My accidental pnpm forkbomb

2026-09-17

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I did something funny by accident the other night.

I have been working on a project where I have two subprojects, web and backend. To write the package.json, I took advantage of an example I had lying around. That example had its scripts set up as follows.

"scripts": {
    ...
    "dev": "concurrently -n web,backend -c green,blue \"npm run dev --workspace web\" \"npm run dev --workspace backend\"",
    "backend": "npm run dev --workspace backend",
    "web": "npm run dev --workspace web",
    ...
}

There were a few more, but mostly just different variations of these. Now, knowing that npm is fairly similar to pnpm in usage, I assumed I could just replace npm with pnpm in all of these places. So I did so. I then ran pnpm dev to test it out.

My terminal then filled up with a bunch of blue and green, and the processes wouldn't stop spawning. I literally couldn't even kill the processes, because kill was malfunctioning at the CPU and memory pressure I had. Turns out, this configuration will not run things in the workspaces, it will instead run it in the root without questioning that pesky workspace flag. Ergo, pnpm dev immediately started a subprocess running pnpm dev, which recursed infinitely, creating a forkbomb. Even worse, the concurrently call made it spawn two processes per iteration. My roommate, watching from across the room, laughed at me as I forkbombed my laptop 3-4 times trying to debug this one.

All that to say, don't try to use the --workspace flag with pnpm. Go google the proper way to set up a monorepo, and use the -r flag to automatically recurse into the appropriate subprojects. Save yourself the reboots.

(I guess, also don't put pnpm dev as the dev script. That's the other lesson.)