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Known Limitations

NSmithy is still a preview-stage implementation.

Protocol Coverage Is Still Narrow

Section titled “Protocol Coverage Is Still Narrow”

Current protocol support is intentionally selective:

  • alloy#simpleRestJson is the most complete path and the best-covered end-to-end preview flow; the current pinned official request/response corpus passes at 43/43
  • aws.protocols#restJson1 client and ASP.NET Core server generation work, and the current pinned official request/response corpus passes at 268/272
  • alloy.proto#grpc is available through .proto generation and generated client/server adapters, but it is still the least mature path

Not yet implemented:

  • AWS JSON protocols
  • EC2 Query and AWS Query

For restJson1, the remaining gap is not one single kind of missing feature. The current uncovered slice is the Glacier-specific fixture set, which still needs broader projection support.

gRPC Is Experimental

Section titled “gRPC Is Experimental”

The gRPC path exists, but it should still be treated as an early adopter track.

Current constraints include:

  • smaller test and example coverage than the HTTP/JSON paths
  • more explicit model requirements such as alloy.proto#protoIndex
  • more implementation details that are still expected to move

Server Support Is Narrow

Section titled “Server Support Is Narrow”

Server support is currently centered on generated ASP.NET Core endpoints for alloy#simpleRestJson and aws.protocols#restJson1.

Current limitations include:

  • no general non-ASP.NET server story
  • no broad server protocol matrix across multiple Smithy protocols
  • response binding and error behavior that still need broader conformance coverage

Validation Is Incomplete

Section titled “Validation Is Incomplete”

Generated constructors do not implement full Smithy validation semantics. Generated C# nullability is authoritative, but external request binding and deserialization still need more protocol-aware runtime validation.

Codec And Serialization Boundaries Are Still Maturing

Section titled “Codec And Serialization Boundaries Are Still Maturing”

NSmithy.Codecs.Json is reflection-based and intentionally small. It is not yet optimized for:

  • NativeAOT
  • source-generated serializer metadata
  • every Smithy edge case across future protocol families

Broader protocol coverage (rpcv2Cbor, restXml) will drive further validation of the codec and transport abstractions.

Client And Server Generation Are Still Coupled In Places

Section titled “Client And Server Generation Are Still Coupled In Places”

For alloy#simpleRestJson, the current generator still emits both client and server surfaces for service shapes. Client-only projects that generate from simpleRestJson services currently need server runtime references as well.

This is a known design debt and should be split into clearer generation modes.

Generated Model Scope Can Be Too Broad By Default

Section titled “Generated Model Scope Can Be Too Broad By Default”

By default, the generator emits all supported shapes in the assembled model. When using Smithy build dependencies for traits or shared model packages, configure SmithyBaseNamespace so dependency model shapes are not emitted as C#.