diff --git a/clients/web/src/test/core/auth/requestTimeout.test.ts b/clients/web/src/test/core/auth/requestTimeout.test.ts
index 1875d878..c7cb609f 100644
--- a/clients/web/src/test/core/auth/requestTimeout.test.ts
+++ b/clients/web/src/test/core/auth/requestTimeout.test.ts
@@ -88,6 +88,36 @@ describe("withOAuthRequestTimeout", () => {
     expect(timeout.timeoutMs).toBe(1000);
   });
 
+  it("redacts sensitive query values from the endpoint it names", async () => {
+    vi.useFakeTimers();
+    // This message is recorded verbatim by `createFetchTracker` into the
+    // Network log and the persisted session, and an OAuth endpoint's query
+    // string can carry a `code`, an `access_token` or a `client_secret` —
+    // which `fetchTracking` already redacts everywhere else it records a URL.
+    const sensitive =
+      "https://as.example.com/token?code=abc123&client_secret=shhh&state=keepme";
+    const wrapped = withOAuthRequestTimeout(neverSettles, 1000);
+
+    const assertion = wrapped(sensitive).catch((err: unknown) => err);
+    await vi.advanceTimersByTimeAsync(1000);
+    const err = (await assertion) as OAuthRequestTimeoutError;
+
+    for (const secret of ["abc123", "shhh"]) {
+      expect(err.message).not.toContain(secret);
+      expect(err.url).not.toContain(secret);
+    }
+    // Still identifiable, which was the point of naming the endpoint: the path
+    // and every non-sensitive parameter survive. Read through `URL`, since
+    // `URLSearchParams.toString()` percent-encodes the redaction marker.
+    const redacted = new URL(err.url);
+    expect(redacted.origin + redacted.pathname).toBe(
+      "https://as.example.com/token",
+    );
+    expect(redacted.searchParams.get("state")).toBe("keepme");
+    expect(redacted.searchParams.get("code")).toBe("[REDACTED]");
+    expect(redacted.searchParams.get("client_secret")).toBe("[REDACTED]");
+  });
+
   it("takes the URL off a Request object too", async () => {
     vi.useFakeTimers();
     const wrapped = withOAuthRequestTimeout(neverSettles, 1000);
diff --git a/core/auth/requestTimeout.ts b/core/auth/requestTimeout.ts
index 3ccca28d..ba06e53f 100644
--- a/core/auth/requestTimeout.ts
+++ b/core/auth/requestTimeout.ts
@@ -63,6 +63,8 @@
  * halves the 60s the SDK handshake incidentally provides, and it is the only
  * bound at all on the legs that sit outside an SDK request.
  */
+import { redactUrlQuery } from "../mcp/fetchTracking.js";
+
 export const DEFAULT_OAUTH_REQUEST_TIMEOUT_MS = 30_000;
 
 /**
@@ -73,13 +75,26 @@ export const DEFAULT_OAUTH_REQUEST_TIMEOUT_MS = 30_000;
  * hosts, and which of them stalled is the whole diagnostic.
  */
 export class OAuthRequestTimeoutError extends Error {
+  /**
+   * The endpoint that stalled, with sensitive query values redacted.
+   *
+   * Redacted in the constructor rather than at each display site, so every
+   * consumer is covered by construction: this error's message is recorded
+   * verbatim by `createFetchTracker` into the Network log and the persisted
+   * session, and an OAuth endpoint can carry a `code`, an `access_token` or a
+   * `client_secret` in its query string — which `fetchTracking` already
+   * deliberately redacts everywhere else it records a URL (Copilot). The path
+   * and every non-sensitive parameter survive, so the endpoint stays
+   * identifiable, which was the point of naming it.
+   */
   readonly url: string;
   readonly timeoutMs: number;
 
   constructor(url: string, timeoutMs: number) {
-    super(`OAuth request to ${url} timed out after ${timeoutMs}ms`);
+    const safeUrl = redactUrlQuery(url);
+    super(`OAuth request to ${safeUrl} timed out after ${timeoutMs}ms`);
     this.name = "OAuthRequestTimeoutError";
-    this.url = url;
+    this.url = safeUrl;
     this.timeoutMs = timeoutMs;
   }
 }
diff --git a/core/mcp/remote/node/server.ts b/core/mcp/remote/node/server.ts
index 62819249..ccdc7a8b 100644
--- a/core/mcp/remote/node/server.ts
+++ b/core/mcp/remote/node/server.ts
@@ -29,6 +29,7 @@ import { watch as chokidarWatch, type FSWatcher } from "chokidar";
 import { createTransportNode } from "../../node/transport.js";
 import { createProxyFetch } from "../../node/proxyFetch.js";
 import { OAUTH_TIMEOUT_WIRE_CODE } from "../../../auth/requestTimeout.js";
+import { redactUrlQuery } from "../../fetchTracking.js";
 import type {
   RemoteConnectRequest,
   RemoteSendRequest,
@@ -1266,6 +1267,11 @@ export function createRemoteApp(
       Number.isFinite(requestedTimeoutMs)
         ? Math.min(2_147_483_647, Math.max(0, Math.round(requestedTimeoutMs)))
         : undefined;
+    // Redacted for the same reason `OAuthRequestTimeoutError` redacts: this
+    // message and this URL are handed back to the browser, recorded in the
+    // Network log and persisted, and an OAuth endpoint's query string can carry
+    // a `code`, an `access_token` or a `client_secret` (Copilot).
+    const safeUrl = redactUrlQuery(url);
     const timer =
       deadlineMs === undefined
         ? undefined
@@ -1273,7 +1279,7 @@ export function createRemoteApp(
             deadlineFired = true;
             controller.abort(
               new Error(
-                `proxied request to ${url} timed out after ${deadlineMs}ms`,
+                `proxied request to ${safeUrl} timed out after ${deadlineMs}ms`,
               ),
             );
           }, deadlineMs);
@@ -1338,7 +1344,7 @@ export function createRemoteApp(
           {
             error: msg,
             code: OAUTH_TIMEOUT_WIRE_CODE,
-            url,
+            url: safeUrl,
             timeoutMs: deadlineMs,
           },
           504,