`startVitest` with `runner: forks` has incorrect SIGTERM fallback on windows; fails to produce profiling logs

Describe the bug

Long story short, I made a script to run Vitest with Node.JS profiling logs enabled.

To my surprise, what should be an extremely simple task ended up being platform-dependent - no profiling output would be written when running on Windows machines.

Delving a bit deeper into Vitest source, it appears the SIGTERM workaround for nodejs/node#55094 is the culprit at hand:

https://github.com/vitest-dev/vitest/blob/fe9ed7ac857c2e3d44217f87ad78bc2f20c6b2be/packages/vitest/src/runtime/workers/init-forks.ts#L16-L28

Windows does not emit SIGTERM events on a process being killed (mapping to a native TerminateProcess API that kills without running handlers).
This means that --heap-prof and similar flags are effectively platform-dependent and will not work on non-Linux platforms.

[!IMPORTANT]
Switching to threads runner does solve the issue, though having the default runner option be platform-dependent is obviously not very ideal.

Reproduction

import { startVitest } from 'vitest/node';
import { glob } from 'node:fs/promises';
import { basename, join } from 'node:path';

const execArgv = [
  '--heap-prof',
  `--heap-prof-name=vitest.heapprofile`,
  `--heap-prof-dir=./temp`,
];
const vitest = await startVitest('test', undefined, { execArgv });
await vitest.close();

This outputs to ./temp only on UNIX-like systems vs. everything else.

MRE for SIGTERM behavior

import { fork } from "node:child_process";
import { writeFileSync } from "node:fs";

writeFileSync(
  "./example.mjs",
  `

process.on("SIGTERM", () => {
    // only runs on windows
    console.log("[child] SIGTERM received, exiting cleanly...");
    process.exit(0);
});
console.log("[child] Hello world");

// Keep alive
setInterval(() => {}, 1_000);
`,
  "utf8",
);

console.log(`Platform: ${process.platform}`);
console.log("[parent] Forking child...\n");

const child = fork("./example.mjs", { stdio: "inherit" });

// Give the child a moment to set up its SIGTERM handler
setTimeout(() => {
    console.log("\n[parent] Sending kill() to child (pid %d)...", child.pid);
    child.kill(); // sends SIGTERM on Linux; calls TerminateProcess on Windows

child.on("exit", (code, signal) => {
    console.log("[parent] Child exited — code: %s, signal: %s", code, signal);
});
}, 500);

System Info

System:
    OS: Windows 11 10.0.26200
    CPU: (8) x64 AMD Ryzen 5 7520U with Radeon Graphics         
    Memory: 2.82 GB / 15.24 GB
  Binaries:
    Node: 24.14.0 - C:\Users\taylo\AppData\Local\Volta\tools\image\node\24.14.0\node.EXE
    npm: 11.9.0 - C:\Users\taylo\AppData\Local\Volta\tools\image\node\24.14.0\npm.CMD
    pnpm: 10.28.2 - C:\Program Files\Volta\pnpm.EXE
  Browsers:
    Chrome: 146.0.7680.80
    Edge: Chromium (140.0.3485.54)
    Internet Explorer: 11.0.26100.7309
  npmPackages:
    @vitest/coverage-v8: ^4.0.18 => 4.0.18 
    @vitest/expect: ^4.0.18 => 4.0.18 
    @vitest/utils: ^4.0.18 => 4.0.18 
    vite: ^7.3.1 => 7.3.1 
    vitest: ^4.0.18 => 4.0.18 
    vitest-canvas-mock: ^1.1.3 => 1.1.3

(The linux one was on stackblitz, also with vitest 4.0.18. I also have reproduced it working on my local WSL installation running Ubuntu, but it really doesn't matter.)

Used Package Manager

pnpm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

Start with packages/vitest/src/runtime/workers/init-forks.ts at the linked SIGTERM workaround, then run the provided startVitest reproduction with runner: forks on Windows and a Unix-like system. Compare the process termination behavior and profiling output; done means the Windows run produces the expected profiling logs without regressing the Unix-like case.