GitHub: more than 40% of pull requests now start with an agent's first draft

GitHub reports that by September 2026 more than 40% of pull requests started with an agent's first draft, up from 17% in March. That is 110 million in September alone, about six times March's volume. Agent-started pull requests changed multiple files more often (about 87%, against 79% for pull requests without detected agent involvement). In September 90% of agent pull requests merged within two weeks, against about 86% for the comparison group; in February the agent figure was 83%. GitHub says its agent detection is "a floor", so the true share is likely higher. It also reports that repositories created this year with an agent configuration file logged eight times as many commits as new repositories without one, and that Copilot cloud agent, where a developer assigns a task and the agent works independently, grew 230% year over year against 85% for agent chat.

Review tooling grew alongside. AI-assisted code review usage grew more than 90% year over year, and more than 264,000 developers had used stacked pull requests, which launched as a preview on July 30. GitHub sells Copilot, and all figures are its own telemetry; the post does not report defect, revert or incident rates.

Why it matters: Merge rate cannot separate good agent output from lightly reviewed agent output, and this report measures only the first. If a team's review capacity is flat while agent-started pull requests triple, the merge numbers will look healthy either way, so a team should track what happens after merge, not just whether review approved it.