code-on-incus (coi)

Security-Hardened Container Runtime for AI Coding Agents with Real-Time Threat Detection

Run AI coding assistants (Claude Code, opencode, Aider, and more) in isolated, production-grade Incus containers with zero permission headaches, perfect file ownership, and true multi-session support.

Limited Blast Radius: Prepare your workspace upfront, let the AI agent run in isolation, validate the outcome. No SSH keys, no environment variables, no credentials exposed. If compromised, damage is contained to your workspace. Network isolation helps prevent data exfiltration. Your host system stays protected.

Security First: Unlike Docker or bare-metal execution, your environment variables, SSH keys, and Git credentials are never exposed to AI tools. Containers run in complete isolation with no access to your host credentials unless explicitly mounted.

Proactive Defense: COI doesn't just isolate AI tools — it can actively watch them. Enable the built-in security monitoring daemon ([monitoring] enabled = true) to detect reverse shells, credential scanning, and large data reads in real time, automatically pausing or killing the container before damage can occur. No manual intervention needed.

Think Docker for AI coding tools, but with system containers that actually work like real machines.

Watch the BetterStack video about Code on Incus

Table of Contents

• Supported AI Coding Tools
• Supported Tools (detailed)
• Features
• Quick Start
• Why Incus Instead of Docker or Docker Sandboxes?
• Installation
• macOS Support
• Usage
• Session Resume
• Persistent Mode
• Configuration
• Profiles
• Resource and Time Limits
• Container Lifecycle & Session Persistence
• Network Isolation
• Security Monitoring
• Security Best Practices
• Snapshot Management
• System Health Check
• Troubleshooting
• FAQ

Supported AI Coding Tools

Currently supported:

• Claude Code (default) - Anthropic's official CLI tool
• opencode - Open-source AI coding agent (https://opencode.ai)

Coming soon:

• Aider - AI pair programming in your terminal
• Cursor - AI-first code editor
• And more...

Tool selection:

coi shell                    # Uses default tool (Claude Code)
coi shell --tool opencode    # Use opencode instead

Permission mode - Control whether AI tools run autonomously or ask before each action:

# ~/.coi/config.toml or .coi/config.toml
[tool]
name = "claude"              # Default AI tool
permission_mode = "bypass"   # "bypass" (default) or "interactive"

See the Supported Tools wiki page for detailed configuration, API key setup, and adding new tools.

Features

Core Capabilities

• Multi-slot support - Run parallel AI coding sessions for the same workspace with full isolation
• Session resume - Resume conversations with full history and credentials restored (workspace-scoped)
• Persistent containers - Keep containers alive between sessions (installed tools preserved)
• Workspace isolation - Each session mounts your project directory
• Slot isolation - Each parallel slot has its own home directory (files don't leak between slots)
• Workspace files persist even in ephemeral mode - Only the container is deleted, your work is always saved
• Container snapshots - Create checkpoints, rollback changes, and branch experiments with full state preservation

Host Integration

• SSH agent forwarding - Use git-over-SSH inside containers without copying private keys ([ssh] forward_agent = true)
• Environment variable forwarding - Selectively forward host env vars by name (forward_env in config)
• Host timezone inheritance - Containers automatically inherit the host's timezone (configurable via [timezone] config)
• Sandbox context file - Auto-injected ~/SANDBOX_CONTEXT.md tells AI tools about their environment (network mode, workspace path, persistence, etc.). Automatically loaded into each tool's native context system: Claude Code via ~/.claude/CLAUDE.md, OpenCode via the instructions field in opencode.json (opt out with auto_context = false)

Security & Isolation

• Credential protection - SSH keys, .env files, Git credentials, and environment variables are never exposed unless explicitly mounted
• Privileged container guard - Refuses to start when security.privileged=true is detected, which defeats all container isolation
• Security posture verification - coi health checks seccomp, AppArmor, and privilege settings to confirm full isolation
• Kernel version enforcement - Warns on host kernels below 5.15 that may lack security features for safe isolation
• Real-time threat detection - Kernel-level nftables monitoring detects reverse shells, C2 connections, data exfiltration, DNS tunneling, and credential scanning
• Automated response - Auto-pause on HIGH threats, auto-kill on CRITICAL — no manual intervention needed
• Network isolation - Firewalld-based restricted/allowlist/open modes block private network access and prevent exfiltration
• Protected paths - .git/hooks, .git/config, .husky, .vscode mounted read-only to prevent supply-chain attacks
• System containers - Full OS isolation with unprivileged containers, better than Docker privileged mode
• Automatic UID mapping - No permission hell, files owned correctly
• Audit logging - All security events logged to JSONL for forensics and compliance

