Claude Code On Sandbox

claude-code-on-sandbox

Claude Code does not ship an officially maintained standalone OCI image. The supported path is the @anthropic-ai/claude-code npm CLI plus the Anthropic-published Dev Container Feature (ghcr.io/anthropics/devcontainer-features/claude-code:1.0). For sandboxed Kubernetes deployment, the pattern is: build a Dockerfile that installs Claude Code via mise (using the registry short name), wire it into a SandboxTemplate that pins a runtimeClassName, and let agent-sandbox provision per-session pods from that template.

Mise-based Dockerfile

The plugin ships templates/Dockerfile.claude-code and templates/mise.toml.claude-code. Use them verbatim or adapt.

Dockerfile.claude-code:

# syntax=docker/dockerfile:1.7
FROM debian:13-slim AS base

ARG MISE_VERSION=v2026.5.0
ENV MISE_DATA_DIR=/opt/mise \
    CLAUDE_CONFIG_DIR=/home/agent/.claude \
    PATH=/opt/mise/shims:/home/agent/.local/bin:$PATH

RUN --mount=type=cache,target=/var/cache/apt \
    --mount=type=cache,target=/var/lib/apt/lists \
    apt-get update && apt-get install -y --no-install-recommends \
      ca-certificates curl git jq iproute2 iptables sudo gnupg

RUN useradd -m -u 1000 -s /bin/bash agent
USER agent
WORKDIR /home/agent

RUN curl -fsSL https://mise.run | MISE_VERSION=${MISE_VERSION} sh

COPY --chown=agent:agent mise.toml /home/agent/mise.toml

RUN --mount=type=cache,uid=1000,target=/home/agent/.cache/mise \
    /home/agent/.local/bin/mise install

ENTRYPOINT ["/home/agent/.local/bin/mise", "exec", "--", "claude"]
CMD ["--print", "--output-format", "json"]

mise.toml.claude-code:

[tools]
node = "lts"
claude-code = "latest"

Use the mise registry short name claude-code — not npm:@anthropic-ai/claude-code. mise's registry maps the short name to the npm package internally, and the short form keeps the template clean.

BuildKit cache mounts

The Dockerfile uses two BuildKit cache mounts:

• /var/cache/apt + /var/lib/apt/lists — apt package cache, so repeated builds don't re-download.
• /home/agent/.cache/mise — mise's per-tool download cache. The uid=1000 is critical; mise runs as the agent user so the cache must be owned by UID 1000.

Build:

docker buildx build \
  --tag REGISTRY/claude-code:$(date +%Y%m%d) \
  --push \
  -f templates/Dockerfile.claude-code \
  --build-context templates=templates/ \
  templates/

Or with --load instead of --push for local-only iteration.

Authentication: ANTHROPIC_API_KEY vs OAuth token

Two auth modes:

1. ANTHROPIC_API_KEY (env var) — direct API key. Simplest. Inject via the SandboxClaim's spec.env.
2. CLAUDE_CODE_OAUTH_TOKEN (env var) — OAuth token from claude setup-token. Useful when the operator already has a Claude account and wants billing/usage tied to it.

See references/auth.md for the secret/SecretProviderClass patterns and rotation guidance.

The ~/.claude named volume

Claude Code stores auth state, session history, and settings at $CLAUDE_CONFIG_DIR (defaults to ~/.claude). For headless, ephemeral sandboxes you can omit this entirely and re-auth per session. For continuity (resume sessions, preserve preferences), mount a PVC:

spec:
  podTemplate:
    spec:
      containers:
        - name: claude
          volumeMounts:
            - { name: claude-home, mountPath: /home/agent/.claude }
      volumes:
        - name: claude-home
          persistentVolumeClaim:
            claimName: claude-home

The PVC can be shared across SandboxClaims for a single user, or distinct per tenant. See references/home-volume.md for storage class recommendations and the per-tenant pattern.

Headless invocation

The Dockerfile entrypoint runs claude --print --output-format json by default. Override per claim if needed:

kubectl exec -it sandbox/session-abc -- claude --print "summarize TODO list" --output-format json

--print skips the TUI and writes a single JSON object to stdout. --dangerously-skip-permissions short-circuits permission prompts but the CLI rejects this as root, so the Dockerfile's USER agent (UID 1000) is required to use it.

SandboxTemplate variants

Three variants in templates/:

• SandboxTemplate.kata.yaml — runtimeClassName: kata-qemu. Pairs with kata-on-kind or kata-on-gke.
• SandboxTemplate.gvisor.yaml — runtimeClassName: gvisor. Pairs with GKE managed Agent Sandbox or any cluster with gVisor RuntimeClass installed.
• SandboxTemplate.kina.yaml — no runtimeClassName. Pairs with kina-microvm because the node IS the microVM.

All three reference the same Claude Code image. Swap runtimeClassName to match the substrate; the rest of the template stays identical.

End-to-end flow

# 0. Pick your substrate skill (kata-on-kind / kata-on-gke / kina-microvm) and bring up the cluster.

# 1. Build + push the image
docker buildx build -t REGISTRY/claude-code:v1 --push -f templates/Dockerfile.claude-code templates/

# 2. Create the Anthropic secret
kubectl create secret generic anthropic --from-literal=api-key=sk-ant-...

# 3. Apply the SandboxTemplate (kata variant shown)
kubectl apply -f templates/SandboxTemplate.kata.yaml

# 4. Apply a per-session SandboxClaim
SESSION_ID=$(uuidgen | tr 'A-Z' 'a-z' | tr -d '-' | head -c 12)
sed "s/\${SESSION_ID}/${SESSION_ID}/" templates/SandboxClaim.session.yaml | kubectl apply -f -

# 5. Run Claude Code
kubectl wait --for=condition=Bound sandboxclaim/session-${SESSION_ID} --timeout=60s
kubectl exec -it sandbox/session-${SESSION_ID} -- claude --print "list files" --output-format json

# 6. Reap
kubectl delete sandboxclaim/session-${SESSION_ID}

See also

• references/auth.md — ANTHROPIC_API_KEY and OAuth token patterns with k8s Secrets.
• references/home-volume.md — ~/.claude PVC sizing and per-tenant separation.
• core:mise — mise discipline (registry short names per [[feedback-mise-registry-short-names]]).
• k8s-agent-sandbox — the controller, CRDs, and per-session lifecycle.
• kata-on-kind / kata-on-gke / kina-microvm — substrate setup.
• Upstream devcontainer reference: https://code.claude.com/docs/en/devcontainer

Anti-fabrication

• The npm package is @anthropic-ai/claude-code; the mise registry short name is claude-code. The ghcr.io/anthropics/claude-code:latest image is referenced by community guides but NOT by Anthropic's official devcontainer docs — do not depend on it. Build your own image from this skill's Dockerfile.
• --dangerously-skip-permissions requires non-root. If the Dockerfile is changed to run as root, the flag will fail at runtime.
• Test the built image locally (docker run --rm IMAGE claude --version) before pushing to a registry and applying SandboxTemplate. A broken image leaves SandboxClaims in CrashLoopBackOff.
• Confirm ANTHROPIC_API_KEY reaches the pod via kubectl exec -- env | grep ANTHROPIC — the SandboxClaim's spec.env injection only takes effect if the controller version supports it (check API version per the k8s-agent-sandbox skill).