diff --git a/.github/workflows/release-please-reusable.yml b/.github/workflows/release-please-reusable.yml
index a3da862..3fc4423 100644
--- a/.github/workflows/release-please-reusable.yml
+++ b/.github/workflows/release-please-reusable.yml
@@ -116,6 +116,22 @@ jobs:
     permissions:
       contents: write
       pull-requests: write
+    # Serialize runs within the caller's repo. GitHub occasionally delivers
+    # one push as two workflow runs; unserialized, both build the same release
+    # commit and the slower one fails updating the release branch ref. The
+    # group is repo-wide, not per-ref, because release-please always targets
+    # the default branch. GitHub keeps one pending run per group and cancels
+    # it when a newer run queues. That loses no release work, because
+    # release-please reads the branch's current HEAD; `queue: max` would avoid
+    # the canceled run once actionlint accepts the key (#40). A caller that
+    # declares a group of this name deadlocks with this job.
+    concurrency:
+      group: release-please-reusable
+      cancel-in-progress: false
+    # Bound a hung run: it holds the concurrency group, so no later run in
+    # the repo can start until it ends. The slowest caller's job takes just
+    # under five minutes.
+    timeout-minutes: 30
     # Hoist credentials to job env so step-level `if:` can read them — GitHub
     # allows the `env` context in step `if:` only when env is defined at the
     # workflow or job level, and the `secrets` context isn't allowed in `if:`
diff --git a/README.md b/README.md
index ebee68d..71a9abc 100644
--- a/README.md
+++ b/README.md
@@ -80,6 +80,8 @@ jobs:
 
 Treat `body`, `pr`, `prs` and `name` as untrusted text: they come from commit messages and PR titles. Pass them to a script through `env:` — never interpolate them directly into a `run:` block.
 
+The job runs in a repo-wide `release-please-reusable` concurrency group without `cancel-in-progress`, so overlapping pushes (or a single push GitHub delivers twice) wait instead of racing to update the release PR branch. GitHub keeps one pending run per group, so a third overlapping run cancels the one already waiting. The canceled run shows as a failed check on its commit, but no release work is lost: the replacement reads the branch's current HEAD, not the commit that triggered it. [#40](https://github.com/openCoreEMR/github-workflows-public/issues/40) tracks removing that case with `queue: max`. The job times out after 30 minutes so a hung run cannot hold the group indefinitely. Don't declare a concurrency group of the same name in the caller; caller and callee would deadlock on it.
+
 Inputs:
 
 | Name                   | Type   | Default                          | Description                              |