From 8a479bc301d0ca27ada600e76a52034f5e5e2fb9 Mon Sep 17 00:00:00 2001
From: owenpearson <owen.pearson@ably.com>
Date: Tue, 29 Sep 2026 14:02:31 +0100
Subject: [PATCH] ci: run one workflow per pull request with concurrency groups

All three CI workflows fire on `pull_request` and on `push` to main. A
single push that moves several branches in a stacked chain makes GitHub
fire a `pull_request` synchronize both for the PR whose head moved and
for the PR whose base moved, so one PR gets two runs on the identical
head SHA a second apart. Each duplicate costs a full seven-version check
matrix plus lint and build.

Group by workflow and pull request number so those two synchronizes
share a group and the later one supersedes the earlier. Keying on
`github.workflow` holds the three workflows in separate groups, so the
22-second lint run cannot cancel the 19-minute check run. The
`github.ref` fallback covers `push` to main and `workflow_dispatch`,
where `pull_request.number` is empty.

`cancel-in-progress` is limited to pull request events: every merge
commit on main gets a run that finishes, which keeps the required status
check history intact.

`check.yml` gains a name, so the Actions UI and the concurrency group
use `Check` rather than the workflow's file path.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 .github/workflows/check.yml    | 8 ++++++++
 .github/workflows/features.yml | 6 ++++++
 .github/workflows/lint.yml     | 6 ++++++
 3 files changed, 20 insertions(+)

diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index f69bf097..36089c36 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -4,6 +4,8 @@
 # As directed from:
 #   https://docs.github.com/en/actions/guides/building-and-testing-python#starting-with-the-python-workflow-template
 
+name: Check
+
 on:
   workflow_dispatch:
   pull_request:
@@ -11,6 +13,12 @@ on:
     branches:
       - main
 
+# One run per pull request; a new event supersedes the one in flight.
+# Pushes to main and manual runs group by ref and always run to completion.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 permissions: {}
 
 jobs:
diff --git a/.github/workflows/features.yml b/.github/workflows/features.yml
index 03c6b07d..47f9bc36 100644
--- a/.github/workflows/features.yml
+++ b/.github/workflows/features.yml
@@ -6,6 +6,12 @@ on:
     branches:
       - main
 
+# One run per pull request; a new event supersedes the one in flight.
+# Pushes to main and manual runs group by ref and always run to completion.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 permissions: {}
 
 jobs:
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index d1027713..cfbcfed0 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -6,6 +6,12 @@ on:
     branches:
       - main
 
+# One run per pull request; a new event supersedes the one in flight.
+# Pushes to main and manual runs group by ref and always run to completion.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 permissions: {}
 
 jobs: