Accumulating detached-flush.js processes

[ellisio]

Summary

I tend to restart my laptop about once a week. Over the course of a week of development I'll see processes accumulating related to telemetry. All I'm doing is switching Git branches, running next dev. Nothing too crazy. What are these? I can't find any open issues regarding this.

➜ ps aux | grep next-demo
andrew           14291   0.0  0.4 447176208 164480   ??  Ss    5:01PM   0:00.79 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.3_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_8408217755477e33beda28f603d6fe3c/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_13899.json
andrew           13692   0.0  0.4 447176752 164416   ??  Ss    5:00PM   0:00.86 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.3_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_8408217755477e33beda28f603d6fe3c/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_77046.json
andrew           84846   0.0  0.2 447182944  79760   ??  Ss   Fri03PM   0:01.38 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.2_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_b442eb4e8c2e31e27523c5b6e3304138/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_81975.json
andrew           84749   0.0  0.2 447184016  92960   ??  Ss   Fri03PM   0:01.47 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.3_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_8408217755477e33beda28f603d6fe3c/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_84678.json
andrew           57766   0.0  0.2 447187072  73232   ??  Ss   Fri09AM   0:02.06 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.3_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_8408217755477e33beda28f603d6fe3c/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_57312.json
andrew           29607   0.0  0.2 447182896  74208   ??  Ss   Fri08AM   0:02.76 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.2_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_b442eb4e8c2e31e27523c5b6e3304138/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_20793.json
andrew            4818   0.0  0.1 447184672  56272   ??  Ss   Wed02PM   0:02.82 /Users/andrew/.nvm/versions/node/v24.11.1/bin/node /Users/andrew/Developer/next-demo/node_modules/.pnpm/next@16.2.2_@babel+core@7.29.0_@opentelemetry+api@1.9.1_@playwright+test@1.59.1_babel-p_b442eb4e8c2e31e27523c5b6e3304138/node_modules/next/dist/telemetry/detached-flush.js dev /Users/andrew/Developer/next-demo _events_67663.json
andrew           29242   0.0  0.0 435300496   1392 s002  S+    5:24PM   0:00.00 grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --exclude-dir=.idea --exclude-dir=.tox --exclude-dir=.venv --exclude-dir=venv next-demo

Additional information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.3.0: Wed Jan 28 20:56:35 PST 2026; root:xnu-12377.91.3~2/RELEASE_ARM64_T6030
  Available memory (MB): 36864
  Available CPU cores: 12
Binaries:
  Node: 24.11.1
  npm: 11.6.2
  Yarn: 1.22.22
  pnpm: 10.33.0
Relevant Packages:
  next: 16.2.3 // Latest available version is detected (16.2.3).
  eslint-config-next: N/A
  react: 19.2.5
  react-dom: 19.2.5
  typescript: 5.9.3
Next.js Config:

[Sumit-Mayani]

These are Next.js telemetry processes. The detached-flush.js script runs as a separate detached Node.js process to flush anonymous usage statistics to Vercel asynchronously, without blocking your dev server.

The accumulation happens because each next dev run (including after branch switches) spawns a new detached telemetry process, and they are not always cleaned up when the dev server is stopped.

Fix — disable telemetry permanently:

npx next telemetry disable

Or set the environment variable in your shell profile (~/.zshrc / ~/.bashrc):

export NEXT_TELEMETRY_DISABLED=1

You can also add it to your project's .env.local:

NEXT_TELEMETRY_DISABLED=1

Kill the existing accumulated processes:

pkill -f "detached-flush.js"

After setting NEXT_TELEMETRY_DISABLED=1, Next.js will no longer spawn detached-flush.js processes on future next dev runs.

[ellisio]

Opt-ed out, which fixed it for me locally. However, this does seem like a bug, right?

[ellisio]

Weeks later, it seems this did not actually fix the issue. Found a bug, I think? Reported a few weeks ago here: #92927

Seems to really make things ugly when you're working with next-intl.