Using the Repo's .nvmrc in Cloud Environments

#!/bin/bash
# Cloud environment setup: nvm, with `node` following the repo's .nvmrc / .node-version (default 24).
set -euo pipefail

DEFAULT_NODE=24
export NVM_DIR=/opt/nvm

# 1. nvm. The installer also adds its loader to ~/.bashrc, so interactive shells get `nvm`.
if [ ! -s "$NVM_DIR/nvm.sh" ]; then
  mkdir -p "$NVM_DIR"
  curl -fsSL https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash
fi
# Anything that assumes nvm's default location finds the same install.
[ -e ~/.nvm ] || ln -s "$NVM_DIR" ~/.nvm

# 2. use-repo-node [dir]           point `node` at the version dir pins (latest $DEFAULT_NODE.x if none)
#    use-repo-node --version <v>   point `node` at <v> for the rest of the session
cat > /usr/local/bin/use-repo-node <<EOF
#!/bin/bash
set -euo pipefail
export NVM_DIR=$NVM_DIR
want=""
if [ "\${1:-}" = --version ]; then
  [ -n "\${2:-}" ] || { echo "usage: use-repo-node [dir] | --version <version>" >&2; exit 2; }
  repo="--version"; want="\${2#v}"
else
  repo="\${1:-\$PWD}"
  for f in .nvmrc .node-version; do
    if [ -f "\$repo/\$f" ]; then
      want=\$(grep -v '^[[:space:]]*#' "\$repo/\$f" | tr -d '[:space:]'); want="\${want#v}"; break
    fi
  done
fi
case "\$want" in ""|system) want=$DEFAULT_NODE ;; esac   # lts/*, node etc. are resolved by nvm
set +eu; . "\$NVM_DIR/nvm.sh"; set -eu                 # nvm.sh exits non-zero and reads unset vars
nvm install "\$want" >/dev/null 2>&1 || { echo "use-repo-node: nvm could not install '\$want'" >&2; exit 1; }
nvm alias default "\$want" >/dev/null   # so shells that source nvm.sh agree
ln -sfn "\$(dirname "\$(nvm which "\$want")")" /opt/node-default
if [ -n "\${CLAUDE_ENV_FILE:-}" ] && ! grep -qs '/opt/node-default:' "\$CLAUDE_ENV_FILE"; then
  # Bash-tool shells never read ~/.bashrc: load nvm here (--no-use: define the command,
  # leave PATH alone), then put the repo's version first.
  cat >> "\$CLAUDE_ENV_FILE" <<'ENV'
export NVM_DIR=$NVM_DIR
[ -s "\$NVM_DIR/nvm.sh" ] && . "\$NVM_DIR/nvm.sh" --no-use || true
export PATH="/opt/node-default:\$PATH"
ENV
fi
echo "node \$(/opt/node-default/node --version) (from \${repo}: \$want)"
EOF
chmod +x /usr/local/bin/use-repo-node

# 3. Default version now, so /opt/node-default exists before the first session.
use-repo-node /nonexistent

# 4. At each Claude Code session start, once the repo is checked out: pick the repo's version,
#    then put /opt/node-default ahead of the image's preinstalled Node dirs for every Bash
#    command, via CLAUDE_ENV_FILE. Nothing preinstalled is overwritten. Merged into existing
#    user settings rather than overwriting them.
SETTINGS=~/.claude/settings.json
mkdir -p ~/.claude
[ -s "$SETTINGS" ] || echo '{}' > "$SETTINGS"
jq '.hooks.SessionStart = ((.hooks.SessionStart // [])
      | map(select((.hooks // []) | all(.command != "use-repo-node \"$CLAUDE_PROJECT_DIR\"")))
      + [{"hooks": [{"type": "command", "command": "use-repo-node \"$CLAUDE_PROJECT_DIR\""}]}])' \
  "$SETTINGS" > "$SETTINGS.tmp" && mv "$SETTINGS.tmp" "$SETTINGS"

/opt/node-default/node --version