Set up the review sandbox (one-time)

Installs and verifies everything the reproduce-issue skill / reproduce-verifier agent need to run untrusted PR code in isolation. Idempotent — each step checks first and only acts if needed. Steps needing sudo are handed to the user to run in their terminal (this skill cannot sudo non-interactively).

Run uname -s first — the path differs on Linux vs macOS.

1. Docker

docker info >/dev/null 2>&1 && echo "docker OK" || echo "docker MISSING"

• MISSING, Linux: install Docker Engine, then sudo systemctl enable --now docker and add yourself to the docker group (sudo usermod -aG docker $USER, then re-login).
• MISSING, macOS: brew install colima docker then colima start (or install Docker Desktop).

2. Isolation runtime

Linux — gVisor (runsc)

docker info --format '{{range $k,$v := .Runtimes}}{{$k}} {{end}}' | grep -q runsc && echo "runsc OK" || echo "runsc MISSING"

If MISSING, have the user run this in their terminal (needs sudo; their shell is fish — exit codes are $status):

sudo apt-get update && sudo apt-get install -y apt-transport-https ca-certificates curl gnupg
curl -fsSL https://gvisor.dev/archive.key | sudo gpg --dearmor -o /usr/share/keyrings/gvisor-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/gvisor-archive-keyring.gpg] https://storage.googleapis.com/gvisor/releases release main" | sudo tee /etc/apt/sources.list.d/gvisor.list
sudo apt-get update && sudo apt-get install -y runsc
sudo runsc install          # registers runsc as a Docker runtime
sudo systemctl restart docker

Then re-check the runtime line above.

macOS — the Docker VM is the sandbox

No runsc. Just confirm the VM is up:

docker info >/dev/null 2>&1 && echo "docker VM OK" || echo "start it: colima start"

3. Container networking (catches the veth class of breakage)

docker run --rm --network none alpine true && echo "sandbox OK"
docker run --rm alpine true && echo "networking OK" || echo "networking BROKEN"

If the first passes but the second fails with veth ... operation not supported:

sudo modprobe veth

If modprobe errors with a BTF / version mismatch (failed to validate module [veth] BTF), the running kernel no longer matches its on-disk modules (a kernel update landed while it was booted) — reboot, after which it auto-loads. Persist it: echo veth | sudo tee /etc/modules-load.d/veth.conf.

4. The toolchain image (nx-review-sandbox)

Needed only to build an unreleased PR's nx in the sandbox (reproduce-verifier Level 2). Reproducing against a published nx version does NOT need it.

docker image inspect nx-review-sandbox:latest >/dev/null 2>&1 && echo "image OK" || echo "image MISSING"

If MISSING (or stale — check the created date against the Dockerfile), build it. The Dockerfile only needs mise.toml, so build from a minimal context — do NOT pass . (the repo root), which would ship the whole monorepo (node_modules / .git / dist — many GB) to the daemon:

mkdir -p tmp/review-sandbox-ctx && cp mise.toml tmp/review-sandbox-ctx/
docker build -t nx-review-sandbox:latest -f tools/review-sandbox/Dockerfile tmp/review-sandbox-ctx

This installs the repo's exact toolchain — node/java/dotnet/maven/rust/bun via mise — and takes a while + several GB. Requires steps 1 + 3 to pass first (build needs working networking). If disk is tight, /sandbox-prune first.

5. Verify (smoke test)

Confirm the sandbox actually isolates and carries the tools:

# RUNTIME="--runtime=runsc"  on Linux, ""  on macOS
docker run --rm $RUNTIME nx-review-sandbox:latest bash -c '
  cd /work    # mise resolves versions from the mise.toml here; do NOT use bash -l (a login shell resets PATH, dropping the mise dirs)
  echo "kernel: $(uname -r)"       # Linux+gVisor: 4.19.0-gvisor ; macOS: the VM kernel
  mise ls | head
  node --version; java --version 2>&1 | head -1; dotnet --version
'

Green when: the kernel is NOT your host kernel, and node/java/dotnet report versions. Report a concise ✅/❌ per step and what (if anything) the user still needs to run.