skein

One thread, one loop, no async.

A Rust kit for network services written as step machines over an I/O loop: counted, bounded, and testable whole in a simulated world.

The idea

• Step machines, not async. A service is plain state machines: a domain that decides, a protocol layer that speaks bytes, and a loop of about ten lines that feeds them what the kernel completed. One thread per process; a service that needs more cores runs more processes.
• A kit, not a framework. skein has no service trait, no scheduler and no callbacks. A service calls its parts by name, and nothing in skein calls into a service.
• Counted and bounded. Every part exports its limits and its worst case, and a service adds them up: what it can hold is known before it runs.
• Tested whole, and reproducibly. io speaks to the kernel in owned records, over io_uring or over a simulator that plays the kernel and its faults. A world runs every process of a system in one seeded loop, over either.
• Built when pulled. A part is built when its first user needs it, and that user is its first test.

What it holds

• The base: bounded containers, cursors and time; io, from sockets to processes; the shell that runs the loop; a durable key-value store.
• Protocols: HTTP/1.1, JSON, TLS, framed channels, and codecs generated from schemas.
• What services share: LLM calls and their connections, OAuth, and a code forge's calls, client and setup.
• Interfaces: an application's state as a semantic tree, shown in a terminal or a browser.
• Testing: the simulator, the world harness, a counting allocator, a browser driver, and fakes of an LLM, an issuer, a forge, a checkout and a person.

skein also holds the foundation that every repository of the family follows, and the tools of its development process.

Start here

• docs/foundation/programming-model.md: how code is written, in skein and in everything built on it; testing-strategy.md: how it is tested; notes.md: what is still open.
• docs/design/README.md: the parts, each with its design, and their crates.
• docs/design/examples.md: the example services, and how a service is built on skein.
• docs/design/STATUS.md: how far the code is from the design.
• docs/foundation/owners.md: how work goes from a draft to main, here and downstream; director.md: the director, who runs the owners.

Before changing code, read AGENTS.md. main moves only through land, which runs the gate, scripts/check.sh.

The family

These are the repositories of Fabrig, an agent-driven software factory: write, prove, run.

Repository		Builds on
skein	One thread, one loop, no async
smith	Protocol-driven agent loop for AI applications	skein
jig	Engine for agentic applications	skein, smith
temper	Agent-driven software development on a forge	skein, smith, jig
hearth	Immutable machines, built from a revision	skein