What you actually touch in 2026
The dominant frontend for research and most production work is PyTorch. JAX has a strong following in research-heavy labs (Google DeepMind, Apple ML). TensorFlow still ships in some legacy systems. For most learners and most teams, learning PyTorch deeply is the highest-leverage choice.
Hugging Face sits on top of PyTorch as the de-facto distribution layer for pretrained models. transformers for text, vision, and multi-modal; diffusers for image/video generation; datasets for streaming and processing; accelerate for multi-GPU and mixed-precision boilerplate.
Inference is a separate stack. vLLM and TGI for high-throughput LLM serving. ONNX Runtime and TensorRT-LLM for production. llama.cpp and Ollama for local quantized models. MLX for Apple Silicon native inference and training.
What lives at the boundary
Experiment tracking — Weights & Biases, MLflow, plain JSON files. Hyperparameter search — Optuna, Ray Tune. Vector storage for retrieval — FAISS, ChromaDB, Qdrant. Each of these is a small library that solves a focused job; pick one of each and use it consistently.