# Ossature

An open-source build system that turns written specifications and architecture into working code, having an LLM generate each step under tight constraints and rebuilding only what changed.

Ossature works from a spec file describing what software should do, an optional architecture file describing how components fit together and their contracts, and optional verification files holding test cases you write yourself as concrete inputs and expected results. Three commands drive the workflow: validate parses and structurally checks everything without an LLM, audit has an LLM read the specs, flag problems, and generate an editable build plan, and build runs that plan task by task, generating a few files per task, running its verification command, and entering a fix loop on failure.

Builds are incremental: changing one spec only rebuilds the tasks it affects, and an upstream change that leaves a spec's public interface unchanged does not pull its dependents along. When a task has a verification file, the plan includes deterministic test tasks built from those cases, and the LLM is never shown the expected values, so it cannot write code that fits the tests without actually passing them; with review turned on, an LLM also checks generated code against the spec and component contracts before marking a task done. It works with several hosted model providers as well as local models through Ollama, requires a recent Python version, and is currently an unstable pre-1.0 release.

Website: https://ossature.dev