PRs were built for open source. A non-maintainer wanted to contribute, a maintainer needed a gate, and you opened the PR early so the two of you could work through the change together while it was still forming. That was the point. The PR was where the thinking happened.

Copilot writes the PR description for you now. Look at what it's actually doing. It reads a finished diff and narrates it back to you. It describes something that already happened. It never captured why the change started in the first place.

That's the question a description can't answer. What was the intent behind the change before anyone wrote code. What acceptance criteria was it satisfying. What todos did it come from, and what agent session acted on them. You can't get that from a diff, and you can't get it from a summary of a diff. You have to record it as the change happens, as its own structure, connected to the record it eventually produces. That connected structure is the semantic change graph, and it's what turns a diff into something you can triage instead of just read.

I'll show what that looks like end to end. Intent, acceptance criteria, the session that acted on them, the change record they produced. Then a live merge blocked by a query against that graph, with the reason and the fix generated from the graph itself, not summarized from a diff after the fact.