Lifecycle scripts

Packages can define lifecycle scripts such as preinstall, install, postinstall, and prepare. scpm treats root scripts and dependency scripts differently.

Root scripts

Root package scripts run during install unless scripts are ignored:

scpm install --ignore-scripts

Dependency scripts

Dependency lifecycle scripts follow the pnpm v11 build approval model. Packages must be explicitly allowlisted before their install-time scripts run.

scpm ignored-builds
scpm approve-builds
scpm rebuild

Supported policy fields — scpm reads all of these at install time:

In scpm-workspace.yaml or pnpm-workspace.yaml (pnpm v11's build-review map, and what scpm writes to — scpm creates scpm-workspace.yaml from scratch, but mutates an existing pnpm-workspace.yaml in place):

allowBuilds:
  esbuild: true
  sharp: true
  untrusted-package: false

The old onlyBuiltDependencies and neverBuiltDependencies list keys are still honored as read-only compatibility inputs, but new approvals go into allowBuilds. When install sees an unreviewed dependency build, it adds that package to allowBuilds with false; scpm approve-builds flips reviewed entries to true.

In package.json (legacy — still honored as a read source). Every key under pnpm.* is also accepted under scpm.*; when both are present for the same key, scpm.* wins. Disjoint entries from either namespace merge.

{
  "scpm": {
    "allowBuilds": {
      "esbuild": true,
      "untrusted-package": false
    }
  }
}

Deny rules win over allow rules. Workspace-yaml entries and package.json entries merge; you don't have to migrate a legacy pnpm.allowBuilds to start using scpm approve-builds.

Entry keys support a bare package name (matches every version), an exact version pin (esbuild@0.19.0), an exact version union (esbuild@0.19.0 || 0.20.0), or a * wildcard name (@babel/*, *-loader, or bare * for everything). Wildcards can't be combined with a version pin — the point of a version pin is to assert a specific build was audited, and a wildcard defeats that. Semver ranges aren't supported for the same reason.

Jailed dependency builds

Build approval controls whether a dependency script may run at all. Jailed builds add a second boundary for approved packages:

jailBuilds: true

With jailBuilds enabled, approved dependency preinstall, install, and postinstall scripts run with a scrubbed environment and a temporary HOME. On macOS and Linux, scpm also applies a native jail that denies network access and restricts filesystem writes to the package directory and temporary directories.

jailBuilds defaults to false today and is planned to default to true in the next major version.

For packages that need a narrow exception, grant only that privilege:

jailBuildPermissions:
  "@vendor/*":
    env:
      - SHARP_DIST_BASE_URL
    write:
      - ~/.cache/sharp

For packages that cannot run in the jail yet, disable the jail for a package glob while keeping the build approval requirement:

jailBuildExclusions:
  - "@legacy-native/*"

See Jailed builds for the full profile, supported permissions, and platform behavior.

Git dependencies

Git dependencies with prepare scripts get a nested install in the clone before scpm snapshots the package. The final linked package uses the packed result, not the raw checkout.

Side effects cache

Allowlisted dependency builds can cache their post-build package tree and reuse it on future installs with the same input hash.

Bun comparison

Bun also treats dependency scripts as a security boundary and uses an allowlist model through trustedDependencies. scpm reads the top-level trustedDependencies array as an additional allow-source alongside pnpm.onlyBuiltDependencies, so bun projects work without rewriting the manifest. pnpm.neverBuiltDependencies still wins when both sides list the same package.