# CLAUDE.md

This file provides guidance to Claude Code when working with the mckicad codebase.

## Development Commands

- `make install` - Install dependencies with uv (creates .venv)
- `make run` - Start the MCP server (`uv run python main.py`)
- `make test` - Run all tests (`uv run pytest tests/ -v`)
- `make test <file>` - Run a specific test file
- `make lint` - Lint with ruff + mypy (`src/mckicad/` and `tests/`)
- `make format` - Auto-format with ruff
- `make build` - Build package
- `make clean` - Remove build artifacts and caches

Python 3.10+ required. Uses `uv` for everything. Configure via `.env` (copy `.env.example`).

## Architecture

mckicad is a FastMCP 3 server for KiCad electronic design automation. It uses src-layout packaging with `hatchling` as the build backend.

### Project Structure

```
src/mckicad/
  __init__.py           # __version__ only
  server.py             # FastMCP 3 server + lifespan + module imports
  config.py             # Lazy config functions (no module-level env reads)
  tools/
    schematic.py        # kicad-sch-api: create/edit schematics (9 tools)
    project.py          # Project discovery and structure (3 tools)
    drc.py              # DRC checking + manufacturing constraints (4 tools)
    bom.py              # BOM generation and export (2 tools)
    export.py           # Gerber, drill, PDF, SVG via kicad-cli (4 tools)
    routing.py          # FreeRouting autorouter integration (3 tools)
    analysis.py         # Board validation + real-time analysis (3 tools)
    pcb.py              # IPC-based PCB manipulation via kipy (5 tools)
  resources/
    projects.py         # kicad://projects resource
    files.py            # kicad://project/{path} resource
  prompts/
    templates.py        # debug_pcb, analyze_bom, design_circuit, debug_schematic
  utils/
    kicad_cli.py        # KiCad CLI detection and execution
    path_validator.py   # Path security / directory traversal prevention
    secure_subprocess.py # Safe subprocess execution with timeouts
    ipc_client.py       # kipy IPC wrapper for live KiCad connection
    freerouting.py      # FreeRouting JAR engine
    file_utils.py       # Project file discovery
    kicad_utils.py      # KiCad path detection, project search
tests/
  conftest.py           # Shared fixtures (tmp dirs, project paths)
  test_*.py             # Per-module test files
main.py                 # Entry point: .env loader + server start
```

### Key Design Decisions

**Lazy config** (`config.py`): All environment-dependent values are accessed via functions (`get_search_paths()`, `get_kicad_user_dir()`) called at runtime, not at import time. Static constants (`KICAD_EXTENSIONS`, `TIMEOUT_CONSTANTS`, `COMMON_LIBRARIES`) remain as module-level dicts since they don't read env vars. This eliminates the .env load-order race condition.

**Decorator-based tool registration**: Each tool module imports `mcp` from `server.py` and decorates functions with `@mcp.tool()` at module level. `server.py` imports the modules to trigger registration. No `register_*_tools()` boilerplate.

**Schematic abstraction point**: `tools/schematic.py` uses `kicad-sch-api` for file-level schematic manipulation. The `_get_schematic_engine()` helper exists as a swap point for when kipy adds schematic IPC support.

**Dual-mode operation**: PCB tools work via IPC (kipy, requires running KiCad) or CLI (kicad-cli, batch mode). Tools degrade gracefully when KiCad isn't running.

### Tool Registration Pattern

```python
# tools/example.py
from mckicad.server import mcp

@mcp.tool()
def my_tool(param: str) -> dict:
    """Tool description for the calling LLM."""
    return {"success": True, "data": "..."}
```

### Tool Return Convention

All tools return dicts with at least `success: bool`. On failure, include `error: str`. On success, include relevant data fields.

## Adding New Features

1. Choose the right module (or create one in `tools/`)
2. Import `mcp` from `mckicad.server`
3. Decorate with `@mcp.tool()` and add a clear docstring
4. If new module: add import in `server.py`
5. Write tests in `tests/test_<module>.py`

## Security

- All file paths validated via `utils/path_validator.py` before access
- External commands run through `utils/secure_subprocess.py` with timeouts
- KiCad CLI commands sanitized — no shell injection
- `main.py` inline .env loader runs before any mckicad imports

## Environment Variables

- `KICAD_USER_DIR` - KiCad user config directory
- `KICAD_SEARCH_PATHS` - Comma-separated project search paths
- `KICAD_CLI_PATH` - Explicit kicad-cli path
- `FREEROUTING_JAR_PATH` - Path to FreeRouting JAR
- `LOG_LEVEL` - Logging level (default: INFO)

## Testing

Markers: `unit`, `integration`, `requires_kicad`, `slow`, `performance`

```bash
make test                          # all tests
make test tests/test_schematic.py  # one file
uv run pytest -m "unit"            # by marker
```

## Entry Point

```toml
[project.scripts]
mckicad = "mckicad.server:main"
```

Run via `uvx mckicad`, `uv run mckicad`, or `uv run python main.py`.

## FreeRouting Setup

1. Download JAR from https://freerouting.app/
2. Place at `~/freerouting.jar`, `/usr/local/bin/freerouting.jar`, or `/opt/freerouting/freerouting.jar`
3. Install Java runtime
4. Verify with `check_routing_capability()` tool
5. Or set `FREEROUTING_JAR_PATH` in `.env`

## Logging

Logs go to `mckicad.log` in project root, overwritten each start. Never use `print()` — MCP uses stdin/stdout for JSON-RPC transport.