The timing rules are in two tests (upgrade_and_discovery_deadlines, stop_deadlines). All other tests use a grace period of 0 or core.stop, poll with deadlines instead of sleeping, and use the persistent cache in CARGO_TARGET_TMPDIR. The 128-cycle singleton test is an ignored stress test that nix flake check runs; the normal run has a 4-cycle sample. Warm, the activation suite takes 12 s (was 47 s), and cargo test --workspace takes 65 s.