```dart title="Dart" import 'package:kreuzberg/kreuzberg.dart'; Future main() async { // A stateful Dart `PostProcessor` that captures mutable counters in its // closure cannot be plugged into the global registry. // `Kreuzberg.registerPostProcessor(impl)` exists, but the // `createPostProcessorDartImpl` factory takes opaque `BoxFn*` closure // values whose constructors are not surfaced through flutter_rust_bridge, // so the closure-capture pattern is unreachable from Dart. // // Implement stateful plugins in Rust using `Mutex`/`AtomicU64` for // interior mutability, then register them in a Rust shim crate. } ```