diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74fa2bd..61af171 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
 CHANGELOG
 =========
 
+# 9.1.0 / 2026-04-27
+
+## Changes
+
+* [FEATURE] Add synchronous mode for serverless environments. Set `StatsdConfig.SynchronousMode = true` to bypass the async background worker and route metrics on the calling thread. Call `Flush()` at the end of each handler invocation to send any remaining buffered metrics before the sandbox freezes. See [#227][].
+
 # 9.0.0 / 2025-08-18
 
 ## Breaking Changes
@@ -285,6 +291,10 @@ DogStatsD-CSharp-Client `2.2.1` is the last version to support .NET Framework 3.
 [#186]: https://github.com/DataDog/dogstatsd-csharp-client/issues/186
 [#187]: https://github.com/DataDog/dogstatsd-csharp-client/issues/187
 [#188]: https://github.com/DataDog/dogstatsd-csharp-client/issues/188
+[#209]: https://github.com/DataDog/dogstatsd-csharp-client/issues/209
+[#211]: https://github.com/DataDog/dogstatsd-csharp-client/issues/211
+[#213]: https://github.com/DataDog/dogstatsd-csharp-client/issues/213
+[#227]: https://github.com/DataDog/dogstatsd-csharp-client/issues/227
 [@DanielVukelich]: https://github.com/DanielVukelich
 [@albertofem]: https://github.com/albertofem
 [@alistair]: https://github.com/alistair
@@ -306,4 +316,4 @@ DogStatsD-CSharp-Client `2.2.1` is the last version to support .NET Framework 3.
 [@sqdk]: https://github.com/sqdk
 [@windsnow98]: https://github.com/windsnow98
 [@wjdavis5]: https://github.com/wjdavis5
-[@yori-s]: https://github.com/yori-s
+[@yori-s]: https://github.com/yori-s
\ No newline at end of file
diff --git a/src/StatsdClient/StatsdClient.csproj b/src/StatsdClient/StatsdClient.csproj
index c013ff1..a9e9d29 100644
--- a/src/StatsdClient/StatsdClient.csproj
+++ b/src/StatsdClient/StatsdClient.csproj
@@ -4,6 +4,7 @@
     <PackageId>DogStatsD-CSharp-Client</PackageId>
     <TargetFrameworks>net461;netstandard2.0;netcoreapp3.1;net6.0</TargetFrameworks>
     <LangVersion>latest</LangVersion>
+    <PackageVersion>9.1.0</PackageVersion>
     <Version>9.0.0</Version>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>StatsdClient.snk</AssemblyOriginatorKeyFile>