diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b2060726..0f36f359 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,7 +21,7 @@ jobs:
     permissions:
       contents: read
       id-token: write
-    runs-on: ${{ startsWith(github.repository, 'stainless-sdks/') && 'depot-ubuntu-24.04' || 'ubuntu-latest' }}
+    runs-on: ${{ startsWith(github.repository, 'stainless-sdks/') && 'depot-ubuntu-24.04' || 'ubuntu-24.04' }}
     if: |-
       github.repository == 'stainless-sdks/courier-ruby' &&
       (github.event_name == 'push' || github.event.pull_request.head.repo.fork) && (github.event_name != 'push' || github.event.head_commit.message != 'codegen metadata')
@@ -56,7 +56,7 @@ jobs:
   lint:
     timeout-minutes: 10
     name: lint
-    runs-on: ${{ startsWith(github.repository, 'stainless-sdks/') && 'depot-ubuntu-24.04' || 'ubuntu-latest' }}
+    runs-on: ${{ startsWith(github.repository, 'stainless-sdks/') && 'depot-ubuntu-24.04' || 'ubuntu-24.04' }}
     if: github.event_name == 'push' || github.event.pull_request.head.repo.fork
 
     steps:
@@ -73,7 +73,7 @@ jobs:
   test:
     timeout-minutes: 10
     name: test
-    runs-on: ${{ startsWith(github.repository, 'stainless-sdks/') && 'depot-ubuntu-24.04' || 'ubuntu-latest' }}
+    runs-on: ${{ startsWith(github.repository, 'stainless-sdks/') && 'depot-ubuntu-24.04' || 'ubuntu-24.04' }}
     if: github.event_name == 'push' || github.event.pull_request.head.repo.fork
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
diff --git a/.github/workflows/publish-gem.yml b/.github/workflows/publish-gem.yml
index 21ef3120..7a7b19ff 100644
--- a/.github/workflows/publish-gem.yml
+++ b/.github/workflows/publish-gem.yml
@@ -11,7 +11,8 @@ on:
 jobs:
   publish:
     name: publish
-    runs-on: ubuntu-latest
+    # Pinned: ubuntu-latest is 26.04, which has no prebuilt Ruby 3.2.0 (.ruby-version).
+    runs-on: ubuntu-24.04
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2