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Cratis Arc

Arc is an open-source (MIT) opinionated CQRS application framework for ASP.NET Core with commands, queries, validation, authorization, and TypeScript proxy generation. It works without event sourcing, with optional Chronicle integration.

Arc hosts application behavior, executes command and query pipelines, exposes recognized contracts over HTTP, and generates TypeScript clients for them. Its packages also cover observable queries, validation, identity and tenancy, React integration, current-state persistence, OpenAPI, analyzers, and testing. Chronicle event sourcing and Cratis Components are optional integrations.

Arc reflects a broader Cratis conviction: application plumbing should not be the hard part. Commands, queries, validation, and authorization are written as plain, idiomatic .NET code, designed to reduce friction and boilerplate in service of productivity, quality, and reliability. Arc is part of one deliberately simple ecosystem — AI-friendly by design, with free AI skills for building with the stack.

Start here

• Browse the Arc documentation
• Read why Arc exists
• Map familiar concepts when coming from MediatR and MVC
• Try runnable samples — including Idea Loom and Library
• Choose a documented application path
• Understand Arc's independent boundary
• Start an Arc host
• Inspect packages and repository layout

What Arc owns

Boundary	Arc provides
Hosting	ASP.NET Core hosting plus an Arc.Core HTTP host for workers, consoles, and custom services
Commands	Model-bound and controller-based execution, validation, authorization, filters, scopes, typed results, and generated endpoints
Queries	Model-bound and controller-based reads, paging and sorting, observable updates, WebSocket or Server-Sent Events transport, and query diagnostics
Validation	Data annotations, FluentValidation, concept/command/query validators, generated client rules, and optional server preflight from React forms
Identity and tenancy	Pluggable authentication, identity details, role-based authorization, and header, query, claim, subdomain, fixed, or development tenant resolution
Generated contracts	TypeScript proxies, referenced types, validation metadata, identity details, incremental output cleanup, and package/type mapping
Frontend packages	TypeScript command/query runtimes, React hooks and forms, dialogs, observable-query composition, and optional React/MVVM integration
Persistence integration	MongoDB and Entity Framework Core current-state adapters plus optional Chronicle-backed event-sourced behavior
Evaluation and tooling	OpenAPI, runtime introspection, analyzers, source generators, command scenarios, proxy-generation checks, Vite helpers, and ESLint rules

Each row is a documented capability area, not a promise of compatibility with every package, host, provider, browser, or product version.

Choose a path

Arc documentation is organized around the job you need to complete:…