https://www.xlabs.club/tags/node.js/Recent content in Node.js on XLabsHugozh-CNCopyright (c) 2020-2025 XLabs ClubWed, 16 Sep 2026 00:05:15 +0800https://www.xlabs.club/blog/mcp-2026-07-28-version-negotiation/Tue, 15 Sep 2026 00:00:00 +0800https://www.xlabs.club/blog/mcp-2026-07-28-version-negotiation/<p>2026-07-28 这一版 MCP 把 <code>initialize</code> 握手删了。协议版本不再是&quot;协商一次、存在连接里&quot;的状态，而是每个请求自己在 <code>_meta</code> 里声明；server 则必须实现 <code>server/discover</code>。</p> <p>实测下来四件事：</p> <ul> <li>老客户端（官方 v1 SDK <code>@modelcontextprotocol/sdk@1.29.0</code>，<code>LATEST_PROTOCOL_VERSION = '2025-11-25'</code>）不做探测，首包永远是 <code>initialize</code>。</li> <li>新客户端（<code>mcporter@0.13.10</code>，依赖 v2 的 <code>@modelcontextprotocol/client@2.0.0</code>）先发 <code>server/discover</code>，拿到非 modern 错误就回退 <code>initialize</code>。<strong>只认老协议的 server 不用改，照样能被新客户端用。</strong></li> <li>老客户端撞上只支持 2026-07-28 的 server 会直接失败。它没有&quot;向前兼容&quot;机制，只能人肉改。</li> <li>最容易翻车的不是版本号，是缓存字段：<code>tools/list</code> 漏 <code>ttlMs</code> / <code>cacheScope</code>，v2 客户端直接判定整个结果非法。</li> </ul> <h2 id="先确认手上的包属于哪一代">先确认手上的包属于哪一代</h2> <div class="expressive-code"> <figure class="frame is-terminal not-content"> <figcaption class="header"> <span class="title"></span> </figcaption> <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-bash" data-lang="bash"><span class="line"><span class="cl"><span class="c1"># v1 线：还是 initialize 握手</span> </span></span><span class="line"><span class="cl">node -p <span class="s2">&#34;require(&#39;@modelcontextprotocol/sdk/package.json&#39;).version&#34;</span> </span></span><span class="line"><span class="cl">node -p <span class="s2">&#34;require(&#39;@modelcontextprotocol/sdk/dist/cjs/types.js&#39;).LATEST_PROTOCOL_VERSION&#34;</span> </span></span><span class="line"><span class="cl"> </span></span><span class="line"><span class="cl"><span class="c1"># v2 线：实现 2026-07-28</span> </span></span><span class="line"><span class="cl">node -p <span class="s2">&#34;require(&#39;@modelcontextprotocol/server/package.json&#39;).version&#34;</span></span></span></code></pre></div> </figure> </div> <p>本机实测值（Node 26.3.0）：</p> <table> <thead> <tr> <th>包</th> <th>版本</th> <th>协议</th> </tr> </thead> <tbody> <tr> <td><code>@modelcontextprotocol/sdk</code></td> <td>1.29.0</td> <td><code>LATEST_PROTOCOL_VERSION = '2025-11-25'</code>，SUPPORTED 一路到 <code>2024-10-07</code></td> </tr> <tr> <td><code>@modelcontextprotocol/core</code> / <code>server</code> / <code>client</code></td> <td>2.0.0</td> <td>2026-07-28，v2 是官方 README 里写明的 stable release line</td> </tr> <tr> <td><code>mcporter</code></td> <td>0.13.10</td> <td>依赖 <code>@modelcontextprotocol/client@^2.0.0</code></td> </tr> </tbody> </table> <p>同一台机器上两代 SDK 并存，这就是断层。</p>