Shared state ladder

This is the vocabulary for shared state in fak. It keeps five related but different things from being treated as one feature:

Rung Meaning Shipped shape
Live addressed message One value delivered now between agents internal/a2achan Send/Recv and Publish/Subscribe over scoped Ref bodies
Live shared object A named mutable cell during one run Planned first-class region/window work; today compose from refs and messages
Durable handoff State that survives a process/session/window boundary Session image and snapshot primitives; internal/sharedtask journal is a task-local materialized handoff
Disaggregated state Bytes live outside the task record Shared task refs carry digest, taint, scope, store, and deletion certificate
User-level collaboration A human and agents co-edit task state Shared task record contract plus in-memory fold, conflicts, scoped views, and scoped live topics

Collaboration Spine

The collaborative task surface uses a single record with explicit patch semantics:

  1. A task has a stable task_id, current rev, scoped body ref, artifact refs, note refs, and open decisions.
  2. A human or agent submits a patch against the rev it saw.
  3. Append-only notes, artifacts, and open decisions can commute when their ids are new.
  4. Scalar edits such as replace /title and replace /state require the current base and return a typed conflict when stale.
  5. Disaggregated refs must carry digest shape and deletion witnesses before the record advances.
  6. Adapters read View and EventsView so scoped readers get the same redaction behavior for snapshots and catch-up event history.
  7. Live adapters use SubscribeScopedView and scoped event topics so future tenant-scoped events do not land in a fleet-scoped inbox.

Honest Scope

Shipped today: in-process a2achan delivery, scoped/tainted refs, the internal/sharedtask in-memory patch fold, scoped read and event-history projection, scoped live event fanout, disaggregated ref admission, and a materialized task journal. Not claimed here: a durable cross-process mailbox, a networked task-store daemon, external L3 artifact transport, or a browser/editor UI.