SMP guests, scoped Cap<Fs>, generational GC, and a fail-closed security sweep
Release notes
Multi-vCPU guests
The microVM monitor gained SMP: microvm_create_smp spawns a VM with n vCPUs, each its own KVM vCPU on its own host thread, with per-vCPU CPUID topology and an Intel MP 1.4 floating-pointer table the monitor writes so the guest kernel discovers every core. Block-image volumes mount into the guest under the same capability that gates the VM itself, with a copy-on-write rootfs so tenants share a base image without writing to it, and an ext4 image writer, written in pure Kern, that produces the disk from a directory.
Scoped Cap<Fs>
fs_scope(fs, root) confines a filesystem capability to a single directory: every path is resolved component by component via openat(O_DIRECTORY|O_NOFOLLOW), so an absolute path, .. or a symlink pointing outside is Err, never a read or write outside. The root is pinned by device and inode, so renaming the directory and planting an impostor at the same path is refused. Scopes nest.
Generational GC
A nursery collects short-lived values without scanning the full heap, auto-GC is on by default, and a write barrier promotes nursery values stored into old-gen collections. Alongside it: HTTP thread pool, str length cache, GC lock elision, zero-copy str.split, in-place list append (the compiler lowers xs = xs + [e] to an append), and single-pass code emission, taking bootstrap from 35 seconds to 14.
C-layer fail-closed sweep
Two systematic passes across every C leaf in HTTP, TLS, sync, event log, KMS, netlink, Redis, MQTT and WebSocket, converting every "succeed on error" path to a fail-closed return. A static-analyser sweep, an init_globals-per-TU fix and a W0003 SSRF lint round out the hardening.