+*******
+ Agent
+*******
+
+Start the daemon, and then the client in another terminal:
+
+.. code:: console
+
+ onechat daemon
+ onechat chat
+
+The daemon owns the root agent in ``agent/`` in the data directory and
+listens on the Unix socket ``onechat.sock`` there. In the client, each
+line is a message to the agent, the line ``/stop`` interrupts the
+running turn, the line ``/stop NAME`` stops the subagent NAME, and
+Ctrl-D ends the client. The client shows the replies, the tool calls,
+and the first lines of each tool result as they happen. It also shows
+each message that the user sends from another client, with the client as
+a mark, such as ``[telegram] text``. The daemon is the only process that
+uses the token file while it runs, so ``onechat login`` and ``onechat
+probe`` refuse to start until it stops.
+
+The agent runs commands with bash as the user in its working directory,
+with no sandbox. It has the rights of the user, also on the token file.
+
+When the user asks for it, the agent starts subagents for long tasks.
+Each subagent has a name, such as ``GreenOtter``, and runs in the
+background while the agent answers other messages. It gets the view of
+the agent and its task, and it runs its tools as the agent does, in
+``agent/subagents/NAME/work``. A task in a repository gives the path of
+the repository. The steps of a subagent go to its own log in
+``agent/subagents/NAME``, not to the chat, and its final reply comes
+back to the agent as one message that starts with ``[NAME]``. The agent
+can send a subagent more messages: a running subagent reads them between
+its tool calls, and a finished one goes on from its log, and its reply
+comes back in the same way. When the user stops a subagent, the chat
+gets a note, and the report of the subagent is logged, but it starts no
+turn. Each model call of a subagent has the name in the ``agent`` field
+of ``agent/usage.jsonl``.
+
+``agent/config.json`` holds the settings of the agent. The first start
+writes it with the defaults and a random ID. Do not change the ID: the
+prompt cache key comes from it.
+
+.. code:: json
+
+ {
+ "name": "OneChat",
+ "id": "0123456789abcdef0123456789abcdef",
+ "model": "gpt-6.1-sol",
+ "effort": "medium",
+ "workdir": "/home/user"
+ }
+
+``workdir`` is an absolute path, and its default is the home directory.
+``agent/instructions.md`` holds the user's instructions: who they are,
+how their files are organized, and how they want work done. The prompt
+ends with them, and a change applies at the next call.
+
+**********
+ Telegram
+**********
+
+The daemon also connects the agent to a Telegram bot when
+``telegram.json`` exists in the data directory. It polls the Bot API for
+new messages, so it needs no open port.
+
+#. Make a bot with BotFather and keep its token.
+
+#. Find your numeric Telegram user ID.
+
+#. Write the token and the ID to ``telegram.json``, and give the file
+ mode 0600, because the token is a secret. The daemon refuses the file
+ with any other mode.
+
+#. Start the daemon, open a private chat with the bot, and write.
+
+.. code:: json
+
+ {"token": "123456:ABC-token-from-BotFather", "owner": 123456789}
+
+The bot reads only the private chat of the owner and ignores all other
+updates. Each text message goes to the agent as a user message, the line
+``/stop`` interrupts the running turn, and the line ``/stop NAME`` stops
+the subagent NAME. The bot sends the replies in parts of at most 4096
+characters, with their Markdown as Telegram formats: bold, italic,
+strikethrough, code, code blocks, links, and headings as bold text. When
+Telegram refuses the formats of a part, the bot sends the part again as
+plain text. Each error goes as a short message in plain text. It shows
+the typing action while a turn runs. It does not send the tool calls. It
+sends each message that the user types in the terminal client, with the
+mark ``[terminal]``.
+
+``agent/telegram-offset.json`` holds the ID of the next update. The bot
+moves it past an update only after the message is durable in the log, so
+a restart of the daemon does not lose a message. A crash just after the
+write of a message can make the message repeat once. A network failure
+or a rate limit makes the bot wait and try again, and does not stop the
+daemon.
+