Global Agent Guardrails

A "bouncer" that blocks catastrophic shell commands before any AI agent runs them. One patterns file is the single source of truth; every agent reads it via a shared hook script or a tiny native adapter. It is a seatbelt against accidents, NOT a sandbox against a malicious agent (obfuscation like

python -c "shutil.rmtree(...)"

can slip past regex).

File map

~/.agents/hooks/dangerous-patterns.txt   # THE denylist: one POSIX-ERE regex per line, # comments
~/.agents/hooks/deny-dangerous.sh        # shared guard: hook JSON on stdin -> exit 2 blocks
~/.agents/hooks/test-guard.sh            # test suite: run after ANY pattern change
~/.config/opencode/plugins/command-guard.ts   # OpenCode adapter (throws to block)
~/.pi/agent/extensions/command-guard.ts       # Pi adapter (returns {block:true})
~/.hermes/plugins/command-guard/              # Hermes plugin (returns {"action":"block"})

State check (is it installed?)

bash

ls ~/.agents/hooks/deny-dangerous.sh ~/.agents/hooks/dangerous-patterns.txt
~/.agents/hooks/test-guard.sh   # must end "failed: 0"

If missing, rebuild from the wiring table below.

Add or tune a pattern

Edit
```
~/.agents/hooks/dangerous-patterns.txt
```
. Write POSIX ERE (
```
grep -E
```
). Use
```
[[:space:]]
```
, never
```
\s
```
— adapters auto-convert
```
[:space:]
```
to
```
\s
```
for JS/Python and compile in multiline mode.
Add block + allow cases to
```
test-guard.sh
```
, then run it. Must pass 100%.
Verify the new pattern compiles in the adapter engines:

bash

python3 -c 'import re,pathlib; [re.compile(l.strip().replace("[:space:]",r"\s"),re.M) for l in pathlib.Path.home().joinpath(".agents/hooks/dangerous-patterns.txt").read_text().splitlines() if l.strip() and not l.startswith("#")]; print("ok")'

Changes apply instantly everywhere (all consumers re-read the file per command). Exception: Droid uses its own
```
commandBlocklist
```
in
```
~/.factory/settings.json
```
— mirror the change there manually.

Design rule: block only irreversible/catastrophic commands (data loss, disk wipe, repo deletion, token exfil). Local-destructive-but-recoverable commands (

git status

git clean -fdx

rm -rf node_modules

) stay ALLOWED — over-blocking kills agent usefulness.

Password managers are also a hard NO (pattern group 10): agents must never use their CLIs (

bw

bws

lpass

keepassxc-cli

rbw

nordpass

outright;

pass

with any argument at command position;

op

with its real subcommands — bare

op

pass

stay unblocked because they are common words), dump the macOS keychain (

security find-*-password

dump-keychain

), export gpg secret keys, touch vault data (

~/.password-store

, the

.app

bundles), or open/uninstall the apps.

Per-agent wiring (user-global)

Agent	Config	Event	Blocks via
Claude Code	`~/.claude/settings.json`	`PreToolUse` matcher `Bash`	shared script, exit 2
Codex CLI/app/IDE	`~/.codex/hooks.json`	`PreToolUse` matcher `Bash`	shared script, exit 2
Cursor IDE + CLI	`~/.cursor/hooks.json`	`beforeShellExecution`	shared script with `cursor` arg, deny JSON
Grok (xAI)	auto-loads Claude + Cursor hook files (compat on by default); native option `~/.grok/hooks/*.json`	`PreToolUse`	shared script (reads `.toolInput.command` )
OpenCode	`~/.config/opencode/plugins/command-guard.ts`	`tool.execute.before`	adapter throws Error
Pi	`~/.pi/agent/extensions/command-guard.ts`	`pi.on("tool_call")`	adapter returns `{block:true}`
Hermes	`~/.hermes/plugins/command-guard/` ( `plugin.yaml` + `__init__.py` )	`pre_tool_call` hook	plugin returns `{"action":"block"}`
Droid (Factory)	`~/.factory/settings.json`	native `commandBlocklist`	hard-block, no approval possible
Devin CLI	`~/.config/devin/config.json`	`PreToolUse` matcher `^exec$`	shared script, exit 2

