diff --git a/.github/workflows/pr-review-mention.yml b/.github/workflows/pr-review-mention.yml
index ce69a49..cab0456 100644
--- a/.github/workflows/pr-review-mention.yml
+++ b/.github/workflows/pr-review-mention.yml
@@ -37,12 +37,6 @@ on:
 
 permissions: {}
 
-concurrency:
-  group: >-
-    pr-review-mention-${{ format('{0}-{1}', github.event_name,
-       github.event.issue.number || github.event.pull_request.number) }}
-  cancel-in-progress: false
-
 jobs:
   pr-review-mention:
     permissions:
diff --git a/scripts/tests/dev-lead-workflow.bats b/scripts/tests/dev-lead-workflow.bats
index 8633fd2..4aedc12 100644
--- a/scripts/tests/dev-lead-workflow.bats
+++ b/scripts/tests/dev-lead-workflow.bats
@@ -82,7 +82,8 @@ print('ok')
   # follow-up traffic. A per-repo concurrency block would drift the stub and
   # fight the centralised grouping — re-inflating the failure/cancellation rate.
   # This is the one point where dev-lead deliberately diverges from the
-  # add-to-project / pr-review-mention stubs (which DO carry a concurrency block).
+  # add-to-project stub (which carries a concurrency block); pr-review-mention
+  # no longer carries one either after issue #404 re-synced it to the central standard.
   run python3 -c "
 import sys, yaml
 wf = yaml.safe_load(open(sys.argv[1])) or {}
diff --git a/scripts/tests/pr-review-mention-workflow.bats b/scripts/tests/pr-review-mention-workflow.bats
index 7b8aa2b..2134751 100644
--- a/scripts/tests/pr-review-mention-workflow.bats
+++ b/scripts/tests/pr-review-mention-workflow.bats
@@ -1,14 +1,20 @@
 #!/usr/bin/env bats
 # Tests for .github/workflows/pr-review-mention.yml
-# Guards the concurrency fix (issue #333). The #323 attempt used
-# `cancel-in-progress: true`, but when it superseded a *pending* reusable-caller
-# run (before the reusable resolved) GitHub recorded the cancellation as a
-# startup failure — a burst of comment events on one conversation produced a
-# wave of 0-job "failure" runs that inflated the Fleet Monitor failure rate.
-# The fix mirrors add-to-project.yml (#331): `cancel-in-progress: false` with a
-# group keyed on the event name AND the PR/issue number, so superseded runs are
-# recorded as clean `cancelled` (not `failure`) and distinct event types on the
-# same conversation don't cross-cancel.
+#
+# This file is a THIN CALLER STUB. Its `on:` triggers, `permissions:` grants and
+# `concurrency:` surface are owned centrally by the canonical
+# standards/workflows/pr-review-mention.yml and are not repo-adjustable
+# (ci-standards.md → centralization tiers). The canonical stub carries NO
+# top-level `concurrency:` block, so the stub must not declare one either —
+# issue #404 re-synced the surface by removing a local block that had drifted in.
+#
+# History: #333 previously added a local `concurrency:` block here (group keyed
+# on event name + PR/issue number, `cancel-in-progress: false`) to stop a comment
+# burst from producing a wave of 0-job "failure" runs that inflated the Fleet
+# Monitor failure rate. That protection is centrally owned now: if it is still
+# wanted it belongs in the org reusable (pr-review-mention-reusable.yml), never
+# re-added to this caller stub. These tests therefore assert the stub carries no
+# local concurrency surface.
 
 WORKFLOW=".github/workflows/pr-review-mention.yml"
 
@@ -28,52 +34,17 @@ setup() {
   [ "$status" -eq 0 ]
 }
 
-@test "pr-review-mention workflow declares a concurrency block" {
+@test "pr-review-mention stub declares no local concurrency block (centrally owned, #404)" {
+  # The canonical standards/workflows/pr-review-mention.yml carries no top-level
+  # concurrency surface, and the concurrency surface of a thin caller stub is not
+  # repo-adjustable (ci-standards.md → centralization tiers). A local block is
+  # drift; #404 removed one that had crept in. If comment-burst concurrency
+  # control is needed it must live in the org reusable, not this stub.
   run python3 -c "
 import sys, yaml
 wf = yaml.safe_load(open(sys.argv[1])) or {}
-assert 'concurrency' in wf, 'workflow has no top-level concurrency block'
-c = wf.get('concurrency')
-assert isinstance(c, dict), 'concurrency must be a mapping with group/cancel-in-progress'
-assert c.get('group'), 'concurrency.group must be set'
-print('ok')
-" "$WORKFLOW"
-  [ "$status" -eq 0 ]
-  [[ "$output" == "ok" ]]
-}
-
-@test "pr-review-mention concurrency does not cancel in-progress runs" {
-  # cancel-in-progress must be false: superseding a pending reusable-caller run
-  # makes GitHub record it as a startup failure, so a comment burst inflates the
-  # failure rate (#333). With false, superseded runs are recorded as clean
-  # `cancelled`. Mirrors add-to-project.yml (#331).
-  run python3 -c "
-import sys, yaml
-wf = yaml.safe_load(open(sys.argv[1])) or {}
-c = wf.get('concurrency') or {}
-val = c.get('cancel-in-progress')
-assert val is False, f'cancel-in-progress must be false, got: {val!r}'
-print('ok')
-" "$WORKFLOW"
-  [ "$status" -eq 0 ]
-  [[ "$output" == "ok" ]]
-}
-
-@test "pr-review-mention concurrency group is keyed per event and conversation" {
-  # The workflow fires on issue_comment, pull_request_review_comment and
-  # pull_request events, whose github.ref is the default branch for comment
-  # events. Keying only on github.ref would collapse runs across unrelated PRs,
-  # so the group keys on the PR/issue number. It also keys on github.event_name
-  # so distinct event types on the same conversation get distinct groups and do
-  # not cross-cancel (mirrors add-to-project.yml, #333/#331).
-  run python3 -c "
-import sys, yaml
-wf = yaml.safe_load(open(sys.argv[1])) or {}
-c = wf.get('concurrency') or {}
-group = c.get('group', '')
-assert 'github.event_name' in group, f'group must key on the event name, got: {group!r}'
-assert 'github.event.issue.number' in group, f'group must key on issue number, got: {group!r}'
-assert 'github.event.pull_request.number' in group, f'group must key on PR number, got: {group!r}'
+concurrency = wf.get('concurrency')
+assert 'concurrency' not in wf, f'stub must not declare a local concurrency block (centrally owned), got: {concurrency!r}'
 print('ok')
 " "$WORKFLOW"
   [ "$status" -eq 0 ]