https://wlsc.de/tags/migration/ Recent content in Migration on wlsc Hugo en Sun, 11 Oct 2026 00:00:00 +0000 https://wlsc.de/posts/2026-10-11-mcp-v2/ Sun, 11 Oct 2026 00:00:00 +0000 https://wlsc.de/posts/2026-10-11-mcp-v2/ <h2 id="one-sentence"> One sentence <a class="heading-link" href="#one-sentence"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <p>The <a href="https://modelcontextprotocol.io/specification/2026-07-28" class="external-link" target="_blank" rel="noopener">2026-07-28 MCP spec</a> removes the connection. Every request now carries everything the server needs.</p> <p>Everything else follows from that.</p> <p><img src="https://wlsc.de/images/2026/10/mcp-v1-vs-v2.svg" alt="MCP before and after"></p> <h2 id="what-changed"> What changed <a class="heading-link" href="#what-changed"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <table> <thead> <tr> <th>Area</th> <th>Before (2025-11-25)</th> <th>Now (2026-07-28)</th> </tr> </thead> <tbody> <tr> <td>Handshake</td> <td><code>initialize</code> + <code>initialized</code></td> <td>Gone. Version and capabilities ride in <code>_meta</code> on each call</td> </tr> <tr> <td>Discovery</td> <td>Learned during handshake</td> <td>New mandatory <code>server/discover</code></td> </tr> <tr> <td>Sessions</td> <td><code>Mcp-Session-Id</code></td> <td>Gone</td> </tr> <tr> <td>HTTP</td> <td>POST + standalone GET stream, resumable</td> <td>POST only. No <code>Last-Event-ID</code>, a broken stream means retry</td> </tr> <tr> <td>Routing</td> <td>Parse the body</td> <td><code>Mcp-Method</code>, <code>Mcp-Name</code> headers, checked against the body</td> </tr> <tr> <td>Server asks client</td> <td><code>sampling</code>, <code>elicitation</code>, <code>roots</code> requests</td> <td>Return <code>input_required</code>, client retries with answers</td> </tr> <tr> <td>Notifications</td> <td>GET stream, <code>resources/subscribe</code></td> <td>One <code>subscriptions/listen</code> stream</td> </tr> <tr> <td>Caching</td> <td>None</td> <td><code>ttlMs</code> + <code>cacheScope</code> on list and read results</td> </tr> <tr> <td>Tasks</td> <td>Core</td> <td>Extension</td> </tr> <tr> <td>Client registration</td> <td>Dynamic Client Registration</td> <td>Client ID Metadata Documents preferred, DCR deprecated</td> </tr> </tbody> </table> <h2 id="what-it-means-for-you"> What it means for you <a class="heading-link" href="#what-it-means-for-you"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <p><strong>Servers get simpler to run.</strong> No session store, no sticky routing. Any instance behind any load balancer can answer any request. Gateways can route on headers without parsing JSON.</p>