&chatType=file&theme=dark&x=1'));
+    expect(out.get('view')).toBeNull();
+    expect(out.get('ephemeral')).toBeNull();
+    expect(out.get('chatType')).toBeNull();
+    expect(out.get('theme')).toBe('dark');
+    expect(out.get('x')).toBe('1');
+  });
+
+  test('every overlay key is covered, not just the obvious two', () => {
+    const all = VIEWER_PARAMS.map((k) => `${k}=x`).join('&');
+    expect(withoutViewerParams(all)).toBe('');
+  });
+
+  test('an empty or overlay-free query is unchanged', () => {
+    expect(withoutViewerParams('')).toBe('');
+    expect(withoutViewerParams('a=1')).toBe('a=1');
+  });
+});

src/workspaces/officerdev/src/apps/FileBrowser/FileBrowserApp/files-route.ts

@@ -91,3 +91,36 @@ export function relativeToFolder(folder: string, absPath: string): string {
   const rest = absPath.slice(prefix.length);
   return rest && !rest.includes('/') ? rest : absPath;
 }
+
+// ── Which params belong to the overlay, in one place ──
+//
+// The list used to live inside `useFileViewerPanels` and nowhere else, so every other site that touched
+// the query string worked from memory. That is how `onCloseViewer` came to wipe the whole search — the
+// folder included — and why walking into a folder had to decide for itself what to carry. One list, three
+// readers, no memory.
+//
+// This module is a leaf with no imports of its own, which is why the list lives here rather than in the
+// hook: both the hook and the browser can depend on it without depending on each other.
+
+export const VIEWER_PARAMS = [
+  'view',
+  'ephemeral',
+  'ephemeralRoot',
+  'ephemeral2',
+  'ephemeral2Root',
+  'ephemeral2Auto',
+  'chatContext',
+  'chatType',
+] as const;
+
+/**
+ * The query string with every overlay param removed, and everything else left alone.
+ *
+ * "Everything else" is not hypothetical — `useGlobalQueryString` puts arbitrary state in the URL, and a
+ * wholesale `''` would take it with it.
+ */
+export function withoutViewerParams(search: string): string {
+  const next = new URLSearchParams(search);
+  VIEWER_PARAMS.forEach((key) => next.delete(key));
+  return next.toString();
+}

src/workspaces/officerdev/src/apps/FileBrowser/FileBrowserApp/useFileBrowserApp.ts

@@ -5,7 +5,7 @@ import { useFilesAPI, type DirEntry } from '../../../hooks/useFilesAPI';
 import { usePinnedFiles } from '../usePinnedFiles';
 import { EDITOR_FILE_PARAM } from '../../CodeEditor/useEditorState';
 import { getFileType } from '../../FileViewer';
-import { folderFromPathname, folderHref, relativeToFolder } from './files-route';
+import { folderFromPathname, folderHref, relativeToFolder, withoutViewerParams } from './files-route';
 import { useTasks, type TaskSummary } from '../useTasks';
 import { useAgents, type AgentSummary } from '../useAgents';
 import { useUserState } from 'state/useUserState';
@@ -37,9 +37,11 @@ export const useFileBrowserApp = (basePath: string, rootOverride?: string, urlPa
   // default a new dashboard's cwd to it.
   const currentPath = urlPath ? folderFromPathname(location.pathname) : localPath;
   const setCurrentPath = (path: string) => {
-    // The search string rides along, so walking into a folder does not close an open pane — the same
-    // property the old `withPath` had, now expressed as "change the pathname, keep the query".
-    if (urlPath) navigate({ pathname: folderHref(path), search: location.search });
+    // Leaving a folder closes what was open in it. A pane shows a file from the folder you were in, so
+    // carrying it into the next one leaves the two disagreeing — the listing says one place, the pane
+    // another. Only the OVERLAY params go; anything else in the query (global UI state) is left alone,
+    // which is the distinction a wholesale reset kept getting wrong.
+    if (urlPath) navigate({ pathname: folderHref(path), search: withoutViewerParams(location.search) });
     else setLocalPath(path);
     if (!scoped) setGlobalPath(path);
   };
@@ -55,7 +57,15 @@ export const useFileBrowserApp = (basePath: string, rootOverride?: string, urlPa
    * open. The folder is no longer among them — it is the pathname — so it survives without being copied
    * across, which is what used to be needed here.
    */
-  const setViewerParams = (params: Record<string, string>) => setSearchParams(new URLSearchParams(params));
+  const setViewerParams = (params: Record<string, string>) =>
+    setSearchParams((prev) => {
+      // Clear the previous overlay — opening a file closes whatever was open — but only the overlay.
+      // Replacing the whole search would take global UI state with it, which is the mistake this file
+      // has now made twice in two different places.
+      const next = new URLSearchParams(withoutViewerParams(prev.toString()));
+      for (const [key, value] of Object.entries(params)) next.set(key, value);
+      return next;
+    });
 
   /**
    * Links from before the folder moved into the path still say `?path=/Tests`. Rewrite them once, in

src/workspaces/officerdev/src/hooks/useFileViewerPanels/useFileViewerPanels.tsx

@@ -9,17 +9,7 @@ import {
   singleChatLayout,
 } from './layouts';
 import { ViewerProvider, EphemeralProvider, Ephemeral2Provider, ChatEphemeralBody } from './Providers';
-
-const EPHEMERAL_KEYS = [
-  'view',
-  'ephemeral',
-  'ephemeralRoot',
-  'ephemeral2',
-  'ephemeral2Root',
-  'ephemeral2Auto',
-  'chatContext',
-  'chatType',
-];
+import { withoutViewerParams } from '../../apps/FileBrowser/FileBrowserApp/files-route';
 
 export const useFileViewerPanels = (): EphemeralPanels | null => {
   const [searchParams, setSearchParams] = useSearchParams();
@@ -82,12 +72,7 @@ export const useFileViewerPanels = (): EphemeralPanels | null => {
    * `onCloseEphemeral` directly below has always done.
    */
   const onCloseViewer = useCallback(
-    () =>
-      setSearchParams((prev) => {
-        const next = new URLSearchParams(prev);
-        EPHEMERAL_KEYS.forEach((k) => next.delete(k));
-        return next;
-      }),
+    () => setSearchParams((prev) => new URLSearchParams(withoutViewerParams(prev.toString()))),
     [setSearchParams],
   );