omamori

Safety guard for AI CLI tools. Blocks dangerous commands — and resists being disabled.

When AI tools like Claude Code, Codex, or Cursor run shell commands, omamori intercepts destructive operations and replaces them with safe alternatives.

Unlike other guards, omamori defends itself — AI agents cannot disable or bypass its protection (#22).

macOS only. Terminal commands are never affected — omamori only activates when it detects an AI tool's environment variable.

Quick Start

# Install (macOS)
brew install yottayoshida/tap/omamori

# Setup (shims + hooks + config — all in one)
omamori install --hooks

# Add to your shell profile (~/.zshrc or ~/.bashrc)
export PATH="$HOME/.omamori/shim:$PATH"

That's it. Works with Claude Code Auto mode — no extra config needed.

Cursor users: After upgrades, re-merge the hook snippet. See Auto-sync.

What It Blocks

--delete, --del, --delete-before, --delete-during, --delete-after, --delete-excluded, --delete-delay, --remove-source-files

All rules are customizable via TOML config. See Configuration below.

How It Works

AI CLI tool → CLAUDECODE=1 → rm -rf src/
                                ↓
                          [omamori shim]
                                ↓
                        blocked (protected path)

Terminal → rm -rf src/
                ↓
          [/usr/bin/rm]
                ↓
          deleted normally

Layer 1 — PATH shim: Symlinks for rm, git, chmod, find, rsync point to omamori. Rules apply only when an AI environment variable is detected.

Layer 2 — Hooks: Evaluates commands against the same rules as Layer 1, with three additional capabilities:

• Recursively unwraps shell wrappers (sudo env bash -c "..." → extracts inner command)
• Blocks pipe-to-shell patterns (curl | bash)
• Blocks dynamic command generation (bash -c "$(cmd)")

Available for Claude Code, Cursor, and Codex CLI.

Layer 3 — Audit (v0.7.0+): Records every command decision in a tamper-evident log — if an AI agent modifies any entry, the chain breaks and tampering is detected.

• HMAC-SHA256 signed and hash-chained JSONL (~/.local/share/omamori/audit.jsonl)
• Per-install secret; file paths HMAC-hashed (never stored in plaintext)
• Auto-retention (v0.7.2+): set retention_days in config to automatically prune old entries — chain integrity is preserved across pruning
• Logging enabled by default; retention is opt-in via config

Self-defense (#22): AI agents cannot config disable, uninstall, or edit config.toml while detected. Hooks block env var unsetting, config modification, and audit log/secret access via shell commands. This is a key differentiator from other CLI guards — omamori assumes adversarial AI behavior and defends against it.

Auto mode compatible (v0.6.2+): Works seamlessly with Claude Code's Auto mode — safe commands proceed without prompts, dangerous commands are still hard-blocked.

Auto-sync: After brew upgrade, the shim detects version mismatch and auto-regenerates hook files on the next invocation.

• Claude Code: Hooks are applied automatically. No action needed.
• Codex CLI: Hooks and config are auto-configured during install (v0.6.3+). If you install Codex later, the shim sets up hooks on first invocation. Auto-sync regenerates the wrapper on upgrade.
• Cursor: Run omamori install --hooks to regenerate the snippet, then merge ~/.omamori/hooks/cursor-hooks.snippet.json into your .cursor/hooks.json.

Core policy: The 7 built-in rules cannot be disabled via config.toml — an AI agent setting enabled = false is silently ignored. For legitimate overrides, see omamori override in CLI Reference.

Integrity monitoring (omamori status): Verifies all defense layers are intact — shims, hooks, config, core policy, PATH order. Detects tampering including subtle hook edits where the version comment is preserved but the body is rewritten.

Sandbox complementarity: omamori operates at the semantic layer — it understands what a command does (Layer 1: shim, Layer 2: hooks). A filesystem sandbox operates at the OS boundary — it restricts where processes can read and write. These are complementary: omamori catches rm -rf src/ before it runs; a sandbox prevents damage if something slips through. For defense in depth, combine omamori with your AI tool's sandbox (Codex CLI sandbox (on by default), Claude Code /sandbox, Cursor agent sandbox) or a dedicated tool like nono.

