Cursor has run experiments to test the limits of scaling agents to cooperate toward a goal. Their hypothesis is they can unlock a new tier of task scale and complexity. They are looking to speed up by thousands of times from 1000 commits per hour to 1000 commits per second.

Tools like Git and Cargo rely on coarse locks for concurrency control. This is fine for one developer but unworkable for the volume of work produced by hundreds of concurrent agents.

The browser swarm from earlier this year peaked at roughly 1,000 commits per hour on Git. The new system peaks at around 1,000 commits per second.

To facilitate this rate of activity, they built a new version control system (VCS) from scratch. Throughput was not the only reason to own this layer. Every change in the system passes through the VCS, so it is where collisions first become visible, and several of the coordination mechanisms in the next section are implemented directly inside of it.

Failure modes at 1,000 commits per second

Human engineering teams have standard coordination mechanisms like code review, ownership, standups, and merge queues. Those systems work at human tempo, but at the commit-rate of the swarm, we see failure modes that human teams don’t routinely encounter.

Split-brain design

Two planners, unaware of each other, implement the same concept in different ways in different parts of the codebase.

Cursor fixed this through prompting. Planners make design decisions themselves rather than delegating them, and we require them to ensure that no two delegated subtrees decide the same question.

Contention between planners

A harder form of contention is when two planners know about each other and fight through back-and-forth changes over the same files.

The problem is two pictures of reality, and merge tooling can’t fix a disagreement. Instead, they have agents record decisions in shared design docs. Code that depends on a decision carries a compile-checked reference back to its doc. When planners unknowingly contradict each other, a reconciler merges the docs and the references propagate the resolution downstream.