diff --git a/src/broadcaster.zig b/src/broadcaster.zig
index 109a3fd..1356d33 100644
--- a/src/broadcaster.zig
+++ b/src/broadcaster.zig
@@ -628,6 +628,8 @@ pub fn formatPrometheusMetrics(stats: *const Stats, cache_entries: usize, migrat
     return fbs.getWritten();
 }
 
+const malloc_h = @cImport(@cInclude("malloc.h"));
+
 fn appendProcMetrics(w: anytype) void {
     // RSS from /proc/self/statm (field[1] * page_size)
     if (std.fs.openFileAbsolute("/proc/self/statm", .{})) |f| {
@@ -650,27 +652,56 @@ fn appendProcMetrics(w: anytype) void {
         }
     } else |_| {}
 
-    // thread count from /proc/self/status
+    // thread count + memory detail from /proc/self/status
     if (std.fs.openFileAbsolute("/proc/self/status", .{})) |f| {
         defer f.close();
         var status_buf: [4096]u8 = undefined;
         const n = f.readAll(&status_buf) catch 0;
         if (n > 0) {
             const content = status_buf[0..n];
-            if (std.mem.indexOf(u8, content, "Threads:")) |pos| {
-                const rest = content[pos + "Threads:".len ..];
-                const trimmed = std.mem.trimLeft(u8, rest, " \t");
-                const end = std.mem.indexOfScalar(u8, trimmed, '\n') orelse trimmed.len;
-                if (std.fmt.parseInt(u64, trimmed[0..end], 10)) |threads| {
-                    std.fmt.format(w,
-                        \\# TYPE relay_threads_total gauge
-                        \\relay_threads_total {d}
-                        \\
-                    , .{threads}) catch {};
-                } else |_| {}
+            const fields = .{
+                .{ "Threads:", "relay_threads_total" },
+                .{ "VmHWM:", "relay_vm_hwm_kb" },
+                .{ "RssAnon:", "relay_rss_anon_kb" },
+            };
+            inline for (fields) |entry| {
+                if (std.mem.indexOf(u8, content, entry[0])) |pos| {
+                    const rest = content[pos + entry[0].len ..];
+                    const trimmed = std.mem.trimLeft(u8, rest, " \t");
+                    const end = std.mem.indexOfScalar(u8, trimmed, ' ') orelse
+                        (std.mem.indexOfScalar(u8, trimmed, '\n') orelse trimmed.len);
+                    if (std.fmt.parseInt(u64, trimmed[0..end], 10)) |val| {
+                        std.fmt.format(w,
+                            \\# TYPE {s} gauge
+                            \\{s} {d}
+                            \\
+                        , .{ entry[1], entry[1], val }) catch {};
+                    } else |_| {}
+                }
             }
         }
     } else |_| {}
+
+    // glibc malloc arena stats — distinguishes in-use heap from fragmentation
+    const mi = malloc_h.mallinfo2();
+    std.fmt.format(w,
+        \\# TYPE relay_malloc_arena_bytes gauge
+        \\# HELP relay_malloc_arena_bytes total bytes claimed from OS by malloc
+        \\relay_malloc_arena_bytes {d}
+        \\
+        \\# TYPE relay_malloc_in_use_bytes gauge
+        \\# HELP relay_malloc_in_use_bytes bytes actively allocated (in-use heap)
+        \\relay_malloc_in_use_bytes {d}
+        \\
+        \\# TYPE relay_malloc_free_bytes gauge
+        \\# HELP relay_malloc_free_bytes free bytes held by malloc (fragmentation)
+        \\relay_malloc_free_bytes {d}
+        \\
+        \\# TYPE relay_malloc_mmap_bytes gauge
+        \\# HELP relay_malloc_mmap_bytes bytes allocated via mmap (large blocks)
+        \\relay_malloc_mmap_bytes {d}
+        \\
+    , .{ mi.arena, mi.uordblks, mi.fordblks, mi.hblkhd }) catch {};
 }
 
 const posix_vfs = @cImport(@cInclude("sys/statvfs.h"));