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Mathieu Virbel da3a2ac3a4 rename Fence to Greywall as GreyHaven sandboxing component

Rebrand the project from Fence to Greywall, the sandboxing layer of the
GreyHaven platform. This updates:

- Go module path to gitea.app.monadical.io/monadical/greywall
- Binary name, CLI help text, and all usage examples
- Config paths (~/.config/greywall/greywall.json), env vars (GREYWALL_*)
- Log prefixes ([greywall:*]), temp file prefixes (greywall-*)
- All documentation, scripts, CI workflows, and example files
- README rewritten with GreyHaven branding and Fence attribution

Directory/file renames: cmd/fence → cmd/greywall, pkg/fence → pkg/greywall,
docs/why-fence.md → docs/why-greywall.md, example JSON files, and banner.

2026-02-10 16:00:24 -06:00

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Greywall

The sandboxing layer of the GreyHaven platform.

Greywall wraps commands in a sandbox that blocks network access by default and restricts filesystem operations. It is the core sandboxing component of the GreyHaven platform, providing defense-in-depth for running untrusted code.

# Block all network access (default)
greywall curl https://example.com  # → 403 Forbidden

# Allow specific domains
greywall -t code npm install  # → uses 'code' template with npm/pypi/etc allowed

# Block dangerous commands
greywall -c "rm -rf /"  # → blocked by command deny rules

Greywall also works as a permission manager for CLI agents. Greywall works with popular coding agents like Claude Code, Codex, Gemini CLI, Cursor Agent, OpenCode, Factory (Droid) CLI, etc. See agents.md for more details.

Install

macOS / Linux:

curl -fsSL https://gitea.app.monadical.io/monadical/greywall/raw/branch/main/install.sh | sh

Other installation methods

Go install:

go install gitea.app.monadical.io/monadical/greywall/cmd/greywall@latest

Build from source:

git clone https://gitea.app.monadical.io/monadical/greywall
cd greywall
go build -o greywall ./cmd/greywall

Additional requirements for Linux:

bubblewrap (for sandboxing)
socat (for network bridging)
bpftrace (optional, for filesystem violation visibility when monitoring with -m)

Usage

Basic

# Run command with all network blocked (no domains allowed by default)
greywall curl https://example.com

# Run with shell expansion
greywall -c "echo hello && ls"

# Enable debug logging
greywall -d curl https://example.com

# Use a template
greywall -t code -- claude  # Runs Claude Code using `code` template config

# Monitor mode (shows violations)
greywall -m npm install

# Show all commands and options
greywall --help

Configuration

Greywall reads from ~/.config/greywall/greywall.json by default (or ~/Library/Application Support/greywall/greywall.json on macOS).

{
  "extends": "code",
  "network": { "allowedDomains": ["private.company.com"] },
  "filesystem": { "allowWrite": ["."] },
  "command": { "deny": ["git push", "npm publish"] }
}

Use greywall --settings ./custom.json to specify a different config.

Import from Claude Code

greywall import --claude --save

Features

Network isolation - All outbound blocked by default; allowlist domains via config
Filesystem restrictions - Control read/write access paths
Command blocking - Deny dangerous commands like rm -rf /, git push
SSH Command Filtering - Control which hosts and commands are allowed over SSH
Built-in templates - Pre-configured rulesets for common workflows
Violation monitoring - Real-time logging of blocked requests (-m)
Cross-platform - macOS (sandbox-exec) + Linux (bubblewrap)

Greywall can be used as a Go package or CLI tool.

Documentation

Attribution

Greywall is based on Fence by Use-Tusk.

Inspired by Anthropic's sandbox-runtime.

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