GitHub stacked pull requests GA: review AI code in small pieces

GitHub made stacked pull requests generally available on October 6, on every github.com plan. You split one big change into a chain of small PRs, each reviewed on its own, then merge the chain as a group. Tools like Graphite have sold this workflow for years. Now it ships in the box, and it lands right when AI agents are producing more code than humans can read in one sitting.

What actually happened

Per the GitHub changelog:

• Availability. All github.com plans now. GitHub Enterprise Server gets it in an upcoming release.
• In the UI. Each PR in a stack shows a persistent stack header. You can see stacks from the PR list, and step through them with Shift+J and Shift+K. The timeline logs when a PR joins or leaves a stack.
• In the CLI. The gh stack extension for GitHub CLI now supports Git worktrees and has better init, checkout, and navigation.
• Merging. Approvals survive a rebase if the code didn't change. Commits stay signed through rebases. A stack enters the merge queue as one merge group but keeps one merge commit per PR. Stacks retarget on their own when a base branch is deleted. Auto-merge is rolling out over the coming weeks.
• GitHub's numbers. GitHub says repos using stacks saw 9% more merged code, and the top 1% of repos saw a 5% improvement in time-to-merge. Those are GitHub's own figures, not an independent study.

Docs are here.

Why it matters for your business

Review is now the bottleneck, not typing. A coding agent can hand you a 2,000-line PR in ten minutes. Nobody reviews 2,000 lines well. They skim it and click approve, and that is how bugs and secrets get to production.

Stacks give you a cheap way to force structure:

1. Make agents stack. Tell your agent, in its instructions file, to split work into ordered PRs: schema, then API, then UI. Each one small enough to read.
2. Review the risky layer hardest. The migration PR gets a careful read. The CSS PR gets a glance. One big PR hides that difference.
3. Keep approvals honest. Because approvals stay on unchanged code, a fix to PR 3 does not reset review on PRs 1 and 2. That removes the main excuse for giant PRs.
4. Check before you pay for a tool. If you pay for a third-party stacking tool, compare it to the free built-in now. Keep it only if it does something you use.

Sources: GitHub Changelog: Stacked pull requests generally available, GitHub stacked pull requests docs.