diff --git a/.github/workflows/current-head-run-coalescer.yml b/.github/workflows/current-head-run-coalescer.yml
index 23575204de..bf160f452d 100644
--- a/.github/workflows/current-head-run-coalescer.yml
+++ b/.github/workflows/current-head-run-coalescer.yml
@@ -6,10 +6,15 @@ on:
 
 concurrency:
   group: current-head-run-coalescer-${{ github.repository }}-${{ github.event.pull_request.number }}
-  # Do not restore cancel-in-progress: true here. This job is the control-plane
-  # worker that retires redundant runs; cancelling it during a push burst lets
-  # the redundant runs survive and worsens the 60-job ceiling.
+  # The active worker must finish because it retires redundant runs that consume
+  # the shared Actions ceiling. A later synchronize event must not kill it.
   cancel-in-progress: false
+  # Keep exactly one pending successor. GitHub replaces that pending run when a
+  # newer event enters the group, so the retained successor always represents
+  # the latest head instead of accumulating up to 100 stale-head invocations.
+  # The script still verifies the event-bound expected head against the live PR
+  # before any mutation and fails closed if the head moved again.
+  queue: single
 
 permissions:
   actions: write
diff --git a/tests/test_current_head_coalescer_self_cancellation.py b/tests/test_current_head_coalescer_self_cancellation.py
index 82eb9c4d71..eb84cd1306 100644
--- a/tests/test_current_head_coalescer_self_cancellation.py
+++ b/tests/test_current_head_coalescer_self_cancellation.py
@@ -1,4 +1,4 @@
-"""Regression contract for the run-coalescer worker's own concurrency policy."""
+"""Regression contracts for the run-coalescer worker's concurrency policy."""
 
 from pathlib import Path
 
@@ -7,8 +7,8 @@
 WORKFLOW_PATH = REPOSITORY_ROOT / ".github" / "workflows" / "current-head-run-coalescer.yml"
 
 
-def test_current_head_coalescer_cannot_cancel_its_active_cleanup_worker() -> None:
-    """Push bursts must queue the next cleanup instead of killing the active cleanup."""
+def test_current_head_coalescer_preserves_active_worker_and_latest_pending_event() -> None:
+    """Push bursts must keep the active cleanup plus the latest pending trigger."""
     workflow_text = WORKFLOW_PATH.read_text(encoding="utf-8")
     concurrency_block = workflow_text.split("concurrency:", 1)[1].split("\npermissions:", 1)[0]
     active_lines = [
@@ -19,3 +19,5 @@ def test_current_head_coalescer_cannot_cancel_its_active_cleanup_worker() -> Non
 
     assert "cancel-in-progress: false" in active_lines
     assert "cancel-in-progress: true" not in active_lines
+    assert "queue: single" in active_lines
+    assert "queue: max" not in active_lines