diff --git a/src/app/api/auth/send-otp/route.ts b/src/app/api/auth/send-otp/route.ts
index 8a8cff3..6041e61 100644
--- a/src/app/api/auth/send-otp/route.ts
+++ b/src/app/api/auth/send-otp/route.ts
@@ -2,7 +2,7 @@ import type { NextRequest } from "next/server";
 import { z } from "zod";
 import { rateLimit } from "@/lib/rate-limit";
 import { getClientIp } from "@/lib/current-user";
-import { getRedis } from "@/lib/redis";
+import { storeOtp } from "@/lib/otp-store";
 import { sendOtpSms } from "@/lib/sms";
 import { ok, ERR } from "@/lib/api-response";
 
@@ -35,13 +35,13 @@ export async function POST(req: NextRequest) {
       if (!ipRl.allowed) return ERR.RATE_LIMITED();
     }
 
-    // 生成 6 位验证码
+    // 生成 6 位验证码 + 存储 (Redis 可用走 Redis, 否则走进程内 Map; 始终 5min TTL)
     const code = String(Math.floor(100000 + Math.random() * 900000));
+    await storeOtp(phone, code);
 
-    // 缓存到 Redis（5 分钟过期）。Redis 未配置时 dev 仍能通过万能码 123456 走完整流程
-    const redis = getRedis();
-    if (redis) {
-      await redis.set(`sms:otp:${phone}`, code, "EX", 300);
+    // 开发环境下把验证码打在终端, 方便本地 QA / 排错; 生产不打
+    if (process.env.NODE_ENV !== "production") {
+      console.log(`[dev-otp] phone=${phone} code=${code} (dev 环境也接受 123456)`);
     }
 
     // 调阿里云短信发送
diff --git a/src/lib/auth.ts b/src/lib/auth.ts
index 9d249c1..e1589c8 100644
--- a/src/lib/auth.ts
+++ b/src/lib/auth.ts
@@ -1,7 +1,7 @@
 import NextAuth, { type NextAuthConfig } from "next-auth";
 import Credentials from "next-auth/providers/credentials";
 import { prisma } from "./prisma";
-import { getRedis } from "./redis";
+import { consumeOtp } from "./otp-store";
 import { z } from "zod";
 
 /**
@@ -103,27 +103,14 @@ export const { handlers, signIn, signOut, auth } = NextAuth(authConfig);
 
