Deliver routed WhatsApp batches to children

[onechat] / README.rst

#########
 OneChat
#########

OneChat is one AI agent in a single chat that never ends. A daemon owns
the agent and its files, and a terminal client and a Telegram bot talk
to it. It is in early development. Linux is supported.

****************
 Data directory
****************

OneChat keeps its data and its token file in one directory. It uses the
first of these:

#. ``ONECHAT_DIR``, when it is set.
#. ``$XDG_DATA_HOME/onechat``, when ``XDG_DATA_HOME`` is an absolute
   path. A relative value is ignored.
#. ``~/.local/share/onechat``. With no home directory, OneChat exits
   with an error.

OneChat creates the directory with mode 0700.

***************
 Configuration
***************

``config.json`` in the data directory holds the settings. OneChat does
not create it. A missing file or field takes the default, and an unknown
field is an error.

.. code:: json

   {
     "endpoint": "chatgpt",
     "compactor": {"model": "gpt-6.1-sol", "effort": "high"}
   }

``endpoint``
   ``chatgpt`` (the default) sends model calls to the ChatGPT backend
   with the subscription login. ``api`` sends them to the OpenAI API
   with the key in ``OPENAI_API_KEY``, which must then be set. With
   ``chatgpt``, OneChat ignores ``OPENAI_API_KEY``.

``compactor``
   The model and the reasoning effort of the summaries. The defaults are
   ``gpt-6.1-sol`` and ``high``.

*******
 Login
*******

The ``chatgpt`` endpoint needs a login with a ChatGPT account:

.. code:: console

   onechat login

The command shows a link and a code. Open the link on any device, enter
the code, and approve the login. Device code login must be allowed in
the ChatGPT security settings. OneChat writes the tokens to
``auth.json`` in the data directory, with mode 0600, and refreshes them
before they expire. The file belongs to OneChat only. Do not share it
with the Codex CLI, because each program rotates the refresh token and
logs the other out.

*******
 Agent
*******

Start the daemon, and then the client in another terminal:

.. code:: console

   onechat daemon
   onechat

``onechat`` with no command is the same as ``onechat chat``. ``onechat
help`` lists the commands.

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. On terminal output, the client shows ``> ``
after each event while idle and clears it before the next event. An
event can interrupt a line while the user types. The client shows the
replies, the tool calls, and the first lines of each tool result as they
happen. Replies and subagent reports render Markdown with styles and
wrapped tables only when the output is a terminal, and stay unchanged in
a pipe or file. It also shows each message that the user sends from
another client, with the client as a mark, such as ``[telegram] text``.
When a subagent starts, the client shows ``[NAME] started``, and it
shows the whole report of the subagent, which starts with ``[NAME]``,
but not the tool calls of the subagent. 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/work.json`` holds the names of the
running subagents. A subagent that runs when the daemon stops goes on at
the next start: the chat gets the note that the daemon restarted, and
the subagent gets the same note and goes on from its log.

``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. The agent can
propose a change to the file, and it makes the change only after the
user agrees.

A permanent child agent lives in ``agent/children/NAME/`` with the same
files as the root. The root's ``agent_create(name, responsibility)``
tool creates and starts it with the root's model, effort, and working
directory, and a separate random ID. A name describes the area, such as
``House`` or ``Calendar``. It is one word of 2 to 32 ASCII letters,
starts with a capital letter, and cannot name the root, an existing
child, or a subagent. The daemon opens all children at startup. A
missing or invalid child config stops startup. Only one level of
children is supported. Remove a child by hand while the daemon is
stopped. The root's turn state lists each child and its responsibility.
The root passes area messages from mixed chats with sender, date, and
words, and asks the user before it sends a child's draft to WhatsApp.

Each child has its own memory, model client, usage file, subagents,
schedules, and turn loop. Its prompt limits work to its area, asks for
only reports that need the parent or the user, and permits an empty
reply. Children have no WhatsApp tools and draft replies instead of
sending them. Clients 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.

**************
 User service
**************

The Nix package includes ``share/systemd/user/onechat.service``. It runs
``onechat daemon`` from that package, starts at login when enabled, and
restarts 5 seconds after a failure. A stop sends SIGTERM to the daemon
and allows up to 120 seconds for cleanup. Its output goes to the user
journal. The service has the rights of the user, as the terminal daemon
does.

