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NSmithy

Protocol Status

NSmithy is still preview-stage. “Supported” here means there is working generator and runtime support for a usable slice, not that the protocol is complete or fully conformant across the Smithy surface.

Current Status

Section titled “Current Status”

Conformance is reported separately for the generated client and server, each counted against the official cases that actually apply to that direction (appliesTo) in the pinned protocol-test models. A case that only applies to a server is never counted toward client coverage and vice versa.

ProtocolSurfacesStageClientServer
alloy#simpleRestJsonbothPreview (most complete)43/43 (100%)43/43 (100%)
aws.protocols#restJson1bothPreview243/247 (98.4%)224/227 (98.7%)
aws.protocols#awsJson1_1clientEarly previewrequests 6/57 (10.5%), responses 19/61 (31.1%)—
aws.protocols#awsJson1_0clientEarly previewruntime support; no conformance project yet—
aws.protocols#restXmlclientEarly previewrequests 4/109 (3.7%), responses 42/84 (50.0%)—
smithy.protocols#rpcv2CborbothPreview68/68 (100%)60/60 (100%)
alloy.proto#grpcbothExperimentaltested via examples¹tested via examples¹

¹ alloy.proto#grpc is not covered by Smithy’s HTTP conformance suite; it is validated through end-to-end examples instead, and has the least maturity, the smallest test surface, and more explicit model requirements such as alloy.proto#protoIndex.

Notes:

  • alloy#simpleRestJson’s protocol tests all declare appliesTo: both; both the client and the generated ASP.NET Core server now run every applicable case.
  • AWS restJson1 exercises both surfaces against nearly every applicable case. The handful of unmet cases are curated out of the client allowlist; on the server, cases whose operation has no generated handler (auxiliary services like Glacier that ship fixtures but aren’t part of the RestJson service) are out of scope rather than counted as failures.
  • AWS JSON support is client-only. The current conformance project targets aws.protocols#awsJson1_1; the runtime also exposes AwsJson10Protocol for aws.protocols#awsJson1_0, but there is not yet a separate awsJson1_0 conformance project.
  • AWS restXml is client-only and now runs a verified slice of the official AWS protocol tests, mostly response deserialization plus a small request-binding subset.
  • smithy.protocols#rpcv2Cbor, alloy#simpleRestJson, and aws.protocols#restJson1 all exercise both the client and the generated server against their applicable cases.
Section titled “Recommended Use”
  • Prefer simpleRestJson for the most complete client and server support in the current preview, especially when your consumers are primarily .NET or Scala (via Smithy4s).
  • Use AWS restJson1 when you need generated AWS-style REST/JSON clients or ASP.NET Core server surfaces, broad cross-ecosystem compatibility (most official Smithy generators target it), or OpenAPI/Scalar generation.
  • Use smithy.protocols#rpcv2Cbor for binary CBOR-encoded services; client and server generation are both available.
  • Use AWS JSON or AWS restXml when you want to evaluate AWS-compatible client generation and are comfortable with a smaller preview slice.
  • Treat alloy.proto#grpc as experimental: it has the smallest test surface and the most explicit model requirements (see the footnote above).

What “Early Stage” Means Here

Section titled “What “Early Stage” Means Here”

In practice, earlier-stage protocols may still have one or more of these traits:

  • narrower protocol binding coverage
  • fewer end-to-end examples
  • less conformance-suite coverage
  • more implementation details that are still expected to move
  • more explicit project wiring or modeling constraints

Not Supported Yet

Section titled “Not Supported Yet”

These protocols are not current NSmithy targets:

  • EC2 Query and AWS Query