test(server): keep loader messages out of config responsiveness probes

packages/server/src/test-utils/main-thread-work.ts

@@ -24,8 +24,6 @@ export async function measureMainThreadWork<T>(label: string, action: () => T |
   let previousCpu = threadCpuUsage();
   let probe: ReturnType<typeof setInterval>;
   let drain: ReturnType<typeof setImmediate>;
-  const types = new Map<number, string>();
-  const stacks = new Map<number, string>();
   const callbacks = new Map<number, { wall: number; cpu: NodeJS.CpuUsage }>();
   const record = (wallMs: number, cpu: NodeJS.CpuUsage) => {
     const cpuMs = (cpu.user + cpu.system) / 1_000;
@@ -48,10 +46,6 @@ export async function measureMainThreadWork<T>(label: string, action: () => T |
   gc.observe({ entryTypes: ["gc"] });
   const activity = createHook({
     init(_id, type) {
-      if (label === "project config main-thread work") {
-        types.set(_id, type);
-        stacks.set(_id, new Error().stack ?? "");
-      }
       if (type.startsWith("FSREQ")) filesystemRequests++;
       if (!draining && type === "Immediate") yields++;
       if (type === "WORKER") workerEvents++;
@@ -66,13 +60,7 @@ export async function measureMainThreadWork<T>(label: string, action: () => T |
       const start = callbacks.get(id);
       if (!start) return;
       callbacks.delete(id);
-      const wall = performance.now() - start.wall;
-      record(wall, threadCpuUsage(start.cpu));
-      if (wall > 10 && label === "project config main-thread work") {
-        process.stderr.write(
-          JSON.stringify({ wall, type: types.get(id), stack: stacks.get(id) }) + "\n",
-        );
-      }
+      record(performance.now() - start.wall, threadCpuUsage(start.cpu));
     },
   }).enable();
   const sample = () => {

packages/server/src/utils/paseo-config-file.test.ts

@@ -5,7 +5,8 @@ import { fileURLToPath } from "node:url";
 import { writeFile, truncate, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import { build } from "esbuild";
 import { isPlatform } from "../test-utils/platform.js";
 import {
   readPaseoConfig,
@@ -20,21 +21,40 @@ import {
   writePaseoConfigForEdit,
 } from "./paseo-config-file.js";
 
+let probeDirectory: string;
+let probePath: string;
+
+beforeAll(async () => {
+  probeDirectory = mkdtempSync(join(tmpdir(), "paseo-config-probe-"));
+  probePath = join(probeDirectory, "config-responsiveness.mjs");
+  // Compile before starting the measured process. A runtime TypeScript loader
+  // owns MessagePorts that the responsiveness probe otherwise charges as work.
+  await build({
+    entryPoints: [
+      fileURLToPath(new URL("./test-fixtures/config-responsiveness.ts", import.meta.url)),
+    ],
+    outfile: probePath,
+    bundle: true,
+    platform: "node",
+    format: "esm",
+  });
+});
+
+afterAll(() => {
+  rmSync(probeDirectory, { recursive: true, force: true });
+});
+
 async function measureConfigRead(directory: string) {
-  const fixture = fileURLToPath(
-    new URL("./test-fixtures/config-responsiveness.ts", import.meta.url),
-  );
-  const { stdout, stderr } = await promisify(execFile)(
-    process.execPath,
-    ["--import", "tsx", fixture, directory],
-    { timeout: 15_000 },
-  );
+  const { stdout, stderr } = await promisify(execFile)(process.execPath, [probePath, directory], {
+    timeout: 15_000,
+  });
   process.stderr.write(stderr);
   return JSON.parse(stdout) as {
     result: Awaited<ReturnType<typeof readPaseoConfigForEdit>>;
     blockingMs: number;
     filesystemRequests: number;
     yields: number;
+    workerMessages: number;
   };
 }
 
@@ -84,7 +104,7 @@ describe("paseo config file substrate", () => {
     );
   });
 
