Outlines

Structured generation library by .txt (dottxt-ai). Guarantees schema-valid outputs at generation time via FSM-based logits masking — no post-processing or retries. Supports regex, JSON schema (Pydantic or raw), CFG, and multiple-choice constraints. Backends: Transformers, vLLM, llama.cpp, MLX, Ollama, OpenAI, Mistral, Gemini. Core FSM engine split into separate outlines-core package (Rust). Two coexisting APIs: legacy outlines.models + outlines.generate.* style, and new 1.x outlines.from_* + model(prompt, Schema) style.