diff --git a/status_panel.py b/status_panel.py
index 119309d..16b4fe5 100644
--- a/status_panel.py
+++ b/status_panel.py
@@ -845,7 +845,7 @@ def check_identity(chk):
 
 def write_json(path, obj):
     """Write a small JSON file in one go (a reader never sees half of it)."""
-    tmp = path + ".tmp"
+    tmp = "%s.%d-%x.tmp" % (path, os.getpid(), threading.get_ident() & 0xFFFF)   # one per writer: two threads never trip over one file
     with open(tmp, "w") as f:
         json.dump(obj, f, indent=1, sort_keys=True)
     os.replace(tmp, path)
@@ -2290,11 +2290,21 @@ def stream_remote_midi(snap, cfg, host, stop):
                                     stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL, text=True)
             proc.stdin.write(script)
             proc.stdin.close()
+            empty_since = None
             for line in proc.stdout:
                 data = parse_remote_midi(line)
                 if data is not None:
                     snap.remote_midi[host], snap.remote_midi_time[host] = data, time.time()
                     remember_peers(snap, host, data)
+                    # A reader started while that Mac was still at the login window never sees the
+                    # user's MIDI sessions: it reports none, for ever. Start again after a minute of nothing.
+                    if data == {}:
+                        empty_since = empty_since or time.time()
+                        if time.time() - empty_since > 60:
+                            log.info("MIDI stream from %s reports no sessions for a minute: reconnecting", host)
+                            break
+                    else:
+                        empty_since = None
                 if stop.is_set():
                     break
         except (OSError, ValueError) as e: