Add rate-limiting fixes include file for preview4

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Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>

Author: Copilot

aspnetcore/release-notes/aspnetcore-11.md

@@ -5,7 +5,7 @@ author: wadepickett
 description: Learn about the new features in ASP.NET Core in .NET 11.
 ms.author: wpickett
 ms.custom: mvc
-ms.date: 05/13/2026
+ms.date: 05/14/2026
 uid: aspnetcore-11
 ---
 # What's new in ASP.NET Core in .NET 11
@@ -80,6 +80,8 @@ This section describes miscellaneous new features in .NET 11.
 
 [!INCLUDE[](~/release-notes/aspnetcore-11/includes/runtime-async-shared-framework-preview4.md)]
 
+[!INCLUDE[](~/release-notes/aspnetcore-11/includes/rate-limiting-retry-after-preview4.md)]
+
 ## Breaking changes
 
 Use the articles in [Breaking changes in .NET](/dotnet/core/compatibility/breaking-changes) to find breaking changes that might apply when upgrading an app to a newer version of .NET.

aspnetcore/release-notes/aspnetcore-11/includes/rate-limiting-retry-after-preview4.md

@@ -0,0 +1,11 @@
+### Rate-limiting middleware returns accurate `Retry-After` headers
+
+The <xref:System.Threading.RateLimiting.FixedWindowRateLimiter> now reports a <xref:System.Threading.RateLimiting.MetadataName.RetryAfter> metadata value that accurately reflects the next window boundary. The rate-limiting middleware uses this metadata to set the `Retry-After` response header, so clients that exceed the rate limit automatically receive a meaningful retry interval without any extra configuration.
+
+Previously, the `RetryAfter` metadata wasn't reliably set, which meant rejected responses either lacked the header or contained an unhelpful value. With this fix, any app that uses the rate-limiting middleware with a <xref:System.Threading.RateLimiting.FixedWindowRateLimiter> benefits from correct `Retry-After` headers automatically.
+
+Additional fixes in `System.Threading.RateLimiting` resolve an issue where <xref:System.Threading.RateLimiting.TokenBucketRateLimiter> mishandled partial token refills during zero-permit acquisition, and improve <xref:System.Threading.RateLimiting.ChainedRateLimiter%601> to correctly forward idle-duration and replenishment behavior from its inner limiters.
+
+For more information, see [Rate limiting middleware in ASP.NET Core](/aspnet/core/performance/rate-limit).
+
+Thank you [@asbjornvad](https://github.com/asbjornvad) and [@apoorvdarshan](https://github.com/apoorvdarshan) for these contributions!