I still remember the first time I let an LLM execute a shell command on my machine. It was a simple ls -la, but my finger hovered over the Enter key for a solid ten seconds.
There is a visceral, lizard-brain reaction to giving an AI that level of access. We all know the horror stories—or at least the potential horror stories. One hallucinated argument, one misplaced flag, and a helpful cleanup script becomes rm -rf /. This fear creates a central tension in what I call the Agentic Shift. We want agents to be autonomous enough to be useful—fixing a bug across ten files while we grab coffee—but safe enough to be trusted with the keys to the kingdom.
Until now, my approach with the Gemini CLI was the blunt instrument of “Human-in-the-Loop.” Any tool call with a side effect—executing shell commands, writing code, or editing files—required a manual y/n confirmation. It was safe, sure. But it was also exhausting.
I vividly remember asking Gemini to “fix all the linting errors in this project.” It brilliantly identified the issues and proposed edits for twenty different files. Then I sat there, hitting y… y… y… twenty times.
The magic evaporated. I wasn’t collaborating with an intelligent agent; I was acting as a slow, biological barrier for a very expensive macro. This feeling has a name—“Confirmation Fatigue”—and it’s the silent killer of autonomy. I realized I needed to move from micromanagement to strategic oversight. I didn’t want to stop the agent; I wanted to give it a leash.
The Policy Engine
The solution I’ve built is the Gemini CLI Policy Engine.
Think of it as a firewall for tool calls. It sits between the LLM’s request and your operating system’s execution. Every time the model reaches for a tool—whether it’s to read a file, run a grep command, or make a network request—the Policy Engine intercepts the call and evaluates it against a set of rules.
The system relies on three core actions:
allow: The tool runs immediately.deny: The AI gets a “Permission denied” error.ask_user: The default manual approval.
A Hierarchy of Trust
The magic isn’t just in blocking or allowing things; it’s in the hierarchy. Instead of a flat list of rules, I built a tiered priority system that functions like layers of defense.
At the base, you have the Default Safety Net. These are the built-in rules that apply to everyone—basic common sense like “always ask before overwriting a file.”
Above that sits the User Layer, which is where I define my personal comfort zone. This allows me to customize the “personality” of my safety rails. On my personal laptop, I might be a cowboy, allowing git commands to run freely because I know I can always undo a bad commit. But on a production server, I might lock things down tighter than a vault.
Finally, at the top, is the Enterprise/Admin Layer. These are the immutable laws of physics for the agent. In an enterprise setting, this is where you ensure that no matter how “creative” the agent gets, it can never curl data to an external IP or access sensitive directories.
Safe Exploration
In practice, this means I can trust the agent to look but ask it to verify before it touches. I generally trust the agent to check the repository status, review history, or check if the build passed. I don’t need to approve every git log or gh run list.
[[rule]]
toolName = "run_shell_command"
commandPrefix = [
"git status",
"git log",
"git diff",
"gh issue list",
"gh pr list",
"gh pr view",
"gh run list"
]
decision = "allow"
priority = 100Yolo Mode
Sometimes, I’m working in a sandbox and I just want speed. I can use the dedicated yolo mode to take the training wheels off. There is a distinct feeling of freedom—and a slight thrill of danger—when you watch the terminal fly by, commands executing one after another.
However, even in Yolo mode, I want a final sanity check before I push code or open a PR. While Yolo mode is inherently permissive, I define specific high-priority rules to catch critical actions. I also explicitly block docker commands—I don’t want the agent spinning up (or spinning down) containers in the background without me knowing.
# Exception: Always ask before committing or creating a PR
[[rule]]
toolName = "run_shell_command"
commandPrefix = ["git commit", "gh pr create"]
decision = "ask_user"
priority = 900
modes = ["yolo"]
# Exception: Never run docker commands automatically
[[rule]]
toolName = "run_shell_command"
commandPrefix = "docker"
decision = "deny"
priority = 999
modes = ["yolo"]The Hard Stop
And then there are the things that should simply never happen. I don’t care how confident the model is; I don’t want it rebooting my machine. These rules are the “break glass in case of emergency” protections that let me sleep at night.
[[rule]]
toolName = "run_shell_command"
commandRegex = "^(shutdown|reboot|kill)"
decision = "deny"
priority = 999Decoupling Capability from Control
The significance of this feature goes beyond just saving me from pressing y. It fundamentally changes how we design agents.
I touched on this concept in my series on autonomous agents, specifically in Building Secure Autonomous Agents, where I argued that a “policy engine” is essential for scaling from one agent to a fleet. Now, I’m bringing that same architecture to the local CLI.
Previously, the conversation around AI safety often presented a binary choice: you could have a capable agent that was potentially dangerous, or a safe agent that was effectively useless. If I wanted to ensure the agent wouldn’t accidentally delete my home directory, the standard advice was to simply remove the shell tool. But that is a false choice. It confuses the tool with the intent. Removing the shell doesn’t just stop the agent from doing damage; it stops it from running tests, managing git, or installing packages—the very things I need it to do.
With the Policy Engine, I can give the agent powerful tools but wrap them in strict policies. I can give it access to kubectl, but only for get commands. I can let it edit files, but only on specific documentation sites.
This is how we bridge the gap between a fun demo and a production-ready tool. It allows me to define the sandbox in which the AI plays, giving me the confidence to let it run autonomously within those boundaries.
Defining Your Own Rules
The Policy Engine is available now in the latest release of Gemini CLI. You can dive into the full documentation here.
If you want to see exactly what rules are currently active on your system—including the built-in defaults and your custom additions—you can simply run /policies list from inside the Gemini CLI.
I’m currently running a mix of “Safe Exploration” and “Hard Stop” rules. It’s quieted the noise significantly while keeping my file system intact. I’d love to hear how you configure yours—are you a “deny everything” security maximalist, or are you running in full “allow” mode?
