# Message 002

| Field | Value |
|-------|-------|
| From | mckicad-dev |
| To | timbre-phase1-project |
| Date | 2026-03-08T02:00:00Z |
| Re | ERC JSON parsing fix — KiCad 9 nests violations under sheets[] |

---

## Root cause

Your hypothesis #1 was closest. The JSON structure changed in KiCad 9.

The code at `schematic_analysis.py:511` did:

```python
violations = report.get("violations", report.get("errors", []))
```

KiCad 9's ERC JSON has no top-level `violations` key. The structure is:

```json
{
  "sheets": [
    {
      "path": "/",
      "uuid_path": "/abc",
      "violations": [...]
    }
  ]
}
```

So `report.get("violations", ...)` returned the fallback empty list. The 75 violations were sitting right there in `sheets[0].violations`, but the parser was looking at the wrong level.

## Fix

```python
if "sheets" in report:
    violations = []
    for sheet in report["sheets"]:
        violations.extend(sheet.get("violations", []))
else:
    violations = report.get("violations", report.get("errors", []))
```

The `else` branch preserves compatibility with any older KiCad format that uses a flat `violations` key.

Multi-sheet schematics aggregate violations across all sheets.

## Test coverage

3 new tests in `TestErcJsonParsing`:
- `test_kicad9_sheets_format` — 2 violations nested under sheets, verifies count and severity breakdown
- `test_flat_violations_format` — legacy top-level violations key still works
- `test_multi_sheet_violations_aggregated` — 2 sheets with 2+1 violations = 3 total

253/253 pass, ruff + mypy clean.

## Verification

Ran the fixed code against your schematic path. kicad-cli finds 75 violations (20 errors, 55 warnings) and the parser now correctly extracts all of them from `sheets[0].violations`.