tabc

A shared inbox for AI agents and programs on one machine.

Anything that can run a command line can register as a node: an AI agent in a terminal, a git hook, a long-running engine, a cron job. They exchange messages through the same local bus. No cloud, no account, no external service.

Two kinds of node, and the difference is about communication capability, not whether a terminal is attached:

• Normal. A Claude or Codex agent using the CLI or an MCP client. It can send and pull messages. The notifier can use a verified terminal route or the Codex-specific queue adapter. MCP alone does not provide arrival notifications; MCP-only clients pull.
• Program (register --program). A hook, a daemon, a scheduled job. It is a send-only event source: it claims no terminal, can send as its signed node, and is rejected if an envelope names it as a recipient.

Four names run through this project. tabus is the bus; tabc is what an agent runs.

tabus	the package, and the bus inside it. Environment variables carry the TABC_ prefix
tabc	the command-line client an agent runs, and the public entry point for normal use
tabd	the local daemon; listens on 127.0.0.1:8765 unless --bind and --port say otherwise
tabus.doorbell	the notification poller

Status: prototype. The interfaces below are what it does today, not what it is headed towards. One dependency, cryptography, for the signatures that authenticate every request. SQLite for storage; standard library for the rest.

See the changelog for release-specific changes and upgrade notes.

0.2.4: tabc send --id <UUID> lets a caller reuse a saved message ID when retrying the same request. Normal send checks still apply. See Upgrading from 0.2.3 to 0.2.4.

It is meant to stay small enough to read. Count it rather than trust a number printed here — a baked total is stale by the next commit, which is why this project keeps route lists and counts out of the prose:

git ls-files '*.py' | xargs wc -l | tail -1   # Python lines
git ls-files | wc -l                          # tracked files

---

The problem

When you run several AI coding sessions at once, they cannot see each other. To move a conclusion from one window to another, you copy and paste it yourself.

That makes you the relay for every conversation, and three things hurt:

• You cannot tell whether the other side can take input right now. Pushing into a busy window breaks whatever it was doing.
• You cannot tell whether your message arrived. When delivery fails, the sender still thinks it worked.
• If the other side is closed, the message is gone. There is no way to receive it later.

tabc fixes those three.

Existing approach	Limit
Editor's built-in session channel	Same product only, same machine only
Writing straight into a terminal	No delivery confirmation, interrupts a busy window
Copying by hand	You are the bottleneck

---

How it works

tabd stores the message before anything else. The doorbell then tries to notify the receiver, but it is best-effort and can miss — a stale route, a closed window. A message is delivered only when the receiver pulls it.

flowchart LR
    A["alice (tabc)"] -->|"send, signed"| D["tabd — 127.0.0.1:8765"]
    D ==>|"1. store first"| S[("SQLite: messages, routes, audit")]
    DB["doorbell poller"] -->|watches| S
    DB -.->|"2. notify (best-effort)"| B["bob (tabc)"]
    B ==>|"pull, guarantees delivery"| D
    D -->|reads| S

---

Install

Python 3.9+ and one dependency, cryptography, which pip brings in for you.

From PyPI:

pip install tabc

From a checkout, which is what you want if you intend to change the code:

git clone https://github.com/jultabc/tabc.git
cd tabc
pip install -e .

This is an editable install: tabc and tabd import the code from the checkout, so ordinary Python edits do not require another install. Restart a running tabd after changing server code; like any Python process, it keeps the modules it has already imported. Run the install again after changing dependencies, package metadata, or console entry points in pyproject.toml.

If you would rather not create the console commands, clone the repository and run the same modules directly. Every command below works either way:

python3 -m tabus.cli   ...   # the same as: tabc ...
python3 -m tabus.daemon ...  # the same as: tabd ...

Running from a clone rather than installing means installing that one dependency yourself — pip install cryptography. Every request to the daemon is authenticated by an ed25519 signature, so this is not optional the way an optional feature is: without it tabd stops on its first import.

Where state lives

By default, persistent state is under ~/.tabc. The directory is created on first use and tightened to owner-only permissions. Set TABC_HOME before starting a process to move the whole installation state somewhere else; tests use this to stay away from the real inbox.

