@OnAnswer

The @OnAnswer(AgentClass) method decorator ("@agboss/core") marks the per-agent evaluation method inside a DecidedBy.Code @Arbiter class. During a .joinQuorum() or .joinQuorumGroups() step, AGBoss invokes the matching @OnAnswer(AgentClass) method as each parallel branch finishes so your arbiter can return true (count toward quorum) or false (reject the branch answer) in real time.

Complete @OnAnswer example

src/arbiters/margin-threshold.arbiter.ts

import {
  Agent,
  Arbiter,
  DecidedBy,
  ExecutionContext,
  Injectable,
  OnAnswer,
} from "@agboss/core";
import { Integer, Text } from "@agboss/core/dto";

export class PricingQuoteDto {
  @Text({ prompt: "Pricing tier name" })
  tierName!: string;

  @Integer({ min: 0, max: 100, prompt: "Gross margin percentage (0-100)" })
  marginPercent!: number;
}

@Agent({
  name: "enterprise-pricing-agent",
  description: "Generates enterprise tier quote",
  model: "moonshotai/kimi-k2.6",
  prompt: "Propose an enterprise pricing quote.",
  output: PricingQuoteDto,
})
export class EnterprisePricingAgent {}

@Agent({
  name: "self-serve-pricing-agent",
  description: "Generates self-serve tier quote",
  model: "moonshotai/kimi-k2.6",
  prompt: "Propose a self-serve pricing quote.",
  output: PricingQuoteDto,
})
export class SelfServePricingAgent {}

@Injectable()
export class MarginPolicyService {
  minMarginForTenant(_tenantId: string): number {
    return 30;
  }
}

@Arbiter({
  name: "margin-threshold-arbiter",
  decidedBy: DecidedBy.Code,
  deps: [ExecutionContext, MarginPolicyService],
})
export class MarginThresholdArbiter {
  constructor(
    private readonly ctx: ExecutionContext,
    private readonly policy: MarginPolicyService,
  ) {}

  @OnAnswer(EnterprisePricingAgent)
  fromEnterprisePricing(answer: PricingQuoteDto): boolean {
    const minMargin = this.policy.minMarginForTenant(this.ctx.tenant.tenantId);
    return answer.marginPercent >= minMargin;
  }

  @OnAnswer(SelfServePricingAgent)
  fromSelfServePricing(answer: PricingQuoteDto): boolean {
    return answer.marginPercent >= 20;
  }
}

test/margin-threshold.arbiter.test.ts

import { expect, it } from "vitest";
import { testArbiter } from "@agboss/core/testing";
import {
  EnterprisePricingAgent,
  MarginThresholdArbiter,
} from "../src/margin-threshold.js";

it("accepts quotes meeting the margin threshold via @OnAnswer", async () => {
  const runArbiter = testArbiter(MarginThresholdArbiter);
  const { output } = await runArbiter(EnterprisePricingAgent, {
    tierName: "Enterprise",
    marginPercent: 42,
  });
  expect(output).toBe(true);
});

How @OnAnswer(AgentClass) works inside @Arbiter

Signature Part	Type	Description
@OnAnswer(AgentClass)	Method decorator	Binds the method on a DecidedBy.Code @Arbiter to a specific @Agent class launched by .toParallelAgents(...). Every agent in the launch must have a corresponding @OnAnswer method ([arbiter.unhandled-agent]).
answer parameter	ArbiterAnswerOf<typeof AgentClass>	The plain validated output DTO produced by that @Agent branch. TypeScript rejects mismatched DTO types at compile time.
Return value	boolean | Promise<boolean>	Returns true if the branch’s answer counts toward the quorum, or false to reject it.