diff --git a/.gitea/workflows/ui-test.yaml b/.gitea/workflows/ui-test.yaml
index 5924d3c..cb7812d 100644
--- a/.gitea/workflows/ui-test.yaml
+++ b/.gitea/workflows/ui-test.yaml
@@ -16,6 +16,15 @@ on:
       - '.gitea/workflows/ui-test.yaml'
       - '!**/*.md'
 
+# Playwright launches its own `pnpm dev` on :5173. In host-mode the
+# runner shares the host's port namespace, so two parallel ui-test
+# jobs (e.g. a push event racing with a pull_request event for the
+# same commit) collide on EADDRINUSE. Group by branch/ref and cancel
+# the in-progress run so only one ui-test is alive at a time per ref.
+concurrency:
+  group: ui-test-${{ gitea.ref }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -59,6 +68,15 @@ jobs:
         working-directory: ui/frontend
         run: pnpm test
 
+      - name: Clear stale Vite from :5173
+        # Defence in depth in case a previous job's webServer survived
+        # the concurrency-cancel — `pkill` does not fail when there is
+        # nothing to kill, and `fuser -k` cleans up anything else
+        # holding the port.
+        run: |
+          pkill -f 'vite dev' || true
+          fuser -k 5173/tcp 2>/dev/null || true
+
       - name: Run Playwright
         working-directory: ui/frontend
         run: pnpm exec playwright test