diff --git a/.github/workflows/ci3-external.yml b/.github/workflows/ci3-external.yml
index cc296439dd77..2f7a85683dd5 100644
--- a/.github/workflows/ci3-external.yml
+++ b/.github/workflows/ci3-external.yml
@@ -9,9 +9,10 @@ on:
     types: [opened, synchronize, reopened, ready_for_review, labeled]
 
 concurrency:
-  # Only allow one run per <forked-repo>/<branch>.
+  # Only allow one run per <forked-repo>/<branch> and full concurrency on merge queue.
   group: |
-    ci3-external-${{format('{0}/{1}', github.event.pull_request.head.repo.full_name, github.head_ref)}}
+    ci3-external-${{ github.event_name == 'pull_request' && format('{0}/{1}', github.event.pull_request.head.repo.full_name, github.head_ref)
+                                                         || github.run_id} }
   cancel-in-progress: true
 
 jobs:
diff --git a/.github/workflows/ci3.yml b/.github/workflows/ci3.yml
index cb89bc0acc8c..e8eef4a05774 100644
--- a/.github/workflows/ci3.yml
+++ b/.github/workflows/ci3.yml
@@ -183,7 +183,7 @@ jobs:
     if: github.event_name == 'merge_group'
     strategy:
       matrix:
-        number: [1, 2, 3, 4, 5]
+        number: [1, 2]
       fail-fast: false
     steps:
       #############