--- title: "What is CIHub" description: "CIHub is a self-hosted merge queue for GitHub. It tests each pull request on top of the ones ahead of it and merges it only if the result passes." canonical_url: "https://cihub.io/docs" markdown_url: "https://cihub.io/docs.md" --- # What is CIHub CIHub is an open-source, self-hosted merge queue for GitHub. It keeps the target branch green with the CI you already have, installs with one image and one Postgres, and explains each of its decisions. ## The problem a merge queue solves Two pull requests pass CI on their own. You merge both. `main` is red, and nobody knows why: each one was tested without the other. CIHub makes that impossible. Approve a pull request, type `/cihub merge`, and go back to work. CIHub lines it up behind the others, tests it together with everything that lands before it, and merges it only if the result still passes. ## How the merge queue works 1. **Approve.** A pull request is approved and its checks are green. 2. **Queue.** Comment `/cihub merge`. CIHub tests it on top of everything ahead of it, alone or in a batch. 3. **Merge.** If that exact combination passes, CIHub merges it. If not, the pull request leaves the queue, with the reason on it. ## What CIHub does and does not do - CIHub never runs your CI. It pushes a test branch and waits for the required statuses and check runs: GitHub Actions, Buildkite, CircleCI and Jenkins work without changes. - The required checks are read on the target branch, never from the pull request, so that a pull request cannot weaken its own gate. - One instance serves several GitHub organizations. Postgres is its only dependency. - GitLab and Bitbucket are not supported. ## Status CIHub is in active development (v0.x). The queue, its batches and its dashboard work; metrics, parallel queues for monorepos and flaky test detection come next. Do not use it in production yet: its behavior, its configuration and its data can change without notice from one version to the next. ## Next steps