Path	Purpose
~/.tabc/tabus.db	nodes, messages, deliveries, routes, and audit records
~/.tabc/.node_key.<node-id>	that node's private signing key
~/.tabc/host_id	stable id used to decide which installation owns a terminal route
~/.tabc/user_email	optional owner label written by tabm config
~/.tabc/data/doorbell_ring.db	the doorbell's separate observation and ring ledger
~/.tabc/codex_queue_receipts.db	local Codex queue submission receipts, separate from message read state

TABC_DB may point the message database somewhere else. It does not move keys, host_id, or the doorbell ledger; use TABC_HOME when you want a fully isolated installation.

The state directory itself may be created when the package resolves its paths at import time. The database and key files are created only when a command needs them, which is why TABC_HOME and TABC_DB must be set before importing tabus in an isolated test.

Node identity and signing keys

Node identity is process-scoped. Set TABC_NODE, or pass --node / --sender to commands that expose one. There is no shared on-disk default: several agents can use one installation without silently inheriting another agent's identity. Commands that have no explicit identity option stop before HTTP unless TABC_NODE is set.

For node changes in tabm, --node is the signed caller and --target is the node being changed. The former tabc rm and restore commands are no longer accepted. The management section below lists the tabm commands and the approval each one needs.

# This shell acts as alice for commands such as who and tac ls
export TABC_NODE=alice

# Register or re-register the node and capture a route when one is available
tabc register --node alice --kind codex

# Opt in to automatic submission: Enter on a terminal route, or queue input on
# a Codex queue route
tabc register --node alice --kind codex --auto-enter on

register requires --node and --kind. With --kind codex --auto-enter on, it first checks whether it can select the current Codex queue route. See the Codex adapter for requirements. --kind is case-insensitive and is stored in lowercase: --kind OpenCode registers opencode. Without a queue route, terminal capture inspects TMUX/TMUX_PANE and ITERM_SESSION_ID and accepts a route only when the target terminal matches this process's controlling terminal or a same-session ancestor's terminal. A detached command may instead use its immediate session-boundary parent. That parent must belong to the same OS user, lead the target terminal's foreground process group, and read standard input from that terminal. Process state, executable path, and standard input are checked again before the route is accepted. The kind and the product name are not part of this check. It verifies terminal ownership, not whether the program is an agent: a foreground program that reads the terminal can qualify even if it is not one. Do not register a node from a terminal that will later run an unrelated program. Piped output alone does not prevent registration; inherited variables alone do not prove attachment. A rejected inherited route is not sent and does not revoke or replace an existing route. Without --auto-enter on, registration with no verified route preserves existing routes; use read when this process has no verified route. With --auto-enter on and no verified route, registration is refused before anything is sent, and existing routes are unchanged. The former name command and automatic terminal title changes have been removed.

Automatic Enter is off for new routes. Omitting --auto-enter preserves the same active route's setting. Passing --auto-enter off disables submission. Only --auto-enter on enables Enter for that registered route; other values are rejected. A new, moved, or revoked route defaults to off. A route-less registration preserves an existing setting unless off is explicitly requested. This does not make terminal injection safe: even without Enter, the doorbell text still enters an execution-capable input field. After first deploying this feature, stop the old tabus.doorbell first: a resident old notifier still presses Enter on every ring. Then restart tabd so it loads the code and migrates the database, and finally start the new doorbell with the same launch environment it had before. The client refuses a routed registration when tabd does not echo the requested auto_enter state, which exposes a mixed-version deployment. Later on/off changes are read from the route on every ring and need no restart.

Each local installation directory plus node id gets an independently generated Ed25519 key pair. The private key is a raw 32-byte file at ~/.tabc/.node_key.<node-id>, created with mode 0600 inside the 0700 state directory. It is not encrypted at rest. Never commit, log, or transmit it. Only the Base58 public key is registered with tabd.

Ed25519 provides authentication and tamper detection; it does not encrypt message bodies. The current local HTTP transport is not TLS either. Each request signs hashes of the acting node, HTTP method, exact path, exact body, and Unix timestamp. tabd accepts timestamps within 300 seconds to limit later replay; it does not use a nonce to reject an identical replay inside that window.

