fix: devtools is causing a severe memory leak

まず、Node v22+ を使用する Windows 上で、提供されている nuxi init と npm run dev の手順によりリークを再現し、次に devtools を有効にした場合と無効にした場合の実行を比較します。unstorage/readdirp、readable-stream、defineNuxtSchema 周辺のスナップショットを調査し、nuxt.config.ts によってトリガーされる再起動も含めます。繰り返し Dev サーバーを起動しても、メモリが無制限に増加したり CPU 使用率が異常になったりしなくなれば完了です。

🐛 The bug

Creating a bare Nuxt project with npx nuxi@latest init project and starting it with npm run dev causes severe memory leak (most of the time). This happens on Windows with Node v22+. This happens on a bare Nuxt starter with no additional Nuxt modules or npm packages added. Importantly, the memory leak occurs without any incoming requests happening or the app open in a browser. You only need to npm run dev after doing the nuxi project init and it will start leaking immediately. This is going to be a pain in the ass because I noticed it usually doesn't happen on the first run of npm run dev but if you stop the dev server and run the command again it will happen (you know you have it when the CPU is high and the memory starts incrementing).

I believe this is different than https://github.com/nuxt/nuxt/issues/30164 as that is in a built project with requests.

Observations:

• It does not leak when building and running npm run preview.
• Requests to the dev server are not needed to leak memory.
• Disabling devtools prevents the memory leak.
• It does not leak every time the dev server is started, maybe 10% of the time it will run normally on the bare project.
• It also leaks with Node v22.12.0 in addition to v23.3.0.
• Abnormally high CPU usage is occurring.
• It ticks up by 2.7-2.9 MB per second.

Proof

These images were taken after enabling/disabling Nuxt devtools and running npm run dev and waiting for exactly 5 minutes.

devtools: { enabled: true }

devtools: { enabled: false}

Snapshots

These make it seem like there is something with \node_modules\unstorage\node_modules\readdirp\index.js and/or are-we-there-yet\node_modules\readable-stream. But also defineNuxtSchema.

Here's how I did this:

1. npx nuxi dev --inspect with devtools disabled
2. Open Chrome and go to chrome://inspect and inspect the Node project
3. Let it run 5 minutes, collect garbage and take another snapshot (Snapshot 1, control)
4. Edit nuxt.config.ts and enable devtools, let it restart with HMR
5. Let it run 10 minutes, then collect garbage and take another snapshot (Snapshot 2)
6. Let it run 10 more minutes, then collect garbage and take final snapshot (Snapshot 3)

Snapshot 2 vs Snapshot 3 (devtools enabled short vs longer leak)

Full reproduction

Since I don't think stackblitz is going to show this issue:

1. npx nuxi init@latest project
2. cd project
3. npm run dev
4. Quit the process and re-run npm run dev
5. Observe memory leak
6. npx nuxi devtools disable
7. npm run dev
8. Observe no memory leak

🛠️ To reproduce

https://stackblitz.com/edit/github-4exzk3tl

🌈 Expected behavior

devtools should not be causing a memory leak in a bare project created with npx nuxi@latest init project

ℹ️ Additional context

npx nuxi info

• Operating System: Windows_NT
• Node Version: v23.3.0
• Nuxt Version: 3.14.1592
• CLI Version: 3.16.0
• Nitro Version: 2.10.4
• Package Manager: npm@10.9.1
• Builder: -
• User Config: default
• Runtime Modules: -
• Build Modules: -

---

Full nuxt.config.ts (devtools enabled)

// https://nuxt.com/docs/api/configuration/nuxt-config
export default defineNuxtConfig({
  devtools: {
    enabled: true,
    timeline: { enabled: true },
  },

  compatibilityDate: '2024-11-01',
})

Full nuxt.config.ts (devtools disabled)

// https://nuxt.com/docs/api/configuration/nuxt-config
export default defineNuxtConfig({
  devtools: {
    enabled: false,
    timeline: { enabled: true },
  },

  compatibilityDate: '2024-11-01',
})