diff --git a/src/platform/redox/mod.rs b/src/platform/redox/mod.rs
index b10573e937..24b65441b6 100644
--- a/src/platform/redox/mod.rs
+++ b/src/platform/redox/mod.rs
@@ -2223,3 +2223,9 @@ unsafe { libredox::fstat(fd, &raw mut st) }?;
         }
     }
 }
+
+// DIAG(temporary, uncommitted): spawn milestone tracer. Raw fd-2 writes so a
+// parked spawn names its last completed phase in the boot log.
+#[inline(always)]
+    let _ = syscall::write(2, m);
+}