Sandbox Setup

Wave provides defense-in-depth isolation for AI agent sessions through two complementary layers:

1. Outer sandbox (Nix + bubblewrap) — isolates the entire development session at the OS level
2. Adapter sandbox (manifest-driven) — projects persona permissions into Claude Code's settings.json and CLAUDE.md

Quick Start

# Install Nix if you haven't already
# https://nixos.org/download.html

# Enter sandboxed development shell
nix develop

# Everything you run inside is sandboxed:
wave run speckit-flow "add user authentication"

Nix Dev Shell (Outer Sandbox)

The flake.nix at the project root defines two dev shells:

Default Shell (Sandboxed)

nix develop

On Linux, this automatically enters a bubblewrap sandbox with:

Protection	Detail
Read-only filesystem	--ro-bind / / — entire root is mounted read-only
Hidden home directory	--tmpfs $HOME — ~/.aws, ~/.gnupg, etc. are invisible
Selective home read-only	~/.ssh, ~/.gitconfig, ~/.config/gh, ~/.npmrc mounted read-only
Writable project dir	--bind $PROJECT_DIR — the project directory is writable
Writable Go cache	--bind ~/go — Go module cache persists across steps
Writable Wave binary	--bind ~/.local/bin/wave — build target for go build
Writable Claude config	--bind ~/.claude — Claude Code session state persists
Shared temp	--bind /tmp — shared with host (Nix tooling needs it)
Inherited environment	Nix-provided environment inherited (no --clearenv)
Process isolation	--die-with-parent ensures sandbox dies with the shell

On macOS, bwrap requires kernel namespaces not available on Darwin. The default shell runs unsandboxed — Claude Code's built-in Seatbelt sandbox provides OS-level isolation for Bash commands.

Yolo Shell (No Sandbox)

nix develop .#yolo

Use this when you need Docker (can't run inside bwrap), or for debugging sandbox-related issues.

What the Sandbox Protects Against

Attack Vector	Protected?	Mechanism
Write outside project	Yes	--ro-bind / makes filesystem read-only
Access ~/.aws credentials	Yes	--tmpfs $HOME hides home directory
Access ~/.gnupg keys	Yes	--tmpfs $HOME hides home directory
Modify ~/.ssh keys	Partial	--ro-bind-try mounts read-only (readable for git)
Modify git config	Partial	--ro-bind-try mounts read-only
Process escape	Yes	--unshare-all + --die-with-parent

What the Sandbox Allows

The sandbox is intentionally permissive for things AI agents need:

Access	Why
~/.ssh (read-only)	Git push/pull over SSH
~/.gitconfig (read-only)	Git commit identity
~/.config/gh (read-only)	GitHub CLI authentication
~/.local/bin/wave (read-write)	Build target for go build / make install
~/.local/bin/notesium (read-only)	Local tooling
~/.local/bin/claudit (read-only)	Local tooling
~/go (read-write)	Go module cache avoids re-downloads
~/.claude (read-write)	Claude Code session state and OAuth
/tmp (shared)	Nix store paths and tooling
Full network	API calls, package downloads, git remotes

Passed Environment Variables

The sandbox inherits the Nix-provided environment (no --clearenv), which includes:

• All Nix dev shell variables (PATH, GOPATH, etc.)
• SANDBOX_ACTIVE=1 (set inside sandbox)
• ANTHROPIC_API_KEY (if set before nix develop)
• GH_TOKEN (if set, or derived from gh auth token)

Manifest-Driven Adapter Config

The second layer projects manifest permissions into Claude Code's configuration files.

Persona Sandbox Configuration

personas:
  navigator:
    adapter: claude
    permissions:
      allowed_tools: [Read, Glob, Grep, "Bash(git log*)"]
      deny: ["Write(*)", "Edit(*)"]
    sandbox:
      allowed_domains:
        - api.anthropic.com

  implementer:
    adapter: claude
    permissions:
      allowed_tools: [Read, Write, Edit, Bash, Glob, Grep]
    sandbox:
      allowed_domains:
        - api.anthropic.com
        - github.com
        - "*.github.com"
        - proxy.golang.org
        - sum.golang.org

Runtime Sandbox Configuration

runtime:
  sandbox:
    enabled: true
    default_allowed_domains:
      - api.anthropic.com
      - github.com
    env_passthrough:
      - ANTHROPIC_API_KEY
      - GH_TOKEN

Field	Description
enabled	Enable sandbox configuration generation
default_allowed_domains	Default network domains for all personas (persona config overrides)
env_passthrough	Environment variables to pass to adapter subprocesses

How Permissions Flow

wave.yaml                    →  settings.json                →  CLAUDE.md
─────────────────────────────────────────────────────────────────────────
persona.permissions.allowed  →  permissions.allow            →  "Allowed Tools" section
persona.permissions.deny     →  permissions.deny             →  "Denied Tools" section
persona.sandbox.allowed_domains → sandbox.network.allowedDomains → "Network Access" section
runtime.sandbox.env_passthrough → curated subprocess env     →  (not in CLAUDE.md)

Claude Code reads both settings.json (enforced) and CLAUDE.md (model awareness), providing defense-in-depth.

Environment Hygiene

The adapter constructs a curated environment instead of passing the full host environment:

Always included:

• HOME, PATH, TERM, TMPDIR=/tmp
• DISABLE_TELEMETRY=1, DISABLE_ERROR_REPORTING=1
• CLAUDE_CODE_DISABLE_FEEDBACK_SURVEY=1, DISABLE_BUG_COMMAND=1

Conditionally included:

• Variables listed in runtime.sandbox.env_passthrough (if set in host env)
• Step-specific env vars from pipeline configuration

Never included:

• Any other host environment variable (e.g., AWS_SECRET_ACCESS_KEY, DATABASE_PASSWORD)

Note: The curated environment model applies to the Claude adapter. Other adapters using the ProcessGroupRunner currently inherit the full host environment.

Defense-in-Depth Summary

From innermost to outermost:

Layer	What It Does	Enforced By
CLAUDE.md restrictions	Model is told what it can/cannot do	Prompt-level (advisory)
settings.json permissions	Allow/deny rules enforced by Claude Code	Claude Code runtime
Claude Code sandbox	Bubblewrap/Seatbelt restricts Bash commands	OS-level (Bash only)
Nix dev shell sandbox	Bubblewrap restricts the entire session	OS-level (everything)
Manifest	Single source of truth for all above	Wave configuration

Troubleshooting

"bwrap: No permissions to create new namespace"

Your kernel may not support unprivileged user namespaces. Check:

cat /proc/sys/kernel/unprivileged_userns_clone
# Should be 1

If 0, enable it (requires root):

sudo sysctl -w kernel.unprivileged_userns_clone=1

Or use the yolo shell: nix develop .#yolo

"command not found" inside sandbox

The sandbox inherits the Nix-provided PATH. If a tool isn't found, add the package to commonPackages in flake.nix.

Docker doesn't work inside sandbox

Docker cannot run inside bubblewrap (it needs its own namespaces). Use nix develop .#yolo for steps that require Docker.