Build a package with a separate result link. Keep this link so that Nix
does not collect the package while the service uses it:

.. code:: console

   nix build --out-link result-service
   systemctl --user link --force "$PWD/result-service/share/systemd/user/onechat.service"
   systemctl --user edit onechat.service

In the editor, set the data directory with this drop-in. Replace
``DATA_DIR`` with an absolute path to the data directory. Set the same
``ONECHAT_DIR`` for each terminal client. Without a drop-in, the data
directory rules above apply to the environment of the user manager, not
to the development shell.

.. code:: ini

   [Service]
   Environment="ONECHAT_DIR=DATA_DIR"

The service does not read the environment of an open terminal. If the
agent needs tools from a shell, set ``Environment="PATH=TOOLS_PATH"`` in
the same drop-in, with ``TOOLS_PATH`` replaced by the complete search
path, including bash. For the API endpoint, use
``EnvironmentFile=ENV_FILE``, with ``ENV_FILE`` replaced by an absolute
path to a mode 0600 file that sets ``OPENAI_API_KEY``. Keep secrets out
of the unit and Nix sources.

Use the existing data directory, or copy the development data before the
first service start. For a copy, first stop the terminal daemon with
Ctrl-C and wait for it to exit. Replace ``DATA_DIR`` below with a new,
empty destination. If the development shell uses a custom
``ONECHAT_DIR``, replace ``.devenv/onechat`` with that source. Copy the
whole directory so that ``auth.json``, ``telegram.json``,
``config.json``, ``agent/``, and ``whatsapp/`` stay together, including
the WhatsApp session and its database files. The copy preserves the file
modes and the source as a backup. Do not copy or use the same data from
two running daemons.

.. code:: console

   install -d -m 0700 DATA_DIR
   cp -a .devenv/onechat/. DATA_DIR/

After the terminal daemon exits and the data is ready, enable and start
the service:

.. code:: console

   systemctl --user daemon-reload
   systemctl --user enable --now onechat.service
   systemctl --user status onechat.service
   ONECHAT_DIR=DATA_DIR ./result-service/bin/onechat
   journalctl --user -u onechat.service -f

After a pull, update the package and unit with:

.. code:: console

   git pull
   bin/service-update

The script builds with the same ``result-service`` link, reloads the
user manager, and restarts the service only if it is active. The unit
link follows ``result-service``, so no new link is needed.

The service starts with the user manager at login, not at boot without a
login. To stop it, or also remove its start at login:

.. code:: console

   systemctl --user stop onechat.service
   systemctl --user disable onechat.service

********************
 Backup and restore
********************

Back up the running daemon to one mode 0600 ``.tar.gz`` archive. The
command prints its path and size in bytes. With no daemon, it fails.

.. code:: console

   onechat backup BACKUP_FILE.tar.gz
   ONECHAT_DIR=EMPTY_DATA_DIR onechat restore BACKUP_FILE.tar.gz

The daemon flushes memory and holds its write locks during the agent
copy. It also flushes and locks the child agents and all subagent logs.
It copies the WhatsApp session with SQLite ``VACUUM INTO``, not as raw
database files. It then compresses the copy and installs the archive
through a temporary file and a rename. Use a backup path outside the
data directory.

The archive includes configuration, instructions, the log, tree,
indexes, views, layout, schedules, subagents, children, Telegram offset,
tokens, and WhatsApp state and session. It excludes sockets, lock files,
``probe/``, and the ``agent-backup-*`` import copies. Links and special
files fail, rather than enter the archive. **The archive holds
secrets**, including login tokens, the Telegram bot token, and the
WhatsApp link. Keep it private. There is no encryption or remote copy.

Restore needs a stopped daemon and an empty destination. It checks the
token lock and validates the archive before it installs files, with
their modes. It rejects unsafe paths, links, and special files. A failed
restore can leave ``auth.lock`` in the destination. Use another empty
directory for a retry. Do not run the source and restored WhatsApp links
at the same time. Check the restored log and view before you use it in
place of the source.

