App Store 和 Google Play 上的 AI 聊天应用：真正会被执行的规则

// POST /api/chat  (server only; the API key never reaches the client)
export async function POST(req) {
  const user = await requireSession(req);                 // 401 if not signed in
  const { message, conversationId } = await req.json();

  const usage = await getDailyUsage(user.id);             // messages and tokens today
  if (usage.messages >= user.plan.dailyMessages) {
    return json({ error: "limit", message: "Daily limit reached. Resets at midnight." }, 429);
  }

  const flagged = await moderate(message);                // provider moderation endpoint
  if (flagged.blocked) {
    await logModeration(user.id, conversationId, flagged);
    return json({ error: "moderated", message: "That request cannot be processed." }, 400);
  }

  const reply = await callModel({
    messages: await history(conversationId, 20),          // bounded context window
    maxTokens: 600,                                       // caps cost per answer
    userTag: hash(user.id),                               // abuse attribution at the provider
  });

  const outFlag = await moderate(reply.text);
  const text = outFlag.blocked ? "I cannot help with that." : reply.text;

  await recordUsage(user.id, reply.tokens);
  await saveTurn(conversationId, message, text, { reportable: true });
  return json({ text, conversationId });
}