The NPC and state-machine plugins

The NPC plugin (priority 100) walks every entity with the npc trait, dispatches to the behavior its behaviorId names, and executes what comes back: attacks, emotes, and movement (with npc-moved events and witnessed variants a story can narrate). It also fires enter/leave hooks when the player's action moved them, which is the greeting-guard pattern. Built-ins: guard (stationary, attacks the visible player when hostile), passive, and factory-made wanderers, followers, and patrol routes; stories register richer behaviors. A Chord story gets all of this without opting in, because NPCs are core: a person, a guard (or passive, wanderer with move-chance 50, follower, patrol with route [ … ]) composes the built-ins directly, with with-fields for movement permissions, routes, and chances. Configuration lives on the trait; the deep-NPC layers (character model, lucidity) tick here too.

The author writes:

create the Orchard
  a room
  east to the Cider House

  Apple trees in crooked rows.

create the Cider House
  a room
  west to the Orchard

  Presses, barrels, and the sweet reek of last year's crop.

create Mairead
  aka warden
  a person, proper, patrol with route [the Orchard, the Cider House]
  pronouns she
  in the Orchard

  The orchard warden, mid-round.

create the player
  starts in the Orchard

The player sees:

> look
Orchard
Apple trees in crooked rows.

You can see Mairead here.

> wait
Time passes...

> look
Orchard
Apple trees in crooked rows.

> wait
Time passes...

> look
Orchard
Apple trees in crooked rows.

You can see Mairead here.

Mairead walks her two-room route on the plugin's turns, silently by default: the plugin emits the npc-moved events, and narrating them (or not) is the story's choice.

The state-machine plugin (priority 75) evaluates declarative machines (states, guarded transitions triggered by actions, events, or conditions, enter/exit effects, terminal states), and it applies at most one transition per machine per turn. A Chord story reaches it by opting in: use state-machines in the story header, then define machine, which exposes the plugin's full depth, with Chord conditions as guards and Chord bodies as effects. Writing define machine without the use line is a compile error.

The author writes:

story "The Ferry" by "ref"
  id: plugins-machine
  version: 0.0.1
  states: waiting, signaled
  use state-machines

create the Slipway
  a room

  A cobbled slipway running down into grey water.

create the capstan
  in the Slipway

  A tarred capstan wound with ferry rope.

  on turning it
    phrase capstan-turns
      You lean into the capstan and it comes round, pawls clacking.
  end on

create the signal cord
  aka cord
  scenery, pullable
  in the Slipway

  A cord for ringing the bell on the far bank.

  on pulling it
    change the story to signaled
    phrase cord-rings
      Far across the water, a bell answers the cord.
  end on

create the player
  starts in the Slipway

define machine ferry
  role capstan is the capstan
  starts moored

  state moored
    when turning the capstan: casting-off

  state casting-off
    on enter
      phrase rope-pays-out
    end on
    when signaled: underway

  state underway, terminal
    on enter
      phrase ferry-underway
    end on
end machine

define phrase rope-pays-out
  The rope pays out and the ferry noses off the far bank.
end phrase

define phrase ferry-underway
  The ferry is underway, beating slowly toward you.
end phrase

The player sees:

> turn the capstan
You lean into the capstan and it comes round, pawls clacking.

The rope pays out and the ferry noses off the far bank.

> pull the cord
Far across the water, a bell answers the cord.

The ferry is underway, beating slowly toward you.

Two trigger kinds in two turns: the action trigger fires the turn the capstan turns (the on turning it clause makes the turn succeed and the transition's on enter speaks in the same turn's output), and the condition trigger fires the turn the cord's clause moves the story to signaled.

It is worth being precise that Chord's states:/change/select on still do not use it. Chord states are plain world-state values with a forward-march ratchet (reversible opts out); they give the effect of a simple state machine without the plugin's machinery (no enter/exit effects, no terminal states, no multi-machine registry). Dungeo's death-penalty policy (the veto window) is a real state machine; the cloak's states are Chord world-state.