For a daily local archive with the last 14 kept, save this script as
``BACKUP_SCRIPT``. Replace ``BACKUP_DIR`` with a private archive
directory outside the data directory. Replace ``ONECHAT_BINARY`` with
the absolute path through the stable ``result-service/bin/onechat``
package link. Make the archive directory with mode 0700 before you
enable the timer.

.. code:: sh

   #!/bin/sh
   set -eu
   umask 077
   cd BACKUP_DIR
   ONECHAT_BINARY backup "onechat-$(date +%F).tar.gz"
   find . -maxdepth 1 -type f -name 'onechat-????-??-??.tar.gz' -printf '%f\n' |
     sort -r | tail -n +15 |
     while IFS= read -r file; do
       rm -- "$file"
     done

Save these units as ``onechat-backup.service`` and
``onechat-backup.timer`` in the systemd user unit directory. Replace
``DATA_DIR`` and ``BACKUP_SCRIPT`` with absolute paths. The service uses
the daemon unit from User service above.

.. code:: ini

   [Unit]
   Description=Back up OneChat data
   Requires=onechat.service
   After=onechat.service

   [Service]
   Type=oneshot
   Environment="ONECHAT_DIR=DATA_DIR"
   UMask=0077
   ExecStart=/bin/sh BACKUP_SCRIPT

.. code:: ini

   [Unit]
   Description=Back up OneChat each day

   [Timer]
   OnCalendar=daily
   Persistent=true

   [Install]
   WantedBy=timers.target

Enable the timer with the user manager. A failed backup leaves the
existing archives in place and skips removal of old archives.

.. code:: console

   systemctl --user daemon-reload
   systemctl --user enable --now onechat-backup.timer
   systemctl --user list-timers onechat-backup.timer

************
 Daemon log
************

The daemon writes short events with the part prefix and ordered
``key=value`` attributes. An error cause comes last. Normal events use
info, failures that can be retried or lose nothing use warning, and
failures that lose data or stop work use error.

With ``JOURNAL_STREAM`` set, each line carries a syslog priority without
a time stamp or level word. The user journal can show only warnings and
errors:

.. code:: console

   journalctl --user -u onechat -p warning

The summary warning names its node. A schedule run has ``late`` only
when it ran late:

.. code:: text

   <4>onechat: summary failed level=0 index=0: fake failure
   <6>onechat: schedule ran id=1
   <6>onechat: schedule ran id=2 late=1m0s

Outside the journal, each line starts with the time stamp and level.

**********
 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.
For a subagent it sends only ``[NAME] started`` and ``[NAME] finished``,
``[NAME] stopped``, or ``[NAME] failed``, because the reply of the agent
carries the content of the report. 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.

**********
 WhatsApp
**********

The daemon connects to the WhatsApp account of the user as a linked
device. The terminal client and Telegram take three commands:

``/whatsapp pair PHONE``
   Links the account of PHONE, the number with its country code, such as
   ``+15550001111``. The daemon answers with the steps and then with a
   pairing code in its own message: in WhatsApp on the phone, open
   Linked devices, tap Link a device, then tap Link with phone number
   instead, and enter the code. The code expires in about 2 minutes, and
   the same command gives a new code. When the link succeeds, the daemon
   answers with the linked number. Linked devices on the phone shows the
   device as OneChat. The name applies at the pairing, so an existing
   link keeps its old name until ``/whatsapp unlink`` and a new
   ``/whatsapp pair PHONE``.

``/whatsapp status``
   Shows the link: not linked, linked and connected, or linked and
   disconnected, with the times of the connection and the WhatsApp
   routes.

``/whatsapp unlink``
   Ends the link and deletes the session. When WhatsApp is disconnected,
   the phone does not get the logout, so remove the device in Linked
   devices on the phone.

The answers go only to the client that asked, and the commands do not go
to the agent, so the agent never gets the phone number or the code. The
chat gets only the notes that WhatsApp is linked or unlinked.

The session is ``whatsapp/session.db`` in the data directory, with mode
0600 in a directory with mode 0700. It gives full access to the WhatsApp
account, so the daemon refuses the file when its mode is not 0600. The
shell of the agent runs as the user, so it can read the session. If the
session leaks, remove the linked device in WhatsApp on the phone, and
the session stops working. Without the file, WhatsApp is not linked.

