[CLI] Fix Node 26 MCP Timeout

src/mcp.ts

@@ -12,6 +12,20 @@ const MCP_URL = "https://mcp2.readwise.io/mcp";
 // replies.
 const MCP_TIMEOUT_MS = 30_000;
 
+export function createMcpFetch(baseFetch: typeof fetch = fetch): typeof fetch {
+  return (url, init) => {
+    const method = (init?.method ?? (url instanceof Request ? url.method : "GET")).toUpperCase();
+    if (method === "GET") {
+      // The CLI never consumes server-initiated MCP messages; opting out avoids
+      // Node 26/undici stalls when the SDK keeps this optional SSE stream open.
+      return Promise.resolve(new Response(null, { status: 405, statusText: "Method Not Allowed" }));
+    }
+    return baseFetch(url, init);
+  };
+}
+
+export const mcpFetch = createMcpFetch();
+
 function createTransport(token: string, authType: "oauth" | "token"): StreamableHTTPClientTransport {
   const authHeader = authType === "token" ? `Token ${token}` : `Bearer ${token}`;
   return new StreamableHTTPClientTransport(new URL(MCP_URL), {
@@ -20,6 +34,7 @@ function createTransport(token: string, authType: "oauth" | "token"): Streamable
         Authorization: authHeader,
       },
     },
+    fetch: mcpFetch,
   });
 }
 

tests/mcp.test.ts

@@ -0,0 +1,46 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { createMcpFetch } from "../src/mcp.js";
+
+test("mcp fetch opts out of the optional GET SSE stream", async () => {
+  let delegated = false;
+  const wrappedFetch = createMcpFetch(async () => {
+    delegated = true;
+    return new Response(null, { status: 500 });
+  });
+
+  const response = await wrappedFetch("https://mcp2.readwise.io/mcp", { method: "GET" });
+
+  assert.equal(response.status, 405);
+  assert.equal(response.statusText, "Method Not Allowed");
+  assert.equal(delegated, false);
+});
+
+test("mcp fetch delegates non-GET requests", async () => {
+  let seenUrl = "";
+  let seenMethod = "";
+  const wrappedFetch = createMcpFetch(async (url, init) => {
+    seenUrl = String(url);
+    seenMethod = init?.method ?? "";
+    return new Response("{}", { status: 200 });
+  });
+
+  const response = await wrappedFetch("https://mcp2.readwise.io/mcp", { method: "POST", body: "{}" });
+
+  assert.equal(response.status, 200);
+  assert.equal(seenUrl, "https://mcp2.readwise.io/mcp");
+  assert.equal(seenMethod, "POST");
+});
+
+test("mcp fetch reads the method from Request inputs", async () => {
+  let delegated = false;
+  const wrappedFetch = createMcpFetch(async () => {
+    delegated = true;
+    return new Response("{}", { status: 200 });
+  });
+
+  const response = await wrappedFetch(new Request("https://mcp2.readwise.io/mcp", { method: "POST" }));
+
+  assert.equal(response.status, 200);
+  assert.equal(delegated, true);
+});