+While the daemon is stopped or disconnected, the WhatsApp servers keep
+the messages for the linked device and send them at the next connection.
+They keep them only for a limited time, so a long stop can lose
+messages. These messages form batches by their original times, as live
+messages do. The daemon waits for the end of this catch-up, or one
+minute at the most, and then gives all its batches to the agent in one
+turn, not one turn for each chat. The batches of ``whatsapp/state.json``
+at the start wait for the first catch-up in the same way.
+
+The agent finds a chat with the tool ``whatsapp_find``: it gives the
+contacts and the groups whose name holds a text, with no regard to case
+and accents, with their IDs. The names of the contacts come from the
+session, and the names of the groups from WhatsApp, kept in memory for
+one hour. The names arrive from the phone some minutes after the link,
+and until then the tool says that they are not ready. The agent sends a
+text message with the tool ``whatsapp_send``, only when the user asks
+for it. Each send has an ID that the agent gives: a repeated call with
+the same ID gives the answer of the first call and sends nothing. The
+state file keeps the last 1000 send records. When the daemon stops
+during a send, the result is not known, and the tool tells the agent to
+ask the user to look at the chat in WhatsApp. Without a link, both tools
+tell the agent to ask the user to run ``/whatsapp pair PHONE``. Only the
+agent has the WhatsApp tools, not its subagents.
+