The daemon reads the text messages of the private chats and the groups,
from other people and from the user. It does not read media, reactions,
edits, deletions, view-once and disappearing messages, or the history
from before the link. The messages of one chat form one batch until the
chat is quiet for 20 seconds, for 2 minutes or 50 messages at the most.
Each batch goes to the chat of the agent as one work message that starts
with ``[WhatsApp]``, with the name and the ID of the chat, and the time,
the sender, and the text of each message. The messages of the user show
as ``You``. ``whatsapp/state.json``, with mode 0600, keeps the batches
that are not in the chat yet, so they survive a restart, and the records
of the sends. A crash just after a batch goes to the chat can make the
batch repeat once.

A batch of a private chat with a message of another person starts a
turn, and so does a batch of a group with a message that mentions the
user or replies to a message of the user. The other batches go to the
chat with no turn, and the agent sees them at its next turn. A batch
that starts a turn ends with a line that tells the agent to end its turn
with an empty reply when nothing in the batch needs the user. No client
shows an empty reply, so such a batch gives no message in Telegram. The
terminal client shows each batch, and Telegram shows none.

The phone number of the user never goes to the chat: a mention of the
user shows as ``@you``, the number shows as ``OWN``, and the chat of the
user with itself is not read. But the IDs of the other chats go to the
chat and to the model, because the agent needs them to send. The ID of a
private chat holds the phone number of the contact, such as
``15550002222@s.whatsapp.net``, and the ID of a group can hold the
number of the person who made it.

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 unrouted batches to the root
in one turn, not one turn for each chat. Routed batches wake their
child. 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.

Each batch of a group goes to the chat, also with no turn, and the
memory tree summarizes it with model calls, which use the quota.

The root manages source routes with ``route(source, agent)``,
``unroute(source)``, and ``routes()``, only after the user agrees. A
source is ``whatsapp:CHAT-ID``, with the ID from ``whatsapp_find`` or a
``[WhatsApp]`` message, and the agent must be its child. The root keeps
the map in ``agent/routes.json`` with mode 0600. Children and subagents
have no route tools. There is no command to change routes. Each routed
batch enters only its child's log and wakes it, including a group batch
with no mention. The durable agent queue prevents a second log entry
after a restart. An unrouted source or a missing child uses the root. A
queued batch whose child is removed while stopped goes to the root.

When the session holds a linked device, the daemon connects at its
start. If the first connection fails, it tries again after 2 seconds,
then doubles the wait up to 5 minutes. The inbox and commands stay
active during each wait. An unlink or a logout stops these retries.
After a network failure of an open connection, the library connects
again by itself. When a disconnection lasts 10 minutes, all clients get
one notice, and one more when the connection comes back. When WhatsApp
ends the connection for good, for example because another program uses
the same session, all clients get a notice at once. When the user
removes the device in the phone, the daemon deletes the session and
tells all clients one time.

*************************
 Import WhatsApp history
*************************

Stop the daemon and finish all subagents before an import. Export each
chat from WhatsApp as a ZIP with ``_chat.txt``. Keep the chat name in
the ZIP name, such as ``WhatsApp Chat - Example.zip``. Read the plan
first:

.. code:: console

   onechat import -n CHAT.zip OTHER.zip
   onechat import CHAT.zip OTHER.zip

``-n`` makes no model call and prints the chats, chat-day batches, local
dates, cutoff, text bytes, merged message count, and estimated calls.
The import keeps multiline text, system lines, and omitted-media
markers. It maps the session's profile name to ``You``. Without that
name, it keeps the senders as written and says so in the plan. An exact,
unambiguous local contact or batch name supplies the chat ID when known.
No network lookup is made.

Each chat and local day becomes one work message marked ``(imported)``.
Only messages before the first message of the earliest live WhatsApp
batch enter the import. Live times have minute precision, so the cutoff
excludes that whole minute. A chat-day already imported is skipped.
Overlapping chat-days in the supplied ZIPs are refused. Review the
exports before import: their text goes to the model as chat history.

