Merge pull request #2363 from modelcontextprotocol/v2/fix/2028-stdio-delayed-responses

fix: reset relay request-response waits on progress notifications (#2028)

core/mcp/remote/node/remote-session.ts

@@ -10,6 +10,7 @@ import type { AuthChallenge } from "../../../auth/challenge.js";
 import { AuthChallengeError } from "../../../auth/challenge.js";
 import type { RemoteAuthProviderHandle } from "./tokenAuthProvider.js";
 import type { RemoteAuthState } from "../types.js";
+import { progressTokenOf } from "../progressToken.js";
 
 export interface SessionEvent {
   type: RemoteEvent["type"];
@@ -19,6 +20,14 @@ export interface SessionEvent {
 type RequestWait = {
   resolve: () => void;
   reject: (error: Error) => void;
+  /**
+   * Re-arm this wait's timeout for another full window. Called when a
+   * `notifications/progress` for this request arrives, mirroring the SDK
+   * client's `resetTimeoutOnProgress` so the relay's own deadline never fires
+   * before the client's progress-aware one (#2028). A no-op when the wait was
+   * created without a timeout.
+   */
+  resetTimeout: () => void;
 };
 
 export class RemoteSession {
@@ -172,35 +181,57 @@ export class RemoteSession {
     timeoutMs = 60_000,
   ): Promise<void> {
     return new Promise((resolve, reject) => {
-      const timer =
-        timeoutMs > 0
-          ? setTimeout(() => {
-              this.requestWaits.delete(requestId);
-              reject(
-                new Error(
-                  `MCP request ${String(requestId)} timed out after ${timeoutMs}ms`,
-                ),
-              );
-            }, timeoutMs)
-          : undefined;
+      let timer: ReturnType<typeof setTimeout> | undefined;
+      const arm = () => {
+        if (timeoutMs <= 0) return;
+        timer = setTimeout(() => {
+          this.requestWaits.delete(requestId);
+          reject(
+            new Error(
+              `MCP request ${String(requestId)} timed out after ${timeoutMs}ms`,
+            ),
+          );
+        }, timeoutMs);
+      };
+      const clear = () => {
+        if (timer !== undefined) {
+          clearTimeout(timer);
+          timer = undefined;
+        }
+      };
+      arm();
 
       this.requestWaits.set(requestId, {
         resolve: () => {
-          if (timer !== undefined) {
-            clearTimeout(timer);
-          }
+          clear();
           resolve();
         },
         reject: (error) => {
-          if (timer !== undefined) {
-            clearTimeout(timer);
-          }
+          clear();
           reject(error);
         },
+        // A progress notification for this request re-arms the full window, so
+        // a tool that keeps reporting progress never trips the relay's own
+        // deadline — the same guarantee the SDK client's `resetTimeoutOnProgress`
+        // gives on a direct transport (#2028).
+        resetTimeout: () => {
+          if (timer === undefined) return;
+          clear();
+          arm();
+        },
       });
     });
   }
 
+  /**
+   * Re-arm a pending request's wait timeout. Invoked from {@link onMessage} when
+   * a `notifications/progress` carrying this request's `progressToken` arrives.
+   * A no-op when no wait is pending for the id.
+   */
+  noteRequestProgress(requestId: string | number): void {
+    this.requestWaits.get(requestId)?.resetTimeout();
+  }
+
   cancelRequestWait(requestId: string | number): void {
     const wait = this.requestWaits.get(requestId);
     if (!wait) {
@@ -265,6 +296,15 @@ export class RemoteSession {
     ) {
       this.settleRequestWait(message.id);
     }
+    // A `notifications/progress` carries the originating request's id in
+    // `params.progressToken` (the SDK stamps `progressToken: messageId`). Re-arm
+    // that request's wait so the relay's deadline tracks the client's
+    // progress-aware one instead of firing at a flat 60s (#2028). Log messages
+    // (`notifications/message`) deliberately do NOT reset it, matching the SDK.
+    const progressToken = progressTokenOf(message);
+    if (progressToken !== undefined) {
+      this.noteRequestProgress(progressToken);
+    }
     this.pushEvent({ type: "message", data: message });
   }
 

