The reference implementation#

Simcraft is the reference implementation of OSDL: an engine and a visual editor built around the document format. This page describes its public surfaces.

The engine#

The engine executes OSDL documents with the standard des, abm, and sd libraries on one calendar. It implements the core execution semantics: escrowed entity transfer, pinned samplers, deterministic replay of a run tuple, structured run reports, and the typed event stream.

Conformance is checked against the Lean reference machine: engine traces are compared with machine traces for the same cases, and trace equality is the bar.

The editor#

The Simcraft IDE is a node-and-wire editor over OSDL documents. The diagram is the model: components are placed and connected on a canvas, parameters are edited in schema-generated forms, and the same document is available as code. The IDE uses the WebAssembly engine for local execution. Runs animate the diagram and stream results into charts, with timeline scrubbing, live sessions, and branching.

The editor produces and consumes ordinary OSDL documents. Nothing it writes is private to it.

SDKs and machine authoring#

A Python SDK builds OSDL documents programmatically. An MCP server exposes model authoring and validation to language-model agents.

Both are producers and consumers in the specification's sense: views over the document, replaceable without loss.

Execution API#

The execution API schema defines batch runs and interactive sessions. Public API access is not yet available.

Status#

Simcraft is version 0.1.0. Published interfaces can change before 1.0.0. The open specification, schemas, libraries, examples, and reference machine are public at github.com/simcrafthq/osdl.

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