diff --git a/.github/workflows/integration-tests-reusable.yml b/.github/workflows/integration-tests-reusable.yml
index 2381ee9007..40974f7ac4 100644
--- a/.github/workflows/integration-tests-reusable.yml
+++ b/.github/workflows/integration-tests-reusable.yml
@@ -27,7 +27,7 @@ jobs:
       - name: Populate OS list (all platforms)
         id: populate-os-list-all
         if: inputs.all_platforms
-        run: echo "os-list=[\"ubuntu-20.04\", \"macos-latest\", \"windows-2019\"]" >> $GITHUB_OUTPUT
+        run: echo "os-list=[\"ubuntu-20.04\", \"macos-11\", \"windows-2019\"]" >> $GITHUB_OUTPUT
       - name: Populate OS list (one platform)
         id: populate-os-list-one
         if: "!inputs.all_platforms"
@@ -35,7 +35,7 @@ jobs:
       - name: Populate OS mapping for package.py
         id: populate-os-mapping
         run: |
-          echo "os-mapping={\"ubuntu-20.04\": \"ubuntu\", \"macos-latest\": \"macos\", \"windows-2019\": \"windows\"}" >> $GITHUB_OUTPUT
+          echo "os-mapping={\"ubuntu-20.04\": \"ubuntu\", \"macos-11\": \"macos\", \"windows-2019\": \"windows\"}" >> $GITHUB_OUTPUT
       - name: Populate target runtime version list (all platforms)
         id: populate-target-runtime-version-all
         if: inputs.all_platforms
diff --git a/.github/workflows/msbuild.yml b/.github/workflows/msbuild.yml
index 8d4e3b9d7e..ed866d16e7 100644
--- a/.github/workflows/msbuild.yml
+++ b/.github/workflows/msbuild.yml
@@ -75,7 +75,7 @@ jobs:
       # label, and skip checking the nightly build above.
       # This is the best way to fix an issue in master that was only caught by the nightly build.
       all_platforms: ${{ contains(github.event.pull_request.labels.*.name, 'run-deep-tests') || contains(github.event.push.labels.*.name, 'run-deep-tests')}}
-      num_shards: 5
+      num_shards: ${{ (contains(github.event.pull_request.labels.*.name, 'run-deep-tests') || contains(github.event.push.labels.*.name, 'run-deep-tests')) && 10 || 5 }}
 
   test-coverage-analysis:
     runs-on: ubuntu-20.04
diff --git a/.github/workflows/release-brew.yml b/.github/workflows/release-brew.yml
index 00c910954f..2ffca171c1 100644
--- a/.github/workflows/release-brew.yml
+++ b/.github/workflows/release-brew.yml
@@ -10,7 +10,7 @@ concurrency:
 jobs:
   build:
 
-    runs-on: macos-latest
+    runs-on: macos-11
 
     steps:
     - name: Install dafny
diff --git a/.github/workflows/release-downloads-nuget.yml b/.github/workflows/release-downloads-nuget.yml
index 31d0e91d58..6f584c636f 100644
--- a/.github/workflows/release-downloads-nuget.yml
+++ b/.github/workflows/release-downloads-nuget.yml
@@ -111,7 +111,7 @@ jobs:
         # but note we need to skip Dafny since nuget install doesn't work for dotnet tools.
         library-name: [ DafnyPipeline, DafnyServer, DafnyLanguageServer, DafnyRuntime, DafnyCore, DafnyDriver ]
         # This workflow breaks on windows-2022: https://github.com/dafny-lang/dafny/issues/1906
-        os: [ ubuntu-latest, ubuntu-20.04, macos-latest, windows-2019 ]
+        os: [ ubuntu-latest, ubuntu-20.04, macos-11, windows-2019 ]
 
     steps:
     # Verify that the dependencies of the libraries we publish (e.g. DafnyLanguageServer)
diff --git a/.github/workflows/release-downloads.yml b/.github/workflows/release-downloads.yml
index f6158a53d4..84b7e34fd0 100644
--- a/.github/workflows/release-downloads.yml
+++ b/.github/workflows/release-downloads.yml
@@ -18,13 +18,13 @@ jobs:
       fail-fast: false
       matrix:
         # This workflow breaks on windows-2022: https://github.com/dafny-lang/dafny/issues/1906
-        os: [ ubuntu-latest, ubuntu-20.04, macos-latest, windows-2019 ]
+        os: [ ubuntu-latest, ubuntu-20.04, macos-11, windows-2019 ]
         include:
         - os:  'ubuntu-latest'
           osn: 'ubuntu-20.04'
         - os:  'ubuntu-20.04'
           osn: 'ubuntu-20.04'
-        - os:  'macos-latest'
+        - os:  'macos-11'
           osn: 'x64-macos-11'
         - os:  'windows-2019'
           osn: 'windows-2019'