diff --git a/nix/host-modules/swarm-otel.nix b/nix/host-modules/swarm-otel.nix
index b79258aa..f3294def 100644
--- a/nix/host-modules/swarm-otel.nix
+++ b/nix/host-modules/swarm-otel.nix
@@ -1107,10 +1107,12 @@ in
                 # "everything except user sessions" is not expressible.
                 #
                 # Attribution is journald's either way — these fields are
-                # written by it rather than by the logging process. ⚠️ But
-                # `_MACHINE_ID` is the only one that separates containers:
-                # none sets `networking.hostName`, so `_HOSTNAME` is the
-                # NixOS default `nixos` everywhere but the host itself.
+                # written by it rather than by the logging process. ⚠️ Use
+                # `_MACHINE_ID` to tell machines apart, not `_HOSTNAME`: an
+                # agent container reports the NixOS default `nixos`. Whether
+                # every container does, and why the `networking.hostName`
+                # nixos-containers sets does not reach them, is unresolved —
+                # so rely on the field that is per-machine by construction.
                 // lib.optionalAttrs collectLogs {
                   journald = {
                     directory = hostJournalDir;
@@ -1158,11 +1160,13 @@ in
                 # literal `missing _msg field` as its message and text search
                 # finds nothing, while ingest keeps answering 200.
                 # `_stream_fields` is one stream per unit per machine.
-                # `_MACHINE_ID` is what makes that true: `_HOSTNAME` reads
-                # `nixos` in every container, so naming it alone merges every
-                # container's stream for a unit name into one — which is how
-                # two collectors sharing `opentelemetry-collector.service`
-                # became one series.
+                # `_MACHINE_ID` is what makes that true — it is per-machine by
+                # construction, where `_HOSTNAME` is only as distinct as the
+                # hostnames happen to be, and an agent container's is the
+                # NixOS default `nixos`. Keying on the hostname alone merges
+                # the streams of any two machines sharing one, which is what
+                # the host and containerised `opentelemetry-collector.service`
+                # would do.
                 "otlphttp/victorialogs" = {
                   logs_endpoint =
                     logsPushUrl + "?_msg_field=MESSAGE&_stream_fields=_HOSTNAME,_MACHINE_ID,_SYSTEMD_UNIT";