diff --git a/.github/workflows/check_only_keyword.yml b/.github/workflows/check_only_keyword.yml
index 94e2fe95a..4a8a5c9f3 100644
--- a/.github/workflows/check_only_keyword.yml
+++ b/.github/workflows/check_only_keyword.yml
@@ -8,7 +8,7 @@ on:
 
 jobs:
   grep-only-verification-keyword:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     permissions:
       issues: write
       pull-requests: write
diff --git a/.github/workflows/dafny_interop_test_net.yml b/.github/workflows/dafny_interop_test_net.yml
index d7c83596f..2fefcb3cc 100644
--- a/.github/workflows/dafny_interop_test_net.yml
+++ b/.github/workflows/dafny_interop_test_net.yml
@@ -36,7 +36,7 @@ jobs:
       matrix:
         os: [
           windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/dafny_interop_test_vector_net.yml b/.github/workflows/dafny_interop_test_vector_net.yml
index 66e9438a1..8ca08f3af 100644
--- a/.github/workflows/dafny_interop_test_vector_net.yml
+++ b/.github/workflows/dafny_interop_test_vector_net.yml
@@ -35,7 +35,7 @@ jobs:
       matrix:
         os: [
           windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{matrix.os}}
@@ -145,7 +145,7 @@ jobs:
     strategy:
       matrix:
         os: [
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
@@ -250,7 +250,7 @@ jobs:
     strategy:
       matrix:
         os: [
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/library_codegen.yml b/.github/workflows/library_codegen.yml
index d534b5733..500950e02 100644
--- a/.github/workflows/library_codegen.yml
+++ b/.github/workflows/library_codegen.yml
@@ -21,7 +21,7 @@ jobs:
         # in this workflow
         dotnet-version: ["6.0.x"]
         go-version: [1.23]
-        os: [ubuntu-latest]
+        os: [ubuntu-22.04]
     runs-on: ${{ matrix.os }}
     defaults:
       run:
@@ -53,6 +53,10 @@ jobs:
         with:
           dotnet-version: ${{ matrix.dotnet-version }}
 
+      # even though we just installed dotnet 6, maybe dotnet 8 is out there somewhere
+      - name: Create temporary global.json
+        run: echo '{"sdk":{"rollForward":"latestFeature","version":"6.0.0"}}' > ./global.json
+
       - name: Setup Java 17 for codegen
         uses: actions/setup-java@v3
         with:
diff --git a/.github/workflows/library_go_tests.yml b/.github/workflows/library_go_tests.yml
index 1d84cd991..e3e44b54e 100644
--- a/.github/workflows/library_go_tests.yml
+++ b/.github/workflows/library_go_tests.yml
@@ -24,7 +24,7 @@ jobs:
         os: [
           # Sed script doesn't work properly on windows
           # windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/library_interop_test_vectors.yml b/.github/workflows/library_interop_test_vectors.yml
index 36f83068e..84b6f874d 100644
--- a/.github/workflows/library_interop_test_vectors.yml
+++ b/.github/workflows/library_interop_test_vectors.yml
@@ -22,7 +22,7 @@ jobs:
         os: [
             # https://taskei.amazon.dev/tasks/CrypTool-5283
             # windows-latest,
-            ubuntu-latest,
+            ubuntu-22.04,
             macos-13,
           ]
         language: [java, net, rust, go]
@@ -200,7 +200,7 @@ jobs:
         os: [
             # https://taskei.amazon.dev/tasks/CrypTool-5283
             # windows-latest,
-            ubuntu-latest,
+            ubuntu-22.04,
             macos-13,
           ]
         encrypting_language: [java, net, rust, go]
diff --git a/.github/workflows/library_interop_tests.yml b/.github/workflows/library_interop_tests.yml
index a2e162743..579dd42b5 100644
--- a/.github/workflows/library_interop_tests.yml
+++ b/.github/workflows/library_interop_tests.yml
@@ -26,7 +26,7 @@ jobs:
       matrix:
         os: [
           windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
@@ -123,7 +123,7 @@ jobs:
     strategy:
       matrix:
         os: [
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
@@ -228,7 +228,7 @@ jobs:
     strategy:
       matrix:
         os: [
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/library_java_tests.yml b/.github/workflows/library_java_tests.yml
index cfba10bc0..5fbf911c9 100644
--- a/.github/workflows/library_java_tests.yml
+++ b/.github/workflows/library_java_tests.yml
@@ -24,7 +24,7 @@ jobs:
         os: [
           # TODO just test on mac for now
           #windows-latest,
-          #ubuntu-latest,
+          #ubuntu-22.04,
           macos-13
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/library_legacy_interop_test_vectors.yml b/.github/workflows/library_legacy_interop_test_vectors.yml
index 75257db64..3cd760996 100644
--- a/.github/workflows/library_legacy_interop_test_vectors.yml
+++ b/.github/workflows/library_legacy_interop_test_vectors.yml
@@ -22,7 +22,7 @@ jobs:
         os: [
             # https://taskei.amazon.dev/tasks/CrypTool-5283
             # windows-latest,
-            ubuntu-latest,
+            ubuntu-22.04,
             macos-13,
           ]
         # java struggles with the json parsing
diff --git a/.github/workflows/library_net_tests.yml b/.github/workflows/library_net_tests.yml
index c50c854e6..976769cf2 100644
--- a/.github/workflows/library_net_tests.yml
+++ b/.github/workflows/library_net_tests.yml
@@ -33,7 +33,7 @@ jobs:
         library: [AwsEncryptionSDK]
         os: [
           windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
@@ -139,7 +139,7 @@ jobs:
         os: [
           # Sed script doesn't work properly on windows
           # windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/library_rust_tests.yml b/.github/workflows/library_rust_tests.yml
index c0ffca8b1..72693b220 100644
--- a/.github/workflows/library_rust_tests.yml
+++ b/.github/workflows/library_rust_tests.yml
@@ -22,7 +22,7 @@ jobs:
         library: [AwsEncryptionSDK]
         os: [
           windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
@@ -135,7 +135,7 @@ jobs:
         os: [
           # Sed script doesn't work properly on windows
           # windows-latest,
-          ubuntu-latest,
+          ubuntu-22.04,
           macos-13,
         ]
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/nighly_dafny.yml b/.github/workflows/nighly_dafny.yml
index fb8ea0f89..85316b99e 100644
--- a/.github/workflows/nighly_dafny.yml
+++ b/.github/workflows/nighly_dafny.yml
@@ -45,7 +45,7 @@ jobs:
       regenerate-code: true
   
   cut-issue-on-failure:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     permissions:
       id-token: write
       contents: read
diff --git a/.github/workflows/pull.yml b/.github/workflows/pull.yml
index 2eb130b8c..a4727c23c 100644
--- a/.github/workflows/pull.yml
+++ b/.github/workflows/pull.yml
@@ -51,7 +51,7 @@ jobs:
       - pr-test-vectors
       - pr-dafny-test-vectors
       - pr-dafny-legacy-test-vectors
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     steps:
       - name: Verify all required jobs passed
         uses: re-actors/alls-green@release/v1
diff --git a/.github/workflows/smithy-diff.yml b/.github/workflows/smithy-diff.yml
index 3092c9470..7661bc580 100644
--- a/.github/workflows/smithy-diff.yml
+++ b/.github/workflows/smithy-diff.yml
@@ -8,7 +8,7 @@ on:
 
 jobs:
   require-approvals:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     permissions:
       issues: write
       pull-requests: write