test(web): isolate event router browser harness

Author: redxzeta

apps/web/package.json

@@ -11,7 +11,7 @@
     "typecheck": "tsc --noEmit",
     "test": "vitest run --passWithNoTests",
     "test:browser": "vitest run --config vitest.browser.config.ts",
-    "test:browser:stable": "vitest run --config vitest.browser.stable.config.ts",
+    "test:browser:stable": "vitest run --config vitest.browser.stable.config.ts && vitest run --config vitest.browser.event-router.config.ts",
     "test:browser:geometry": "vitest run --config vitest.browser.geometry.config.ts",
     "test:personality:smoke": "vitest run --config vitest.browser.personality.config.ts",
     "test:electron:e2e": "playwright test --config playwright.electron.config.ts",

apps/web/vitest.browser.event-router.config.ts

@@ -0,0 +1,18 @@
+import { defineConfig, mergeConfig } from "vitest/config";
+
+import browserConfig from "./vitest.browser.config";
+
+// EventRouter drives an MSW service worker plus a WebSocket transport singleton.
+// Run it in its own browser process so unrelated browser files cannot retain
+// page-global transport state across the mount that exercises recovery ordering.
+export default mergeConfig(
+  browserConfig,
+  defineConfig({
+    test: {
+      include: ["src/components/EventRouter.browser.tsx"],
+      fileParallelism: false,
+      maxConcurrency: 1,
+      sequence: { concurrent: false },
+    },
+  }),
+);

apps/web/vitest.browser.stable.config.ts

@@ -6,7 +6,11 @@ export default mergeConfig(
   browserConfig,
   defineConfig({
     test: {
-      testNamePattern: /^(?!.*\[geometry:linux\])/,
+      // EventRouter owns an MSW service worker and transport singleton. Give
+      // its fixture-backed cases a fresh browser process after this suite.
+      // Vitest's file exclude is applied before the browser include set is
+      // merged, so filter this describe at the test-name layer instead.
+      testNamePattern: /^(?!.*\[geometry:linux\])(?!.*EventRouter scoped orchestration sync)/,
       // Browser suites share one page and some legacy fixture-backed suites
       // deliberately mutate their transport state between assertions.
       sequence: { concurrent: false },