Lightweight Core overview

A worker or small HTTP service does not always need MVC and Kestrel. Cratis.Arc.Core gives you Arc’s command/query pipelines and a lightweight HttpListener host without an ASP.NET Core dependency. Cratis.Arc adds the ASP.NET integration when you need that ecosystem. Neither package requires event sourcing.

What Core provides

• Model-bound commands and queries, validation, authorization, and result handling.
• Identity details and tenant context; application authorization and tenant membership still need deliberate configuration.
• Correlation IDs, dependency injection, and convention-based discovery.
• GET/POST manual endpoints, static files and SPA fallback, and basic OpenAPI route metadata.

Persistence integrations do not require Chronicle. Adding an integration can introduce its own dependencies; the Core-only dependency boundary is not a promise about every combined package graph.

Comparison with ASP.NET Core

Capability	Arc.Core lightweight host	Arc with ASP.NET Core
Package	Cratis.Arc.Core	Cratis.Arc
HTTP server	HttpListener	ASP.NET hosting, commonly Kestrel
Request handling	Arc’s simplified route/static/fallback handling	ASP.NET middleware ecosystem
Manual routing	Literal-path GET/POST helpers	ASP.NET routing APIs
Static files	Built-in support and SPA fallback	ASP.NET static-file middleware
MVC/Razor	Not included	Available through ASP.NET
OpenAPI	Basic route metadata in Core	Optional Cratis.Arc.OpenApi or Cratis.Arc.Swagger
Pipelines, validation, identity, tenant context	Available	Available

Core does have request-processing middleware internally; it does not expose ASP.NET’s full middleware pipeline. Native AOT compatibility, startup time, memory usage, deployment size, and throughput depend on discovery, serialization, integrations, and deployment. Validate your actual publish configuration and benchmark your workload rather than treating “lightweight” as an AOT or performance guarantee.

When to choose each host

Choose Core for small standalone HTTP services, workers with management endpoints, or learning the pipelines without a web-framework dependency. Choose ASP.NET Core for controllers, Razor, advanced routing, standard authentication middleware, or other ASP.NET libraries. Arc pipelines can participate in other application architectures, but Core does not itself supply a gRPC server or arbitrary protocol implementation.

Architecture

The builder registers services; activation maps Arc endpoints and schedules listener startup. This bootstrap fragment belongs in a console project’s Program.cs with using Cratis.Arc;:

var builder = ArcApplication.CreateBuilder(args);
builder.AddCratisArc();
var app = builder.Build();
app.UseCratisArc();
await app.RunAsync();

The default listener binds http://+:5001/; the getting-started checkpoint uses an explicit loopback URL. Review anonymous discovery defaults before exposing the host.

Next steps

• Getting started — run a complete command/query example.
• Authentication and authorization — establish and enforce trust.
• Configuration — all runtime options and host differences.
• Invariant culture — culture-sensitive behavior.
• Chronicle integration — optional event sourcing, not a prerequisite.