How It Works

Rivet is a Roslyn-based extractor, not a runtime reflector. The pipeline, as implemented in Rivet.Tool:

1. Load — --project x.csproj loads the project through MSBuild and gets the full Roslyn Compilation; bare .cs arguments are compiled directly. Compilation errors abort the run.
2. Discover — a single pass over the source assembly finds [RivetContract] classes, [RivetClient] classes, [RivetEndpoint] methods, and [RivetType] types.
3. Walk — TypeWalker lowers C# types into an internal type model (primitives with formats, brands, monomorphised generics, enums, nullability); ContractWalker reads Define.* builder chains from contract fields; EndpointWalker reads controller/minimal-API endpoints (routes, parameter binding, [ProducesResponseType], typed results). Contract endpoints win when both describe the same endpoint.
4. Emit — EmitPipeline extracts repeated inline object types into named components, then OpenApiEmitter writes the OpenAPI 3.1 document with the x-rivet-* vendor extensions.

Two side doors feed the same emit pipeline:

• --from contract.json — a contract JSON document produced by the sibling runtimes (rivet-ts, rivet-php). This is an internal IR, not a public format.
• --from-openapi spec.json — the one-shot importer generates C# contracts/DTOs which then go through the normal Roslyn path.

There is no runtime spec generation and no middleware: the Rivet.Attributes package contains only the attributes, the Define/RouteDefinition builder, and contract-owned Bind/terminal APIs with first-party host adapters. Their enforcement scope is described in Runtime Validation.