JavaScript

SlowShield serves the npm registry at https://slowshield.example.com/npm/. npm, pnpm, Yarn and Bun use it like registry.npmjs.org, and so does everything that installs through them, such as npx, MCP servers and CI steps.

Set it up

npm and pnpm read npm_config_registry, so a line in your shell profile covers them in every new terminal (the Setup page has bash on macOS, zsh and fish too):

cat >> ~/.bashrc <<'EOF'
export PIP_INDEX_URL=https://slowshield.example.com/pypi/simple/
export UV_DEFAULT_INDEX=https://slowshield.example.com/pypi/simple/
export npm_config_registry=https://slowshield.example.com/npm/
export GOPROXY=https://slowshield.example.com/go
export PIP_UPLOADED_PRIOR_TO=P3D
export npm_config_min_release_age=3
EOF
source ~/.bashrc

Yarn 2 and later ignores .npmrc and the npm variables, and Bun's bunfig.toml loses to an npm_config_registry in the environment. Each tool, with the version its own release age needs:

npm

Release age: npm 11.10 or later (11.0 to 11.9 warn about an unknown setting, 10 ignores it)

command

npm config set registry https://slowshield.example.com/npm/
npm config set min-release-age 3

.npmrc (project or ~)

registry=https://slowshield.example.com/npm/
min-release-age=3

pnpm

Release age: pnpm 10.16 or later (older versions ignore it)

command

pnpm config set registry https://slowshield.example.com/npm/

pnpm-workspace.yaml

minimumReleaseAge: 4320  # 3 days, in minutes

Yarn

Release age: Yarn 4.10 or later (older versions refuse to run with it)

.yarnrc.yml (Yarn Berry)

npmRegistryServer: "https://slowshield.example.com/npm/"
npmMinimalAgeGate: "3d"

Bun

Release age: Bun 1.3 or later (older versions ignore it)

bunfig.toml

[install]
registry = "https://slowshield.example.com/npm/"
minimumReleaseAge = 259200  # 3 days, in seconds

What changes

Versions wait. A version becomes installable 7 days after the time the registry recorded for it. Versions younger than that are left out of the package documents (packuments), and latest moves to the newest stable version that is old enough. Other dist-tags that point at a held version are removed.
A pin that is too new. npm install pkg@1.2.3 for a held version reports that no matching version exists. A lockfile that names it downloads the tarball directly and gets 403 with Retry-After and the time it becomes available.
Malware from the OSV and GitHub feeds is refused with 451 and the advisory.
Brand-new packages none of whose versions is old enough are served and recorded as fail-open, unless your administrator set fail_open = false. That's what the second layer is for.
Lockfiles record SlowShield. npm needs absolute tarball URLs, so SlowShield's point at itself (https://slowshield.example.com/npm/pkg/-/pkg-1.2.3.tgz) and package-lock.json records them. Integrity hashes don't change: the tarballs are npm's, byte for byte.

The second layer

npm 11.10, pnpm 10.16, Yarn 4.10 and Bun 1.3 can refuse releases younger than a few days themselves (Deno 2.6 too). Set them to 3 days, below SlowShield's 7, and they stay silent on a normal day. Mind the units, checked on 2026-10-06: npm's min-release-age counts days, pnpm's minimumReleaseAge minutes and Bun's minimumReleaseAge seconds. npm 11.0 to 11.9 warn about the unknown setting, npm 10 ignores it, and Yarn before 4.10 refuses to run with it. To let one package through early: min-release-age-exclude in npm.

In Docker and CI

A build container doesn't read your shell profile. Pass the registry as a build argument: an ARG is visible to RUN as an environment variable and isn't kept in the image.

FROM node:22-slim
ARG npm_config_registry=https://slowshield.example.com/npm/
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci

Tarball URLs come from SlowShield's public URL, so the build must be able to reach SlowShield under that name. Building images covers the base image too, and how to check that nothing in a build goes around SlowShield. In CI, set the variables for the job:

# GitHub Actions (workflow or job)
env:
  PIP_INDEX_URL: https://slowshield.example.com/pypi/simple/
  UV_DEFAULT_INDEX: https://slowshield.example.com/pypi/simple/
  npm_config_registry: https://slowshield.example.com/npm/
  GOPROXY: https://slowshield.example.com/go
  PIP_UPLOADED_PRIOR_TO: P3D
  npm_config_min_release_age: 3

Limits

Dependencies from git or a tarball URL don't go through the registry, so SlowShield doesn't see them.
Scoped registries (@company:registry=…) stay as they are: private packages keep coming from your private registry.
Block registry.npmjs.org at the firewall for machines that should only use SlowShield.

For agents: this page as Markdown · llms.txt · the SlowShield skill