diff --git a/package.json b/package.json
index c43a3759..1f88aa82 100644
--- a/package.json
+++ b/package.json
@@ -38,15 +38,15 @@
     "lint:colors": "npm run check:raw-hex",
     "test": "npm run test:unit",
     "test:fast": "npm run test:unit",
-    "test:unit": "TEST_BUDGET_SUITE=unit TEST_BUDGET_MS=55000 LOG_LEVEL=warn vitest run --project=unit-client --project=unit-node --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
-    "test:related": "TEST_BUDGET_SUITE=related TEST_BUDGET_MS=15000 LOG_LEVEL=warn vitest related --run --project=unit-client --project=unit-node --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
+    "test:unit": "TEST_BUDGET_SUITE=unit TEST_BUDGET_MS=55000 LOG_LEVEL=warn vitest run --project=unit-client --project=unit-node --project=unit-node-http --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
+    "test:related": "TEST_BUDGET_SUITE=related TEST_BUDGET_MS=15000 LOG_LEVEL=warn vitest related --run --project=unit-client --project=unit-node --project=unit-node-http --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
     "test:integration": "TEST_BUDGET_SUITE=integration-toolchain TEST_BUDGET_MS=120000 LOG_LEVEL=warn vitest run --project=integration-toolchain --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
     "test:docker": "TEST_BUDGET_SUITE=integration-docker TEST_BUDGET_MS=180000 FORCE_DOCKER=1 DOCKER_SANDBOX_IMAGE=unosim-sandbox:latest SKIP_HEAVY_TESTS=false LOG_LEVEL=warn vitest run --project=integration-docker --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
-    "test:security:inputs": "TEST_BUDGET_SUITE=security-inputs TEST_BUDGET_MS=15000 LOG_LEVEL=warn vitest run --project=unit-node tests/shared/input-limits.test.ts tests/shared/websocket-direction-schemas.test.ts tests/server/security/safe-paths.test.ts tests/server/routes/compiler.routes.test.ts tests/integration/simulation-state-sequence.test.ts --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
+    "test:security:inputs": "TEST_BUDGET_SUITE=security-inputs TEST_BUDGET_MS=15000 LOG_LEVEL=warn vitest run --project=unit-node --project=unit-node-http tests/shared/input-limits.test.ts tests/shared/websocket-direction-schemas.test.ts tests/server/security/safe-paths.test.ts tests/server/routes/compiler.routes.test.ts tests/integration/simulation-state-sequence.test.ts --reporter=default --reporter=./scripts/test-budget-reporter.mjs",
     "test:all": "npm run test:unit && npm run test:integration && npm run test:docker",
-    "test:watch": "LOG_LEVEL=info vitest --project=unit-client --project=unit-node",
-    "test:coverage": "node scripts/coverage-guard.mjs prepare && TEST_BUDGET_SUITE=unit-coverage TEST_BUDGET_WARN_MS=60000 TEST_BUDGET_FAIL_MS=70000 LOG_LEVEL=warn vitest run --coverage --project=unit-client --project=unit-node --reporter=default --reporter=./scripts/test-budget-reporter.mjs && node scripts/coverage-guard.mjs validate",
-    "test:debug": "LOG_LEVEL=debug vitest run --project=unit-client --project=unit-node",
+    "test:watch": "LOG_LEVEL=info vitest --project=unit-client --project=unit-node --project=unit-node-http",
+    "test:coverage": "node scripts/coverage-guard.mjs prepare && TEST_BUDGET_SUITE=unit-coverage TEST_BUDGET_WARN_MS=60000 TEST_BUDGET_FAIL_MS=70000 LOG_LEVEL=warn vitest run --coverage --project=unit-client --project=unit-node --project=unit-node-http --reporter=default --reporter=./scripts/test-budget-reporter.mjs && node scripts/coverage-guard.mjs validate",
+    "test:debug": "LOG_LEVEL=debug vitest run --project=unit-client --project=unit-node --project=unit-node-http",
     "test:ci": "npm run test:unit",
     "test:e2e": "ARDUINO_CACHE_DIR=./server/arduino-cache playwright test",
     "test:e2e:ci": "ARDUINO_CACHE_DIR=./server/arduino-cache playwright test && ./check-leaks.sh --cleanup",
diff --git a/vitest.config.ts b/vitest.config.ts
index 8089350f..54c285c5 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -11,6 +11,27 @@ process.env.NODE_ENV = "test";
 
 const __dirname = path.resolve();
 
+// These tests open real local HTTP listeners; parallel file execution has
+// caused sporadic ECONNRESET and 30-second HTTP timeouts despite stable
+// isolated runs, so keep only this group serial.
+const serializedHttpUnitTests = [
+  "tests/server/cache-optimization.test.ts",
+  "tests/server/cli-label-isolation.test.ts",
+  "tests/server/routes/compiler.routes.test.ts",
+  "tests/server/routes/examples.routes.test.ts",
+  "tests/server/routes/routes-core.test.ts",
+  "tests/server/routes/server-status-observability.test.ts",
+  "tests/server/routes/server-status.test.ts",
+  "tests/server/routes/simulation-admission.test.ts",
+  "tests/server/routes/simulation-start-readiness.test.ts",
+  "tests/server/routes/test-reset.routes.test.ts",
+  "tests/server/routes/tutor.routes.test.ts",
+  "tests/server/routes/websocket-lifecycle-handlers.test.ts",
+  "tests/server/security/access-control.test.ts",
+  "tests/server/services/protocol-version.test.ts",
+  "tests/integration/simulation-state-sequence.test.ts",
+] as const;
+
 export default defineConfig({
   plugins: [tsconfigPaths()],
   resolve: {
@@ -87,11 +108,23 @@ export default defineConfig({
             "tests/integration/docker-security-contract.test.ts",
             "tests/server/telemetry-heartbeat-integration.test.ts",
             "tests/core/sandbox-stress.test.ts",
+            ...serializedHttpUnitTests,
           ],
           environment: "node",
           setupFiles: ["./tests/setup.node.ts"],
         },
       },
+      {
+        extends: true,
+        test: {
+          name: "unit-node-http",
+          include: [...serializedHttpUnitTests],
+          environment: "node",
+          setupFiles: ["./tests/setup.node.ts"],
+          fileParallelism: false,
+          maxWorkers: 1,
+        },
+      },
       {
         extends: true,
         test: {