core/mcp/remote/progressToken.ts

@@ -0,0 +1,40 @@
+/**
+ * Shared helper for the remote relay's progress-aware request-response waits
+ * (#2028). Pure and browser-safe, so both the browser `RemoteClientTransport`
+ * and the Node `RemoteSession` import it rather than each carrying a copy.
+ */
+
+import { ProgressTokenSchema } from "@modelcontextprotocol/core";
+import type { JSONRPCMessage } from "@modelcontextprotocol/client";
+
+/**
+ * The token identifying the request a `notifications/progress` belongs to, or
+ * `undefined` for any other message. The SDK stamps `progressToken: messageId`
+ * on the outbound request, so a progress notification's `progressToken` is the
+ * id of the request whose wait should be re-armed.
+ *
+ * Validation is delegated to the SDK's own `ProgressTokenSchema` rather than a
+ * hand-rolled `typeof` check — the protocol allows only a string or a *safe*
+ * integer, and zod's `.int()` rejects a fractional or past-`MAX_SAFE_INTEGER`
+ * value that a bare `typeof token === "number"` would wave through (the same
+ * drift `isProgressToken` in `core/mcp/inspectorClient.ts` exists to avoid).
+ */
+export function progressTokenOf(
+  message: JSONRPCMessage,
+): string | number | undefined {
+  if (
+    "method" in message &&
+    message.method === "notifications/progress" &&
+    "params" in message &&
+    typeof message.params === "object" &&
+    message.params !== null
+  ) {
+    const parsed = ProgressTokenSchema.safeParse(
+      (message.params as { progressToken?: unknown }).progressToken,
+    );
+    if (parsed.success) {
+      return parsed.data;
+    }
+  }
+  return undefined;
+}

core/mcp/remote/remoteClientTransport.ts

@@ -31,6 +31,7 @@ import type {
   RemoteSendResponse,
 } from "./types.js";
 import { oauthTokensToRemoteAuthState } from "./types.js";
+import { progressTokenOf } from "./progressToken.js";
 
 export interface AuthRecoveryHandlers {
   handleAuthChallenge(
@@ -85,6 +86,12 @@ const DEFAULT_SSE_RESPONSE_TIMEOUT_MS = 60_000;
 type SseResponseWait = {
   resolve: () => void;
   reject: (error: Error) => void;
+  /**
+   * Re-arm this wait's timeout for another full window when a
+   * `notifications/progress` for the request arrives, mirroring the SDK
+   * client's `resetTimeoutOnProgress` (#2028).
+   */
+  resetTimeout: () => void;
 };
 
 function requestIdForMessage(
@@ -524,6 +531,13 @@ export class RemoteClientTransport implements Transport {
           if (parsed.type === "message") {
             const msg = parsed.data as JSONRPCMessage;
             this.settleSseResponseWait(msg);
+            // Keep the SSE wait alive while progress flows for a long call
+            // (#2028) — the settle above never matches a notification, so this
+            // is the only place a progress note touches the wait.
+            const progressToken = progressTokenOf(msg);
+            if (progressToken !== undefined) {
+              this.resetSseResponseWait(progressToken);
+            }
             this.onmessage?.(msg, undefined);
           } else if (
             parsed.type === "fetch_request" &&
@@ -675,14 +689,18 @@ export class RemoteClientTransport implements Transport {
 
   private waitForSseResponse(requestId: string | number): Promise<void> {
     return new Promise((resolve, reject) => {
-      const timer = setTimeout(() => {
-        this.sseResponseWaits.delete(requestId);
-        reject(
-          new Error(
-            `Timed out waiting for MCP response on SSE (${this.sseResponseTimeoutMs}ms)`,
-          ),
-        );
-      }, this.sseResponseTimeoutMs);
+      let timer: ReturnType<typeof setTimeout>;
+      const arm = () => {
+        timer = setTimeout(() => {
+          this.sseResponseWaits.delete(requestId);
+          reject(
+            new Error(
+              `Timed out waiting for MCP response on SSE (${this.sseResponseTimeoutMs}ms)`,
+            ),
+          );
+        }, this.sseResponseTimeoutMs);
+      };
+      arm();
       this.sseResponseWaits.set(requestId, {
         resolve: () => {
           clearTimeout(timer);
@@ -692,10 +710,22 @@ export class RemoteClientTransport implements Transport {
           clearTimeout(timer);
           reject(error);
         },
+        // A progress notification for this request re-arms the full window so
+        // the browser-side deadline tracks the SDK client's progress-aware one
+        // rather than firing at a flat 60s (#2028).
+        resetTimeout: () => {
+          clearTimeout(timer);
+          arm();
+        },
       });
     });
   }
 
+  /** Re-arm a pending request's SSE wait timeout on a matching progress note. */
+  private resetSseResponseWait(requestId: string | number): void {
+    this.sseResponseWaits.get(requestId)?.resetTimeout();
+  }
+
   private async postSend(
     message: JSONRPCMessage,
     options: TransportSendOptions | undefined,