Half of all valid KiCAD schematic pin positions are on the 50-mil
(1.27mm) grid but not the 100-mil (2.54mm) grid — e.g. 26.67mm = 21 ×
1.27mm. Snapping to 2.54mm displaced those coordinates by 1.27mm,
moving labels off their pins and increasing floating-label count.
KiCAD source confirms: DEFAULT_CONNECTION_GRID_MILS = 50 and the ERC
off-grid check uses exact integer modulo against this value, so any
displacement breaks connectivity unconditionally.
Also update the kicad-source absolute path in CLAUDE.md.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds a new MCP tool that snaps wire endpoints, junction positions, and
net label coordinates to the nearest grid point (default 2.54 mm). Off-grid
coordinates cause wires that appear visually connected to fail ERC checks
because KiCAD uses exact IU integer matching internally; this tool eliminates
that class of error before running ERC.
- python/commands/schematic_snap.py: core snap logic with in-place sexp mutation
- python/kicad_interface.py: route + handler
- python/schemas/tool_schemas.py: JSON schema (gridSize, elements params)
- src/tools/schematic.ts: TypeScript MCP tool registration
- tests/test_snap_to_grid.py: 20 unit + integration tests (all passing)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
