mallinfo() only reports the main arena, so the dashboard was blind to per-thread-arena fragmentation — the actual shape of the 18:40Z post-burst RSS floor. add relay_malloc_system_bytes / relay_malloc_free_total_bytes / relay_malloc_arena_count, parsed from malloc_info() XML across every arena. validated against real glibc malloc_info output in a container. operator mitigation (MALLOC_ARENA_MAX env, no rebuild) documented in docs/incident-2026-05-30-arena-bloat.md. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>