diff --git a/packages/ui/src/stores/useFilesViewTabsStore.test.ts b/packages/ui/src/stores/useFilesViewTabsStore.test.ts
new file mode 100644
index 00000000..11472c07
--- /dev/null
+++ b/packages/ui/src/stores/useFilesViewTabsStore.test.ts
@@ -0,0 +1,31 @@
+import { beforeEach, describe, expect, test } from 'bun:test';
+import { useFilesViewTabsStore } from './useFilesViewTabsStore';
+
+describe('useFilesViewTabsStore', () => {
+  beforeEach(() => {
+    useFilesViewTabsStore.setState({ byRoot: {} });
+  });
+
+  test('ignores runtime paths outside the requested root', () => {
+    const root = '/repo';
+    const store = useFilesViewTabsStore.getState();
+
+    store.addOpenPath(root, '/other/file.ts');
+    store.setSelectedPath(root, '/other/file.ts');
+    store.expandPath(root, '/other');
+    store.toggleExpandedPath(root, '/other');
+
+    expect(useFilesViewTabsStore.getState().byRoot).toEqual({});
+  });
+
+  test('filters expanded path batches to the requested root', () => {
+    const root = '/repo';
+
+    useFilesViewTabsStore.getState().expandPaths(root, [
+      '/repo/src',
+      '/other/src',
+    ]);
+
+    expect(useFilesViewTabsStore.getState().byRoot[root]?.expandedPaths).toEqual(['/repo/src']);
+  });
+});
diff --git a/packages/ui/src/stores/useFilesViewTabsStore.ts b/packages/ui/src/stores/useFilesViewTabsStore.ts
index d84e4bc7..721783b4 100644
--- a/packages/ui/src/stores/useFilesViewTabsStore.ts
+++ b/packages/ui/src/stores/useFilesViewTabsStore.ts
@@ -166,7 +166,7 @@ export const useFilesViewTabsStore = create<FilesViewTabsStore>()(
         addOpenPath: (root, path) => {
           const normalizedRoot = normalizePath((root || '').trim());
           const normalizedPath = normalizePath((path || '').trim());
-          if (!normalizedRoot || !normalizedPath) {
+          if (!normalizedRoot || !normalizedPath || !isPathWithinRoot(normalizedPath, normalizedRoot)) {
             return;
           }
 
@@ -265,7 +265,7 @@ export const useFilesViewTabsStore = create<FilesViewTabsStore>()(
         setSelectedPath: (root, path) => {
           const normalizedRoot = normalizePath((root || '').trim());
           const normalizedPath = path ? normalizePath(path.trim()) : null;
-          if (!normalizedRoot) {
+          if (!normalizedRoot || (normalizedPath && !isPathWithinRoot(normalizedPath, normalizedRoot))) {
             return;
           }
 
@@ -314,7 +314,7 @@ export const useFilesViewTabsStore = create<FilesViewTabsStore>()(
         toggleExpandedPath: (root, path) => {
           const normalizedRoot = normalizePath((root || '').trim());
           const normalizedPath = normalizePath((path || '').trim());
-          if (!normalizedRoot || !normalizedPath) {
+          if (!normalizedRoot || !normalizedPath || !isPathWithinRoot(normalizedPath, normalizedRoot)) {
             return;
           }
 
@@ -344,7 +344,7 @@ export const useFilesViewTabsStore = create<FilesViewTabsStore>()(
         expandPath: (root, path) => {
           const normalizedRoot = normalizePath((root || '').trim());
           const normalizedPath = normalizePath((path || '').trim());
-          if (!normalizedRoot || !normalizedPath) {
+          if (!normalizedRoot || !normalizedPath || !isPathWithinRoot(normalizedPath, normalizedRoot)) {
             return;
           }
 
@@ -374,7 +374,12 @@ export const useFilesViewTabsStore = create<FilesViewTabsStore>()(
             return;
           }
 
-          const normalizedPaths = paths.map((p) => normalizePath((p || '').trim())).filter(Boolean);
+          const normalizedPaths = paths
+            .map((p) => normalizePath((p || '').trim()))
+            .filter((p) => p && isPathWithinRoot(p, normalizedRoot));
+          if (normalizedPaths.length === 0) {
+            return;
+          }
 
           set((state) => {
             const prev = state.byRoot[normalizedRoot];