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openspec/changes/enterprise-gaming-r3f-physics-cascade/proposal.md

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+# OpenSpec Change: enterprise-gaming-r3f-physics-cascade
+
+- **Change ID**: enterprise-gaming-r3f-physics-cascade
+- **Package**: `@suaveplan/r3f-physics-cascade`
+- **Category**: gaming/physics
+- **Target path**: `gaming/physics/r3f-physics-cascade`
+- **Status**: PROPOSED
+- **Date**: 2026-04-24
+
+---
+
+## Summary
+
+Deliver `@suaveplan/r3f-physics-cascade` on the genesis branch from scratch at enterprise quality. The package provides cascading physics effects for React Three Fiber: chain-reaction impulse propagation (impact → impulse list → rigid bodies receive forces), structural collapse simulation (rigid-body sleep/wake thresholds), and `CascadeZone` spatial boundaries that limit propagation extent. Wires to `@suaveplan/r3f-physics-rapier` via the core `PhysicsBackend` interface. Genesis adds structured errors, OTel cascade-event counter, and 100% coverage.
+
+---
+
+## Available workspace deps
+
+`@suaveplan/error`, `@suaveplan/types`, `@suaveplan/events`, `@suaveplan/r3f-physics-core`, react, `@react-three/fiber`, three.
+
+---
+
+## Public API surface
+
+```ts
+function CascadeZone(props: CascadeZoneProps): JSX.Element
+// center, radius, maxPropagations
+
+function useCascade(): CascadeController
+// trigger(origin, force, radius): void
+```
+
+---
+
+## File layout
+
+```text
+gaming/physics/r3f-physics-cascade/
+  package.json / tsconfig.json / vitest.config.ts
+  src/
+    index.ts / error-codes.ts
+    types/common.ts + md
+    core/
+      cascade-propagator/ (ts + md + types + test + index)
+    context/cascade-provider.tsx + md + test
+    hooks/use-cascade.ts + md + test
+    components/
+      CascadeZone/ (tsx + md + test + stories + index)
+  tests/integration.test.ts
+```