4. Session lifetime and history spaces

The goal

Preserve a useful in-progress quote without treating an old rate as indefinitely valid.

Give each stage the right conversational memory

QuoteGraph.getGraphDefinition() assigns a history space to each node:

historySpaces: [
  [DriverNode, "quote-intake"],
  [VehicleNode, "quote-intake"],
  [HistoryNode, "quote-incidents"],
  [CoverageNode, "quote-intake"],
  [QuoteNode, "quote-present"],
  [TerminateSessionNode, "quote-terminal"],
],

Driver, vehicle, and coverage share the intake conversation. Incident collection and quote presentation get separate histories so the prompt does not carry unrelated conversational detail into a sensitive incident discussion or a tier explanation.

Reset a stale quote

QuoteGraph overrides onRestoreSessionDoc(), which the engine calls with the persisted session document before the next turn runs:

protected override async onRestoreSessionDoc(
  sessionDoc: SessionDocument<QuoteGraphStateType>,
): Promise<SessionDocument<QuoteGraphStateType> | null> {
  if (this.idleMs(sessionDoc) >= readMs("QUOTE_GRAPH_IDLE_MS", DEFAULT_IDLE_MS)) {
    return null;
  }
  return sessionDoc;
}

Returning null starts a new run rather than resuming a quote whose inputs and pricing window are no longer valid. The default idle window is 30 minutes; QUOTE_GRAPH_IDLE_MS may override it for a deployment, but the policy remains graph-owned rather than prompt-owned.

Why it is written this way

History is model context; node state is the operational record. Separating them means a shorter prompt history cannot erase durable driver, coverage, or accepted-tier facts. Expiry likewise changes session behavior explicitly rather than relying on the model to notice an old message.

Next

Continue to 5. Deterministic rating.