Agents for Humans: How We Built Relay, an Autonomous WhatsApp Book Matchmaker

export const processWhatsAppInbound = async (payload: MetaWebhookPayload) =\> {
  return await withDurableExecution(async (step) =\> {
    // Step 1: Idempotency check (acknowledges Meta in \<200ms)
    const message = await step.run('validate-payload', async () =\> {
      const msg = extractWhatsAppMessage(payload);
      if (await checkIdempotency(msg.id)) throw new IdempotentSkipError();
      return msg;
    });

    // Step 2: Redact PII in-memory before reaching LLM
    const sanitized = await step.run('redact-pii', async () =\> inMemoryPiiRedactor(message.text));

    // Step 3: Fast-path routing or Strands Bedrock reasoning
    const intentResult = await step.run('agent-reasoning', async () =\> {
      if (isDeterministicFastPath(sanitized.sanitizedText)) {
        return executeFastPath(sanitized.sanitizedText, message.from);
      }
      return await booksAgent.processMessage(sanitized.sanitizedText, message.from);
    });

    // Step 4: Dispatch outbound WhatsApp response
    await step.run('dispatch-response', async () =\>
      sendWhatsAppResponse(message.from, intentResult)
    );
  });
};

{
  "intents": ["offer", "demand"],
  "language": "fr",
  "offers": [
    { "subject": "Mathematics", "grade": "Year 8", "condition": "good" },
    { "subject": "Biology", "grade": "Year 8", "condition": "good" }
  ],
  "demands": [{ "subject": "Physics", "grade": "Year 11" }]
}