Update changelog

---

applies_to: ["client"]

authors: ["greenwoodcm"]

references: ["smithy-rs#4299"]

breaking: false

new_feature: true

bug_fix: false

---

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. 

```rs

// 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()

    });

```

---

applies_to: ["client"]

authors: ["haydenbaker"]

references: ["smithy-rs#4226"]

breaking: false

new_feature: false

bug_fix: true

---

Fixed problematic assertion on HttpApiKeyAuthTrait `scheme`, which was causing client-codegen to fail when the correct settings for api-key based auth were set.

 No newline at end of file

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

October 1st, 2025

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

**New this release:**

- :tada: (client, [smithy-rs#4299](https://github.com/smithy-lang/smithy-rs/issues/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. 

    ```rs

    // 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()

        });

    ```

- :bug: (client, [smithy-rs#4226](https://github.com/smithy-lang/smithy-rs/issues/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](https://github.com/smithy-lang/smithy-rs/issues/4299))

- @haydenbaker ([smithy-rs#4226](https://github.com/smithy-lang/smithy-rs/issues/4226))

September 10th, 2025

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

**New this release:**

{

  "smithy-rs": [],

  "aws-sdk-rust": [

    {

      "message": "Add the ability to insert `hints.mostly-unused = true` in Cargo.toml. Enable this hint for the below crates:\n- aws-sdk-cloudformation\n- aws-sdk-dynamodb\n- aws-sdk-ec2\n- aws-sdk-s3\n- aws-sdk-sns\n- aws-sdk-sqs\n- aws-sdk-ssm\n- aws-sdk-sts\n\nSee more information about this hint at https://blog.rust-lang.org/inside-rust/2025/07/15/call-for-testing-hint-mostly-unused/\n",

      "meta": {

        "bug": false,

        "breaking": false,

        "tada": true

      },

      "author": "landonxjames",

      "references": [

        "smithy-rs#4208"

      ],

      "since-commit": "fd54b8282920c862db4604f620ab188ec4a235b9",

      "age": 5

    },

    {

      "message": "Enable `hints.mostly-unused = true` for `aws-sdk-lambda` (taking a release\nbuild from 57s to 40s) and `aws-sdk-rds` (taking a release build from 1m34s to\n49s).\n",

      "meta": {

        "bug": false,

        "breaking": false,

        "tada": true

      },

      "author": "joshtriplett",

      "references": [

        "smithy-rs#4208"

      ],

      "since-commit": "fd54b8282920c862db4604f620ab188ec4a235b9",

      "age": 5

    },

    {

      "message": "pin crc-fast to <1.4 to workaround SIGILL\n",

      "meta": {

      "author": "aajtodd",

      "references": [],

      "since-commit": "01aece8b664968ac63354e52b88915e8f8546738",

      "age": 4

      "age": 5

    },

    {

      "message": "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.\n",

        "aws-sdk-rust#169"

      ],

      "since-commit": "520d073c2d739e95d112842be13c924097155d47",

      "age": 3

      "age": 4

    },

    {

      "message": "Enable rustls post-quantum by default.\n",

      "author": "WillChilds-Klein",

      "references": [],

      "since-commit": "520d073c2d739e95d112842be13c924097155d47",

      "age": 3

      "age": 4

    },

    {

      "message": "fix `aws-smithy-eventstream` feature `derive-arbitrary` on `arbitrary` >= 1.4.2\n",

      "author": "aajtodd",

      "references": [],

      "since-commit": "520d073c2d739e95d112842be13c924097155d47",

      "age": 3

      "age": 4

    },

    {

      "message": "Make [`TokenBucket`](https://docs.rs/aws-smithy-runtime/latest/aws_smithy_runtime/client/retries/struct.TokenBucket.html) and [`ClientRateLimiter`](https://docs.rs/aws-smithy-runtime/latest/aws_smithy_runtime/client/retries/struct.ClientRateLimiter.html) configurable through [`RetryPartition`](https://docs.rs/aws-smithy-runtime/latest/aws_smithy_runtime/client/retries/struct.RetryPartition.html).\n",

        "smithy-rs#4263"

      ],

      "since-commit": "f18c70d36c40fa0f40860547394c134566704e69",

      "age": 2

      "age": 3

    }

  ],

  "aws-sdk-model": []