Deliberately exposed and out of scope#

Anything not in the lockdown list (see the threat model) is reachable from inside Claude. This page reproduces the two reference tables: what the sandbox deliberately exposes, and what is out of scope.

Deliberately exposed#

These paths are bound into the sandbox on purpose. Modes are r (read-only) or rw (read-write).

Path

Mode

Why

Workspace

rw

The whole point of Claude. Default: $PWD (only the current project is writable). Override: set CLAUDE_SANDBOX_WORKSPACE_ROOT=/workspaces in remoteEnv to restore the old broad bind and make sibling devcontainer projects writable. Extra paths: allow-write = <abs-path> lines in /etc/claude-sandbox.conf (one path per line; blank lines and # comments ignored)

/etc/claude-sandbox.conf

r

Host-global sandbox config (workspace-root, no-forge, allow-write, egress-jail, allow-ip), placed by install.sh from the clone’s .devcontainer/claude-sandbox.conf and read by the shadow at launch. Lives at /etc, not in the rw-bound workspace, so a compromised session can’t rewrite it to widen the next launch’s binds. Edit the clone conf + re-run ./install (a rebuild does it via postCreate) to change it

/etc/claude-gitconfig

r

Curated gitconfig: gh/glab credential helpers for https://github.com and https://gitlab.diamond.ac.uk, ssh→https insteadOf rewrites, regenerated at every shadow launch from your host’s current user.name/user.email

/etc/gitconfig

r

Host’s system gitconfig is reachable read-only but neutralised for git because GIT_CONFIG_SYSTEM=/dev/null

/root/.claude/

rw

Claude’s state, settings, skills, hooks. install.sh symlinks this to /user-terminal-config/.claude so the tree persists across rebuilds and is shared with every other devcontainer that mounts the same terminal-config dir

/root/.claude.json

rw

Account-level state (OAuth token, recent-projects list, settings). Symlinked alongside ~/.claude/; without it the strict-under-/root tmpfs would swallow the token and re-prompt login every launch

/root/.cache/

rw

Tool caches Claude needs across runs (if present)

/root/.config/gh/

rw

gh CLI’s token store. Required so gh auth status works and the curated gitconfig’s gh auth git-credential helper can authenticate git push to GitHub without an OAuth popup

/root/.config/glab-cli/

rw

glab CLI’s token store. Same reason as gh. Sibling paths under /root/.config/ (VS Code state, other cred helpers, etc.) are NOT bound

/root/.local/share/ + single files /root/.local/bin/{uv,uvx}

rw

Bulk-bound XDG data dir: host-installed plugins for helm, kubectl/krew, uv-managed Python, etc. just work inside the sandbox without per-tool allowlist additions. applications/ and claude/ are tmpfs-masked so Claude Code’s own writes (URL handler .desktop, versioned binary cache) stay ephemeral. .config/ stays strict-allowlist — credentials live there, not under .local/share/

/usr/libexec/claude-sandbox/claude

r

The real Claude binary, relocated here by the installer from ~/.local/bin/claude so plain claude on the user’s PATH always resolves to the shadow. The shadow exec’s this same file via bwrap; a bind back to ~/.local/bin/claude inside the sandbox keeps Claude Code’s installMethod=native self-check happy

Network (egress-jailed by default, ADR 0015)

—

Claude runs in a private network namespace (pasta-bridged) with a routing allowlist: the internet, DNS, and configured allow-ip devices stay reachable so Claude works (api.anthropic.com, GitHub/GitLab), while RFC1918 (10/8, 172.16/12, 192.168/16) and 169.254/16 are blackholed so a compromised session cannot pivot to internal hosts. On by default; CLAUDE_SANDBOX_EGRESS_JAIL=0 restores the shared host netns (--share-net, 5. Leave network egress open; egress filtering is out of scope). See 15. Jail Claude’s egress in a per-process netns with a routing allowlist

For the rationale behind the XDG split, the uv bind discipline, the gitconfig redirect, and the egress jail (and the network-identity disclosure that remains on the CLAUDE_SANDBOX_EGRESS_JAIL=0 path), see the threat model and 15. Jail Claude’s egress in a per-process netns with a routing allowlist.

Out of scope#

The sandbox does not defend against the following. Each row names the mitigation expected from you.

Exposure

Why

Mitigation expected from you

Workspace contents

Claude has to read your workspace to do its job

Keep secrets outside the workspace (e.g. ~/.config/ mounted via your devcontainer’s mounts). Don’t put .env files with production credentials at the workspace root and expect them to be invisible

Container host kernel

A bwrap-aware kernel exploit is out of scope; this is a credential-isolation tool, not a sandbox against arbitrary native code

Keep your kernel patched; treat the devcontainer host as the trust boundary

Internet exfiltration / domain filtering

The default egress jail (ADR 0015) blocks lateral movement to internal RFC1918 hosts, not outbound exfil — the internet, DNS, and allow-ip devices stay reachable so Claude works. Restricting which internet domains Claude reaches (a hostname allowlist) is Claude Code’s native sandbox’s job, not this tool’s

If outbound exfil is in your threat model, run the devcontainer behind your own egress filter, and/or layer Claude Code’s native allowedDomains sandbox on top — the two are complementary (see the egress jail and the native sandbox). See 15. Jail Claude’s egress in a per-process netns with a routing allowlist

Non-standard credential paths

The installer scans mount and warns about /kubeconfig-style binds at install time, but cannot enumerate every custom mount

Audit your devcontainer’s mounts block

Non-root devcontainers; rootful Docker w/ default AppArmor

v1 targets rootless podman + Debian/Ubuntu + remoteUser=root

Tracked for v2