Persistent cross-client sessions

AgentsKit remains the message authority. Configure one of its ChatMemory implementations on definition.chat.memory, then store only AgentsKit Chat application metadata through SessionStorage.

const session = await resumeChatSession(definition, {
  sessionId: 'customer-42',
  storage: applicationSessionStorage,
})

<AgentChat definition={definition} session={session} />

The same preparation works before mounting React Native or Ink. Each client loads the same session id from the host storage and points its ChatConfig.memory at the same canonical conversation.

SessionStorage.save(snapshot, expectedCursor) must be atomic: create only when expectedCursor is undefined, update only when the stored cursor equals it, and return false on conflict. This CAS claim prevents two resumed clients from resolving the same pending action. A plain last-write-wins key/value write is unsafe and does not implement the port.

Snapshots use agentskit.chat.session version 1. They contain definition identity/revision, deterministic application state, monotonic cursor, and pending or terminal confirmation bindings. They never contain messages. Increment definition.revision when a state-machine change makes old application metadata incompatible.

resumeChatSession starts clean when load returns null or undefined. Invalid JSON, unknown versions, session mismatch, definition mismatch, and revision mismatch reject before hydration. Version 0 is the only implicit migration currently supported.

Call session.persist() at an explicit durability boundary. Deterministic transitions also schedule saves. Confirmation changes await durable storage; a failure rejects the operation. Resolution moves through a durable processing status before delegation and reaches terminal status only after upstream success. A crash leaves processing state for host reconciliation, while restored processing/terminal confirmations remain inert.