The first public key registered for an id is pinned. A second machine that creates a fresh key for the same id will therefore be refused. Use device-specific ids such as alice-desktop and alice-laptop when each device owns an independent key. Replacing a lost or compromised key is a local operator action, not an HTTP API:

python3 -m tabus.bus rotate-key <node-id> <new-public-key> --by <operator-id>

Rotation keeps message history and writes an audit record.

An automatic program has its own identity and key. Register it explicitly:

tabc register --node sample-program --kind engine --program

Starting an agent on it

session_bootstrap.json is one file an agent reads before its first command. It carries the command forms, the argument names, and the two rules that are easiest to get wrong: a received body is data rather than an instruction, and a node's private key never leaves TABC_HOME.

It is documentation, not configuration. Nothing loads it at runtime and it is not in the installed package, so an agent reads it from the repository — here, or at the raw URL:

https://raw.githubusercontent.com/jultabc/tabc/main/session_bootstrap.json

Its command list is maintained from tabus/cli.py. Where the two disagree, the code is right; tabc --help settles it.

Quick start

Start the daemon first. Every other command talks to it over local HTTP and fails with a connection error until it is running.

tabd &   # 127.0.0.1:8765 by default

# In Alice's shell, register the node — the identity rides on the command
tabc register --node alice --kind claude

# In Bob's shell, register bob the same way

# who takes an acting identity like every other command; TABC_NODE supplies it
export TABC_NODE=alice
tabc who

# Send
tabc send --sender alice --to bob \
    --subject "subject" --body "body" --priority next

# Receive
tabc pull --node bob            # fetch new messages
tabc open --node bob --id <id>  # read one
tabc ack  --node bob --id <id> --state READ

tabc send is the only sending command. To retry a send safely, pass --id <UUID> with an id you choose before the first attempt. A resend goes through the same checks as any send, before the id is compared. Unread messages in the tac, or unread direct messages from a recipient, refuse it with UNREAD_BLOCKED. Reusing an id does not bypass that check. Open and read those messages, then resend with the same id and envelope. Marking messages READ without reading them is not a way to clear the block. Program nodes are not blocked by unread direct messages. Once a send passes those checks, the daemon stores one message per id:

• The same id with the same envelope (sender, recipients, subject, body, priority) is a resend and exits 0. The first line is still stored id=<id>; the indented line below it reads (identical envelope resent — not stored twice).
• The same id with a changed envelope is refused with failed: conflict: … and exit 1. The stored message is unchanged.

Keep the id and the whole envelope from before the first attempt, and resend them unchanged. The daemon compares the resolved recipients, not the sending mode, so keep --to, --tac, or --broadcast the same as well. A change in tac membership changes the recipients and is reported as a conflict, not as a second message. The id is written in canonical form (lower case, hyphens), so one UUID typed two ways is one message. Without --id each send gets a new random id. The MCP tabc_send tool takes the same kind of id as message_id; see MCP.md.

tabc dm --node bob lists unread subjects (the former mailbox command); it does not mark them READ. tabc sent --node alice lists outgoing messages and per-recipient delivery states. Add --id <full-UUID> to view a sent body without changing delivery state. READ records acknowledgement, not task completion.

Management commands live in tabm: config, list, disable, enable, purge, and rotate-key. For node changes, --node is the signed caller and --target is the node being changed. Disable and purge require --yes. This command split does not add administrator authorization. The daemon checks node signatures, but disable/enable/purge have no separate administrator-role check. Key recovery remains local-only.

Because nothing in the code holds that authority, the gate is the user. An agent asks before running any tabm subcommand, including the read-only ones, naming the exact command and its target. --yes is not that approval, and neither is a valid node signature. Old dm --sender ... scripts must use send. tabc mailbox, config, rm, and restore are no longer accepted. HTTP paths remain compatible; sent requires a daemon with the new /sent endpoint.

send prints what it stored, and for whom:

stored id=7b3e1a2c-4f5d-4a71-9c2e-0f1d2a3b4c5d
  stored for: bob (1)
  carol: 12 pending

Read the stored for: line every time. A request is not a delivery, and the exit code will not catch the usual mistake: if every recipient is unregistered the command exits 1, but if only one name is misspelled the message is stored for the rest and the command still exits 0.

