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Bread Documentation

Contents

Overview

Bread is a reactive automation fabric for Linux desktops. The daemon (breadd) normalizes external signals into semantic events, maintains runtime state, and dispatches events to Lua modules that implement automation.

  • Daemon: long-running Rust process, source of truth for runtime state
  • Lua runtime: dedicated thread inside the daemon; automation logic lives here
  • CLI: talks to the daemon over a Unix socket

If you are new to Bread, start with the quick walkthrough below, then jump to the full dictionary when you need exact API details.

Getting started

1) Create a minimal config

  • Daemon config: ~/.config/bread/breadd.toml
  • Lua entry point: ~/.config/bread/init.lua
  • Lua modules: ~/.config/bread/modules/

2) Minimal init.lua

require("modules.devices")
require("modules.workspaces")

bread.on("bread.system.startup", function()
    bread.profile.activate("default")
end)

3) Add your first module

Create a Lua file under your modules directory and load it from init.lua.

Your first module

local M = bread.module({ name = "hello", version = "0.1.0" })

function M.on_load()
    bread.log("hello from bread")

    bread.on("bread.device.*", function(event)
        bread.log(event.event)
    end)
end

return M

Why this shape?

  • Every module must call bread.module once.
  • on_load is a good place to register subscriptions.
  • Use bread.log early to verify handlers are firing.

Run, reload, and watch

  • Start the daemon, then use bread reload after editing Lua.
  • bread reload --watch will keep reloading on changes.
  • See Examples.md for real-world ports.

Debugging tips

  • Log event payloads with bread.log(event.data.raw) when matching devices.
  • Use bread.events in the CLI to see live normalized events.
  • Use bread state to see runtime state as JSON.

Lua module system

Entry point and module scanning

  • init.lua is executed first.
  • Modules are discovered by scanning ~/.config/bread/modules/ for .lua files.
  • Every module must call bread.module exactly once at top-level.
  • Modules are ordered by the after dependency list.

Module declaration

local M = bread.module({
    name = "my.module",
    version = "0.1.0",
    after = { "bread.devices" },
})

return M

If a module does not call bread.module, it fails to load and is marked as a load error.

Require loader

require("bread.<path>") resolves to a Lua file under the module path. For example:

local utils = require("bread.lib.utils")

This loads ~/.config/bread/modules/lib/utils.lua if it exists. Non-bread.* require calls fall back to standard Lua behavior.

Lifecycle hooks

Modules may export any of the following hooks. All are optional.

function M.on_load()
    -- register subscriptions, initialize module state
end

function M.on_reload()
    -- called after a hot reload completes
end

function M.on_unload()
    -- called before the Lua instance is dropped
end

function M.on_error(err)
    -- called when a handler throws
    -- return true to keep the subscription, false to cancel it
    return true
end

Module storage

Each module has a scoped key-value store that survives reloads:

M.store.set("last_profile", "docked")
local value = M.store.get("last_profile")

The store lives in the daemon runtime state and is not shared across modules.

Dictionary: Lua API

Every API is exposed through the bread global table.

Events

bread.on(pattern, fn) -> id

Subscribe to matching events. Returns a numeric subscription ID.

bread.once(pattern, fn) -> id

Subscribe once. The handler is removed after the first match.

bread.filter(pattern, fn, opts) -> id

Subscribe with a predicate filter. opts must contain filter:

bread.filter("bread.device.*", function(event)
    bread.exec("xset r rate 200 40")
end, {
    filter = function(event)
        return event.data and event.data.class == "keyboard"
    end,
})

bread.off(id)

Unsubscribe an event or state watch by ID.

bread.emit(event, data)

Emit a custom event into the system pipeline.

bread.wait(pattern, opts) -> event | nil

Coroutine-only helper that waits for a matching event.

bread.spawn(function()
    local event = bread.wait("bread.device.dock.connected", { timeout = 5000 })
    if event then
        bread.log("dock arrived")
    end
end)

bread.spawn(fn)

Spawn a coroutine and surface errors if the coroutine fails.

State

bread.state.get(path)

Read a state subtree by dotted path (e.g. "network.online").

Convenience helpers

  • bread.state.monitors()
  • bread.state.active_workspace()
  • bread.state.active_window()
  • bread.state.devices()
  • bread.state.power()
  • bread.state.network()
  • bread.state.profile()

bread.state.watch(path, fn) -> id

Watch a state path. The callback receives (new, old).

bread.state.watch("power.ac_connected", function(new_val, old_val)
    if new_val then
        bread.exec("notify-send 'AC connected'")
    end
end)

Profiles

bread.profile.activate(name)

Update the active profile. The CLI also emits bread.profile.activated over IPC; the Lua API does not emit this event on its own.

Execution

bread.exec(cmd)

Runs cmd in a sh -lc shell. Fire-and-forget (async).

Notifications

bread.notify(message, opts)

Sends a desktop notification via notify-send.

Options:

  • title (string, default: "bread")
  • urgency (string, default from config)
  • timeout (ms, default from config)
  • icon (string, optional)

Calling bread.notify emits bread.notify.sent with { title, message, urgency }.

Timers

bread.after(delay_ms, fn) -> id

Run once after delay.

bread.every(interval_ms, fn) -> id

Run repeatedly on an interval.

bread.cancel(id)

Cancel a timer created by after or every.

Utilities

bread.debounce(delay_ms, fn) -> wrapped_fn

Returns a wrapper that only fires after quiet time.

bread.log(msg) / bread.warn(msg) / bread.error(msg)

Log helpers that accept any Lua value.

