Update changelog

---

applies_to:

- aws-sdk-rust

- client

authors:

- ysaito1001

references:

- smithy-rs#4203

breaking: false

new_feature: true

bug_fix: false

---

Add support for configuring auth schemes manually using an auth scheme preference list.

The preference list allows customers to reprioritize the order of auth schemes originally

determined by the auth scheme resolver.

Customers can configure the auth scheme preference at the following locations, listed in order of precedence:

1. Service Client Configuration

```rust

use aws_runtime::auth::sigv4;

use aws_smithy_runtime_api::client::auth::AuthSchemeId;

use aws_smithy_runtime_api::client::auth::http::HTTP_BEARER_AUTH_SCHEME_ID;

let config = aws_sdk_s3::Config::builder()

    .auth_scheme_preference([AuthSchemeId::from("scheme1"), sigv4::SCHEME_ID, HTTP_BEARER_AUTH_SCHEME_ID])

    // ...

    .build();

```

2. Environment Variable

```

AWS_AUTH_SCHEME_PREFERENCE=scheme1, sigv4, httpBearerAuth

```

3. Configuration File

```

auth_scheme_preference=scheme1, sigv4, httpBearerAuth

```

With this configuration, the auth scheme resolver will prefer to select them in the specified order,

if they are supported.

<!-- Do not manually edit this file. Use the `changelogger` tool. -->

July 21st, 2025

===============

**New this release:**

- :tada: (client, [smithy-rs#4203](https://github.com/smithy-lang/smithy-rs/issues/4203)) Add support for configuring auth schemes manually using an auth scheme preference list.

    The preference list allows customers to reprioritize the order of auth schemes originally

    determined by the auth scheme resolver.

    Customers can configure the auth scheme preference at the following locations, listed in order of precedence:

    1. Service Client Configuration

    ```rust

    use aws_runtime::auth::sigv4;

    use aws_smithy_runtime_api::client::auth::AuthSchemeId;

    use aws_smithy_runtime_api::client::auth::http::HTTP_BEARER_AUTH_SCHEME_ID;

    let config = aws_sdk_s3::Config::builder()

        .auth_scheme_preference([AuthSchemeId::from("scheme1"), sigv4::SCHEME_ID, HTTP_BEARER_AUTH_SCHEME_ID])

        // ...

        .build();

    ```

    2. Environment Variable

    ```

    AWS_AUTH_SCHEME_PREFERENCE=scheme1, sigv4, httpBearerAuth

    ```

    3. Configuration File

    ```

    auth_scheme_preference=scheme1, sigv4, httpBearerAuth

    ```

    With this configuration, the auth scheme resolver will prefer to select them in the specified order,

    if they are supported.

July 17th, 2025

===============

**New this release:**

{

  "smithy-rs": [],

  "aws-sdk-rust": [

    {

      "message": "Temporarily disable fetching account ID from IMDS credentials on EC2.\n",

      "meta": {

        "bug": false,

        "breaking": false,

        "tada": false

      },

      "author": "ysaito1001",

      "references": [

        "smithy-rs#4187"

      ],

      "since-commit": "dd10f0602682dfabafc465dbcd9eb92d3d915c51",

      "age": 5

    },

    {

      "message": "Fix hyper 1.x connection refused errors not marked as retryable\n",

      "meta": {

        "bug": true,

        "breaking": false,

        "tada": false

      },

      "author": "aajtodd",

      "references": [],

      "since-commit": "dd10f0602682dfabafc465dbcd9eb92d3d915c51",

      "age": 5

    },

    {

      "message": "Make Rpc V2 CBOR a compatible protocol for `awsQuery` using `awsQueryCompatible` trait\n",

      "meta": {

        "bug": false,

        "breaking": false,

        "tada": false

      },

      "author": "ysaito1001",

      "references": [

        "smithy-rs#4186"

      ],

      "since-commit": "dd10f0602682dfabafc465dbcd9eb92d3d915c51",

      "age": 5

    },

    {

      "message": "Allows customers to configure the auth schemes and auth scheme resolver. For more information see the GitHub [discussion](https://github.com/smithy-lang/smithy-rs/discussions/4197).\n",

      "meta": {

        "smithy-rs#4198"

      ],

      "since-commit": "ccf374dddc0690ef8aca1ed006b9e9b21299558e",

      "age": 3

      "age": 4

    },

    {

      "message": "re-use checksums on retry attempts for enhanced durability\n",

      "author": "aajtodd",

      "references": [],

      "since-commit": "1378695258e645d2c65a99cc0311b8c3d982e167",

      "age": 2

      "age": 3

    },

    {

      "message": "Event streams now allocate a right-sized buffer avoiding repeated reallocations during serialization\n",

        "smithy-rs#4212"

      ],

      "since-commit": "a23d116a79e8920c2efa813a8f831541a9943e4f",

      "age": 2

    },

    {

      "message": "Add support for configuring auth schemes manually using an auth scheme preference list.\nThe preference list allows customers to reprioritize the order of auth schemes originally\ndetermined by the auth scheme resolver.\nCustomers can configure the auth scheme preference at the following locations, listed in order of precedence:\n1. Service Client Configuration\n```rust\nuse aws_runtime::auth::sigv4;\nuse aws_smithy_runtime_api::client::auth::AuthSchemeId;\nuse aws_smithy_runtime_api::client::auth::http::HTTP_BEARER_AUTH_SCHEME_ID;\n\nlet config = aws_sdk_s3::Config::builder()\n    .auth_scheme_preference([AuthSchemeId::from(\"scheme1\"), sigv4::SCHEME_ID, HTTP_BEARER_AUTH_SCHEME_ID])\n    // ...\n    .build();\n```\n2. Environment Variable\n```\nAWS_AUTH_SCHEME_PREFERENCE=scheme1, sigv4, httpBearerAuth\n```\n3. Configuration File\n```\nauth_scheme_preference=scheme1, sigv4, httpBearerAuth\n```\nWith this configuration, the auth scheme resolver will prefer to select them in the specified order,\nif they are supported.\n",

      "meta": {

        "bug": false,

        "breaking": false,

        "tada": true

      },

      "author": "ysaito1001",

      "references": [

        "smithy-rs#4203"

      ],

      "since-commit": "6649098171e33e1e65eaacffb12be58e858a4782",

      "age": 1

    }

  ],