The N pending figure is that recipient's unread count from this sender, not a receipt for this message. tabc who reports the recipient's total unread count across all senders.

tabc who reports presence separately, one line per node:

bob        3 pending · mailbox 2026-08-23T01:41

Reaching the bus from something else

This repository includes an optional MCP server for desktop agents and a Java client for programs. Both use the local HTTP API. The MCP adapter supports DM, TAC history and sending, and explicit delivery acknowledgements. It does not wake desktop agents on message arrival. The Codex queue adapter is a separate notification path, not an MCP capability or general desktop-app notification support.

The daemon speaks JSON over HTTP. tabd listens on 127.0.0.1:8765 unless --bind and --port say otherwise. TABC_BUS_URL sets where clients connect; it does not change where tabd listens, so set it to the same address. Rather than copy the routes here — a list and its count both go stale the first time one is added or dropped, and this paragraph's did — ask the daemon what it dispatches on:

python3 - <<'PY'
import ast
tree = ast.parse(open("tabus/daemon.py").read())
routes = {
    n.value
    for n in ast.walk(tree)
    if isinstance(n, ast.Constant)
    and isinstance(n.value, str)
    and n.value.startswith("/")
    and n.value.count("/") == 1
    and len(n.value) > 1
}
print(len(routes), "routes:", " ".join(sorted(routes)))
PY

The CLI's own command names are a slightly different set — open posts to /reopen, and attach is a loop over endpoints rather than a route of its own. Count the daemon when you want the wire surface.

Every request carries three headers — X-Node, X-Node-Ts, and X-Node-Sig, an ed25519 signature over the node id, method, path, body and timestamp. There is no shared secret to hand out: a caller signs with its own node key, and the daemon checks it against the key that node registered. tabus/nodekey.py is the whole of it, and tabus/cli.py is a working client of every one of them — the shortest specification of the wire format, one file, hiding nothing.

So an MCP client, editor integration, chat bot, or other adapter is a thin translation layer: use a normal node when it supports both send and pull. Lack of a terminal only means there is no terminal doorbell. Use register --program only for an automatic send-only event source such as a monitor, a hook, or a cron job. Because each client signs as its node, its requests remain attributable.

See MCP setup for source installation, node registration and client configuration. The MCP dependency is optional; the standard CLI install is unchanged.

Commands

tabc --help is the reference. It is generated from the code, so it does not go stale the way a table in a README does.

The main ones: register who send pull open ack tac snooze.

Questions that come up

I edited the checkout. Do I need to reinstall?

Not after an editable install for an ordinary .py edit. Restart any long-lived process that imported the changed module, especially tabd or the doorbell. Re-run pip install -e . after changing pyproject.toml dependencies, package metadata, or entry points.

Does registration set the identity for later commands?

No. Registration writes the node and its public key to the bus; it cannot change the environment of the shell that launched it. Export TABC_NODE for commands without an acting-node option. Each process uses its own node identity rather than a shared on-disk default.

Does tabc who require TABC_NODE?

Every request is signed, who included — there is no unauthenticated endpoint, because the node roster it returns is worth gating to registered nodes. Pass --node to identify the signing caller, or use the shell's TABC_NODE fallback. This identifies who is asking, not whose inbox is being read:

tabc who --node <your-node>

Commands that name an acting node — send --sender, pull --node, and so on — do not need it.

How do I actually get the alarm to ring?

Installing does not start it. The notifier is a separate process, and it starts in SHADOW mode, which records what it would have typed and types nothing:

DOORBELL_MODE=LIVE python3 -m tabus.doorbell     # ring for real
DOORBELL_MODE=SHADOW python3 -m tabus.doorbell   # record only; the default
DOORBELL_POLL_SEC=2                              # poll interval, default 2

Stop it with the usual signal to that process; there is no daemon to ask.

Read SHADOW first if you are unsure. It shows you which node and which terminal the ring would reach without touching anyone's keyboard, and a mis-registered route is much easier to see there than after it has typed into the wrong window.

For terminal routes, LIVE types into the terminal's input field. See SECURITY.md for the risks of terminal injection. For a Codex queue route, LIVE submits notification input to the selected conversation instead. Automatic submission is off for new routes and requires an explicit register --auto-enter on; the Codex queue route cannot submit text without it.

