Introduction

Threadbare is a minimal demo of the Patchwork execution model. It demonstrates how a program can interleave deterministic computation with non-deterministic LLM "thinking" - and crucially, how the LLM can call back into the interpreter to execute more code.

The name is a pun: it's a bare-threads implementation of Patchwork, held together by minimal threads.

The Core Idea

Patchwork programs mix two kinds of computation:

1. Deterministic blocks - traditional code that always produces the same output
2. Think blocks - prompts sent to an LLM, whose output is non-deterministic

The interesting part: a Think block can invoke deterministic subroutines (via a do tool), and those subroutines might themselves contain Think blocks. This creates a recursive interplay between the interpreter and the LLM.

Why This Matters

This execution model enables:

• Auditability: You can trace exactly what decisions the LLM made and why
• Composition: Deterministic scaffolding with LLM "escape hatches" where judgment is needed
• Recursion: LLM decisions can trigger further LLM decisions, nested arbitrarily deep

What's in This Book

• The AST - The three node types: Print, Block, and Think
• An Example - A concrete program that categorizes documents
• The Interpreter - How the interpreter executes Think nodes, with recursive call tracing
• The Agent - How the agent manages concurrent LLM sessions and routes messages