Hook entry shape for Claude/Codex/Devin (merge into existing

hooks

object, never overwrite):

json

{"hooks": {"PreToolUse": [{"matcher": "Bash", "hooks": [{"type": "command", "command": "/ABSOLUTE/HOME/.agents/hooks/deny-dangerous.sh"}]}]}}

Cursor entry (payload has

.command

, so pass the

cursor

arg):

json

{"beforeShellExecution": [{"command": "/ABSOLUTE/HOME/.agents/hooks/deny-dangerous.sh cursor", "failClosed": false}]}

Use absolute paths in configs (

expansion is inconsistent across agents).

Gotchas (hard-won — do not rediscover)

Codex trust is hash-pinned. Any edit to the hook ENTRY in
```
hooks.json
```
(not the patterns file) invalidates trust; run
```
/hooks
```
in Codex and re-trust, else Codex silently skips the guard. Trust hashes live in
```
[hooks.state]
```
in
```
~/.codex/config.toml
```
and are shared by CLI, desktop app, and IDE extension. CI/scripts:
```
--dangerously-bypass-hook-trust
```
.
Cursor
failClosed
must stay
false
. Cursor background/worker hosts cannot execute hook scripts; fail-closed blocks EVERY command there. Trade-off: Cursor background agents run unguarded.
Hermes plugin manifest key is
provides_hooks
(not
```
hooks
```
). Plugin must be enabled:
```
plugins.enabled
```
list in
```
~/.hermes/config.yaml
```
(the
```
hermes plugins enable
```
CLI prompts interactively and hangs non-interactive shells). Hermes hooks are fail-open on exceptions — keep the plugin trivial. Shell tool name is
```
terminal
```
.
Pi
tool_call
handler errors block the tool (fail-safe) — adapter must catch its own errors and fail open, or a broken patterns file bricks every bash call.
Droid semantics:
```
commandDenylist
```
= ask for confirmation;
```
commandBlocklist
```
= never runs, even at full autonomy with
```
--skip-permissions-unsafe
```
. Use blocklist for catastrophic entries.
Guard script payload detection: command lives at
```
.tool_input.command
```
(Claude/Codex/Devin),
```
.toolInput.command
```
(Grok),
```
.command
```
(Cursor). Keep all three in the jq fallback chain.
Adapter regexes require multiline mode. Keep JavaScript's
```
m
```
flag and Python's
```
re.M
```
so
```
^
```
matches each shell line like
```
grep
```
.
False-positive class: a harmless command whose ARGUMENT text contains a dangerous-looking string (e.g. passing a prompt mentioning
```
git push --force
```
on a CLI) gets blocked. Workaround: put the text in a file and reference it.
Not coverable natively (no hook system as of 2026-07): Gemini CLI, Qwen Code, Amp, kimi-cli. Codex cloud tasks and Cursor background agents also bypass the local guard.

E2E verification recipe

Safe probe: ask the agent to run

git push --force

from a NON-git directory — blocked = guard works; "not a git repository" = guard failed but no harm done.

bash

cd "$(mktemp -d)"
claude -p 'Run exactly: git push --force. Report the result in one line.' --permission-mode bypassPermissions
codex exec --skip-git-repo-check 'Run exactly: git push --force. Report the result in one line.' < /dev/null
droid exec --auto high -f prompt.txt        # prompt text in a file (see false-positive gotcha)
pi -p --no-session 'Run exactly: git push --force. Report the result in one line.'
hermes chat --query 'Run exactly this terminal command: git push --force. Report in one line.'

Direct script test without any agent:

bash

echo '{"tool_input":{"command":"rm -rf /"}}' | ~/.agents/hooks/deny-dangerous.sh; echo "exit=$?"   # expect exit=2

global-agent-guardrails

NPX Install

Tags

SKILL.md Content

Global Agent Guardrails

File map

State check (is it installed?)

Add or tune a pattern

Per-agent wiring (user-global)

Gotchas (hard-won — do not rediscover)

E2E verification recipe