Safe Dangerous Operations

• AI coding tools often need broad filesystem access or bypass permission checks
• These operations are safe inside containers because the "root" is the container root, not your host system
• Containers are ephemeral - any changes are contained and don't affect your host
• This gives AI tools full capabilities while keeping your system protected

Quick Start

# Install
curl -fsSL https://raw.githubusercontent.com/mensfeld/code-on-incus/master/install.sh | bash

# Build image (first time only, ~5-10 minutes)
coi build

# Start coding with your preferred AI tool (defaults to Claude Code)
cd your-project
coi shell

# Or use opencode instead
coi shell --tool opencode

# That's it! Your AI coding assistant is now running in an isolated container with:
# - Your project mounted at /workspace
# - Correct file permissions (no more chown!)
# - Full Docker access inside the container
# - GitHub CLI available for PR/issue management
# - All workspace changes persisted automatically
# - No access to your host SSH keys, env vars, or credentials

Why Incus Instead of Docker or Docker Sandboxes?

Incus is a modern Linux container and virtual machine manager, forked from LXD. Unlike Docker (which uses application containers), Incus provides system containers that behave like lightweight VMs with full init systems.

Security Comparison

Capability	code-on-incus	Docker Sandbox	Bare Metal
Credential isolation	Default (never exposed)	Partial	None
Real-time threat detection	Kernel-level (nftables)	No	No
Reverse shell detection	Auto-kill	No	No
Data exfiltration alerts	Auto-pause	No	No
Network isolation	Firewalld (3 modes)	Basic	No
Protected paths	Read-only mounts	No	No
Auto response (pause/kill)	Yes	No	No
Audit logging	JSONL forensics	No	No
Supply-chain attack prevention	Git hooks/IDE configs protected	No	No

Why Incus Instead of Docker Sandboxes?

• Linux-first, not Linux-last. Docker Sandboxes' microVM isolation is only available on macOS and Windows. Linux gets a legacy container-based fallback. COI is built for Linux from the ground up because Incus is Linux-native.

• No Docker Desktop required. Docker Sandboxes is a Docker Desktop feature. Docker Desktop is not open source and has commercial licensing requirements for larger organizations. COI depends only on Incus - fully open source, no vendor lock-in, no additional runtime.

• System containers, not containers-in-VMs. Incus system containers run a full OS with systemd and native Docker support inside - one clean isolation layer. Docker Sandboxes nests application containers inside microVMs, adding architectural complexity.

• No permission hell. Incus automatic UID/GID shifting means files created by agents have correct ownership on the host. No chown, no mapping hacks.

• Credential isolation by default. Host environment variables, SSH keys, and Git credentials are never exposed to AI tools unless explicitly mounted.

• Simple and transparent. No separate daemon, no opaque VM nesting. COI talks directly to Incus - easy to inspect, debug, and extend.

Installation

Automated Installation (Recommended)

# One-shot install
curl -fsSL https://raw.githubusercontent.com/mensfeld/code-on-incus/master/install.sh | bash

# This will:
# - Download and install coi to /usr/local/bin
# - Check for Incus installation
# - Verify you're in incus-admin group
# - Show next steps

Manual installation: Download the binary from GitHub Releases, make it executable, and move to /usr/local/bin/. Requires Linux with Incus installed and user in the incus-admin group. See the Incus installation guide for setting up Incus.

Build Images

# Build the unified coi image (5-10 minutes)
coi build

# Build without compression (faster iteration)
coi build --compression none

# Custom image from your own build script
coi build custom my-rust-image --script build-rust.sh
coi build custom my-image --base coi --script setup.sh

What's included in the coi image:

• Ubuntu 22.04 base with Docker (full Docker-in-container support)
• mise (polyglot runtime manager) — Python 3, pnpm, TypeScript, tsx pre-installed; add more with mise use go@latest, mise use ruby@3, etc.
• Node.js 20 LTS (system, for Claude CLI) + npm
• Claude Code CLI (default AI tool) + GitHub CLI (gh)
• tmux, git, curl, build-essential, and common build tools
• Modern CLI utilities: fd-find, bat, tree
• Debugging tools: strace, lsof
• Database clients: sqlite3, postgresql-client, redis-tools
• imagemagick for image processing

Custom images: Build your own specialized images using build scripts that run on top of the base coi image.

macOS Support

COI works on macOS using Colima or Lima VMs. See the macOS Setup Guide for complete instructions.

