diff --git a/apps/files/src/store/active.spec.ts b/apps/files/src/store/active.spec.ts
new file mode 100644
index 0000000000000..70c005ed2b77e
--- /dev/null
+++ b/apps/files/src/store/active.spec.ts
@@ -0,0 +1,56 @@
+/*!
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { Folder } from '@nextcloud/files'
+import { createPinia, setActivePinia } from 'pinia'
+import { beforeEach, describe, expect, test, vi } from 'vitest'
+import { nextTick } from 'vue'
+import { useActiveStore } from './active.ts'
+
+function buildFolder(id: number, name: string) {
+	return new Folder({
+		id,
+		owner: 'test',
+		source: `http://example.com/remote.php/dav/files/test/${name}`,
+		root: '/files/test',
+	})
+}
+
+describe('Active store syncs the route fileid with the active node', () => {
+	let goToRoute: ReturnType<typeof vi.fn>
+
+	beforeEach(() => {
+		setActivePinia(createPinia())
+		goToRoute = vi.fn()
+		window.OCP = { Files: { Router: { goToRoute, params: {}, query: {} } } } as unknown as typeof window.OCP
+	})
+
+	test('rewrites a stale child fileid when the current folder becomes active', async () => {
+		// The route still deep-links a child (79) left over from a previous
+		// location, while the sidebar is being opened for the current folder (78).
+		window.OCP.Files.Router.params = { fileid: '79' }
+
+		const store = useActiveStore()
+		const folder = buildFolder(78, 'parent')
+		store.activeFolder = folder
+		store.activeNode = folder
+		await nextTick()
+
+		expect(goToRoute).toHaveBeenCalledTimes(1)
+		expect(goToRoute.mock.calls[0][1]).toMatchObject({ fileid: '78' })
+	})
+
+	test('does not touch the route when it already points at the active node', async () => {
+		window.OCP.Files.Router.params = { fileid: '78' }
+
+		const store = useActiveStore()
+		const folder = buildFolder(78, 'parent')
+		store.activeFolder = folder
+		store.activeNode = folder
+		await nextTick()
+
+		expect(goToRoute).not.toHaveBeenCalled()
+	})
+})
diff --git a/apps/files/src/store/active.ts b/apps/files/src/store/active.ts
index 935eee52bf544..12bd3f5136e96 100644
--- a/apps/files/src/store/active.ts
+++ b/apps/files/src/store/active.ts
@@ -47,14 +47,21 @@ export const useActiveStore = defineStore('active', () => {
 
 	// Set the active node on the router params
 	watch(activeNode, () => {
-		if (typeof activeNode.value?.fileid !== 'number' || activeNode.value.fileid === activeFolder.value?.fileid) {
+		if (!activeNode.value?.id) {
 			return
 		}
 
-		logger.debug('Updating active fileid in URL query', { fileid: activeNode.value.fileid })
+		// Sync even when the active node is the current folder: skipping that case
+		// leaves a stale child fileid in the route, which then gets restored into
+		// the sidebar when it reopens.
+		if (activeNode.value.id === String(window.OCP.Files.Router.params?.fileid ?? '')) {
+			return
+		}
+
+		logger.debug('Updating active fileid in URL query', { fileid: activeNode.value.id })
 		window.OCP.Files.Router.goToRoute(
 			null,
-			{ ...window.OCP.Files.Router.params, fileid: String(activeNode.value.fileid) },
+			{ ...window.OCP.Files.Router.params, fileid: activeNode.value.id },
 			{ ...window.OCP.Files.Router.query },
 			true,
 		)