diff --git a/.github/workflows/build-test.yaml b/.github/workflows/build-test.yaml
index 5b23ddf77..0758980b6 100644
--- a/.github/workflows/build-test.yaml
+++ b/.github/workflows/build-test.yaml
@@ -6,6 +6,14 @@ on:
       - master
   pull_request:
 
+# Supersede an in-flight run when a PR gets a new push. Keyed on the PR number
+# so every push to the same PR shares a group; on a master push the key falls
+# back to github.sha (unique per commit) and cancel-in-progress is false, so
+# master runs never cancel each other -- each commit is built on its own.
+concurrency:
+  group: ci-build-test-${{ github.event.pull_request.number || github.sha }}-${{ github.repository }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 jobs:
   build-test:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/secscan.yaml b/.github/workflows/secscan.yaml
index b5bf8e2be..96daa5afa 100644
--- a/.github/workflows/secscan.yaml
+++ b/.github/workflows/secscan.yaml
@@ -7,6 +7,19 @@ on:
   schedule:
   - cron: '0 0 * * 0'
 
+# `push:` is deliberately unfiltered, so this fires on every push to every
+# branch and there is no pull_request event to key on -- the usual
+# `github.event.pull_request.number || github.sha` idiom used elsewhere would
+# key on the unique-per-commit sha and dedup nothing. Group on the ref instead
+# so successive pushes to the same feature branch supersede one another.
+#
+# Cancelling is safe here: the only output is a SARIF upload, and code scanning
+# tracks the latest result per ref, so a superseded scan has nothing to lose.
+# master is excluded anyway -- every commit on master gets its own scan.
+concurrency:
+  group: ci-secscan-${{ github.ref }}-${{ github.repository }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
+
 jobs:
   tests:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/yaml-check.yml b/.github/workflows/yaml-check.yml
index 4a5689e2c..e910ec8d7 100644
--- a/.github/workflows/yaml-check.yml
+++ b/.github/workflows/yaml-check.yml
@@ -1,6 +1,11 @@
 name: 'Yamllint GitHub Actions'
 on:
   - pull_request
+
+concurrency:
+  group: ci-yamllint-${{ github.event.pull_request.number || github.sha }}-${{ github.repository }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 jobs:
   yamllint:
     name: 'Yamllint'