# OpenSpec Change: enterprise-gaming-npc

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

---

## Summary

Deliver `@suaveplan/npc` on the genesis branch from scratch at enterprise quality. The package provides NPC lifecycle management with spawn pools, population control, and daily schedules. A `NpcRegistry` holds typed `NpcDefinition` descriptors; a `SpawnPool` manages active NPC instances with capacity limits, spawn/despawn, and respawn timers; a `PopulationController` enforces per-zone NPC density limits; a `DailySchedule` maps time-of-day windows to NPC activity states. Each NPC instance has a `BehaviorTree` (from `@suaveplan/behavior-tree`) and a typed Blackboard. Genesis adds Zod definition schemas, structured errors, OTel population gauge, injectable clock, and 100% coverage.

---

## Current-state audit (genesis)

Package does not exist on genesis yet — fresh build.

---

## Available workspace deps on genesis

| Package | Role |
|---|---|
| `@suaveplan/error` (`workspace:^`) | `NpcError`; `NPC.*` codes |
| `@suaveplan/types` (`workspace:^`) | `Clock`, `IdGenerator` |
| `@suaveplan/events` (`workspace:^`) | `npc:spawn`, `npc:despawn`, `npc:activity:change` events |
| `@suaveplan/behavior-tree` (`workspace:^`) | Per-NPC behavior tree runner |
| `zod` (`catalog:forms`) | `NpcDefinition`, `DailySchedule` schemas |
| `@opentelemetry/api` (`catalog:observability`) | Population gauge, activity-change counter |

---

## Public API surface

```ts
interface NpcDefinition {
  id: string
  displayName: string
  faction?: string
  behaviorTreeFactory: (bb: Blackboard) => TreeNode
  activities: ActivityDefinition[]
  respawnTime?: number    // seconds; undefined = no respawn
}

interface ActivityDefinition {
  name: string
  startHour: number     // 0–23
  endHour: number
  priority?: number
}

function createNpcRegistry(): NpcRegistry
interface NpcRegistry {
  register(def: NpcDefinition): void
  get(id: string): NpcDefinition | undefined
}

function createSpawnPool(options: SpawnPoolOptions): SpawnPool

interface SpawnPoolOptions {
  maxCapacity: number
  registry: NpcRegistry
  clock?: Clock
}

interface SpawnPool {
  spawn(defId: string, position: Vec3): NpcInstance
  despawn(instanceId: string): void
  tick(dt: number): void
  getActive(): NpcInstance[]
  readonly count: number
}

interface NpcInstance {
  readonly instanceId: string
  readonly definitionId: string
  readonly position: Vec3
  readonly activity: string
  readonly blackboard: Blackboard
  readonly treeRunner: BehaviorTreeRunner
  setPosition(position: Vec3): void
  setActivity(name: string): void
}

function createPopulationController(options: PopulationOptions): PopulationController

interface PopulationController {
  setZoneLimit(zoneId: string, max: number): void
  canSpawn(zoneId: string): boolean
  onSpawn(zoneId: string, instanceId: string): void
  onDespawn(zoneId: string, instanceId: string): void
  getZoneCount(zoneId: string): number
}
```

### Error codes

```ts
type NpcErrorCode =
  | 'NPC_DEF_NOT_FOUND'
  | 'NPC_POOL_FULL'
  | 'NPC_INSTANCE_NOT_FOUND'
  | 'NPC_INVALID_ACTIVITY'
  | 'NPC_ZONE_LIMIT_REACHED'
```

---

## New additions for genesis

1. **Respawn timer** — `SpawnPool.tick()` tracks despawned NPCs with respawn timers, auto-respawns at origin.
2. **Population controller** — per-zone density enforcement prevents spawning if limit reached.
3. **Daily schedule** — `ActivityDefinition` time windows drive `NpcInstance.activity` based on injected clock hour.
4. **OTel** — `npc.population` gauge per zone; `npc.activity_changes_total` counter.

---

## File layout

```text
gaming/ai/npc/
  package.json
  tsconfig.json
  vitest.config.ts
  src/
    index.ts
    error-codes.ts
    constants/index.ts
    types/common.ts
    types/common.md
    core/
      npc-registry/
        npc-registry.ts
        npc-registry.md
        npc-registry.test.ts
        index.ts
      spawn-pool/
        spawn-pool.ts
        spawn-pool.md
        spawn-pool.types.ts
        spawn-pool.test.ts
        index.ts
      population-controller/
        population-controller.ts
        population-controller.md
        population-controller.types.ts
        population-controller.test.ts
        index.ts
      daily-schedule/
        daily-schedule.ts
        daily-schedule.md
        daily-schedule.types.ts
        daily-schedule.test.ts
        index.ts
  tests/
    integration.test.ts
```

---

## Impact

**Downstream**: `@suaveplan/r3f-npc` renders NPC meshes and nameplates; `@suaveplan/fauna` extends spawn-pool for wildlife. Prerequisites: `@suaveplan/error`, `@suaveplan/types`, `@suaveplan/events`, `@suaveplan/behavior-tree`.