The import merges the full log in date order and builds its tree with
real compactor calls, the agent prompt, and the agent cache key. It uses
a limit of 1,500 calls and the probe's 15-quota-point limit, and prints
the same usage report. Its estimate is about 1.3 calls per merged
message, not a cost guarantee. A stopped or failed run leaves the agent
unchanged. A new run starts over. Success keeps the other agent files
and renames the old directory to ``agent-backup-TIMESTAMP`` before it
installs the new one. Keep the backup until the new memory is checked,
then start the daemon. Message IDs change to their positions in the
merged log.

***********
 Schedules
***********

The agent sets reminders and timed tasks when the user asks for them,
such as "remind me tomorrow at 9" or "every weekday at 8, tell me what
my WhatsApp groups talked about". A schedule has a text, the task for
the agent, and either one time or a cron expression. The agent also
lists the schedules with their next times, and removes one when the user
asks. The root and its children have the schedule tools, not their
subagents. Each schedule records its owner and wakes only that agent.

A cron expression has five fields: minute, hour, day of month, month,
and day of week, where 0 and 7 are Sunday. A field is a comma list of
``*``, ``N``, and ``N-M``, and ``*`` and ``N-M`` can have a step ``/S``,
as in ``0 8 * * 1-5`` or ``*/15 9-17 * * *``. When both day fields start
with something other than ``*``, a day matches when either field
matches. Names such as ``MON``, macros such as ``@daily``, the
characters ``? L W #``, and ``N/S`` are refused. The runs must be at
least 5 minutes apart, because each run is a full turn that uses the
quota, so ``*/5 * * * *`` is the shortest schedule.

The times use the time zone of the machine. A time that the clock skips
at the start of daylight saving time runs later by the length of the
skip. A time that the clock repeats at its end runs once, at its first
occurrence.

At its time, a schedule goes to the chat as a work message that starts
with ``[Schedule ID]``, with its time and its text, and it starts a
turn. The message ends with a line that tells the agent to end its turn
with an empty reply when nothing needs the user. The terminal client
shows the message, and Telegram shows only the reply. After its run, a
one-time schedule goes, and a repeating schedule gets its next time.

``agent/schedules.json``, with mode 0600, holds the schedules. Each
change writes it before the tool answers, so the schedules survive a
restart. A schedule that came due while the daemon was stopped runs once
at the next start, with its original time and a line that says that the
run is late. A repeating schedule that missed several times runs once. A
crash just after a run goes to the chat can make the run repeat once.

*******
 Probe
*******

``onechat probe LOG COUNT [BUILDS]`` measures the compactor on a log. It
appends the first COUNT messages of LOG, one JSON object ``{"kind",
"text"}`` on each line, to a new chat in ``probe/`` in the data
directory, and builds its tree with real model calls. The calls use the
quota of the account. The run stops at the first failed call, after 660
calls, or when the used percent of a quota window grows by more than 15
points. At the end it reports the calls per message, the cached share of
the input tokens, the retries, the line sizes, and the quota at the
first and the last call. BUILDS, from 1 to 8, limits the model calls at
once in the run.

A test writes a generated log of readable made-up messages:

.. code:: console

   ONECHAT_PROBE_LOG=probe.jsonl go test -run TestProbeLogHasTheSyntheticMix

*************
 Development
*************

Nix supplies the Go toolchain and all tools. Enter the development shell
with direnv:

.. code:: console

   direnv allow

Or enter it directly:

.. code:: console

   nix develop

The shell sets ``ONECHAT_DIR`` to ``.devenv/onechat`` in the checkout,
unless it is already set. Development data goes there, and Git ignores
``.devenv``.

Build and run:

.. code:: console

   nix build
   ./result/bin/onechat

``onechat version`` prints ``yyyy-mm-dd-gitshort`` for a Nix build, adds
``-dirty`` for a dirty tree, and prints ``dev`` for a direct Go build.

Format and check all files:

.. code:: console

   bin/format
   bin/check
   nix flake check

``bin/check`` and ``nix build`` run a short replay of the synthetic log.
``nix flake check`` also runs the full replay of 100,000 messages.