Hyprland

The bread.hyprland namespace provides compositor bindings:

  • bread.hyprland.dispatch(cmd, args)
  • bread.hyprland.keyword(key, value)
  • bread.hyprland.active_window()
  • bread.hyprland.monitors()
  • bread.hyprland.workspaces()
  • bread.hyprland.clients()
  • bread.hyprland.on_raw(kind, fn) -> id

bread.hyprland.on_raw filters raw Hyprland events by kind and delivers the full event payload (including the original raw string).

Dictionary: Built-in modules

Built-ins are enabled by default. Disable them via [modules].disable in the config.

bread.monitors

local monitors = require("bread.monitors")

monitors.layout("dock", function()
    bread.exec("~/.config/bread/scripts/layout-dock.sh")
end)

monitors.on({
    when = "connected",
    monitors = { "HDMI-A-1" },
    run = monitors.apply("dock"),
})
  • monitors.on({ when, monitors, run })
  • monitors.layout(name, fn)
  • monitors.apply(name) -> fn

when is one of connected, disconnected, changed. run may be a function or a shell command string.

bread.devices

local devices = require("bread.devices")

devices.register("Keychron", "keyboard")

devices.on({
    when = "connected",
    class = "keyboard",
    run = function(event)
        bread.exec("xset r rate 200 40")
    end,
})
  • devices.on({ when, class, name, run })
  • devices.register(pattern, class)

class may be dock, keyboard, mouse, tablet, display, storage, audio, unknown.

bread.workspaces

local workspaces = require("bread.workspaces")

workspaces.assign("1", "HDMI-A-1")
workspaces.pin({ app = "Firefox", workspace = "2" })
  • workspaces.assign(workspace, monitor)
  • workspaces.pin({ app, workspace })
  • workspaces.apply_assignments()

bread.binds

local binds = require("bread.binds")

binds.add({
    mods = { "SUPER" },
    key = "Return",
    dispatch = "exec",
    args = "kitty",
})
  • binds.add({ mods, key, dispatch, args })
  • binds.remove(key)
  • binds.replace(key, opts)

Dictionary: Event reference

Events are delivered as a BreadEvent:

{
  "event": "bread.device.dock.connected",
  "timestamp": 1710000000000,
  "source": "Udev",
  "data": {}
}

Pattern matching

Patterns match event names with glob-style syntax:

  • Exact match: bread.device.dock.connected
  • * matches within a single segment (does not cross .)
  • ** matches across segments (recursive)
  • ? matches a single character within a segment

Examples:

bread.on("bread.device.*", handler)
bread.on("bread.device.**", handler)
bread.on("bread.monitor.?", handler)

Normalized events

System

  • bread.system.startup (data: {})

Devices (udev)

  • bread.device.connected
  • bread.device.disconnected
  • bread.device.changed
  • bread.device.<class>.connected
  • bread.device.<class>.disconnected
  • bread.device.<class>.changed

Payload notes:

  • Device events include id and class; the generic event also includes raw.
  • <class> is one of: dock, keyboard, mouse, tablet, display, storage, audio, unknown.

Hyprland

  • bread.workspace.changed (raw payload)
  • bread.workspace.created ({ "workspace": "..." })
  • bread.workspace.destroyed ({ "workspace": "..." })
  • bread.monitor.connected (raw payload)
  • bread.monitor.disconnected (raw payload)
  • bread.window.focus.changed (raw payload)
  • bread.window.focused ({ "address": "..." })
  • bread.window.opened ({ "address", "workspace", "class", "title" })
  • bread.window.closed ({ "address": "..." })
  • bread.window.moved ({ "address", "workspace" })
  • bread.hyprland.event (raw payload for unhandled kinds)

Raw Hyprland payloads contain kind, raw, and data fields.

Power

  • bread.power.ac.connected
  • bread.power.ac.disconnected
  • bread.power.battery.low
  • bread.power.battery.very_low
  • bread.power.battery.critical
  • bread.power.battery.full
  • bread.power.changed (fallback)

Payload includes ac_connected and battery_percent.

Network

  • bread.network.connected
  • bread.network.disconnected

Payload includes online and interfaces.

Other system events

  • bread.profile.activated (emitted by IPC profile activation)
  • bread.notify.sent (emitted by bread.notify)
  • bread.state.changed.<path> (emitted when a state watch fires)

Dictionary: Runtime state schema

bread.state.get("") returns the full RuntimeState:

{
  "monitors": [ { "name": "HDMI-A-1", "connected": true } ],
  "workspaces": [ { "id": "1", "monitor": "HDMI-A-1" } ],
  "active_workspace": "1",
  "active_window": "Firefox",
  "devices": { "connected": [] },
  "network": { "interfaces": {}, "online": false },
  "power": { "ac_connected": false, "battery_percent": null, "battery_low": false },
  "profile": { "active": "default", "history": [], "profiles": {} },
  "modules": [ { "name": "bread.devices", "status": "loaded", "last_error": null, "builtin": true, "store": {} } ]
}

Dictionary: IPC protocol

The daemon exposes a Unix socket at $XDG_RUNTIME_DIR/bread/breadd.sock. Messages are newline-delimited JSON.

Request:

{ "id": "1", "method": "state.get", "params": { "key": "monitors" } }

Response:

{ "id": "1", "result": [ { "name": "HDMI-A-1", "connected": true } ] }

Available methods:

  • ping
  • health
  • state.get
  • state.dump
  • modules.list
  • modules.reload
  • profile.list
  • profile.activate
  • events.subscribe
  • events.replay
  • emit

events.subscribe upgrades the socket to streaming mode and sends events as they occur.