diff --git a/e2e/timeouts.test.ts b/e2e/timeouts.test.ts
index 4c48f08b..cf9ecb27 100644
--- a/e2e/timeouts.test.ts
+++ b/e2e/timeouts.test.ts
@@ -11,6 +11,10 @@ describe('E2E timeouts', () => {
     expect(config.test?.testTimeout).toBe(15_000 * CI_MULTIPLIER)
   })
 
+  it('runs server-backed test files sequentially', () => {
+    expect(config.test?.maxWorkers).toBe(1)
+  })
+
   it('keeps websocket waits within the per-test budget', () => {
     const budget = 8_000 * CI_MULTIPLIER
     expect(DEFAULT_WAIT_TIMEOUT_MS).toBeLessThanOrEqual(budget)
diff --git a/e2e/vitest.config.ts b/e2e/vitest.config.ts
index 7f8581ce..52ccb73a 100644
--- a/e2e/vitest.config.ts
+++ b/e2e/vitest.config.ts
@@ -14,10 +14,10 @@ export default defineConfig({
     testTimeout: 15_000 * CI_MULTIPLIER,
     hookTimeout: 10_000 * CI_MULTIPLIER,
 
-    // Run tests in parallel with fork pool
-    // Each test file gets its own in-process server on a dynamic port
+    // Each test file starts a full server. Parallel startups contend for enough
+    // CPU and memory to exceed the hook timeout on supported developer machines.
     pool: 'forks',
-    maxWorkers: process.env['CI'] === 'true' ? 1 : 12, // CI runners are resource-constrained
+    maxWorkers: 1,
 
     // No global setup - each test file manages its own server
     // globalSetup: './setup.ts',  // REMOVED - using in-process servers