Yarn PnP "Cannot find module" - Fix Plug’n’Play Resolution in CI

Yarn Berry’s Plug’n’Play has no node_modules - resolution goes through a .pnp.cjs runtime. A tool launched without that runtime falls back to Node’s default resolver, finds no node_modules, and throws "Cannot find module".

What this error means

Under Yarn PnP, a script or tool fails with Cannot find module '<pkg>' even though the package is installed. Running the same thing via yarn <cmd> (which loads the PnP runtime) works, proving the resolver is the issue.

Node output

Error: Cannot find module 'react'
Require stack:
- /app/scripts/build.js
    at Function._resolveFilename (node:internal/modules/cjs/loader)
# but 'yarn node scripts/build.js' resolves fine

Common causes

A tool run without the PnP runtime

Invoking node script.js (or a tool directly) does not load .pnp.cjs, so Node’s default resolver looks for a node_modules that PnP does not create.

A tool incompatible with PnP

Some tools assume a node_modules layout and do not support PnP, so they cannot resolve packages even with the runtime present.

How to fix it

Run through yarn so PnP loads

Launch scripts and tools via yarn (or yarn node) so the PnP runtime is active.

Terminal

# run scripts through yarn's PnP-aware runtime
yarn node scripts/build.js
yarn run build
# generate editor/tool SDKs for PnP support
yarn dlx @yarnpkg/sdks

Handle PnP-incompatible tools

Install Yarn SDKs (yarn dlx @yarnpkg/sdks) for editor/tool integration.
For a tool that cannot support PnP, set nodeLinker: node-modules in .yarnrc.yml.
Always invoke project tooling via yarn so the runtime is present.

How to prevent it

Invoke project tooling through yarn/yarn node.
Generate Yarn SDKs for PnP-aware tooling.
Use nodeLinker: node-modules for tools that cannot support PnP.