The Turn Book

Why Turn

The five failure modes of every agent framework, and how Turn solves them at the language level.

Installation

Install the Turn binary, configure an inference provider, and run your first intelligent program.

Hello Turn

A step-by-step trace of your first Turn program: env, memory, context, call, and return.

Grammar

Formal syntax — statements, expressions, blocks, and type annotations.

Minimal Core

The smallest set of primitives the language needs to exist.

Runtime Model

VM execution model, actor scheduler, suspension/resumption, and durable state.

The infer Primitive

Cognitive Type Safety — how infer generates schemas at compile time and validates LLM output.

Inference Providers

The Wasm sandbox architecture, official providers, and how to write your own driver.

Context Window

The Priority Stack, token budget, and Entropic Expansion Policy — bounded context by construction.

Memory & Recall

Persistent semantic memory backed by HNSW vectors and Ebbinghaus temporal decay.

Concurrency & Actors

spawn, send, receive, link, monitor — the Erlang-style actor model for agent orchestration.

Example Agent

A full multi-agent boardroom simulation with actor coordination.

Types & Errors

Type system, Result/Option monads, Uncertain<T>, and cognitive confidence traps.

Error Handling

Monadic error routing and stochastic failure patterns.

Modules

The module system, use declarations, and package management.

Design Mandate

The philosophy, constraints, and design principles of the Turn language.

Implementation

Compiler pipeline, bytecode instruction set, and VM internals.

LSP

Language Server Protocol integration and editor support.