diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d4d6978..e447cf9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,9 +12,11 @@ on:
 permissions:
   contents: read
 
+# A newer push to the same pull request supersedes the older run. Pushes to
+# main never share a group, so each main commit keeps a complete run.
 concurrency:
-  group: ci-${{ github.ref }}
-  cancel-in-progress: true
+  group: ci-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 jobs:
   check: