---
title: "Writing Classifiers for permission-manager (agent-toolkit)"
description: "Guide to adding new command classifiers to the St0nefish/agent-toolkit permission-manager plugin for Claude Code, covering project structure, conventions, testing, and PR workflow."
type: guide
domain: development
tags: [claude-code, permissions, agent-toolkit, bash, classifier]
---

# Writing Classifiers for permission-manager

## Overview

The `permission-manager@agent-toolkit` plugin (St0nefish/agent-toolkit) provides a `cmd-gate` PreToolUse hook that classifies Bash commands before execution. Classifiers are bash scripts in `plugins-claude/permission-manager/scripts/classifiers/` that decide whether commands should be auto-allowed, require user approval, or be denied.

## Project Structure

```
plugins-claude/permission-manager/
  scripts/
    cmd-gate.sh              # Hook entry point
    lib-classify.sh          # Classification framework + dispatcher
    classifiers/
      cargo.sh               # cargo/rust
      docker.sh              # docker/compose
      find.sh                # find (deny -delete/-exec rm)
      git.sh                 # git (with protected branch logic)
      gh.sh                  # GitHub CLI
      gradle.sh              # gradle/gradlew
      jvm-tools.sh           # java/mvn
      npm.sh                 # npm/node/pnpm/yarn/npx
      pip.sh                 # pip/python/poetry/pyenv
      read-only-tools.sh     # cat, ls, grep, jq, ps, etc.
      tea.sh                 # Gitea CLI
      uv.sh                  # uv/uvx (added 2026-03-18)
tests/permission-manager/
  test-classify.sh           # Main test harness (618+ tests)
```

## Classification Decisions

Three possible outcomes:
- **`allow`** — auto-approve, no prompt (read-only or safe local operations)
- **`ask`** — prompt user for approval (destructive, remote, or elevated operations)
- **`deny`** — block the command (e.g., `find -delete`)
- **passthrough** — `return 0` without calling allow/ask/deny; defers to Claude Code's built-in permission system

## Classifier Conventions

### File Header
```bash
# shellcheck shell=bash
# shellcheck source=../lib-classify.sh
```

### Function Naming
- Entry point: `check_<tool>()` (e.g., `check_uv`, `check_docker`)
- Subcommand extractor: `extract_<tool>_subcommand()` (for tools with global flags)

### Entry Guard Pattern

Simple tools (cargo, npm, pip) use `awk` + `case`:
```bash
local first_token
first_token=$(echo "$command" | awk '{print $1}')
case "$first_token" in
  uv) ;;
  *) return 0 ;;
esac
```

Complex tools (docker, git) use `perl` guard:
```bash
echo "$command" | perl -ne '$f=1,last if /^\s*docker(\s|$)/; END{exit !$f}' || return 0
```

### Reason Message Style
- Read-only: `"<tool> <subcmd> is read-only"`
- Local ops: `"<tool> <subcmd> is a local build/dev operation"`
- Ask: `"<tool> <subcmd> modifies <what>"`
- Deny: `"<tool> <subcmd> is not allowed"`

### Classification Philosophy (from existing classifiers)
| Category | Decision | Examples |
|----------|----------|---------|
| Read-only inspection | allow | `git status`, `docker ps`, `pip list` |
| Local build/install | allow | `npm install`, `pip install`, `cargo build` |
| Global tool install | ask | `cargo install`, `uv tool install` |
| Package uninstall | ask | `pip uninstall`, `uv pip uninstall` |
| Publish/deploy | ask | `npm publish`, `cargo publish`, `uv publish` |
| Execute arbitrary packages | passthrough | `npx`, `uvx`, `uv run --with` |
| Destructive operations | deny | `find -delete` |

## Wiring a New Classifier

In `lib-classify.sh`, add to `classify_single_command()`:
```bash
check_<tool>
[[ "$CLASSIFY_MATCHED" -eq 1 ]] && return 0
```

Place it logically near related classifiers (e.g., `check_uv` after `check_pip`).

## Testing

### Test Format
```bash
run_test_both <expected> "<command>" ["label"]
```
`run_test_both` runs the test in both Claude and Copilot modes. Expected values: `allow`, `ask`, `deny`, `none` (passthrough).

### Test Section Structure
```bash
# ===== ALLOW: <tool> read-only =====
echo "── <tool> read-only ──"
run_test_both allow "<command>"

# ===== ALLOW: <tool> local build/dev =====
echo "── <tool> local build/dev ──"
...
```

### Running Tests
```bash
bash tests/permission-manager/test-classify.sh           # Full suite
bash tests/permission-manager/test-classify.sh uv        # Filter by keyword
```

## PR Workflow

1. Fork `St0nefish/agent-toolkit` on GitHub
2. Branch from `master` (not `main`)
3. Add classifier, wire it, update tests
4. Run full test suite — zero regressions required
5. PR via `gh pr create --repo St0nefish/agent-toolkit --base master`

## Reference PR

- [PR #38: feat: add uv/uvx classifier](https://github.com/St0nefish/agent-toolkit/pull/38) — full uv/uvx classifier with 102 tests, submitted 2026-03-18
