-sending them. Clients and WhatsApp still address only the root. There
-are no messages or tools between parent and child agents. A child's
-saved schedules and subagents can resume at startup. The ready log line
-lists the child names.
+sending them. Clients and WhatsApp still address only the root. A
+child's saved schedules and subagents can resume at startup. The ready
+log line lists the child names.
+
+A message from a parent to its own child enters the child's log as
+``user`` and wakes it. A child's final reply reaches the parent as
+``work`` with the prefix ``[NAME] `` and wakes it. An empty reply sends
+nothing. A busy recipient takes the message between tool calls or in its
+next turn. ``agent/messages.json``, with mode 0600, keeps messages until
+their recipient finishes its turn. A daemon stop preserves queued
+messages and reports for the next start without a second log entry. An
+interrupted turn can repeat its model calls and tools after restart.
+Backups lock this queue with the agent files, including children made
+during the daemon run. The root uses ``tell`` for both children and
+subagents. ``zoom("Name")`` gives a child's view or a subagent's whole
+log. ``spawn`` starts short-lived subagents, not permanent children.