diff --git a/build.zig.zon b/build.zig.zon
index 4541c50..2aa8967 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -13,8 +13,8 @@
             .hash = "websocket-0.1.10-ZPISdUowBQAXIl_X9VpZozIxBLVf_o5wYjOMMdobrXF5",
         },
         .zio = .{
-            .url = "https://tangled.org/zzstoatzz.io/zio/archive/6790455.tar.gz",
-            .hash = "zio-0.0.0-psl_OZh_AgBCz_4i-lIoPKs_wybKDL-tereRD7bh6hjo",
+            .url = "https://tangled.org/zzstoatzz.io/zio/archive/1321be0.tar.gz",
+            .hash = "zio-0.0.0-psl_ORGCAgCYCLRsoLjOIdaYZQI0FSlB81xG20_tPWGn",
         },
         .pg = .{
             .url = "https://tangled.org/zzstoatzz.io/pg.zig/archive/c5a5607.tar.gz",
diff --git a/src/main.zig b/src/main.zig
index e41d25f..32d9f83 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -146,7 +146,61 @@ const MetricsServer = struct {
             };
 
             var metrics_buf: [65536]u8 = undefined;
-            const body = broadcaster.formatPrometheusMetrics(self.stats, cache_entries, attribution, self.data_dir, &metrics_buf, self.io);
+            const base_body = broadcaster.formatPrometheusMetrics(self.stats, cache_entries, attribution, self.data_dir, &metrics_buf, self.io);
+
+            // zio runtime internals. a wedged loop, fibers piling up on a
+            // lost wake, or an eroded poller table are otherwise invisible
+            // from outside the process — the 2026-08-04 canary's failure had
+            // to be inferred from what stopped answering. the scrape is the
+            // one forensic channel that survives a pod dying, so put them
+            // there. this handler runs as a fiber on the loop thread, which
+            // is where debugStats() must be called from.
+            var zio_buf: [2048]u8 = undefined;
+            const body = if (comptime backend_config.use_zio) blk: {
+                const d = backend.debugStats();
+                const extra = std.fmt.bufPrint(&zio_buf,
+                    \\# HELP zio_sched_switches_total fiber context switches (flat = loop wedged)
+                    \\# TYPE zio_sched_switches_total counter
+                    \\zio_sched_switches_total {d}
+                    \\# HELP zio_sched_fibers live fibers by state
+                    \\# TYPE zio_sched_fibers gauge
+                    \\zio_sched_fibers{{state="live"}} {d}
+                    \\zio_sched_fibers{{state="ready"}} {d}
+                    \\zio_sched_fibers{{state="parked"}} {d}
+                    \\# HELP zio_sched_futex_waiters fibers parked on futex words (climbing = lost wakes)
+                    \\# TYPE zio_sched_futex_waiters gauge
+                    \\zio_sched_futex_waiters {d}
+                    \\# HELP zio_sched_timers timer heap depth
+                    \\# TYPE zio_sched_timers gauge
+                    \\zio_sched_timers {d}
+                    \\# HELP zio_sched_inject_pending cross-thread messages awaiting the loop
+                    \\# TYPE zio_sched_inject_pending gauge
+                    \\zio_sched_inject_pending {d}
+                    \\# HELP zio_sched_free_fibers recycled fiber structs
+                    \\# TYPE zio_sched_free_fibers gauge
+                    \\zio_sched_free_fibers {d}
+                    \\# HELP zio_poller_registrations fds with an armed direction (collapse = erosion)
+                    \\# TYPE zio_poller_registrations gauge
+                    \\zio_poller_registrations {d}
+                    \\# HELP zio_dns_spill DNS spill pool depth and workers
+                    \\# TYPE zio_dns_spill gauge
+                    \\zio_dns_spill{{kind="queued"}} {d}
+                    \\zio_dns_spill{{kind="workers"}} {d}
+                    \\zio_dns_spill{{kind="idle"}} {d}
+                    \\
+                , .{
+                    d.sched.switches,       d.sched.live,          d.sched.ready,
+                    d.sched.parked,         d.sched.futex_waiters, d.sched.timers,
+                    d.sched.inject_pending, d.sched.free_list,     d.poller_registrations,
+                    d.dns_queued,           d.dns_workers,         d.dns_idle,
+                }) catch "";
+                if (base_body.len + extra.len <= metrics_buf.len) {
+                    @memcpy(metrics_buf[base_body.len..][0..extra.len], extra);
+                    break :blk metrics_buf[0 .. base_body.len + extra.len];
+                }
+                break :blk base_body;
+            } else base_body;
+
             request.respond(body, .{ .status = .ok, .keep_alive = false, .extra_headers = &.{
                 .{ .name = "content-type", .value = "text/plain; version=0.0.4; charset=utf-8" },
                 .{ .name = "server", .value = "zlay (atproto-relay)" },