 /**
  * 校验 OTP 验证码。
- *  - 开发态万能码 "123456" 始终通过（仅 NODE_ENV !== "production"）
- *  - 否则从 Redis 读取并比对，校验通过后立即 del 避免重放
- *  - Redis 未配置时无法核对，无论环境一律拒绝（不允许"任意 6 位"放行漏洞）
+ *  - 开发态万能码 "123456" 始终通过（仅 NODE_ENV !== "production"，不走 SMS）
+ *  - 真实码通过 consumeOtp 核对（Redis 或进程内 Map，由 otp-store 决定）；
+ *    校验通过后立即销毁该码防止重放
  */
 async function verifyOtp(phone: string, code: string): Promise<boolean> {
   if (process.env.NODE_ENV !== "production" && code === "123456") {
     console.log(`[dev-otp] 手机号 ${phone} 使用万能码 123456 通过`);
     return true;
   }
-
-  const redis = getRedis();
-  if (!redis) {
-    console.error(
-      `[auth] Redis 未配置，无法核对 OTP，拒绝 phone=${phone}（dev 联调请用 123456）`,
-    );
-    return false;
-  }
-
-  const key = `sms:otp:${phone}`;
-  const stored = await redis.get(key);
-  if (!stored || stored !== code) return false;
-  await redis.del(key);
-  return true;
+  return await consumeOtp(phone, code);
 }
diff --git a/src/lib/otp-store.ts b/src/lib/otp-store.ts
new file mode 100644
index 0000000..8bb51be
--- /dev/null
+++ b/src/lib/otp-store.ts
@@ -0,0 +1,65 @@
+/**
+ * OTP 验证码存储抽象层。
+ *
+ * 路由策略:
+ *  - Redis 可用 → 走 Redis (生产, 多实例, 跨重启)
+ *  - Redis 缺失 → 降级到进程内 Map (dev 联调; 单实例; 重启丢失但 5min TTL 无所谓)
+ *
+ * 不能"Redis 缺失就直接通过校验" —— 那会复活之前的安全漏洞。
+ * 必须真实生成 / 真实存储 / 真实核对。
+ */
+import { getRedis } from "./redis";
+
+const TTL_SECONDS = 300;
+const redisKey = (phone: string) => `sms:otp:${phone}`;
+
+// 通过 globalThis 防止 Next dev HMR 重置模块导致 Map 丢失
+declare global {
+  // eslint-disable-next-line no-var
+  var __otpMemStore: Map<string, { code: string; expiresAt: number }> | undefined;
+}
+const mem: Map<string, { code: string; expiresAt: number }> =
+  globalThis.__otpMemStore ?? (globalThis.__otpMemStore = new Map());
+
+/** 清理 mem 里过期的条目, 防止长跑后内存膨胀 */
+function sweep() {
+  const now = Date.now();
+  for (const [phone, entry] of mem) {
+    if (entry.expiresAt <= now) mem.delete(phone);
+  }
+}
+
+/** 存验证码 (覆盖该手机号的旧码) */
+export async function storeOtp(phone: string, code: string): Promise<void> {
+  const redis = getRedis();
+  if (redis) {
+    await redis.set(redisKey(phone), code, "EX", TTL_SECONDS);
+    return;
+  }
+  sweep();
+  mem.set(phone, { code, expiresAt: Date.now() + TTL_SECONDS * 1000 });
+}
+
+/**
+ * 核对验证码;
+ * 通过则立即销毁该码 (防止重放), 返回 true;
+ * 失败 (码不存在 / 已过期 / 不匹配) 返回 false。
+ */
+export async function consumeOtp(phone: string, code: string): Promise<boolean> {
+  const redis = getRedis();
+  if (redis) {
+    const stored = await redis.get(redisKey(phone));
+    if (!stored || stored !== code) return false;
+    await redis.del(redisKey(phone));
+    return true;
+  }
+  const entry = mem.get(phone);
+  if (!entry) return false;
+  if (Date.now() > entry.expiresAt) {
+    mem.delete(phone);
+    return false;
+  }
+  if (entry.code !== code) return false;
+  mem.delete(phone);
+  return true;
+}
diff --git a/tools/test-otp-store.mjs b/tools/test-otp-store.mjs
new file mode 100644
index 0000000..edf59ff
--- /dev/null
+++ b/tools/test-otp-store.mjs
@@ -0,0 +1,26 @@
+// 真实跑 otp-store 的 store/consume 逻辑
+import { storeOtp, consumeOtp } from "../src/lib/otp-store.ts";
+
+const phone = "13900000000";
+const cases = [];
+
+await storeOtp(phone, "654321");
+cases.push(["wrong code 111111 → false", await consumeOtp(phone, "111111"), false]);
+cases.push(["right code 654321 → true",  await consumeOtp(phone, "654321"), true]);
+cases.push(["replay 654321 → false",      await consumeOtp(phone, "654321"), false]);
+cases.push(["never-stored phone → false", await consumeOtp("13800000001", "654321"), false]);
+
+// 过期测试
+await storeOtp(phone, "999000");
+// 直接改 globalThis 里的 expiresAt 模拟过期
+globalThis.__otpMemStore.set(phone, { code: "999000", expiresAt: Date.now() - 1 });
+cases.push(["expired code → false", await consumeOtp(phone, "999000"), false]);
+
+let pass = 0, fail = 0;
+for (const [desc, got, expect] of cases) {
+  const ok = got === expect;
+  console.log(`${ok ? "✓" : "✗"} ${desc.padEnd(35)} got=${got}`);
+  ok ? pass++ : fail++;
+}
+console.log(`\n${pass} passed, ${fail} failed`);
+process.exit(fail === 0 ? 0 : 1);