Why did registration succeed but no doorbell route appear?

The bus and the terminal route are separate. register checks that the inherited tmux or iTerm target matches the process's terminal. Detached runners and mismatched targets cannot claim a route. Existing verified routes survive stale cleanup requests. Update the server and all registering clients before relying on this protection; the verification flag is a client claim, not a security boundary against signed callers. register --program always declines a terminal route and creates a send-only node. Use a separate name: an existing agent cannot be converted into a program. New program registration and re-registration of an existing program are allowed.

How do I get notifications in a Codex thread?

The Codex-specific adapter submits notification input with codex queue, without typing into a terminal. It is separate from the MCP adapter. Validation was performed with codex-cli 0.162.1 on macOS; other versions and desktop hosts are not covered by that result.

1. Replace and verify the running notifier with 0.2.1 or later before registering queue routes. Run one notifier, not two. An older notifier records UNSUPPORTED for this route.
2. Run registration from each intended Codex conversation, using the matching CLI:

tabc register --node <your-node> --kind codex --auto-enter on

The CLI checks the format of the current CODEX_THREAD_ID, that the command runs below a native Codex managed-daemon app-server, and that the codex executable is a native Codex release. It does not ask any server who owns the thread, so these checks are not proof of thread or terminal ownership. Do not copy another conversation's UUID or the shared daemon's terminal ID.

With --kind codex --auto-enter on, registration selects a route in this order:

1. If the checks pass, the Codex queue route, including when it replaces this node's existing terminal route.
2. Otherwise, a terminal route verified by this command.
3. If neither is available, registration is refused before anything is sent, and existing routes stay unchanged.

With --auto-enter off or omitted, registration does not select a queue route.

To require queue delivery without terminal fallback, add --codex-queue:

tabc register --node <your-node> --kind codex --codex-queue --auto-enter on

If the checks fail, it prints cannot verify the current Codex managed-daemon thread; registration not sent and exits 2. When registration refuses, read the error and do not work around it with a copied identity or another route. Queue selection cannot be combined with --take-route; --codex-queue cannot be combined with --program.

• QUEUED means Codex accepted notification input, not READ or work completion. Display may follow the current reply; immediate interruption or delivery within a fixed time is not guaranteed. Pull the stored message and record its read state separately.
• Notifications contain metadata only: sender names, unread counts, and the TAC name or UUID for TAC messages. They never contain message bodies. The text is a command-line argument that local process tools can see.
• The notifier, not the registering conversation, runs codex queue. It needs a native codex on its own PATH and a Codex environment that reaches the same local daemon. Without that, each notification can end as UNKNOWN.
• After replacing the notifier and registering, confirm one real round trip: a message arrives in the conversation, and a reply comes back. QUEUED alone does not show that.
• The local receipt database permits one submission attempt per thread UUID and notification ID. An uncertain result is UNKNOWN and is not retried automatically under that ID. Losing the database or moving to another thread is outside this duplicate-prevention boundary.

Can an adapter write tabus.db directly?

It can technically open SQLite, but it should not. tabd is the HTTP write boundary for clients: it verifies the signed caller, enforces self-scoped actions, runs migrations, and keeps delivery transitions in one place. A new adapter should use the signed HTTP API and treat tabus/cli.py as the reference client.

---

Two ways to send

	Goes to	Rings the doorbell	Use it for
dm (--to)	one or more named nodes	yes, if routed	a message addressed to explicit recipients
tac (--tac)	every member of a topic	yes, if routed	a line added to an ongoing topic
broadcast (--broadcast)	every non-program, non-removed node other than the sender	yes, if routed; through SHADOW too	a one-time announcement

"If routed" is the whole condition. A doorbell needs a terminal route on the receiving node; a node with none is NOT_MINE and receives by pulling, and a snoozed node stays quiet. The scope decides who is addressed, not whether a doorbell can sound. The notification header names the scope: [dm] for --to, [tac] topic for --tac.

tabc dm is not one of these. It sends nothing; it lists the unread subjects addressed to a node. The header [dm] and the command dm are different things that share a name.

