diff --git a/CHANGELOG.md b/CHANGELOG.md
index 05ba5497e..469e4d3ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,7 +34,7 @@
 - Tighten the local MCP server and embed mode. The panel's `panel_request`
   needs the key in its MCP server's panel page, and refuses Provider
   Settings, credential and model endpoints, `/mcp` and development server
-  routes in any letter case or encoding; panels on one server share six
+  routes in any letter case, encoding or dot suffix; panels on one server share six
   requests in flight, and further requests wait their turn. `/mcp` applies Provider Settings' proxy and sharing checks,
   requires a Host on the port it reached and an Origin from that host, and
   times out request bodies after 30 seconds; stdio honors
diff --git a/docs/TOOLS.md b/docs/TOOLS.md
index dcea4be1b..401058d91 100644
--- a/docs/TOOLS.md
+++ b/docs/TOOLS.md
@@ -136,7 +136,7 @@ map imagery, tiles and fonts load directly, from the providers the
 resource's `csp` lists. `panel_request` refuses Provider Settings
 (`/api/setup`), credential and model endpoints (`/api/realtime`,
 `/api/openai`), `/mcp` and the development server's internal routes, in any
-letter case or encoding.
+letter case, encoding or dot suffix.
 
 The panel loads the app's panel build, which `npm run build:panel` writes to
 `dist/panel` and the servers serve at `/panel/`: one app script, one
diff --git a/src/tools/localRoute.test.mjs b/src/tools/localRoute.test.mjs
index d02b3d014..224660ffc 100644
--- a/src/tools/localRoute.test.mjs
+++ b/src/tools/localRoute.test.mjs
@@ -1,6 +1,7 @@
 import assert from 'node:assert/strict';
 import { createServer, request as httpRequest } from 'node:http';
 import test from 'node:test';
+import { fileURLToPath } from 'node:url';
 import { isLocalMcpRequest, localMcpPlugin } from '../../server/mcp/plugin.js';
 
 test('only direct loopback connections to this server are local', () => {
@@ -236,3 +237,96 @@ test('a client that stops sending its request body is answered with a timeout',
   });
   assert.equal(status, 408);
 });
+
+test('panel requests cannot reach /mcp through a suffix the server routes to it', async (t) => {
+  const { createServer: createViteServer } = await import('vite');
+  const vite = await createViteServer({
+    root: fileURLToPath(new URL('../../', import.meta.url)),
+    configFile: false,
+    envFile: false,
+    publicDir: false,
+    logLevel: 'silent',
+    plugins: [localMcpPlugin()],
+    optimizeDeps: { noDiscovery: true, include: [] },
+    server: { host: '127.0.0.1', port: 0, hmr: false, watch: null },
+  });
+  await vite.listen();
+  t.after(() => vite.close());
+  const { port } = vite.httpServer.address();
+  const rpc = (path, message) =>
+    new Promise((resolve, reject) => {
+      const body = JSON.stringify(message);
+      const request = httpRequest(
+        {
+          host: '127.0.0.1',
+          port,
+          path,
+          method: 'POST',
+          headers: {
+            'Content-Type': 'application/json',
+            Host: `localhost:${port}`,
+          },
+        },
+        (response) => {
+          let text = '';
+          response.on('data', (chunk) => (text += chunk));
+          response.on('end', () =>
+            resolve({ status: response.statusCode, text }),
+          );
+        },
+      );
+      request.on('error', reject);
+      request.end(body);
+    });
+
+  // The hazard is real: the server routes /mcp.json to the MCP endpoint.
+  const direct = await rpc('/mcp.json', {
+    jsonrpc: '2.0',
+    id: 1,
+    method: 'ping',
+  });
+  assert.equal(direct.status, 200);
+  assert.deepEqual(JSON.parse(direct.text), {
+    jsonrpc: '2.0',
+    id: 1,
+    result: {},
+  });
+
+  const page = JSON.parse(
+    (
+      await rpc('/mcp', {
+        jsonrpc: '2.0',
+        id: 2,
+        method: 'resources/read',
+        params: { uri: 'ui://gods-eye-view/globe' },
+      })
+    ).text,
+  );
+  const [, key] = page.result.contents[0].text.match(/"panelKey":"([^"]+)"/);
+  const body = Buffer.from(
+    JSON.stringify({ jsonrpc: '2.0', id: 3, method: 'ping' }),
+  ).toString('base64');
+  for (const path of ['/mcp', '/mcp.json', '/MCP.json', '/mcp.anything']) {
+    const answer = JSON.parse(
+      (
+        await rpc('/mcp', {
+          jsonrpc: '2.0',
+          id: 4,
+          method: 'tools/call',
+          params: {
+            name: 'panel_request',
+            arguments: {
+              key,
+              path,
+              method: 'POST',
+              headers: { 'Content-Type': 'application/json' },
+              body,
+            },
+          },
+        })
+      ).text,
+    );
+    assert.equal(answer.result.isError, true, path);
+    assert.match(answer.result.content[0].text, /is not available/, path);
+  }
+});
diff --git a/src/tools/queries/panelRequest.js b/src/tools/queries/panelRequest.js
index 8606d7809..3864c9889 100644
--- a/src/tools/queries/panelRequest.js
+++ b/src/tools/queries/panelRequest.js
@@ -25,13 +25,14 @@ const HELD_LIMIT_BYTES = 256 * 1024 * 1024;
 export const PANEL_RESPONSE_LIMIT_BYTES = 64 * 1024 * 1024;
 const REQUEST_TIMEOUT_MS = 60 * 1000;
 const METHODS = new Set(['GET', 'HEAD', 'POST']);
-// Routes the panel never loads, matched without regard to case as the
-// server routes them: Provider Settings, which only the app's own page may
-// use; credential and model endpoints; the MCP server itself; and the
-// development server's internal routes.
+// Routes the panel never loads, matched as the server routes them: without
+// regard to case, and with a mounted route also matching when a dot follows
+// it (`/mcp.json` reaches `/mcp`). Provider Settings, which only the app's own
+// page may use; credential and model endpoints; the MCP server itself; and
+// the development server's internal routes.
 const REFUSED_PATHS = [
-  /^\/api\/(?:setup|realtime|openai)(?:\/|$)/i,
-  /^\/mcp(?:\/|$)/i,
+  /^\/api\/(?:setup|realtime|openai)(?:[/.]|$)/i,
+  /^\/mcp(?:[/.]|$)/i,
   /^\/(?:@|__)/,
 ];
 const FORWARDED_REQUEST_HEADERS = ['accept', 'content-type'];
diff --git a/src/tools/queries/panelRequest.test.mjs b/src/tools/queries/panelRequest.test.mjs
index 05bce98f9..bdd94bcec 100644
--- a/src/tools/queries/panelRequest.test.mjs
+++ b/src/tools/queries/panelRequest.test.mjs
@@ -234,6 +234,12 @@ test('routes the panel never loads are refused in any case or encoding', async (
     '/api/%4fpenai/hud-summary',
     '/mcp',
     '/MCP',
+    // A dot after a mounted route still reaches it.
+    '/mcp.json',
+    '/MCP.json',
+    '/api/setup.json',
+    '/api/realtime.token',
+    '/api/OpenAI.x/hud-summary',
     '/@fs/etc/passwd',
     '/@vite/client',
     '/%40fs/x',