A specific npm version is tested and bundled with each Node.js release. Upgrading npm to @latest fails under certain conditions (e.g. npm@latest dropping support for an older Node major), so as a workaround we keep a compatibility matrix in install-node.sh:

# Pin npm per Node release to the newest npm that still supports it, so setup
# never pulls an incompatible npm@latest. Do not override if it is already set.
if [[ "$NODE_LTS_VERSION" =~ ^[0-9]+$ && "$NODE_LTS_VERSION" -lt 18 ]]; then
  NPM_VERSION=${NPM_VERSION:-9}
elif [[ "$NODE_LTS_VERSION" =~ ^[0-9]+$ && "$NODE_LTS_VERSION" -lt 20 ]]; then
  NPM_VERSION=${NPM_VERSION:-10}
elif [[ "$NODE_LTS_VERSION" =~ ^[0-9]+$ && "$NODE_LTS_VERSION" -lt 22 ]]; then
  NPM_VERSION=${NPM_VERSION:-11}
else
  NPM_VERSION=${NPM_VERSION:-latest}
fi
export NPM_VERSION=${NPM_VERSION}

This only works when the Node.js version is passed as a bare major (e.g. 22). It fails when the version is a full string (e.g. 20.19.0), because the ^[0-9]+$ guard doesn't match. The Node driver hit exactly this: it pins NODE_LTS_VERSION=20.19.0, so the task tries to install npm@latest on Node 20 and failed.

Proposed fix: add a SKIP_NPM_UPGRADE flag so consumers who prefer the Node-bundled npm can opt out of the upgrade entirely.