GitHub · Pull requests · Stacked pull requests · Checked October 27, 2026

GitHub: checks run on every pull request in a stack

Every pull request in a stack is evaluated as if it targets the base of the stack, such as main. A workflow configured to run on pull_request events targeting main runs for every pull request in the stack, not just the bottom one, so a large stack multiplies your CI usage (GitHub's optimizing CI for stacked pull requests, checked October 27, 2026).

main <- PR1 <- PR2 <- PR3
on: pull_request, branches: [main]   runs for PR1, PR2 and PR3
required status checks               evaluated against the stack base
github.event.pull_request.stack      present only in a stack

Why it runs for every pull request

The stack base counts: GitHub Actions workflows trigger as if each pull request in the stack targets the base of the stack, so no workflow changes are needed for checks to run across the whole stack (GitHub's stacked pull requests).
The rules too: required reviews, required status checks, code owners and code scanning workflows are evaluated against the stack base, not the branch directly below (GitHub's branch protections and required checks). The base is the base branch of the bottom pull request, the repository's default branch by default, and can be any branch, such as a release branch.
Merging needs the ones below: merging PR3 requires PR1 and PR2 to also pass checks (see stacked pull request not merging).

Running jobs only where needed

The stack fields: in workflow expressions, github.event.pull_request.stack gives number (the stack, in the repository), size (pull requests in the stack), position (1 is the bottom), base.ref (the branch the whole stack targets) and base.sha. The property is present only when the pull request belongs to a stack, so check that it is not null first (GitHub's accessing stack metadata).
The lowest unmerged pull request: where github.event.pull_request.stack.base.ref equals github.event.pull_request.base.ref, the one that targets the stack base directly. When the bottom pull request merges, the next one is rebased to target the stack base and becomes the lowest unmerged one on the following run.
The top pull request: where stack.position equals stack.size, the one with the full set of changes. stack.position == 1 picks the original bottom one (GitHub's reducing CI usage).

if: github.event.pull_request.stack != null && github.event.pull_request.stack.position == github.event.pull_request.stack.size

When the job is a required check

Skipped by a condition: a job skipped by a conditional reports Success, so it does not block the merge (GitHub's handling skipped but required checks).
Skipped as a whole workflow: a workflow skipped by path filtering, branch filtering or a commit message leaves its checks Pending, which blocks merging; GitHub advises against requiring workflows that can be skipped (see checks skipped by [skip ci]).
A job after a failed one: a job that depends on a failed job is skipped and may not block merging; GitHub suggests always() with needs for such required checks.

What to do

Too many runs: keep the cheap checks on every pull request, and gate the expensive jobs on the lowest unmerged or the top pull request with the stack fields.
A run you did not expect: compare the workflow filter with the stack base, not with the branch directly below the pull request.
After a rebase: the merge box shows Rebase stack when a rebase is needed; rebasing a stack generates signed commits, and approvals are kept when the diff does not change (GitHub's rebasing).

GitHub pull requests in IntelliJ IDEA

Pull Request Inbox for GitHub, a plugin by Lesstep for JetBrains IDEs 2024.1 or later, lists the checks GitHub reports on a pull request's head commit, with links to their runs, next to the diff. For a pull request in a stack, its merge checks say that it is part of a stack and read the rules of the stack base, and Merge lands it together with the open pull requests below it. It does not rerun checks or change workflows. The review inbox, diffs and conversations are free; approving, commenting, resolving and merging are Pro (US$1.50 a month, with a 30-day trial).

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