[Repo Assist] [Eng] Add CI concurrency settings to cancel superseded PR runs

[github-actions]

🤖 This PR was created by Repo Assist, an automated AI assistant.

Summary

Adds a concurrency group to the CI workflow so that when multiple commits are pushed to the same PR branch in quick succession, only the latest run proceeds — older in-progress runs are automatically cancelled.

This is particularly valuable for this repo because:

• The CI is slow (60-min timeout for JavaScript tests, plus TypeScript, Python, Rust, Dart, BEAM jobs)
• Contributors often push quick follow-up fixes after review feedback
• Without this, each push queues a full separate run, wasting runner minutes

Change

concurrency:
  group: $\{\{ github.workflow }}-$\{\{ github.ref }}
  cancel-in-progress: $\{\{ github.ref != 'refs/heads/main' }}

• PR branches: a new push cancels any running CI for that same PR
• main branch: all pushes always complete (no cancellation), so merge history is fully validated

Closes #4530

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Only the CI workflow configuration was changed — no code logic was modified.

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Warning

Protected Files — Push Permission Denied

This was originally intended as a pull request, but the patch modifies protected files. A human must create the pull request manually.

Protected files

• .github/workflows/build.yml

The push was rejected because GitHub Actions does not have workflows permission to push these changes, and is never allowed to make such changes, or other authorization being used does not have this permission.

Create the pull request manually

# Download the patch from the workflow run
gh run download 24320963492 -n agent -D /tmp/agent-24320963492

# Create a new branch
git checkout -b repo-assist/eng-ci-concurrency-2026-04-9ed9a15555f59fd8 main

# Apply the patch (--3way handles cross-repo patches)
git am --3way /tmp/agent-24320963492/aw-repo-assist-eng-ci-concurrency-2026-04.patch

# Push the branch and create the pull request
git push origin repo-assist/eng-ci-concurrency-2026-04-9ed9a15555f59fd8
gh pr create --title '[Repo Assist] [Eng] Add CI concurrency settings to cancel superseded PR runs' --base main --head repo-assist/eng-ci-concurrency-2026-04-9ed9a15555f59fd8 --repo fable-compiler/Fable

Generated by Repo Assist · ● 6.5M · ◷

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@346204513ecfa08b81566450d7d599556807389f