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## 2.73.1

**`(fix):`** Make the structured `User-Agent` (emitted when `includePlatformHeaders` is
enabled) comply with the RFC 7230 token grammar. The runtime token is now
`dotnet` instead of `.NET`, since a leading dot is not a valid token
character (e.g. `dotnet/8.0.4`). The architecture label is also normalized so
the 64-bit x86 aliases (`x64`, `amd64`, `x86_64`) all report as the canonical
`x86_64`.

## 2.73.0

**`(feat):`** Add opt-in support for a structured `User-Agent` header on generated SDK
clients of the form `{sdkName}/{sdkVersion} ({os}; {arch}) {runtime}/{runtimeVersion}`
(e.g. `my-sdk/1.2.0 (linux; x64) .NET/8.0.4`). The OS, architecture, and
runtime version are resolved at runtime via
`System.Runtime.InteropServices.RuntimeInformation` and `System.Environment`.
This is gated behind a new `include-platform-headers` config option and is
disabled by default, so existing generated output is unchanged. When enabled
it remains subject to the `omit-fern-headers` config option.