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Module install

lattice_multibuffer

Module install 

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BC.7 (2026-06-24): the crate-owned install(boot) entry point.

The multibuffer subsystem registers its own modes + commands + services + off-keystroke wake through the generic [SubsystemBoot] surface, collapsing the host’s ~6 scattered editor_boot sites into one Phase-B line (lattice_multibuffer::install(&mut boot)) — the terminal / claude-code / diff shape.

§What collapses here

  • The registry handle ([InMemoryMultibufferRegistry::handle]) is created inside install — multibuffer-owned, because it carries no host-state dependency (unlike diff’s resolver-backed DiffSubsystemHandle or terminal’s host-BufferRegistry-backed TerminalStoreHandle, both of which the host must construct). It is used for mode registration + the excerpt-jump motion handlers, and published as a service the host reads back at dispatch time (Editor::resolve_narrow_target) via services.get::<MultibufferRegistryHandle>().
  • Modes — multibuffer-mode (+ its DocumentClosed cleanup subscriber), narrow-mode, and the search provider mode.
  • Commands — the excerpt-jump motions (]e/[e/]E/[E), the :multibuffer-* ex-commands, :narrow/:widen, the zn narrow operator SPEC, and the :search ex-command.
  • Services — the registry handle + the project-search service.
  • The off-keystroke wake — boot.wake_on_event::<MultibufferExcerptsReady>(), replacing the host’s hand-rolled mpsc→async_landed forwarder so streamed search excerpts repaint without a keypress. The wake is now a property of the primitive (BC design §3), not by-discipline.

§What stays host-side (documented residue, NOT mode-ownership violations)

  • The zn narrow-operator binding at the universal operator-pending (Builtin) layer. The operator spec/handler lives here (crate::providers::narrow::register_narrow_operator); only the binding is host-side, because zn is universal grammar — it composes with the universal motion/text-object vocabulary and needs the host-resolved Builtins. This is the same category as lattice-syntax’s structural text objects (N.1.4c): registered-in-crate, bound-at-Builtin. There is no single “owning mode” for a universal operator. BC.7 decision (A): the host resolves the operator by name (registry.id_by_name("operator:narrow")), so the registration return value no longer threads through the host — the K.2.5 motion name-resolution pattern.
  • Host Effect appliers — Editor::resolve_narrow_target + the AppEffect::{SearchTrigger,NarrowTrigger,NarrowLines,NarrowWiden,MultibufferExpand} dispatch arms mutate &mut Editor (open buffers, pane tree, splits) — the Effect-vocabulary-is-the-host-boundary rule (diff’s do_diff_* precedent). The trigger substrate fns (project_search, create_narrow_view, multibuffer_expand_excerpt_at) are crate-owned helpers those arms call.
  • The generic event_bus service stays a Phase-A host primitive — many subsystems consume it; it is not multibuffer-owned.

Functions§

install
Wire the multibuffer subsystem’s modes + commands + services + wake into the editor at boot. One Phase-B line in editor_boot.rs.