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* Isolate seccomp workload in nested PID namespace and block io_uring apply-seccomp now creates a nested user+PID+mount namespace before applying the seccomp filter. The user command runs as PID 2 under a non-dumpable PID 1 reaper, with /proc remounted so only the inner process tree is visible. This prevents the sandboxed command from ptracing or patching the unfiltered bwrap init, bash wrapper, or socat helpers via /proc/N/mem, regardless of the host's kernel.yama.ptrace_scope setting. Namespace setup failure aborts rather than silently degrading. The BPF filter now also blocks io_uring_setup/enter/register. IORING_OP_SOCKET (Linux 5.19+) creates sockets without going through socket(), and seccomp cannot inspect SQEs in the shared ring, so denying ring creation entirely is the only safe option. The filter generator now accepts an optional target-arch argument so a single builder can emit both x64 and arm64 filters. Prebuilt binaries and filters are regenerated for both architectures. * Pass CAP_SYS_ADMIN to apply-seccomp and clear ambient caps before exec apply-seccomp needs CAP_SYS_ADMIN to unshare PID+mount namespaces. The original approach obtained it via unshare(CLONE_NEWUSER), but on hosts where an LSM restricts unprivileged user namespaces (Ubuntu 24.04 with AppArmor defaults), the nested userns is created without capabilities and the setgroups write fails. bwrap now passes --cap-add CAP_SYS_ADMIN (scoped to its user namespace) so apply-seccomp can unshare directly. The nested-userns path remains as a fallback for standalone invocation. apply-seccomp clears the ambient capability set after remounting /proc, so the sandboxed command's execve drops to zero capabilities and cannot umount /proc to reveal the outer mount underneath. Two new tests cover CapEff=0 and umount denial. * chore: bump version to 0.0.44 * Add --unshare-user so --cap-add works with setuid bwrap Setuid bwrap rejects --cap-add from non-root because it would grant real host capabilities. --unshare-user forces user-namespace mode so the capability is scoped to that namespace and the flag is accepted. * Disable AppArmor userns restriction in CI instead of using setuid bwrap Setuid bwrap rejects --cap-add from non-root, so that path is a dead end. Instead, disable kernel.apparmor_restrict_unprivileged_userns in CI so apply-seccomp's nested-userns path works without any bwrap cooperation. This matches what production Ubuntu 24.04 users need to do anyway, now documented in the README. * Exit inner init as soon as the worker exits reap_until was waiting for all children including orphaned background processes reparented to PID 1, which hung the sandbox when the user command backgrounded something long-running and then exited. Return immediately when the worker terminates; PID 1 exiting tears down the namespace and SIGKILLs any stragglers.