diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 2b621e3..7bbcfce 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -32,8 +32,6 @@ jobs:
 
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v4
-        with:
-          dotnet-version: 8.0.x
 
       - name: Install GitVersion
         uses: gittools/actions/gitversion/setup@v3
diff --git a/global.json b/global.json
new file mode 100644
index 0000000..d4751a0
--- /dev/null
+++ b/global.json
@@ -0,0 +1,6 @@
+{
+  "sdk": {
+    "version": "9.0.304",
+    "rollForward": "latestMinor"
+  }
+}
\ No newline at end of file
diff --git a/src/Kattbot.Common/Kattbot.Common.csproj b/src/Kattbot.Common/Kattbot.Common.csproj
index 0ef5970..ff24bd8 100644
--- a/src/Kattbot.Common/Kattbot.Common.csproj
+++ b/src/Kattbot.Common/Kattbot.Common.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/Kattbot.Data.Migrations/Kattbot.Data.Migrations.csproj b/src/Kattbot.Data.Migrations/Kattbot.Data.Migrations.csproj
index d6d2443..1c57b02 100644
--- a/src/Kattbot.Data.Migrations/Kattbot.Data.Migrations.csproj
+++ b/src/Kattbot.Data.Migrations/Kattbot.Data.Migrations.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-	<TargetFramework>net8.0</TargetFramework>
+	<TargetFramework>net9.0</TargetFramework>
     <UserSecretsId>bc907d8f-4d2f-41fe-9b68-79e021dd3545</UserSecretsId>
   </PropertyGroup>
 
@@ -18,15 +18,15 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="8.0.8">
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.8">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.Extensions.Configuration" Version="8.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="8.0.1" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="8.0.0" />
-    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="8.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="9.0.8" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="9.0.8" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="9.0.8" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="9.0.8" />
+    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="9.0.4" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
diff --git a/src/Kattbot.Data/Kattbot.Data.csproj b/src/Kattbot.Data/Kattbot.Data.csproj
index 6324f80..70bad29 100644
--- a/src/Kattbot.Data/Kattbot.Data.csproj
+++ b/src/Kattbot.Data/Kattbot.Data.csproj
@@ -1,11 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="8.0.4" />
+    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="9.0.4" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
diff --git a/src/Kattbot/Dockerfile b/src/Kattbot/Dockerfile
index 0482800..8f0d391 100644
--- a/src/Kattbot/Dockerfile
+++ b/src/Kattbot/Dockerfile
@@ -1,6 +1,6 @@
-FROM mcr.microsoft.com/dotnet/runtime:8.0 AS base
+FROM mcr.microsoft.com/dotnet/runtime:9.0 AS base
 
-FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
 ARG BUILD_CONFIGURATION=Debug
 WORKDIR /src
 COPY ["Directory.Build.props", "."]
diff --git a/src/Kattbot/Kattbot.csproj b/src/Kattbot/Kattbot.csproj
index c535560..0e710c1 100644
--- a/src/Kattbot/Kattbot.csproj
+++ b/src/Kattbot/Kattbot.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Worker">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <UserSecretsId>dotnet-Kattbot-79CAD254-2C56-430B-8B4B-16AA8DA8808D</UserSecretsId>
         <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
     </PropertyGroup>
@@ -18,19 +18,19 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="8.0.1" />
+        <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="9.0.8" />
         <PackageReference Include="TiktokenSharp" Version="1.1.7" />
         <PackageReference Include="CommandLineArgumentsParser" Version="3.0.23" />
         <PackageReference Include="DSharpPlus" Version="5.0.0-alpha.5" />
         <PackageReference Include="DSharpPlus.CommandsNext" Version="5.0.0-alpha.5" />
         <PackageReference Include="DSharpPlus.Interactivity" Version="5.0.0-alpha.5" />
-        <PackageReference Include="MediatR" Version="12.5.0" />
-        <PackageReference Include="Microsoft.Extensions.Hosting" Version="8.0.0" />
-        <PackageReference Include="Microsoft.Extensions.Hosting.Systemd" Version="8.0.0" />
-        <PackageReference Include="Microsoft.Extensions.Http" Version="8.0.0" />
-        <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="8.0.4" />
+        <PackageReference Include="MediatR" Version="13.0.0" />
+        <PackageReference Include="Microsoft.Extensions.Hosting" Version="9.0.8" />
+        <PackageReference Include="Microsoft.Extensions.Hosting.Systemd" Version="9.0.8" />
+        <PackageReference Include="Microsoft.Extensions.Http" Version="9.0.8" />
+        <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="9.0.4" />
         <PackageReference Include="SixLabors.ImageSharp" Version="3.1.11" />
-        <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.1.5" />
+        <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.1.7" />
         <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
             <PrivateAssets>all</PrivateAssets>
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
diff --git a/src/Kattbot/prod.Dockerfile b/src/Kattbot/prod.Dockerfile
index e028004..065d80e 100644
--- a/src/Kattbot/prod.Dockerfile
+++ b/src/Kattbot/prod.Dockerfile
@@ -1,4 +1,4 @@
-FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
 ARG BUILD_CONFIGURATION=Release
 WORKDIR /src
 COPY ["Directory.Build.props", "."]
@@ -27,7 +27,7 @@ ARG BUILD_CONFIGURATION=Release
 RUN dotnet ef migrations script --no-build --configuration $BUILD_CONFIGURATION --idempotent -p Kattbot.Data.Migrations -o /output/migrations/database_migration.sql
 COPY --from=build /src/kattbot-backup-db.sh /output/migrations/
 
-FROM mcr.microsoft.com/dotnet/runtime:8.0 AS final
+FROM mcr.microsoft.com/dotnet/runtime:9.0 AS final
 WORKDIR /app
 COPY --from=publish /output/publish .
 COPY --from=migrations /output/migrations ./migrations/
diff --git a/tests/Kattbot.Tests/ImageServiceTests.cs b/tests/Kattbot.Tests/ImageServiceTests.cs
index 3164e0c..5c3c2d4 100644
--- a/tests/Kattbot.Tests/ImageServiceTests.cs
+++ b/tests/Kattbot.Tests/ImageServiceTests.cs
@@ -14,7 +14,7 @@ namespace Kattbot.Tests;
 [Ignore] // Can't save to /tmp on GitHub Actions. TODO: fix
 public class ImageServiceTests
 {
-    [DataTestMethod]
+    [TestMethod]
     [DataRow("cute_cat.jpg")]
     [DataRow("froge.png")]
     public async Task EnsureMaxSize_DownscalesImageIfNeeded(string inputFilename)
@@ -32,7 +32,7 @@ public async Task EnsureMaxSize_DownscalesImageIfNeeded(string inputFilename)
         Assert.IsTrue(resizedImageSize <= maxSizeMb);
     }
 
-    [DataTestMethod]
+    [TestMethod]
     [DataRow("slowpoke.jpg", "jpg")]
     [DataRow("slowpoke.png", "png")]
     [DataRow("slowpoke.webp", "webp")]
diff --git a/tests/Kattbot.Tests/Kattbot.Tests.csproj b/tests/Kattbot.Tests/Kattbot.Tests.csproj
index 11ca518..2cf6813 100644
--- a/tests/Kattbot.Tests/Kattbot.Tests.csproj
+++ b/tests/Kattbot.Tests/Kattbot.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <IsPackable>false</IsPackable>
         <IsPublishable>false</IsPublishable>
     </PropertyGroup>
@@ -10,7 +10,7 @@
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
         <PackageReference Include="MSTest.TestAdapter" Version="3.10.1" />
         <PackageReference Include="MSTest.TestFramework" Version="3.10.1" />
-        <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="8.0.4" />
+        <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="9.0.4" />
         <PackageReference Include="NSubstitute" Version="5.3.0" />
         <PackageReference Include="NSubstitute.Analyzers.CSharp" Version="1.0.17">
             <PrivateAssets>all</PrivateAssets>