Set up proxy generation

Start with an Arc project that already defines commands or queries. This guide adds proxy generation; it does not create or host those endpoints.

Add the build package

Reference Cratis.Arc.ProxyGenerator.Build in each project whose compiled endpoints you intend to generate. Use a version compatible with your Arc packages and pin it through your normal dependency management.

Choose a dedicated output folder

Add this MSBuild fragment inside your existing .csproj’s Project element:

<PropertyGroup>
    <CratisProxiesOutputPath>$(MSBuildThisFileDirectory)../Web/src/generated</CratisProxiesOutputPath>
    <CratisProxiesSkipOutputDeletion>true</CratisProxiesSkipOutputDeletion>
</PropertyGroup>

The example assumes a sibling Web project. Change the path for your layout. Prefer a generated-only directory, with one generation owner, rather than the frontend root. MSBuild defaults to incremental output, but stale generated files are still deleted. Output behavior explains the destructive operations and direct CLI defaults.

Install frontend dependencies

In your React frontend, install:

npm install @cratis/arc @cratis/arc.react @cratis/fundamentals react

Generated command and query files import both Arc core and React hooks unconditionally, even if you only instantiate the classes. Generated model decorators and value types use Fundamentals. Use mutually compatible package versions; @cratis/arc.react declares React 18 or 19 as a peer dependency. A browser React application also needs its usual renderer and TypeScript setup.

See decorator configuration for compiling generated models. These proxies do not generate a Bindings setup file. Wrap React consumers in the Arc provider.

Build and inspect the result

From the backend project, run this checkpoint:

dotnet build -c Debug

After compilation, the build target invokes the generator over the assembly. Look for its command/query counts in the build log and .ts files under Web/src/generated. By default, a query named AllAuthors gets AllAuthors.ts; it is not automatically placed inside Author.ts. Folder paths come from namespaces.

Compile the frontend with its own type-check/build command. This second checkpoint catches missing packages, decorator configuration, and imports that do not match the actual generated paths.

Keep generation predictable

Commit generated proxies if your workflow consumes them without rebuilding the backend. Incremental generation preserves existing files when their generated content hash matches; full deletion recreates metadata timestamps and can cause Git content churn.

Source-file grouping is opt-in and depends on per-type PDB information. Prefer Debug for generation. To verify Release without regenerating the same output:

dotnet build -c Release -p:CratisProxiesOutputPath=

The empty property disables the post-build target for that invocation. Release is not intrinsically excluded from generation.

Next, inspect the generated command and query APIs, or configure namespace roots.