diff --git a/tests/run_tests.py b/tests/run_tests.py
index 99c0c7b..4804f60 100644
--- a/tests/run_tests.py
+++ b/tests/run_tests.py
@@ -134,6 +134,13 @@ def get_node_tests() -> dict:
     return TESTS
 
 
+def get_ui_tests() -> dict:
+    """Load UI tests — toolbar, navigation, scroll (Playwright, no backend needed)."""
+    sys.path.insert(0, os.path.dirname(__file__))
+    from test_ui import TESTS
+    return TESTS
+
+
 SUITES = {
     'engine': get_engine_tests,
     'api': get_api_tests,
@@ -141,6 +148,7 @@ SUITES = {
     'matrix': get_matrix_tests,
     'testcases': get_testcase_tests,
     'roundtrip': get_roundtrip_tests,
+    'ui': get_ui_tests,
 }
 
 
diff --git a/tests/test_ui.py b/tests/test_ui.py
new file mode 100644
index 0000000..9598bd1
--- /dev/null
+++ b/tests/test_ui.py
@@ -0,0 +1,140 @@
+"""
+UI tests — toolbar, navigation, scroll preservation.
+
+Runs against a nyx instance with VITE_AUTH_DISABLED=true (auth skipped).
+
+Local dev (after restarting Vite with .env.local VITE_AUTH_DISABLED=true):
+    NYX_URL=http://localhost:5173 python tests/run_tests.py ui
+
+K3s test build (no restart needed — already built with auth disabled):
+    NYX_URL=http://localhost:30802 python tests/run_tests.py ui
+"""
+
+import os
+from playwright.sync_api import sync_playwright, Page, expect
+
+NYX_URL = os.environ.get('NYX_URL', 'http://localhost:30802')
+
+_pw = None
+_browser = None
+
+
+def _ensure_browser():
+    global _pw, _browser
+    if _browser is None:
+        _pw = sync_playwright().start()
+        _browser = _pw.chromium.launch(headless=True)
+    return _browser
+
+
+def _page(path: str = '/nyx') -> tuple:
+    browser = _ensure_browser()
+    ctx = browser.new_context(viewport={'width': 1280, 'height': 800})
+    page = ctx.new_page()
+    page.goto(f'{NYX_URL}{path}')
+    page.wait_for_selector('.app-toolbar', timeout=15000)
+    page.wait_for_timeout(500)  # let Vue commit reactive toolbar updates
+    return page, ctx
+
+
+def _click_nav(page: Page, text: str):
+    page.locator('.sidebar-link', has_text=text).click()
+    page.wait_for_timeout(800)
+
+
+# ── Tests ────────────────────────────────────────────────────────────────────
+
+def test_toolbar_nyx_has_all_groups():
+    """nyx shows 4 toolbar groups: connection, quad-view, themes, panels."""
+    page, ctx = _page('/nyx')
+    try:
+        expect(page.locator('.toolbar-group')).to_have_count(4, timeout=5000)
+    finally:
+        ctx.close()
+
+
+def test_toolbar_tests_has_two_groups():
+    """tests view shows 2 toolbar groups: connection + themes."""
+    page, ctx = _page('/tests')
+    try:
+        expect(page.locator('.toolbar-group')).to_have_count(2, timeout=5000)
+    finally:
+        ctx.close()
+
+
+def test_toolbar_home_has_one_group():
+    """home page shows 1 toolbar group: themes only."""
+    page, ctx = _page('/')
+    try:
+        expect(page.locator('.toolbar-group')).to_have_count(1, timeout=5000)
+    finally:
+        ctx.close()
+
+
+def test_toolbar_survives_roundtrip():
+    """Navigate nyx→tests→home→nyx — toolbar groups correct at each stop."""
+    page, ctx = _page('/nyx')
+    try:
+        expect(page.locator('.toolbar-group')).to_have_count(4, timeout=5000)
+
+        _click_nav(page, 'Tests')
+        expect(page.locator('.toolbar-group')).to_have_count(2, timeout=3000)
+
+        _click_nav(page, 'Home')
+        expect(page.locator('.toolbar-group')).to_have_count(1, timeout=3000)
+
+        _click_nav(page, 'nyx')
+        expect(page.locator('.toolbar-group')).to_have_count(4, timeout=3000)
+
+        _click_nav(page, 'Tests')
+        expect(page.locator('.toolbar-group')).to_have_count(2, timeout=3000)
+    finally:
+        ctx.close()
+
+
+def test_scroll_preserved_across_navigation():
+    """Scroll down in tests view, navigate away and back — position preserved."""
+    page, ctx = _page('/tests')
+    try:
+        page.wait_for_selector('.tests-view', timeout=5000)
+
+        # Scroll the tests container
+        page.evaluate('() => { const el = document.querySelector(".tests-view"); if (el) el.scrollTop = 200; }')
+        page.wait_for_timeout(200)
+        before = page.evaluate('() => document.querySelector(".tests-view")?.scrollTop ?? 0')
+
+        _click_nav(page, 'Home')
+        _click_nav(page, 'Tests')
+
+        after = page.evaluate('() => document.querySelector(".tests-view")?.scrollTop ?? 0')
+        assert after == before, f'scroll not preserved: was {before}, now {after}'
+    finally:
+        ctx.close()
+
+
+def test_all_views_stay_in_dom():
+    """After visiting nyx and tests, both stay in DOM (hidden not removed)."""
+    page, ctx = _page('/nyx')
+    try:
+        expect(page.locator('.toolbar-group')).to_have_count(4, timeout=5000)
+
+        _click_nav(page, 'Tests')
+        # AgentsView should still be in DOM (just hidden)
+        assert page.locator('.agents-view').count() > 0, 'AgentsView removed from DOM'
+
+        _click_nav(page, 'nyx')
+        # TestsView should still be in DOM
+        assert page.locator('.tests-view').count() > 0, 'TestsView removed from DOM'
+    finally:
+        ctx.close()
+
+
+# Test registry
+TESTS = {
+    'ui_toolbar_nyx_all_groups':    test_toolbar_nyx_has_all_groups,
+    'ui_toolbar_tests_two_groups':  test_toolbar_tests_has_two_groups,
+    'ui_toolbar_home_one_group':    test_toolbar_home_has_one_group,
+    'ui_toolbar_roundtrip':         test_toolbar_survives_roundtrip,
+    'ui_scroll_preserved':          test_scroll_preserved_across_navigation,
+    'ui_views_stay_in_dom':         test_all_views_stay_in_dom,
+}