November 20th, 2025

New this release:

• (client, smithy-rs#4388, @greenwoodcm) Add then_compute_response to Smithy mock

Contributors
Thank you for your contributions! ❤

• @greenwoodcm (smithy-rs#4388)

November 6th, 2025

New this release:

• (client) Bump crc-fast version to 1.6.0
• (client) Validate Region is a valid host label when constructing endpoints.

October 30th, 2025

Breaking Changes:

• ⚠️🎉 (server, smithy-rs#4356) Parse EventStream signed-frames for servers marked with @sigv4.

  This is a breaking change, because events from SigV4 services are wrapped in a SignedEvent frame.

• ⚠️ (all, smithy-rs#4367) Upgrade MSRV to Rust 1.88.0.

New this release:

• 🐛🎉 (server, smithy-rs#4352, smithy-rs#4345) Update smithy-rs servers to support sending initial-response events over event streams.

  Prior to this change, event streams that had initial responses were unsupported. This change also adds a new codegen setting, alwaysSendEventStreamInitialResponse.

  When this setting is set to true, the generated server will unconditionally send initial-response objects, even when empty. This is required for compatibility with smithy-java as well as a few other clients.

  This setting defaults to false currently because smithy-rs based clients do not currently support this behavior.

  "codegen": {
    "alwaysSendEventStreamInitialResponse": true // default false
  }

• 🎉 (all, @arielby) Include the protocol name in package.metadata.smithy.protocol in Cargo.toml
  to allow easily figuring out which protocol was used to generate a crate.

• 🐛🎉 (client, smithy-rs#4349, @arielby) Make Hyper idle pool timeout configurable, and fix the bug where pool timeouts
  would not work if the client was built directly.

• 🎉 (server, smithy-rs#4317, @jasgin) Adds validators and codegen support for the custom traits custom traits @validationException, @validationMessage,
  @validationFieldList, @validationFieldName, and @validationFieldMessage for defining a custom validation exception
  to use instead of smithy.framework#ValidationException.

• 🐛 (client, smithy-rs#4346) Fix bug where httpQueryParams were silently dropped when no other query parameters were modeled.

• 🐛 (server, smithy-rs#4344, smithy-rs#4325) Fix bug where servers did not attempt to parse an initial-request. initial-requests may be sent by clients both when they would contain valid data
  and when they are empty.

• 🐛 (client, smithy-rs#4352, smithy-rs#4353) Update clients to allow initial-response events to be accepted on event streams, even when know modeled initial response exists.

  This is required for spec compliance, backwards compatibility, and compatibility with non-smithy-rs based servers that
  MAY unconditionally send initial-response messages.

• 🐛 (client, smithy-rs#4265, smithy-rs#4189) Adds new with_test_defaults_v2() for all clients supporting region configuration which applies us-east-1 as default region if not set by user. This allows aws-smithy-mocks to work for non AWS SDK generated clients. Also clarify test-util feature requirement when using aws-smithy-mocks.

Contributors
Thank you for your contributions! ❤

• @arielby (smithy-rs#4349)
• @jasgin (smithy-rs#4317)

October 6th, 2025

New this release:

• 🎉 (server, smithy-rs#4321, @jasgin) Adds the custom traits @validationException, @validationMessage, @validationFieldList, @validationFieldName, and @validationFieldMessage
  for defining custom validation exceptions.

Contributors
Thank you for your contributions! ❤

• @jasgin (smithy-rs#4321)

October 2nd, 2025

New this release:

• 🐛 (server) Fix bug where servers rejected application/vnd.amazon.evenstream ACCEPT header for RPCv2Cbor

  This change allows this header while also allowing application/cbor for backwards compatibility.

October 1st, 2025

New this release:

• 🎉 (client, smithy-rs#4299, @greenwoodcm) Added a new then_compute_output to aws-smithy-mocks rule builder that allows using the input type when computing a mocked response, e.g.

  // Return a computed output based on the input
  let compute_rule = mock!(Client::get_object)
      .then_compute_output(|req| {
          let key = req.key().unwrap_or("unknown");
          GetObjectOutput::builder()
              .body(ByteStream::from_static(format!("content for {}", key).as_bytes()))
              .build()
      });

• 🐛 (client, smithy-rs#4226, @haydenbaker) Fixed problematic assertion on HttpApiKeyAuthTrait scheme, which was causing client-codegen to fail when the correct settings for api-key based auth were set.

Contributors
Thank you for your contributions! ❤

• @greenwoodcm (smithy-rs#4299)
• @haydenbaker (smithy-rs#4226)

September 10th, 2025

New this release:

• 🐛 (client, smithy-rs#4274) The HickoryDnsResolver and TokioDnsResolver were not Clone making it impossible to use them in the http_client builder's build_with_resolver method.

August 28th, 2025

New this release:

• 🎉 (client, smithy-rs#4274) Add a new crate, aws-smithy-dns that contains a HickoryDnsResolver. This wraps a hickory_resolver::Resolver and provides some minimal configuration options (timeouts, retries, etc.) Instructions for overriding the DNS resolver on your HTTP client can be found in our documentation at https://docs.aws.amazon.com/sdk-for-rust/latest/dg/http.html#overrideDns
• 🐛 (client, smithy-rs#4282) Set the pool_timer for the default Hyper client. This is required to allow the pool_idle_timeout to work. Now idle connections will be released by the pool after 90 seconds.
• (client, smithy-rs#4263) Make TokenBucket and ClientRateLimiter configurable through RetryPartition.

August 18th, 2025

New this release:

• 🎉 (client, aws-sdk-rust#169) Add support for proxy environment variables (HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, NO_PROXY). Service clients will now automatically respect these proxy environment variables on the latest BehaviorVersion. Older behavior versions do not automatically detect these environment variables and will require manually building a aws_smithy_http_client::Connector with a proxy config explicitly set to use this feature.
• 🎉 (client, @WillChilds-Klein) Enable rustls post-quantum by default.
• (client) fix aws-smithy-eventstream feature derive-arbitrary on arbitrary >= 1.4.2

Contributors
Thank you for your contributions! ❤

• @WillChilds-Klein

August 13th, 2025

New this release:

• 🐛 (client) pin crc-fast to <1.4 to workaround SIGILL