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Serialization

const json = chat.toJSON();           // { sessionId, systemPrompt, messages }
const restored = chatFromJSON(json);  // restore (re-register hooks afterwards)

The sessionId is required in ChatJSON and is preserved across serialization round-trips. When deserializing legacy data that lacks a sessionId, a new UUID is generated.

The systemPrompt field stores the single system prompt. The messages array contains only non-system messages. The system prompt is not duplicated in both places.

Timestamps

Every message has a createdAt: Date set automatically at creation time. When serialized:

  • toJSON() — createdAt is an ISO 8601 string (e.g. "2026-06-04T15:30:00.000Z")
  • fromJSON() — the ISO string is restored back to a Date object

The system prompt (when present) also carries a createdAt.

Hooks are not serialized; re-register after chatFromJSON().