diff --git a/.github/workflows/cpp-ci-serial-programs-mac-intel.yml b/.github/workflows/cpp-ci-serial-programs-mac-intel.yml
index eba6cf90cd..0d21870d54 100644
--- a/.github/workflows/cpp-ci-serial-programs-mac-intel.yml
+++ b/.github/workflows/cpp-ci-serial-programs-mac-intel.yml
@@ -6,6 +6,12 @@ on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
 
+# When a new event arrives on the same ref (e.g. a new commit pushed to a PR),
+# immediately cancel the in-progress workflow started by the older event.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
diff --git a/.github/workflows/cpp-ci-serial-programs-mac.yml b/.github/workflows/cpp-ci-serial-programs-mac.yml
index e97805b76e..287be02dad 100644
--- a/.github/workflows/cpp-ci-serial-programs-mac.yml
+++ b/.github/workflows/cpp-ci-serial-programs-mac.yml
@@ -6,6 +6,12 @@ on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
 
+# When a new event arrives on the same ref (e.g. a new commit pushed to a PR),
+# immediately cancel the in-progress workflow started by the older event.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
diff --git a/.github/workflows/cpp-ci-serial-programs-ubuntu-clang.yml b/.github/workflows/cpp-ci-serial-programs-ubuntu-clang.yml
index b05cd243cb..3473ecd5f0 100644
--- a/.github/workflows/cpp-ci-serial-programs-ubuntu-clang.yml
+++ b/.github/workflows/cpp-ci-serial-programs-ubuntu-clang.yml
@@ -6,6 +6,12 @@ on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
 
+# When a new event arrives on the same ref (e.g. a new commit pushed to a PR),
+# immediately cancel the in-progress workflow started by the older event.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
diff --git a/.github/workflows/cpp-ci-serial-programs-ubuntu-default.yml b/.github/workflows/cpp-ci-serial-programs-ubuntu-default.yml
index d9135a79c6..1d6b3efafb 100644
--- a/.github/workflows/cpp-ci-serial-programs-ubuntu-default.yml
+++ b/.github/workflows/cpp-ci-serial-programs-ubuntu-default.yml
@@ -6,6 +6,12 @@ on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
 
+# When a new event arrives on the same ref (e.g. a new commit pushed to a PR),
+# immediately cancel the in-progress workflow started by the older event.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
diff --git a/.github/workflows/cpp-ci-serial-programs-windows-clang.yml b/.github/workflows/cpp-ci-serial-programs-windows-clang.yml
index beffaae695..806904ca28 100644
--- a/.github/workflows/cpp-ci-serial-programs-windows-clang.yml
+++ b/.github/workflows/cpp-ci-serial-programs-windows-clang.yml
@@ -6,6 +6,12 @@ on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
 
+# When a new event arrives on the same ref (e.g. a new commit pushed to a PR),
+# immediately cancel the in-progress workflow started by the older event.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
diff --git a/.github/workflows/cpp-ci-serial-programs-windows-default.yml b/.github/workflows/cpp-ci-serial-programs-windows-default.yml
index 6ab2489835..bb7f9d7c2a 100644
--- a/.github/workflows/cpp-ci-serial-programs-windows-default.yml
+++ b/.github/workflows/cpp-ci-serial-programs-windows-default.yml
@@ -6,6 +6,12 @@ on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
 
+# When a new event arrives on the same ref (e.g. a new commit pushed to a PR),
+# immediately cancel the in-progress workflow started by the older event.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.event_name != 'pull_request' || github.event.pull_request.draft == false