2. Graph and state ownership

The goal

Make the quote’s stages and durable facts visible in one place. QuoteGraph has no mutable “current quote” object shared among nodes: every accepted fact has a named owner in the graph state registry.

Register the conversational topology

buildGraph() names every node a tool response may enter. The only fixed edge connects TerminateSessionNode to END; ordinary forward and backward movement comes from go(TargetNode), and acceptance completes the graph with finish(...).

const graph = this.createStateGraph(QuoteGraphState);
graph.registerTurnNodes(
  DriverNode, VehicleNode, HistoryNode, CoverageNode, QuoteNode, TerminateSessionNode,
);
graph.addEdge(TerminateSessionNode, END);
return graph.compile();

Registration is an allowlist. A node cannot route to a class that the graph did not register.

Make ownership explicit

The state registry declares the channel each stage may replace:

export type QuoteGraphNodes = {
  DriverNode?: NodeStateValue<{ driver?: DriverProfile }>;
  VehicleNode?: NodeStateValue<{ resolvedVehicleId?: string; vehicle?: VehicleUse }>;
  HistoryNode?: NodeStateValue<{ history?: InsuranceHistory }>;
  CoverageNode?: NodeStateValue<{ coverage?: CoverageSelection }>;
  QuoteNode?: NodeStateValue<{
    tiers?: QuoteTier[];
    acceptedTier?: QuoteTierName;
    referenceNumber?: string;
  }>;
};

createGraphStateAnnotation(DriverNode.name, ...) produces the LangGraph annotation from this map and makes DriverNode the entry node of a new session. It is not a second application-state shape to synchronize.

Why it is written this way

When DriverNode saves a validated driver, no other stage needs to infer whether the name in the transcript is the accepted fact. A downstream policy can read the committed channel, and a test can assert it directly. This matters when the customer corrects coverage after a quote was already calculated.

Next

Continue to 3. Validated collection and catalog lookup.