Bridge Flutter apps to the rwkv-mobile inference runtime. A Flutter FFI plugin and runtime orchestration layer for on-device RWKV, multimodal, and speech workloads.

rwkv_mobile_flutter sits between a Flutter app and the native rwkv-mobile C++ inference engine. It is not just a thin FFI binding: it also owns the isolate boundary, request/response protocol, model lifecycle, native library loading, and part of the runtime coordination needed by apps such as RWKV_APP.

• Built for Flutter-native integration: Expose the native runtime to Dart without forcing app code to manage raw FFI calls directly.
• Designed for real device workloads: Keep inference work off the UI isolate and coordinate model loading, generation, vision, audio, and TTS flows in one place.
• One bridge for multiple backends: Reuse the same Dart-side protocol across CPU, GPU, and NPU-backed runtimes provided by rwkv-mobile.
• Production-oriented packaging: Ship prebuilt native libraries for Android, iOS, macOS, Windows, and Linux as part of the plugin.

• Cross-platform Flutter FFI plugin: Android, iOS, macOS, Windows, and Linux.
• Isolate-based runtime bridge: Run the native inference runtime behind a dedicated Dart isolate.
• Structured request/response protocol: ToRWKV and FromRWKV sealed classes for app-to-runtime messaging.
• Model lifecycle management: Load, unload, switch, and inspect multiple models from Flutter.
• Text generation APIs: Completion, chat with history, batch inference, stop/resume-style polling, and token counting.
• Multimodal support: Vision encoder, adapter-based vision flow, and Whisper-style audio prompt support.
• Speech support: SparkTTS model loading, streaming TTS buffers, global tokens, and property-driven speech generation.
• Runtime diagnostics: Load progress, prefill/decode speed, logs, SoC/platform detection, and state cache inspection.

This repository is best understood as the middle layer in a three-part stack:

flowchart LR
  A["Flutter App (for example RWKV_APP)"] -->|"ToRWKV messages via SendPort"| B["rwkv_mobile_flutter isolate"]
  B -->|"Dart FFI"| C["rwkv-mobile C API"]
  C --> D["Native runtime and backends"]
  D --> E["ncnn / llama.cpp / QNN / MLX / CoreML / WebRWKV / MNN / MTK NP7"]
  B -->|"FromRWKV messages"| A

• App layer: product UI, state management, downloads, business logic.
• This layer: isolate boundary, protocol, platform library loading, runtime orchestration, Dart-facing API surface.
• Engine layer: C++ runtime, backend implementations, native inference, and low-level C API.

For local development, RWKV_APP uses this repository as a path dependency:

dependencies:
  rwkv_mobile_flutter:
    path: ../rwkv_mobile_flutter

You can do the same in your own Flutter app, or point to the Git repository you maintain internally.

import 'dart:isolate';
import 'dart:ui';

import 'package:rwkv_mobile_flutter/rwkv.dart';

final receivePort = ReceivePort();

receivePort.listen((message) {
  if (message is SendPort) {
    // Save this SendPort and use it to send ToRWKV requests.
  } else {
    // Handle FromRWKV responses here.
  }
});

await RWKVMobile().runIsolate(
  StartOptions(
    sendPort: receivePort.sendPort,
    rootIsolateToken: RootIsolateToken.instance!,
  ),
);

Frontend isolate and RWKV isolate communicate through SendPort:

• Requests: lib/to_rwkv.dart
• Responses: lib/from_rwkv.dart
• Runtime bridge: lib/rwkv_mobile_flutter.dart

Typical app flow:

1. Start the RWKV isolate.
2. Receive the isolate SendPort.
3. Send typed requests such as LoadRWKVModel, ChatAsync, GenerateAsync, or StartTTS.
4. Consume typed responses such as LoadModelSteps, ResponseBufferContent, Speed, or TTSStreamingBuffer.

The public Dart-side contract is centered on two sealed hierarchies:

sealed class ToRWKV {}

Representative request types include:

• LoadRWKVModel
• ReleaseRWKVModel
• ChatAsync
• ChatBatchAsync
• GenerateAsync
• GetResponseBufferContent
• LoadVisionEncoder
• LoadVisionEncoderAndAdapter
• LoadWhisperEncoder
• StartTTS
• SaveRuntimeStateByHistory

sealed class FromRWKV {}

Representative response types include:

• LoadModelSteps
• GenerateStart
• GenerateStop
• ResponseBufferContent
• ResponseBatchBufferContent
• Speed
• EvaluationResults
• RuntimeLog
• StateInfo
• TTSStreamingBuffer

This plugin wraps runtime features exposed by rwkv-mobile, including:

• Multiple backend selection through the Backend enum
• Chat/completion inference
• Batch inference
• Sampling and penalty controls
• Seed and prompt management
• Response buffer polling
• Vision encoder loading
• Whisper/audio prompt support
• SparkTTS loading and streaming
• Runtime state save/load
• Platform and SoC inspection

Backends currently represented in Dart include:

• ncnn
• llama.cpp
• web-rwkv
• qnn
• mnn
• coreml
• mlx
• mtk_np7

Actual availability depends on the bundled native binaries you ship for each platform.

This repository includes prebuilt native artifacts for supported platforms, for example:

• Android: android/src/main/jniLibs/arm64-v8a/librwkv_mobile.so
• iOS: ios/librwkv_mobile.a
• macOS: macos/librwkv_mobile.dylib
• Windows: windows/rwkv_mobile.dll, windows/rwkv_mobile-arm64.dll
• Linux: linux/librwkv_mobile-linux-x86_64.so, linux/librwkv_mobile-linux-aarch64.so

The plugin loads these libraries dynamically based on the current platform and ABI.

When you see errors such as:

Invalid argument(s): Failed to lookup symbol 'xxx': undefined symbol: xxx

the bundled native libraries are usually out of sync with the generated FFI bindings or the underlying engine build. Refresh them from the latest rwkv-mobile release:

• Windows:

& ./fetch_latest_libraries.ps1

• Linux / macOS:

./fetch_latest_libraries.sh

These scripts download the latest platform archives from rwkv-mobile releases and copy the extracted artifacts into this plugin repository.

If you are developing the full Flutter app and this bridge together, keep the repositories side by side:

parent/
├─ rwkv_mobile_flutter/
└─ RWKV_APP/

Then use the local path dependency in RWKV_APP/pubspec.yaml:

dependencies:
  rwkv_mobile_flutter:
    path: ../rwkv_mobile_flutter

The demo app previously kept in example/ has been moved to RWKV_APP.

• Flutter / Dart: Cross-platform app layer and isolate model.
• Dart FFI: Native bridge between Flutter and the C API.
• rwkv_mobile_flutter: Protocol, runtime orchestration, and platform packaging layer.
• rwkv-mobile: Native inference runtime with multiple backends and multimodal support.
• Platform runtimes: CPU, GPU, and NPU execution depending on backend and device.

This repository is most useful when kept in sync with the engine and app layers:

• If you change native runtime symbols, regenerate or update the Dart FFI bindings.
• If you add a new runtime capability, update ToRWKV, FromRWKV, and the isolate handler together.
• If you change platform packaging, verify the corresponding native library layout for each target OS.

This project is licensed under the Apache License 2.0. See LICENSE for details.

• RWKV_APP
• rwkv-mobile
• rwkv_mobile_flutter package entrypoint
• Typed requests
• Typed responses