Relay upstream MCP elicitation

tests/gateway.test.ts

@@ -320,3 +320,97 @@ test("tools/call reports upstream SSE idle timeout", async () => {
     await upstream.close();
   }
 });
+
+test("tools/call relays upstream elicitation requests", async () => {
+  let resolveResponse: (() => void) | undefined;
+  const responseSeen = new Promise<void>((resolve) => { resolveResponse = resolve; });
+  let upstreamResponse: any = null;
+  const requests: any[] = [];
+  const server = http.createServer((req, res) => {
+    if (req.method !== "POST" || req.url !== "/mcp") {
+      res.statusCode = 404;
+      res.end();
+      return;
+    }
+    const chunks: Buffer[] = [];
+    req.on("data", (c) => chunks.push(c));
+    req.on("end", () => {
+      const body = JSON.parse(Buffer.concat(chunks).toString("utf8"));
+      requests.push({ headers: req.headers, body });
+      if (body.method === "tools/call") {
+        res.writeHead(200, {
+          "content-type": "text/event-stream",
+          "Mcp-Session-Id": "sess-1",
+        });
+        res.write(
+          `data: ${JSON.stringify({
+            jsonrpc: "2.0",
+            id: "ask-1",
+            method: "elicitation/create",
+            params: { message: "Name?", requestedSchema: { type: "object" } },
+          })}\n\n`,
+        );
+        void responseSeen.then(() => {
+          res.end(
+            `data: ${JSON.stringify({
+              jsonrpc: "2.0",
+              id: body.id,
+              result: {
+                content: [{ type: "text", text: upstreamResponse.result.content.answer }],
+                isError: false,
+              },
+            })}\n\n`,
+          );
+        });
+        return;
+      }
+      if (body.id === "ask-1" && req.headers["mcp-session-id"] === "sess-1") {
+        upstreamResponse = body;
+        res.statusCode = 202;
+        res.end();
+        resolveResponse?.();
+        return;
+      }
+      res.setHeader("content-type", "application/json");
+      res.end(JSON.stringify({ jsonrpc: "2.0", id: body.id, result: {} }));
+    });
+  });
+  const upstream = await new Promise<{ url: string; close: () => Promise<void> }>((resolve) => {
+    server.listen(0, "127.0.0.1", () => {
+      const { port } = server.address() as AddressInfo;
+      resolve({
+        url: `http://127.0.0.1:${port}`,
+        close: () => new Promise((r) => server.close(() => r())),
+      });
+    });
+  });
+  const clientRequests: any[] = [];
+  try {
+    const result = await callGateway(
+      [{ name: "human", url: upstream.url, addedAt: "now" }],
+      null,
+      "tools/call",
+      { name: `human${SEP}run_demo`, arguments: {} },
+      {
+        extra: {
+          requestId: "req-elicitation",
+          sendNotification: async () => {},
+          sendRequest: async (request: any) => {
+            clientRequests.push(request);
+            return { action: "accept", content: { answer: "Alice" } };
+          },
+        },
+      },
+    );
+    assert.equal(result.isError, false);
+    assert.equal(result.content[0].text, "Alice");
+    assert.equal(clientRequests[0].method, "elicitation/create");
+    assert.deepEqual(upstreamResponse.result, {
+      action: "accept",
+      content: { answer: "Alice" },
+    });
+    assert.ok(requests.some((r) => r.body.id === "ask-1"));
+  } finally {
+    await upstream.close();
+  }
+});