# OpenSpec Change: enterprise-gaming-r3f-building

- **Change ID**: enterprise-gaming-r3f-building
- **Package**: `@suaveplan/r3f-building`
- **Category**: gaming/scene
- **Target path**: `gaming/scene/r3f-building`
- **Status**: PROPOSED
- **Date**: 2026-04-24
- **Reference spec**: `/mnt/s/web/suaveplan/enterprise/r3f-building.md`

---

## Summary

Deliver `@suaveplan/r3f-building` on the genesis branch from scratch at enterprise quality. The package provides R3F building mode UI: ghost preview of the piece being placed, snap socket highlight spheres, invalid placement red tint, confirm/cancel keybind integration, and structural instability shake effect. It wires directly to `@suaveplan/building`'s `PlacementEngine` and `StructureGraph`. A `BuildingMode` component activates the placement mode context; `PlacementGhost` renders the translucent preview mesh. Genesis adds structured errors, OTel placement counter, and 100% coverage.

---

## Available workspace deps

`@suaveplan/error`, `@suaveplan/building`, `@suaveplan/controller`, react, `@react-three/fiber`, `@react-three/drei`, three.

---

## Public API surface

```ts
function BuildingMode(props: BuildingModeProps): JSX.Element
// registry, onPlaced, onCancel, controllerManager

function PlacementGhost(props: PlacementGhostProps): JSX.Element
function SnapIndicator(props: SnapIndicatorProps): JSX.Element
function PlacedPieces(props: PlacedPiecesProps): JSX.Element

function useBuildingMode(): BuildingModeCon```text

---

## File layout

```text
gaming/scene/r3f-building/
  package.json / tsconfig.json / vitest.config.ts
  src/
    index.ts / error-codes.ts
    types/common.ts + md
    context/building-mode-provider.tsx + md + test
    hooks/use-building-mode.ts + md + test
    components/
      BuildingMode/ (tsx + md + test + stories + index)
      PlacementGhost/ (tsx + md + test + stories + index)
      SnapIndicator/ (tsx + md + test + stories + index)
      PlacedPieces/ (tsx + md + test + stories + index)
  tests/integration.test.ts
```