I've been conducting a security review of several self-hosted coding agent runtimes, specifically focusing on their permission models and the inherent risks of uncontrolled git operations. Aider, while a powerful tool, operates with a default-open posture that grants the agent significant latitude. This presents a clear attack surface: an exploited or maliciously manipulated agent could, for instance, `git push --force` to a protected branch or introduce vulnerable dependencies.

My immediate thought was to explore whether its native `--policy` flag could be extended or supplemented with a more robust, external policy engine. OpenPolicyAgent (OPA) came to mind, given its prevalence in cloud-native governance. The question is whether anyone has attempted to integrate these systems, creating a gatekeeper that intercepts Aider's proposed actions (shell commands, file writes, git operations) for evaluation against Rego policies before execution.

A theoretical architecture might involve:
* A wrapper or modified version of Aider's `CommandRunner` that sends a structured query (containing command, arguments, target files) to a local OPA sidecar.
* Rego policies that could enforce rules such as:
* Blocking any git command with `--force` or `--delete` on branches matching `main`, `master`, or `prod/*`.
* Preventing writes to files outside the designated project directory (e.g., `/etc/passwd`, `../sibling_repo/`).
* Requiring a manual approval pattern for changes to specific files like `package.json`, `Cargo.toml`, or Dockerfiles.

```rego
# Example rego policy snippet for git command review
package aider.git

default allow := false

allow {
not is_dangerous_git_command
}

is_dangerous_git_command {
input.command[0] == "git"
input.arguments[_] == "push"
input.arguments[_] == "--force"
# Match protected branch patterns
regex.match("^(origin/)?(main|master|prod/.*)$", input.arguments[_])
}
```

The core challenge I foresee is the integration layer. Aider's policy system currently loads Python modules. Would we need a custom policy module that calls out to OPA's HTTP API? Or would a more fundamental fork be required? Furthermore, the evaluation point is critical—policy must be applied *before* the action is executed, not in an audit-log fashion afterward.

I'm interested in any practical experiments, forks, or discussions on this topic. Have you implemented policy-as-code for coding agents? Are there alternative, more agent-runtime-specific frameworks than OPA that might be a better fit for this use case?

ol