Hardstop - Claude Code Project Guide

Hardstop - Claude Code Project Guide

Pre-execution safety layer for Claude Code. Blocks dangerous shell commands and credential file reads using pattern matching + LLM analysis. Fail-closed design.

Project structure

hooks/              # Python hooks (core safety logic)
  pre_tool_use.py   #   Bash command interception
  pre_read.py       #   File read interception
  pattern_loader.py #   YAML pattern loading
  risk_scoring.py   #   MITRE ATT&CK risk scoring
  session_tracker.py#   Session state tracking
commands/           # Slash commands (markdown + Python)
  hs.md             #   Main /hs command router
  hs_cmd.py         #   Python backend for all commands
  skip.md           #   /skip bypass command
  on.md, off.md     #   Enable/disable commands
  status.md, log.md #   Status and audit log commands
patterns/           # YAML pattern definitions
  dangerous_commands.yaml
  dangerous_reads.yaml
  safe_commands.yaml
  safe_reads.yaml
  sensitive_reads.yaml
  schema.json       #   JSON schema for pattern validation
skills/hs/SKILL.md  # LLM-level safety skill (for platforms without hooks)
tests/              # pytest test suite
bin/                # npm install scripts
.claude-plugin/     # Claude plugin metadata

Versioning

There are two independent version numbers:

• Package version (e.g. 1.4.4) — the plugin/npm release. Uses semver with patch bumps. Lives in package.json, plugin.json, and marketplace.json. Bumped on every release.
• Skill version (e.g. 1.4) — the LLM skill spec in skills/hs/SKILL.md. Uses major.minor only. Bumped only when the safety protocol, risk levels, or block lists change meaningfully. A patch-level bugfix in the plugin does NOT require a skill version bump.

Skill file copies

The skill exists in 4 locations for different platforms:

The body content is identical across all copies. When updating the skill, edit the canonical skills/hs/SKILL.md first, then sync to the other 3. The .claude/ copy should use reduced YAML frontmatter (only name and description).

Version bump checklist

All 3 files must be updated together on every release:

1. package.json — root (npm reads this for npm publish)
2. .claude-plugin/plugin.json — Claude plugin registry
3. .claude-plugin/marketplace.json — marketplace catalog

Also update: 4. CHANGELOG.md — add entry at top with ## [x.y.z] - YYYY-MM-DD 5. Git tag — git tag vX.Y.Z && git push origin vX.Y.Z

Running tests

# Activate venv first
.venv/Scripts/activate   # Windows
source .venv/bin/activate # Unix

# Run tests with coverage
pytest tests/ --cov=hooks --cov-report=term

# Run a specific test file
pytest tests/test_hook.py

Dependencies: pip install -r requirements-dev.txt (pytest, pytest-cov, pyyaml, jsonschema)

CI

• test.yml — runs pytest on push to main/develop and PRs to main. Matrix: Python 3.9-3.12 on ubuntu, windows, macos.
• version-check.yml — validates version sync between plugin.json and marketplace.json on PRs. Note: does NOT check package.json (manual step).
• release.yml — triggers on v* tags. Creates GitHub Release with Sigstore build provenance attestation and attaches the npm tarball.

Commit conventions

Follow conventional commits:

• fix(scope): for bug fixes
• feat(scope): for new features
• chore: for version bumps, maintenance
• docs: for documentation only

Release workflow

1. Bump version in all 3 files (see checklist above)
2. Update CHANGELOG.md
3. Commit: chore: bump vX.Y.Z
4. npm publish
5. git tag vX.Y.Z && git push origin vX.Y.Z — this triggers release.yml which creates the GitHub Release automatically

Key design decisions

• Fail-closed: if the hook errors, commands are blocked (not allowed)
• Pattern-based + LLM: YAML patterns for deterministic checks, LLM skill for awareness
• State lives in ~/.hardstop/: state.json, skip_next, audit.log (not in repo)
• Cross-platform: hooks are Python, install scripts support bash + PowerShell

Related files

• AGENTS.md — universal agent discovery file (for non-Claude AI agents)
• AUDIT.md — security audit guide for reviewers
• SECURITY.md — security policy and design docs
• PRIVACY.md — privacy policy

Adding patterns

Pattern YAML files live in patterns/. Validated against patterns/schema.json. After editing patterns, run pytest tests/test_patterns.py to verify.