GitHub's 10-Month Stacked PR Migration Proves AI Can't Fix Complex System Refactors

Vjeux · x · 2026-08-03

Even with highly capable AI agents, complex software engineering remains deeply time-consuming. Take GitHub's official development of "Stacked PRs" as an example: because it touches so many underlying system modules, the project took over 10 months to build, even within a highly AI-driven team.

To properly implement automatic restacking, GitHub needs to migrate its underlying architecture from packed-refs to git reftables, ensuring multi-ref updates run at O(n) efficiency. Such deep architectural overhauls are far beyond what current AI agents can autonomously solve.

Related event: GitHub's Stacked PRs Take 10 Months, Proving AI's Limits in Complex Engineering(2 posts)→

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