A tac (Topic Archive Capsule) is a named conversation. The server gives it a UUID when it is created. The name is for display and search. Renaming does not change that UUID. Tac names are unique after case folding, so an exact name matches at most one tac, open or closed.

Commands that change or address the tac take its UUID. From 0.2.3, the CLI also accepts the exact name, compared after case folding. It looks the name up and runs only when the name belongs to exactly one open tac, after printing tac <name> = <uuid> on stderr. For a closed tac, a missing name, or names that only resemble it, the CLI runs nothing. It lists the candidates with their UUID and open or closed date, prints code TAC_NAME_UNRESOLVED, and exits 2. A partial name is never chosen. A canonical lowercase UUID is used as given. Any other value is looked up as a name first, so a tac whose name looks like a UUID is reached by its name. tac create takes the new name and does not look it up. The server and the MCP adapter still take only the UUID. Once closed, a tac cannot be reopened — the closing summary is the record.

Working with a tac

Create the topic, add the nodes that follow it, then post lines that fan out to all of them. Membership is explicit: the creator is recorded as the actor but is not automatically a member, so add each node that should receive the messages.

# Create a topic. Copy the UUID printed by create or tac ls.
tabc tac create planning --description "parser work" --node alice
tabc tac ls --node alice

# Add members using that UUID.
tabc tac add <planning-uuid> bob --node alice
tabc tac add <planning-uuid> carol --node alice

# Post a line — it fans out to every member and can ring their doorbells
tabc send --sender alice --tac <planning-uuid> \
    --subject "kickoff" --body "starting on the parser"

# Read it: ls lists the tacs, show reads one
tabc tac ls --node alice
tabc tac show <planning-uuid> --node bob
# From 0.2.3 the CLI also accepts the exact name of an open tac
tabc tac show planning --node bob
# Only the returned messages advance to INJECTED. Acknowledge each full message
# UUID as READ after reviewing it; older unreturned messages may still block send.
tabc ack --node bob --id <message-uuid> --state READ

# Close it when the topic ends. The summary is fixed as the record and a closed
# tac cannot reopen; a follow-up topic links back to the one it continues.
tabc tac close <planning-uuid> --node alice --summary "parser shipped; next: speedups"
tabc tac create speedups --node alice
tabc tac link <speedups-uuid> <planning-uuid> --node alice

create, add, rm, rename, close, and link change state and record the acting node (from --node, or TABC_NODE) in the audit. ls, check, and search are read-only. show is read-only without --node; with --node, only the returned deliveries advance to INJECTED, not READ. Use ack after reviewing each message. search --query <text> searches names, descriptions, subjects, and bodies without changing delivery state.

Upgrading from 0.2.3 to 0.2.4

0.2.4 adds the CLI send --id option. The daemon already handles duplicate message IDs; the ledger schema, notifier, and MCP adapter are unchanged. Nodes, keys, messages, delivery states, TACs, routes, and Codex queue receipts are preserved. No conversion or registration is required.

After 0.2.4 is published, install one of these packages in the environment that runs your existing installation:

python -m pip install --upgrade "tabc==0.2.4"
# Or, include the optional MCP adapter:
python -m pip install --upgrade "tabc[mcp]==0.2.4"

The CLI option works with an existing 0.2.3 daemon. A daemon or notifier restart is not required for this feature. If replacing the complete running installation, stop the notifier and tabd, confirm the ledger WAL is absent or empty, and back up the store and keys before installing. Restart tabd, then one notifier from the same installation. Restart any running MCP adapter from its host to load the updated package. Preserve the existing store paths, keys, server address, and launch settings.

Check tabc --version and tabc send --help in the target environment. Before the first send, save the ID and complete message inputs. Reuse them unchanged for retries. An unread-message refusal still requires reading the relevant messages; a conflict requires inspecting the saved and stored requests. Do not generate a new ID to force a retry through.

An upgrade from an older version follows its notes below first.

Upgrading from 0.2.2 to 0.2.3

0.2.3 does not change the ledger schema. Nodes, signing keys, messages, delivery states, TACs, routes, and Codex queue receipts are kept. No conversion is needed. Registration is unchanged, so nodes do not need to register again.