File protection (v0.8.0+): AI Edit/Write operations on omamori's own files (config, hooks, audit log, integrity baseline, Claude Code settings.json) are blocked. See SECURITY.md for the full protected file list.

For what omamori cannot catch, see Structural Limitations.

Supported Tools

Context-Aware Evaluation

omamori can adjust actions based on what the command targets:

Opt-in: Add [context] to ~/.config/omamori/config.toml. Built-in lists for regenerable (target/, node_modules/, etc.) and protected (src/, .git/, .env, etc.) paths activate automatically.

[context]
# Built-in defaults activate with just [context].
# To customize, specify your own lists (replaces built-in defaults):
# regenerable_paths = ["target/", "node_modules/", "my-cache/"]
# protected_paths = ["src/", "lib/", ".git/", ".env", ".ssh/", "secrets/"]

Note: Specifying regenerable_paths or protected_paths replaces the built-in defaults (not appends). Include the built-in entries you want to keep.

Security features: symlink defense via canonicalize(), path traversal normalization, NEVER_REGENERABLE hardcoded list, fail-close on errors.

Configuration

Built-in rules are always inherited. Only write the rules you want to change:

omamori config list                          # show all rules
omamori config disable git-push-force-block  # disable a rule
omamori config enable git-push-force-block   # restore default
omamori test                                 # verify policy

Or edit ~/.config/omamori/config.toml directly. Config is auto-created by install --hooks. See omamori init --stdout for the full template.

Disable a rule:

[[rules]]
name = "git-push-force-block"
enabled = false

Move files to a custom directory:

[[rules]]
name = "rm-to-backup"
command = "rm"
action = "move-to"
destination = "/tmp/omamori-quarantine/"
match_any = ["-r", "-rf", "-fr", "--recursive"]

Override an existing rule:

[[rules]]
name = "rm-recursive-to-trash"
action = "move-to"
destination = "/tmp/omamori-quarantine/"

Enable audit retention (prunes entries older than N days):

[audit]
retention_days = 90  # 0 = keep all (default). Minimum 7 days.

Enable strict mode (block shim-intercepted commands when HMAC secret is unavailable):

[audit]
strict = true  # default: false. Hook-only commands (ls, cat, etc.) are not affected.

Notes: Config requires chmod 600. Destinations must be absolute paths on the same volume. System directories and symlinks are rejected.

CLI Reference

omamori install [--hooks]                # Setup shims + hooks + config (re-run after brew upgrade for Cursor)
omamori test [--config PATH]             # Verify policy rules
omamori status [--refresh]               # Health check all defense layers
omamori exec [--config PATH] -- CMD      # Run command through policy engine

omamori audit verify                     # Verify hash chain integrity (exit 0/1/2)
omamori audit show [--last N] [--json]   # View recent audit entries (default: last 20)
omamori audit show --all                 # View all entries
omamori audit show --rule <name>         # Filter by rule (substring match)
omamori audit show --provider <name>     # Filter by provider

omamori config list                      # Show rules with status
omamori config disable <rule>            # Disable a rule
omamori config enable <rule>             # Re-enable a rule
omamori override disable <rule>          # Override a core safety rule
omamori override enable <rule>           # Restore a core safety rule

omamori init [--force] [--stdout]        # Create/reset config
omamori uninstall                        # Remove shims + hooks
omamori hook-check [--provider NAME]     # Hook detection engine (used internally by hooks)
omamori cursor-hook                      # Cursor hook handler
omamori --version                        # Show version

Structural Limitations

These are inherent to the PATH shim approach and documented honestly:

• Full-path execution (/bin/rm) bypasses the shim — mitigated by Layer 2 hooks
• sudo changes PATH — omamori blocks when it detects elevated execution
• Interpreter commands (python -c "shutil.rmtree(...)") — not detected. Investigated and deferred: zero real-world incidents in target tools
• Obfuscated commands (base64, variable indirection) — cannot be detected by static analysis
• AI self-bypass — config disable/uninstall are blocked; direct file editing blocked by hooks (Claude Code only)

For the full security model, bypass corpus, and known limitations, see SECURITY.md.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.