diff --git a/scripts/lib/ci-node-test-plan.mjs b/scripts/lib/ci-node-test-plan.mjs
index 9fa7b2676b14..f5d063ebc6f3 100644
--- a/scripts/lib/ci-node-test-plan.mjs
+++ b/scripts/lib/ci-node-test-plan.mjs
@@ -1129,6 +1129,7 @@ const SPLIT_NODE_SHARDS = new Map([
           "test/vitest/vitest.media-understanding.config.ts",
           "test/vitest/vitest.tui.config.ts",
           "test/vitest/vitest.ui.config.ts",
+          "test/vitest/vitest.ui-isolated.config.ts",
           "test/vitest/vitest.wizard.config.ts",
         ],
         requiresDist: false,
diff --git a/test/scripts/ci-node-test-plan.test.ts b/test/scripts/ci-node-test-plan.test.ts
index 4c1358936952..51500b1505cb 100644
--- a/test/scripts/ci-node-test-plan.test.ts
+++ b/test/scripts/ci-node-test-plan.test.ts
@@ -664,6 +664,7 @@ describe("scripts/lib/ci-node-test-plan.mjs", () => {
           "test/vitest/vitest.media-understanding.config.ts",
           "test/vitest/vitest.tui.config.ts",
           "test/vitest/vitest.ui.config.ts",
+          "test/vitest/vitest.ui-isolated.config.ts",
           "test/vitest/vitest.wizard.config.ts",
         ],
         requiresDist: false,
diff --git a/test/scripts/test-projects.test.ts b/test/scripts/test-projects.test.ts
index dc57b23baa70..76c8acda9dfb 100644
--- a/test/scripts/test-projects.test.ts
+++ b/test/scripts/test-projects.test.ts
@@ -4731,6 +4731,7 @@ describe("scripts/test-projects full-suite sharding", () => {
       "test/vitest/vitest.tui.config.ts",
       "test/vitest/vitest.tui-pty.config.ts",
       "test/vitest/vitest.ui.config.ts",
+      "test/vitest/vitest.ui-isolated.config.ts",
       "test/vitest/vitest.utils.config.ts",
       "test/vitest/vitest.wizard.config.ts",
       "test/vitest/vitest.gateway-core.config.ts",
diff --git a/test/vitest/vitest.test-shards.mjs b/test/vitest/vitest.test-shards.mjs
index 52dbda6b6233..d3982475ed24 100644
--- a/test/vitest/vitest.test-shards.mjs
+++ b/test/vitest/vitest.test-shards.mjs
@@ -84,6 +84,7 @@ export const fullSuiteVitestShards = [
       "test/vitest/vitest.tui.config.ts",
       "test/vitest/vitest.tui-pty.config.ts",
       "test/vitest/vitest.ui.config.ts",
+      "test/vitest/vitest.ui-isolated.config.ts",
       "test/vitest/vitest.utils.config.ts",
       "test/vitest/vitest.wizard.config.ts",
     ],
diff --git a/test/vitest/vitest.ui-isolated.config.ts b/test/vitest/vitest.ui-isolated.config.ts
new file mode 100644
index 000000000000..f6e3f23a1785
--- /dev/null
+++ b/test/vitest/vitest.ui-isolated.config.ts
@@ -0,0 +1,23 @@
+// Vitest ui-isolated config runs jsdom ui tests that need a fresh module graph.
+// The shared ui shard runs non-isolated for speed, but tests that spy on module
+// internals and assert the component uses that spy must not share a module cache
+// with stateful predecessor files (see UI_ISOLATED_TEST_FILES).
+import { createScopedVitestConfig } from "./vitest.scoped-config.ts";
+import { jsdomOptimizedDeps } from "./vitest.shared.config.ts";
+import { UI_ISOLATED_TEST_FILES } from "./vitest.ui.config.ts";
+
+export function createUiIsolatedVitestConfig(env?: Record<string, string | undefined>) {
+  return createScopedVitestConfig(UI_ISOLATED_TEST_FILES, {
+    deps: jsdomOptimizedDeps,
+    environment: "jsdom",
+    env,
+    excludeUnitFastTests: false,
+    includeOpenClawRuntimeSetup: false,
+    isolate: true,
+    name: "ui-isolated",
+    setupFiles: ["ui/src/test-helpers/lit-warnings.setup.ts"],
+    useNonIsolatedRunner: false,
+  });
+}
+
+export default createUiIsolatedVitestConfig();
diff --git a/test/vitest/vitest.ui.config.ts b/test/vitest/vitest.ui.config.ts
index 551fecdf5516..950c71f23ce0 100644
--- a/test/vitest/vitest.ui.config.ts
+++ b/test/vitest/vitest.ui.config.ts
@@ -2,12 +2,32 @@
 import { createScopedVitestConfig } from "./vitest.scoped-config.ts";
 import { jsdomOptimizedDeps } from "./vitest.shared.config.ts";
 
+// Full chat-pane lifecycle tests instantiate the pane component, which relies on
+// chat-thread/chat-message module-level singletons (thread state maps, module-scoped
+// document context-menu listeners) and spies on those modules. Under the non-isolated
+// ui runner a stateful predecessor file can leave those modules duplicated across the
+// shared graph, so the pane binds to a different instance than the test's spy/registry
+// — surfacing as flaky teardown assertions or 120s session-lifecycle hangs, depending
+// on file order. These tests run in the isolated ui lane for a fresh module graph;
+// keep this list in sync with vitest.ui-isolated.config.ts's include.
+export const UI_ISOLATED_TEST_FILES = [
+  "ui/src/pages/chat/chat-pane-history.test.ts",
+  "ui/src/pages/chat/chat-pane-lifecycle.test.ts",
+  "ui/src/pages/chat/chat-pane-pull-requests.test.ts",
+  "ui/src/pages/chat/chat-pane.message-cut.test.ts",
+  "ui/src/pages/chat/chat-pane.read-marker.test.ts",
+  "ui/src/pages/chat/chat-pane.session-discussion.test.ts",
+  "ui/src/pages/chat/chat-pane.test.ts",
+];
+
 export function createUiVitestConfig(
   env?: Record<string, string | undefined>,
   options?: { includePatterns?: string[]; name?: string },
 ) {
   const includePatterns = options?.includePatterns ?? ["ui/src/**/*.test.ts"];
-  const exclude = options?.includePatterns ? [] : ["ui/src/**/*.e2e.test.ts"];
+  const exclude = options?.includePatterns
+    ? []
+    : ["ui/src/**/*.e2e.test.ts", ...UI_ISOLATED_TEST_FILES];
   return createScopedVitestConfig(includePatterns, {
     deps: jsdomOptimizedDeps,
     environment: "jsdom",