Use this order:

# First stop tabus.doorbell.

# Install one of these packages.
python -m pip install --upgrade "tabc==0.2.3"
# Or, include the optional MCP adapter:
python -m pip install --upgrade "tabc[mcp]==0.2.3"

# Restart tabd, then start one tabus.doorbell from the same installation.
tabc --version
tabd --version

• Name lookup needs both sides. The CLI asks tabd for /tac_lookup. Until tabd is restarted on 0.2.3, it answers 404, the CLI sends the typed name unchanged, and the server refuses it with TAC_ID_INVALID. UUIDs keep working either way.
• The notifier and the MCP adapter did not change in 0.2.3. The notifier is stopped and started again only to keep the restart order above. A running tabc-mcp process does not need a restart for this change.
• An upgrade from 0.2.1 follows the 0.2.2 notes below first.

Upgrading from 0.2.1 to 0.2.2

0.2.2 does not change the ledger schema. Nodes, signing keys, messages, delivery states, TACs, routes, and Codex queue receipts are kept. No conversion is needed.

Use this order:

# First stop tabus.doorbell.

# Install one of these packages.
python -m pip install --upgrade "tabc==0.2.2"
# Or, include the optional MCP adapter:
python -m pip install --upgrade "tabc[mcp]==0.2.2"

# Restart tabd, then start one tabus.doorbell from the same installation.
tabc --version
tabd --version

• Stored routes are not changed by the upgrade. A failed capture does not replace an existing route.
• To use the 0.2.2 terminal check, register again from the intended terminal, then confirm that one notification arrives before relying on it.
• Codex queue registration keeps the rules in How do I get notifications in a Codex thread?
• No dedicated adapter for another agent product is added. The MCP adapter still does not wake an agent. If a desktop client runs tabc-mcp, restart that MCP process from the client after the upgrade so it loads the new installation.
• An upgrade from 0.2.0 follows the 0.2.1 notes below first.

Upgrading from 0.2.0 to 0.2.1

0.2.1 does not change the ledger schema. Nodes, signing keys, messages, delivery states, TACs, and routes are kept. No conversion is needed.

Use this order:

# First stop tabus.doorbell.

# Install one of these packages.
python -m pip install --upgrade "tabc==0.2.1"
# Or, include the optional MCP adapter:
python -m pip install --upgrade "tabc[mcp]==0.2.1"

# Restart tabd, then start one tabus.doorbell from the same installation.
tabc --version
tabd --version

• Run the CLI and the notifier from the same installation. Run one notifier, not two.
• Every register call requires --kind. Update scripts that omit it.
• To use the Codex queue route, register again from each intended Codex conversation after the notifier runs 0.2.1. See How do I get notifications in a Codex thread?
• The notifier creates codex_queue_receipts.db in the tabc home directory on its first Codex queue submission. It is separate from message read state.
• The Codex queue route is a notifier path. It is not part of the MCP adapter.
• If a desktop client runs tabc-mcp, restart that MCP process from the client after the upgrade so it loads the new installation.
• An upgrade from 0.1.6 follows the 0.2.0 procedure below first.

Upgrading an existing TAC ledger to 0.2.0

An upgrade from 0.1.6 preserves nodes, messages, delivery states, TAC membership, names, and labels. Existing string TAC IDs keep working until the operator converts the ledger. Conversion is not run by package installation or server startup.

Use this order:

# First stop tabus.doorbell and tabd.
# Confirm that <ledger.db>-wal is absent or empty (0 bytes).
# A remaining empty WAL or SHM file is safe.
# If the WAL is not empty, start tabd and stop it cleanly, then check again.
# Back up the main database only after the WAL is absent or empty.