Usage

Basic Commands

# Interactive session (defaults to Claude Code)
coi shell

# Use a different AI tool
coi shell --tool opencode

# Persistent mode - keep container between sessions
coi shell --persistent

# Use specific slot for parallel sessions
coi shell --slot 2

# Resume previous session
coi shell --resume

# Run a command in an ephemeral container
coi run "npm test"

# Attach to existing session
coi attach

# List active containers and saved sessions
coi list --all

# Gracefully shutdown / force kill containers
coi shutdown coi-abc12345-1
coi kill --all

# Cleanup stopped containers and orphaned resources
coi clean

# Update coi to the latest release
coi update

Global Flags

--workspace PATH        # Workspace directory to mount (default: current directory)
--slot NUMBER           # Slot number for parallel sessions (0 = auto-allocate)
--persistent            # Keep container between sessions
--resume [SESSION_ID]   # Resume from session (omit ID to auto-detect latest for workspace)
--continue [SESSION_ID] # Alias for --resume
--profile NAME          # Use named profile
--image NAME            # Use custom image (default: coi)

Most container customization (network mode, mounts, environment variables, SSH agent, monitoring, timezone, resource limits, etc.) is configured via config files or profiles. See the Configuration wiki page for the full reference.

Advanced Usage

See the wiki for detailed documentation:

• Container Operations - Container management and low-level operations
• File Transfer - Push/pull files between host and containers
• Tmux Automation - Automate AI sessions with tmux commands
• Image Management - Create and manage custom images
• Snapshot Management - Create checkpoints and rollback changes

Session Resume

Resume a previous AI coding session with full history and credentials restored:

coi shell --resume              # Auto-detect latest session for this workspace
coi shell --resume=<session-id> # Resume specific session
coi list --all                  # List available sessions

What's restored: Full conversation history, tool credentials, user settings, and project context. Sessions are workspace-scoped — --resume only finds sessions from the current workspace directory.

See the Container Lifecycle and Sessions guide for details on how session persistence works.

Persistent Mode

By default, containers are ephemeral (deleted on exit). Your workspace files always persist regardless of mode.

Enable persistent mode to also keep the container and its installed packages:

coi shell --persistent

# Or via config (~/.coi/config.toml)
[defaults]
persistent = true

What persists:

• Ephemeral mode: Workspace files + session data (container deleted)
• Persistent mode: Workspace files + session data + container state + installed packages, system setup

See the Container Lifecycle and Sessions guide for details.

Configuration

Config file: ~/.coi/config.toml

[defaults]
image = "coi"
persistent = true

[tool]
name = "claude"
permission_mode = "bypass"
# auto_context = true          # Auto-inject sandbox context into tool's native system

Configuration hierarchy (highest precedence last):

1. Built-in defaults
2. User config (~/.coi/config.toml)
3. Project config (./.coi/config.toml)
4. COI_CONFIG environment variable
5. Environment variables (CLAUDE_ON_INCUS_*, COI_*)
6. Operational CLI flags (--workspace, --slot, --persistent, --resume, --profile, --image)

Place a .coi/config.toml in any repository root to auto-configure COI for that project — useful for teams to share container image, environment, and resource limits.

See the Configuration wiki page for the full config reference, per-repo setup, profiles, and environment variables.

Profiles

Profiles are reusable container configurations bundling image, tool, limits, mounts, build scripts, context files, and environment into named templates. Each profile is a self-contained directory with its own config.toml and optional supporting files.

.coi/profiles/
├── rust-dev/
│   ├── config.toml      # profile config
│   ├── build.sh         # profile-specific build script
│   └── CONTEXT.md       # AI agent context (appended to sandbox context)
└── python-ml/
    ├── config.toml
    └── setup.sh

Example profile config (.coi/profiles/rust-dev/config.toml):

image = "coi-rust"
persistent = true
context = "CONTEXT.md"
forward_env = ["CARGO_HOME"]

[environment]
RUST_BACKTRACE = "1"

[tool]
name = "claude"
permission_mode = "bypass"

[limits.cpu]
count = "4"

Profile inheritance: Profiles can inherit from a parent using inherits = "parent-name", so you only override what differs:

# .coi/profiles/rust-dev-nightly/config.toml
inherits = "rust-dev"
image = "coi-rust-nightly"

[environment]
RUST_CHANNEL = "nightly"

Environment maps merge (child keys win, "" clears a parent key). Arrays (mounts, forward_env) fully replace if the child defines them. Struct sections (limits, tool, network) deep-merge field by field. Inheritance works across config levels (a project profile can inherit from a user-level profile) and supports chains up to 10 levels with cycle detection.

Profile context files: When a profile includes context = "CONTEXT.md", the referenced markdown file is automatically appended to ~/SANDBOX_CONTEXT.md and tool-native auto-context files (e.g., ~/.claude/CLAUDE.md) under a # User-Provided Profile Context heading. This gives AI agents profile-specific instructions (e.g., "use pytest", "follow PEP 8") without manual setup.