-  it("excludes unrelated test-runner CPU from the config read budget", async () => {
+  it("excludes test-runner and loader activity from the config read budget", async () => {
     await writeFile(join(tempDir, "paseo.json"), JSON.stringify({ worktree: { setup: "npm ci" } }));
     const unrelatedWork = new Promise<void>((resolve) => {
       setImmediate(() => {
@@ -100,8 +120,10 @@ describe("paseo config file substrate", () => {
         resolve();
       });
     });
-    const { result, blockingMs, filesystemRequests } = await measureConfigRead(tempDir);
+    const { result, blockingMs, filesystemRequests, workerMessages } =
+      await measureConfigRead(tempDir);
     await unrelatedWork;
+    expect(workerMessages).toBe(0);
     expect(result).toEqual({
       ok: true,
       config: { worktree: { setup: "npm ci" } },
@@ -111,32 +133,33 @@ describe("paseo config file substrate", () => {
     expect(blockingMs).toBeLessThan(20);
   });
 
-  it.each(Array.from({ length: 25 }, (_, i) => i))(
-    "keeps main-thread work below 20ms while admitting large configs (%i)",
-    async () => {
-      const config = {
-        scripts: Object.fromEntries(
-          Array.from({ length: 7_000 }, (_, i) => [`script${i}`, { command: "echo hi" }]),
-        ),
-        worktree: { setup: "npm ci" },
-      };
-      await writeFile(join(tempDir, "paseo.json"), JSON.stringify(config));
-      const { result, blockingMs, filesystemRequests, yields } = await measureConfigRead(tempDir);
-      expect(result).toEqual({ ok: true, config, revision: await statPaseoConfigPath(tempDir) });
-      expect(blockingMs).toBeLessThan(20);
-      expect(filesystemRequests).toBeGreaterThan(0);
-      expect(yields).toBeGreaterThan(0);
-    },
-  );
+  it("keeps main-thread work below 20ms while admitting large configs", async () => {
+    const config = {
+      scripts: Object.fromEntries(
+        Array.from({ length: 7_000 }, (_, i) => [`script${i}`, { command: "echo hi" }]),
+      ),
+      worktree: { setup: "npm ci" },
+    };
+    await writeFile(join(tempDir, "paseo.json"), JSON.stringify(config));
+    const { result, blockingMs, filesystemRequests, yields, workerMessages } =
+      await measureConfigRead(tempDir);
+    expect(result).toEqual({ ok: true, config, revision: await statPaseoConfigPath(tempDir) });
+    expect(blockingMs).toBeLessThan(20);
+    expect(filesystemRequests).toBeGreaterThan(0);
+    expect(yields).toBeGreaterThan(0);
+    expect(workerMessages).toBe(0);
+  });
 
   it("rejects a 32MiB config with main-thread work below 20ms", async () => {
     await writeFile(
       join(tempDir, "paseo.json"),
       JSON.stringify({ extra: "x".repeat(32 * 1024 * 1024) }),
     );
-    const { result, blockingMs, filesystemRequests } = await measureConfigRead(tempDir);
+    const { result, blockingMs, filesystemRequests, workerMessages } =
+      await measureConfigRead(tempDir);
     expect(blockingMs).toBeLessThan(20);
     expect(filesystemRequests).toBeGreaterThan(0);
+    expect(workerMessages).toBe(0);
     expect(result).toEqual({ ok: false, error: { code: "invalid_project_config" } });
   });
 

packages/server/src/utils/test-fixtures/config-responsiveness.ts

@@ -1,14 +1,24 @@
+import { createHook, executionAsyncResource } from "node:async_hooks";
+import { MessagePort } from "node:worker_threads";
 import assert from "node:assert/strict";
 import { setImmediate as nextTurn } from "node:timers/promises";
 import { measureMainThreadWork } from "../../test-utils/main-thread-work.js";
 import { readPaseoConfigForEdit } from "../paseo-config-file.js";
 
-// Keep Vitest transforms, reporting, and unrelated callbacks outside the measured
-// thread. Read the real file once, without warming the config snapshot or schema.
+// The parent bundles this fixture before launching plain Node, keeping test
+// runner callbacks and runtime loader messages outside the measured thread.
+// Read the real file once, without warming the config snapshot or schema.
 const directory = process.argv[2];
 assert.ok(directory, "Config directory is required");
 await nextTurn();
+let workerMessages = 0;
+const activity = createHook({
+  before() {
+    if (executionAsyncResource() instanceof MessagePort) workerMessages++;
+  },
+}).enable();
 const measured = await measureMainThreadWork("project config main-thread work", () =>
   readPaseoConfigForEdit(directory),
 );
-process.stdout.write(JSON.stringify(measured));
+activity.disable();
+process.stdout.write(JSON.stringify({ ...measured, workerMessages }));