v2.0.0 — the Action Binding Protocol

[2.0.0] - 2026-08-25

The Action Binding Protocol. Declare an action once; bind it to every live
control that can perform it. Four identities with four cardinalities — a
definition is what a capability IS, a binding is where it is connected, an
offer is the facts it was exposed under, a transition is one invocation — and
no consumer ever recovers one from another by string surgery. This is the v2
contract: createActionBindingRuntime is now createActionRuntime, offers are
principal-scoped (runtime.forPrincipal(p).offers() — the principal belongs to
the reader, not the binding), progress reports declared/observed/unreported
at close, abandoned requires an explicit authority (never inferred from a
detach), and offered inputs are revision-exact: an invocation can never read a
newer committed input while carrying an older offer.

Fixed

• Late evidence is kept, marked late, and reopens nothing. A settlement
  arriving after the terminal used to vanish into a return of the first one.
  It now rides the transition as lateSettlements — a QUOTATION of what the
  late caller claimed and the payload it brought, never validated as if
  accepted and never allowed to reopen a terminal. Absent when none arrived,
  because an empty list would claim "we watched and none came."
• A stale offer is no longer called a forgery. Invalidation deletes a
  retired offer from every map, so the old refusal accused a slow caller
  replaying yesterday's offer and an attacker of the same crime. The refusal
  now says what the runtime can still establish: a binding serving a current
  offer names it as the next move; a registered but offerless binding says the
  surface moved on; an unknown binding admits it cannot tell never-ours from
  since-detached, and will not guess.

Added

• Action Binding now joins what was offered, invoked, and settled.
  defineAction() declares one callable action, framework-neutral connections
  bind its live instances, and runtime.available() returns self-describing
  none, bound, or open offers. runtime.invoke() is the single broker for
  offered execution: it accepts only the exact retained offer, captures bound
  input when that offer is minted, validates caller input for open offers, and
  carries a non-secret input receipt through the invocation, transition, and
  settlement history. Definitions explicitly declare invocation: 'inputless' | 'scalar' | 'host'; broker eligibility is never guessed from
  Function.length. Open offers require one caller slot and are withheld when
  no schema tells a UI/agent how to construct that input.
• Channel declarations have a stable Layer 1 home. Callable definitions can
  store typed needs and produces kind declarations. They are validated and
  frozen but deliberately inert until the later channel/surface broker exists.
• Input contracts have an enforcement port. Schemas with synchronous
  .safeParse() or .parse() methods are enforced directly; applications can
  supply inputSchemaAdapter for formats such as JSON Schema plus Ajv. Strict
  activation refuses an unenforceable schema instead of presenting metadata as
  an active gate.
• Live fact generations are explicit. connection.update() is inert when
  facts do not change, while connection.touch() deliberately retires existing
  offers without running application readers. React input bindings require an
  inputKey; changing it atomically publishes the newly committed input reader
  and invalidates the prior offer without changing binding identity.
• Invocation outcomes distinguish refusal from failure. refused means the
  application handler never started; failed means it started and then
  threw/rejected. Preflight input refusals immediately settle their effect as
  not attempted, and connection observers now receive direct, brokered, and
  host-continuation invocations through one narrow settlement capability.
• React availability generations are explicit. availabilityKey names the
  committed facts read by adapter enabled/busy readers. Omitting it chooses a
  conservative revision after every commit; simultaneous input and availability
  changes still publish one revision.

This will be the first public callable Action Binding shape. Its cross-copy brand
is hcifootprint.action-definition.v1; that suffix versions the frozen branded
record, independently of the npm major version. The existing navigation-graph
ActionDef.input field remains unchanged; callable definitions deliberately use
inputSchema.