After the browser closes a request, the node should also have a chance to stop its background simulation. Reth PR #28312 adds cancellation checks between multiple calls to eth_simulateV1, bringing its handling in line with the existing callMany and tracing interfaces. This detail is important: the original text says checks happen between calls; it does not mean that every step currently in progress is interrupted immediately. For application development involving $ETH , cancellation requests, stopping server work, and releasing resources each need to be implemented explicitly; no longer showing a loading indicator in the UI is not enough to prove that the backend is using zero resources. This is a client-side code change and should not be taken to imply that a real transaction has been withdrawn.