@bimetal/headless-core

Domain-neutral controller core shared by the BIMETAL component family (Calendar, Kanban, …). Zero dependencies.

It owns the generic ~30% that every component controller needs and that is treacherous to copy correctly:

• Identity-stable getSnapshot — returns the same reference until the version actually moves. This is the useSyncExternalStore contract; getting it wrong causes render loops or stale UI.
• A version bus — markChanged() bumps the version and notifies subscribers; subscribe(listener) / destroy().
• Errors-as-state — setLastAction / getLastAction / dismissLastAction so rule violations and WIP rejections surface as a snapshot field (a toast) instead of throwing in the render path.

import { createControllerCore } from '@bimetal/headless-core';

const core = createControllerCore({ buildSnapshot: () => buildMySnapshot() });
// component intents mutate local state, then call core.markChanged()

Component controllers (createCalendarController, createKanbanController) compose one of these and add only their interaction semantics. Framework bindings consume the SnapshotSource<TSnapshot> contract — { getSnapshot, subscribe, destroy } — generically, so a single per-framework binding drives every component.