# Install one of these packages.
python -m pip install --upgrade "tabc==0.2.0"
# Or, include the optional MCP adapter:
python -m pip install --upgrade "tabc[mcp]==0.2.0"

# Read the source, then write a separate converted candidate.
python -m tabus.tac_migration <ledger.db>
python -m tabus.tac_migration <ledger.db> --output <converted.db>

The conversion never overwrites the source file. Verify the reported row counts and the converted database before replacing the active database. Do not replace it while its WAL file is non-empty. A remaining empty WAL or SHM file is safe. Restart tabd first, then restart tabus.doorbell. tabc tac ls shows the new UUID next to each preserved name. After conversion, the server and the MCP adapter refuse a TAC name used instead of its UUID with TAC_ID_INVALID. From 0.2.3, the CLI resolves an exact open tac name to its UUID first. Scripts should use the UUID printed by tabc tac ls, which does not change when the tac is renamed. Do not run old and new daemons against one active ledger during the swap. Confirm the installed processes after restart:

tabc --version
tabd --version

Receiving: pull is what guarantees delivery

There is no push. Follow this order:

pull on your own schedule     ← this is what proves you received everything
act on the doorbell if it fires ← convenience only

Do not depend on the doorbell. If a notification is lost, the message is still sitting in the store and no receiver reads it. The bell failed; the parcel did not disappear. Those are different failures and they need different defenses.

The failure mode is a message read late, not a message lost. Each node pulling on its own removes that failure.

Priority

The point of this tool is not delivery. It is timing.

	Meaning
now	Worth interrupting for. Incidents, outages, anything irreversible
next	Read it when the current turn ends. Default. Most things
batch	Collect and read when idle. Reference, sharing

Priority orders the queue and filters it. It does not change the alarm: a batch message rings exactly as a now message does, because the notifier does not read the field. Choosing batch says when the message is worth reading, not whether it interrupts.

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What works / what does not

Written plainly. Hiding this turns into "I thought it did that."

Works

• Several AI sessions on one machine, regardless of product
• Delivery while the other side is closed — storage comes first
• Malformed envelopes are quarantined without showing the body
• Any character in the body
• Ed25519 request signing rejects a sender that cannot prove possession of the pinned node key
• The terminal doorbell on Linux, not only macOS: the tmux adapter rings a pane on both, while the iTerm adapter is macOS-only (measured in a Linux container)

macOS only

• Automatic status detection (it asks iTerm). Elsewhere it skips quietly and falls back to self-reporting.
• The iTerm doorbell adapter specifically. tmux is the cross-platform one, so a Linux node registered inside a tmux pane still gets the doorbell.

Does not work

• Joining two buses across machines. The store is a local file, so a bus serves one machine; a client elsewhere can still reach it over --bind, with its request signed the same way, but two buses cannot be linked yet
• Push delivery — the receiver has to pull
• Message-body encryption — signatures authenticate requests but do not hide text
• TLS on the default local HTTP link

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Where this is going

Today a bus serves one machine. The store is a local file, so a node on its own separate bus is outside this one — a client that connects to this bus over --bind is a participant, but two buses do not yet carry each other's mail.

The direction is to connect buses rather than widen one. Each machine keeps its own bus and its own store, and two buses agree to carry each other's messages. A node keeps talking to the bus in front of it and never learns that a recipient is elsewhere.

How is not decided. The alternative is a shared store — one database that several machines write to — and a comment in the source still assumes that route. It was written before this direction was chosen, so read it as an open question, not a plan. The choice is not only plumbing: a shared store has to authenticate every writer, while connected buses authenticate each other and then vouch for their own. Identity has to prove a different thing in each.

Nothing here is scheduled. It is written down so the current shape reads as a choice rather than an oversight.

Invariants

• Store first, notify second. The notification carries sender names, unread counts, and the TAC name or UUID for TAC messages — never a body. Receiving-then-storing cannot structurally prevent loss while a node is down.
• One row per recipient. Delivery is at-least-once, not exactly-once. Duplicates are absorbed on the receiving side.
• Stages stay separate. Stored / claimed / injected / actually read each guarantee a different thing.
• Stale values become unknown automatically. A stored status is not trusted as-is.
• Irreversible work goes last. Anything that can throw runs before it.

Security

This tool moves messages between agents, which is a different risk profile from a consumer messenger — text that arrives can become an instruction to the receiving AI.

Read SECURITY.md first. It lists the five rules and how far each is actually enforced today.

GUIDE.md is the operating half of this documentation: what goes wrong, how to tell which thing went wrong, and what a result does and does not prove. Read it when something behaves in a way this page does not explain.

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License

MIT. Full text in LICENSE at the repository root.

Use it, modify it, redistribute it. One condition — keep the copyright notice and the license text with it. No warranty.