diff --git a/.forgejo/workflows/ci.yml b/.forgejo/workflows/ci.yml
index ff81a23..e33a1c4 100644
--- a/.forgejo/workflows/ci.yml
+++ b/.forgejo/workflows/ci.yml
@@ -4,6 +4,13 @@ on:
   push:
   pull_request:
 
+# Cancel any running CI for the same PR or branch when a new commit
+# lands. The shared runner has capacity=1, so stacking obsolete runs
+# just pushes useful ones to the back of the queue.
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: docker