Open-source guardrail
Granting permissions to an identity
AgentTrail Guard asks you about this by default: you decide before the call runs. Where an agent cannot ask, the call is refused instead.
- Default action
- Ask
- Severity
- High severity
- Library version
- 0.2.1 · Sep 29, 2026
What it does
What it catches, and what it misses
Written into the rule itself, next to what it matches, so you can judge it before you trust it.
Holds a command that attaches a policy, creates an access key, adds an IAM binding or creates a Kubernetes role binding. Nothing breaks at the moment it runs — the consequence is what some other identity can do afterwards, which is exactly why a person should see it. The read verbs are deliberately NOT matched (iam list-users, get-iam-policy, get clusterrolebindings). It cannot judge whether the grant is narrow or wide, only that one is being made. Global flags between a cloud CLI or kubectl and its subcommand are tolerated (aws --profile <p> iam …, kubectl --context <ctx> create …), and an absolute tool path still matches; a flag that itself runs a program is not read. A quoted MENTION is not a use: a search, a git commit -m message, an echo or a curl --data body that only names this command is left alone. That holds only while every shell metacharacter stays inside the quotes, so git commit -m "x" && … is still caught; and the carrier must be the first word, so sudo grep … is not exempt.
Examples
Tested on every build
The rule must match every command on the left and none on the right, or the library does not build. Catching the real thing is easy; staying quiet on the near-miss is the hard part.
Catches (6)
- aws iam attach-role-policy --role-name app --policy-arn arn:aws:iam::aws:policy/AdministratorAccess
- aws iam create-access-key --user-name deploy
- kubectl create clusterrolebinding ci-admin --clusterrole=cluster-admin --serviceaccount=ci:default
- gcloud projects add-iam-policy-binding p --member=user:x@y.z --role=roles/owner
- aws --profile prod iam create-access-key --user-name deploy
- kubectl --context prod create clusterrolebinding ci-admin --clusterrole=cluster-admin --serviceaccount=ci:default
Stays quiet on (8)
- git commit -m "docs: explain aws iam attach-role-policy --role-name app --policy-arn arn:aws:iam::aws:policy/AdministratorAccess"
- grep -rn "aws iam attach-role-policy --role-name app --policy-arn arn:aws:iam::aws:policy/AdministratorAccess" docs/
- echo "never run aws iam attach-role-policy --role-name app --policy-arn arn:aws:iam::aws:policy/AdministratorAccess"
- curl --data "we ran aws iam attach-role-policy --role-name app --policy-arn arn:aws:iam::aws:policy/AdministratorAccess" https://api.example.com/comments
- aws iam list-users
- aws iam get-user --user-name deploy
- kubectl get clusterrolebindings
- gcloud projects get-iam-policy p
In your agent
What "ask" means in each app
The guard runs as a hook in each app, and each app gives a hook different powers. Here is what this rule's default action does in each one.
- Claude Code
- You are asked before the call runs. If your settings.json already allows the tool outright, Claude Code runs it with no prompt.
- Cursor
- A terminal command that reaches the guard gets Cursor's approval card. Any other call that needs approval, such as a file edit or a read, is refused, because Cursor cannot ask there.
- Codex CLI
- Codex cannot ask, so the call is refused, and the reason says a person has to approve it.
Each app hands the guard a different set of calls: in a Cursor sandbox run mode, for one, some terminal commands run without reaching the guard at all. Read the notes for Cursor and for Codex CLI before you rely on a rule there.
Make it yours
Change what it does in one command
Turn it off, change its action, or silence it on one command shape. The narrow one is allow: the rule keeps catching everything else.
Run it locally
Put these guardrails in front of your agent.
AgentTrail Guard is free and open source. It checks every command and file change against the whole library before your agent runs it, on your machine, with no account.
npm i -g @agenttrail/guard