// Best practices for building on-device AI features in React Native using React Native ExecuTorch. Use when the user wants to add AI to a mobile app without cloud dependencies: chatbots and assistants, image classification, object detection, OCR and document parsing, style transfer, image generation, speech-to-text, text-to-speech, voice activity detection, semantic search with embeddings, real-time camera AI with VisionCamera, or vision-language image understanding. Also use when the user mentions offline AI, on-device ML, privacy-preserving AI, reducing cloud API costs or latency, running models locally on mobile, or downloading and managing ML models. Covers react-native-executorch hooks (useLLM, useClassification, useObjectDetection, useOCR, useSemanticSegmentation, useInstanceSegmentation, useStyleTransfer, useTextToImage, useImageEmbeddings, useSpeechToText, useTextToSpeech, useVAD, useTextEmbeddings, useExecutorchModule), tool calling, structured output, VLMs, model loading, and resource management.
Best practices for building on-device AI features in React Native using React Native ExecuTorch. Use when the user wants to add AI to a mobile app without cloud dependencies: chatbots and assistants, image classification, object detection, OCR and document parsing, style transfer, image generation, speech-to-text, text-to-speech, voice activity detection, semantic search with embeddings, real-time camera AI with VisionCamera, or vision-language image understanding. Also use when the user mentions offline AI, on-device ML, privacy-preserving AI, reducing cloud API costs or latency, running models locally on mobile, or downloading and managing ML models. Covers react-native-executorch hooks (useLLM, useClassification, useObjectDetection, useOCR, useSemanticSegmentation, useInstanceSegmentation, useStyleTransfer, useTextToImage, useImageEmbeddings, useSpeechToText, useTextToSpeech, useVAD, useTextEmbeddings, useExecutorchModule), tool calling, structured output, VLMs, model loading, and resource management.
On-Device AI
Software Mansion's production patterns for on-device AI in React Native using React Native ExecuTorch.
Load at most one reference file per question. For hook API signatures, model constants, and configuration options, webfetch the relevant page from the official docs at https://docs.swmansion.com/react-native-executorch/docs/.
Decision Tree
Pick the right hook based on the AI task.
What AI task does the feature need?
│
├── Text generation, chatbot, or reasoning?
│ └── useLLM → see llm.md
│ ├── Text-only chat → standard useLLM
│ ├── Vision-language (image+text) → useLLM with VLM model
│ ├── Tool calling → configure with toolsConfig
│ └── Structured JSON output → getStructuredOutputPrompt
│
├── Understanding images?
│ ├── What's in this image? → useClassification → see vision.md
│ ├── Where are objects? → useObjectDetection → see vision.md
│ ├── Read text from image? → useOCR / useVerticalOCR → see vision.md
│ ├── Segment by class? → useSemanticSegmentation → see vision.md
│ ├── Segment per-instance? → useInstanceSegmentation → see vision.md
│ ├── Apply artistic style? → useStyleTransfer → see vision.md
│ ├── Generate image from text? → useTextToImage → see vision.md
│ └── Embed image as vector? → useImageEmbeddings → see vision.md
│
├── Speech or audio processing?
│ ├── Transcribe speech → useSpeechToText → see speech.md
│ ├── Synthesize speech → useTextToSpeech → see speech.md
│ └── Detect speech segments → useVAD → see speech.md
│
├── Text utilities?
│ ├── Convert text to vectors → useTextEmbeddings → see vision.md
│ └── Count tokens → useTokenizer
│
├── Real-time camera processing?
│ └── runOnFrame with VisionCamera v5 → see vision.md
│
└── Custom model (.pte)?
└── useExecutorchModule → see setup.md
Critical Rules
Call initExecutorch() before any other API. You must initialize the library with a resource fetcher adapter at the entry point of your app. Without it, all hooks throw ResourceFetcherAdapterNotInitialized.
Always check isReady before calling forward or generate. Hooks load models asynchronously. Calling inference methods before the model is ready throws ModuleNotLoaded.
Interrupt LLM generation before unmounting the component. Unmounting while isGenerating is true causes a crash. Call llm.interrupt() and wait for isGenerating to become false before navigating away.
Use quantized models on mobile. Full-precision models consume too much memory for most devices. React Native ExecuTorch ships quantized variants for all supported models.
Audio for speech-to-text must be 16kHz mono. Mismatched sample rates produce garbled transcriptions silently.
Audio from text-to-speech is 24kHz. Create the AudioContext with { sampleRate: 24000 } for playback.
Set pixelFormat: 'rgb' and orientationSource="device" for VisionCamera frame processing. The default yuv format produces incorrect results with ExecuTorch vision models. Missing orientationSource causes misaligned bounding boxes and masks.
References
File
When to read
llm.md
LLM chat (functional and managed), tool calling, structured output, token batching, context strategy, vision-language models (VLM), model selection, generation config
Speech-to-text (batch and streaming transcription with timestamps), text-to-speech (batch and streaming synthesis, phoneme input), voice activity detection, audio format requirements
setup.md
Installation with initExecutorch, resource fetcher adapters, model loading strategies (bundled, remote, local), download management, error handling with RnExecutorchError, custom models with useExecutorchModule, Metro config for .pte files
