Services that need per-directory lifecycle (created/destroyed per instance) go through the `Instances` LayerMap:
1. Define a `ServiceMap.Service` with a `static readonly layer` (see `FileWatcherService`, `QuestionService`, `PermissionService`, `ProviderAuthService`).
2. Add it to `InstanceServices` union and `Layer.mergeAll(...)` in `src/effect/instances.ts`.
3. Use `InstanceContext` inside the layer to read `directory` and `project` instead of `Instance.*` globals.
4. Call from legacy code via `runPromiseInstance(MyService.use((s) => s.method()))`.
### Instance.bind — ALS context for native callbacks
`Instance.bind(fn)` captures the current Instance AsyncLocalStorage context and returns a wrapper that restores it synchronously when called.
**Use it** when passing callbacks to native C/C++ addons (`@parcel/watcher`, `node-pty`, native `fs.watch`, etc.) that need to call `Bus.publish`, `Instance.state()`, or anything that reads `Instance.directory`.
**Don't need it** for `setTimeout`, `Promise.then`, `EventEmitter.on`, or Effect fibers — Node.js ALS propagates through those automatically.
```typescript
// Native addon callback — needs Instance.bind
const cb = Instance.bind((err, evts) => {
Bus.publish(MyEvent, { ... })
})
nativeAddon.subscribe(dir, cb)
```
## Flag → Effect.Config migration
Flags in `src/flag/flag.ts` are being migrated from static `truthy(...)` reads to `Config.boolean(...).pipe(Config.withDefault(false))` as their consumers get effectified.
- Effectful flags return `Config<boolean>` and are read with `yield*` inside `Effect.gen`.
- The default `ConfigProvider` reads from `process.env`, so env vars keep working.
- Tests can override via `ConfigProvider.layer(ConfigProvider.fromUnknown({ ... }))`.
- Keep all flags in `flag.ts` as the single registry — just change the implementation from `truthy()` to `Config.boolean()` when the consumer moves to Effect.
