# Cratis

> Cratis is an open-source, MIT-licensed platform for building event-sourced and CQRS applications. At its center is Chronicle, an event-sourcing database and processing runtime with a first-class .NET SDK and additional TypeScript, Kotlin/Java (JVM), and Elixir clients — with a Python client coming soon — plus pluggable storage-provider implementations including MongoDB (default), PostgreSQL, SQL Server, and SQLite.

## About Cratis

- Cratis is an open-source (MIT) event sourcing and CQRS platform for .NET, built around the Chronicle event-sourcing database.
- Products: Chronicle (event store and runtime), Arc (CQRS framework with generated TypeScript proxies), Components (React UI library), Fundamentals, Specifications, CLI, Workbench, Chronicle MCP, and Cratis AI (rules and skills for AI agents). Screenplay, Stage, and Prologue are experimental; Studio is a paid product in Preview.
- Licence: the open-source Cratis products are MIT licensed. Studio is paid.
- Languages: Chronicle has a first-class .NET client and clients for TypeScript, Kotlin/Java, and Elixir; a Python client is coming soon and not yet published. Arc runs on ASP.NET Core and Spring Boot; Components targets React.
- Storage: MongoDB (default), PostgreSQL, Microsoft SQL Server, or SQLite.
- Get it from NuGet, npm, Maven Central, Hex, Docker Hub, and GitHub (https://github.com/Cratis).
- Built by Cratis, a small company that builds and maintains the platform.
- Capability map: https://www.cratis.io/cratis-stack/#capability-map. Support matrix: https://www.cratis.io/compatibility/#support-matrix.

## Key facts

- Chronicle exposes a language-agnostic gRPC/protobuf boundary; its kernel runs on Microsoft Orleans.
- Arc is an opinionated CQRS application framework — commands, queries, validation, authorization, and TypeScript proxy generation. It is implemented for ASP.NET Core and for Spring Boot on the JVM, and both generate against the same TypeScript packages. It works without event sourcing; Chronicle integration is optional.
- Components is a React component library aligned with Arc patterns: command dialogs, typed forms, and query-backed data tables.
- The CLI and Workbench are the inspection and diagnosis surfaces for Chronicle: events, observers, projections, read models, and failed partitions.
- Screenplay is the declarative event-modeling language that Stage and Studio build on.

## Product documentation

Choose a product and then a task area. The full-site downloads below are bulk archives, not the best default context for one question.

- [Chronicle documentation](https://www.cratis.io/chronicle/llms.txt)
- [Arc documentation](https://www.cratis.io/arc/llms.txt)
- [Components documentation](https://www.cratis.io/components/llms.txt)
- [AuthProxy documentation](https://www.cratis.io/authproxy/llms.txt)
- [Screenplay documentation](https://www.cratis.io/screenplay/llms.txt)
- [Prologue documentation](https://www.cratis.io/prologue/llms.txt)
- [CLI documentation](https://www.cratis.io/cli/llms.txt)
- [Templates documentation](https://www.cratis.io/templates/llms.txt)
- [Chronicle MCP documentation](https://www.cratis.io/chronicle-mcp/llms.txt)
- [Fundamentals documentation](https://www.cratis.io/fundamentals/llms.txt)
- [Fundamentals.Go documentation](https://www.cratis.io/fundamentals/go/llms.txt)
- [Chronicle.Go documentation](https://www.cratis.io/chronicle/go/llms.txt)
- [Arc.Go documentation](https://www.cratis.io/arc/go/llms.txt)
- [Contributing documentation](https://www.cratis.io/contributing/llms.txt)
- [Architecture documentation](https://www.cratis.io/architecture/llms.txt)
- [Prompter documentation](https://www.cratis.io/prompter/llms.txt)
- [C# documentation](https://www.cratis.io/eventmodelers-ai/csharp/llms.txt)
- [Kotlin documentation](https://www.cratis.io/eventmodelers-ai/kotlin/llms.txt)
- [Java documentation](https://www.cratis.io/eventmodelers-ai/java/llms.txt)

## Cross-product starting points

- [Cratis stack](https://www.cratis.io/cratis-stack/)
- [Build a full-stack feature](https://www.cratis.io/build-a-full-app/)
- [Samples](https://www.cratis.io/samples/)

## Documentation Sets

- [Abridged documentation](https://www.cratis.io/llms-small.txt): a compact version of the documentation for Cratis, with non-essential content removed
- [Complete documentation](https://www.cratis.io/llms-full.txt): the full documentation for Cratis
- [Chronicle first steps](https://www.cratis.io/_llms-txt/chronicle-first-steps.txt): For canonical page URLs and citations see https://www.cratis.io/chronicle/get-started/llms.txt
- [Chronicle events](https://www.cratis.io/_llms-txt/chronicle-events.txt): For canonical page URLs and citations see https://www.cratis.io/chronicle/events/llms.txt
- [Chronicle read models](https://www.cratis.io/_llms-txt/chronicle-read-models.txt): For canonical page URLs and citations see https://www.cratis.io/chronicle/read-models/llms.txt
- [Arc first steps](https://www.cratis.io/_llms-txt/arc-first-steps.txt): For canonical page URLs and citations see https://www.cratis.io/arc/tutorial/llms.txt
- [Components first steps](https://www.cratis.io/_llms-txt/components-first-steps.txt): For canonical page URLs and citations see https://www.cratis.io/components/tutorial/llms.txt

## Notes

- The complete documentation includes all content from the official documentation
- The content is automatically generated from the same source as the official documentation