diff --git a/README.md b/README.md
index 9b8c3c4f..a6b35a44 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,13 @@
 # 卫戍协议：盟约 · Stronghold Protocol: Alliance
 
+> [!WARNING]
+> **开发版（dev 分支）：不稳定，请勿用于公开服务器。** 这里是 0.2.1 的开发中代码，规则、数据和存档格式随时会变，可能有未发现的问题。想玩或开服请使用 [Releases](../../releases/latest) 页面的正式版整合包，或 `master` 分支。反馈问题时请注明「dev」和版本号（标题页底部、启动横幅和 `/healthz` 都会显示 `0.2.1-dev`）。开发版与正式版在同一地址下共用浏览器里保存的设置和登录信息，来回切换后如果界面异常，清除这个网站的数据即可。开发版不提供整合包。
+>
+> *Development branch: unstable — do not run it as a public server. Rules, data and saved settings may change at any time. Play or host the latest release (or the `master` branch) instead; when you report a bug from this branch, say "dev" and the version shown on the title screen. It shares the browser's saved settings with a release served at the same address — clear the site's data if the interface misbehaves after switching. No release zips are built from this branch.*
+
 《明日方舟》季节性自走棋塔防玩法「卫戍协议：盟约」的**非官方同人复刻**：浏览器即开即玩，单人或 1–4 人联机合作。
 
-![version](https://img.shields.io/badge/version-0.2.0-2ea44f)
+![version](https://img.shields.io/badge/version-0.2.1--dev-orange)
 ![license](https://img.shields.io/badge/code%20license-GPL--3.0--or--later-blue)
 ![node](https://img.shields.io/badge/node-22%20%7C%2024-339933)
 
@@ -37,7 +42,7 @@ English summary: [below](#english).
 
 - **独立模拟**（单人）与**同盟模拟**（1–4 人**合作**，没有 PvP；空位可以加 AI 队友）。
 - 服务器是一个 Node.js 程序，**战斗在各玩家的浏览器里模拟**（和官方一样），服务器只管经济与回合，一台低功耗小主机就能开服。
-- 当前版本 0.2.0：加入了补位、自选编队、多语言界面（English、日本語、한국어、繁體中文，后三种的界面文字为机器翻译）和自定义快捷键，并修复了 0.1.4 发布后玩家和 GitHub 上反馈的问题，详见 [CHANGELOG.md](CHANGELOG.md)。仍有少数规则按推断实现，与官方不一致的地方欢迎在 Issue 里反馈。
+- 本分支是 0.2.1 开发版（未发布）；最新正式版是 0.2.0，见 [CHANGELOG.md](CHANGELOG.md)。仍有少数规则按推断实现，与官方不一致的地方欢迎在 Issue 里反馈。
 
 ## 功能一览
 
diff --git a/package-lock.json b/package-lock.json
index 0ffd38c0..86a3c362 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "stronghold-protocol-alliance",
-  "version": "0.2.0",
+  "version": "0.2.1-dev",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "stronghold-protocol-alliance",
-      "version": "0.2.0",
+      "version": "0.2.1-dev",
       "hasInstallScript": true,
       "license": "GPL-3.0-or-later",
       "dependencies": {
diff --git a/package.json b/package.json
index f5de01be..2efcb326 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "stronghold-protocol-alliance",
-  "version": "0.2.0",
+  "version": "0.2.1-dev",
   "private": true,
   "description": "明日方舟「卫戍协议：盟约」非官方同人联机网页复刻（1–4 人合作，Node.js 服务器 + 浏览器客户端）",
   "license": "GPL-3.0-or-later",
diff --git a/shared/constants.js b/shared/constants.js
index e39b9655..6c282fdc 100644
--- a/shared/constants.js
+++ b/shared/constants.js
@@ -5,7 +5,7 @@ import { N_ } from './i18n.js';
 export const PROTOCOL_VERSION = 1;
 /** Release version shown to players (title screen, server banner, /healthz). Kept equal to package.json "version"
  * (test/version.test.js); PROTOCOL_VERSION above is the separate wire-format number. */
-export const APP_VERSION = '0.2.0';
+export const APP_VERSION = '0.2.1-dev';
 /** A development build (the public `dev` branch): the title screen, the boot banner and the README say so, and
  * tools/package.mjs refuses to build a release zip from it without --allow-dev. */
 export const DEV_BUILD = /-dev$/.test(APP_VERSION);