# Use a profile
coi shell --profile rust-dev

# List all available profiles
coi profile list

# Show profile details
coi profile info rust-dev

Profile directories are scanned under ~/.coi/profiles/ (user) and ./.coi/profiles/ (project). When COI_CONFIG is set, its parent directory is also scanned. Profiles from all discovered locations are merged into a single namespace — if the same profile name is defined in more than one location, COI refuses to start and asks you to rename one so it's always unambiguous which profile is being applied. See the Profiles wiki page for complete documentation.

Resource and Time Limits

See the Resource and Time Limits guide for complete documentation on controlling container resource consumption and runtime.

Quick example:

# ~/.coi/config.toml
[limits.cpu]
count = "2"

[limits.memory]
limit = "2GiB"

[limits.runtime]
max_duration = "2h"

What you can limit:

• CPU cores and usage percentage
• Memory and swap
• Disk I/O rates
• Maximum runtime and process count
• Auto-stop on time limits

Container Lifecycle & Session Persistence

See the Container Lifecycle and Sessions guide for detailed explanation of how containers and sessions work.

Key concepts:

• Workspace files: Always saved (regardless of mode)
• Session data: Always saved to ~/.coi/sessions-<tool>/
• Ephemeral mode (default): Container deleted after exit, session preserved
• Persistent mode (--persistent): Container kept with all installed packages
• Resume (--resume): Restore AI conversation in fresh/existing container

Quick reference:

coi shell --persistent        # Keep container between sessions
coi shell --resume            # Resume previous conversation
coi attach                    # Reconnect to running container
coi persist                   # Convert ephemeral session to persistent
coi resume <name>             # Resume paused/frozen container
sudo poweroff                 # Properly stop container (inside)
coi shutdown <name>           # Graceful stop (outside)

Network Isolation

See the Network Isolation guide for complete documentation on network security and firewalld setup.

Network modes:

• Restricted (default) - Blocks private networks, allows internet
• Allowlist - Only specific domains/IPs allowed
• Open - No restrictions (trusted projects only)

# ~/.coi/config.toml
[network]
mode = "restricted"   # Default — blocks private networks, allows internet
# mode = "allowlist"  # Only specific domains/IPs allowed
# mode = "open"       # No restrictions (trusted projects only)

Security Monitoring

COI includes built-in security monitoring to detect and respond to malicious behavior in real-time:

# Enable in config (~/.coi/config.toml)
[monitoring]
enabled = true

Protects against:

• Reverse shells - Detects common reverse shell patterns (auto-kill)
• Data exfiltration - Monitors large workspace reads/writes (auto-pause)
• Environment scanning - Flags processes searching for API keys and secrets
• Network threats (NFT) - Kernel-level detection of C2 connections, private network access, DNS tunneling, and allowlist violations

Automated response levels:

• INFO/WARNING: Logged (+ alert for WARNING)
• HIGH: Container paused (requires coi resume to continue)
• CRITICAL: Container killed immediately

Audit logs are stored at ~/.coi/audit/<container-name>.jsonl in JSON Lines format.

See the Security Monitoring wiki page for monitoring commands, configuration options, NFT setup, and audit log management.

Security Best Practices

See the Security Best Practices guide for detailed security recommendations.

COI automatically mounts security-sensitive paths as read-only to prevent supply-chain attacks:

• .git/hooks, .git/config, .husky, .vscode

Set [git] writable_hooks = true in config to opt out, or customize protected paths via config. See the wiki for details.

System Health Check

See the System Health Check guide for detailed information on diagnostics and what's checked.

Run diagnostics:

coi health                    # Basic health check
coi health --format json      # JSON output
coi health --verbose          # Additional checks

What it checks: System info, kernel version, Incus setup, permissions, security posture (seccomp/AppArmor), privileged container detection, network configuration, storage, monitoring prerequisites, and running containers.

Exit codes: 0 (healthy), 1 (degraded), 2 (unhealthy)

Troubleshooting

See the Troubleshooting guide for common issues and solutions.

Common issues:

• DNS issues during build - COI automatically fixes systemd-resolved conflicts
• Run coi health to diagnose setup problems
• Check the troubleshooting guide for detailed solutions

Frequently Asked Questions

See the FAQ for answers to common questions.

Topics covered:

• Orphaned firewalld zone bindings (Docker + firewalld interaction)
• How COI compares to Docker Sandboxes and DevContainers
• Windows support (WSL2)
• Security model and prompt injection protection
• API key security and trust model
• What is Incus? (vs tmux)