diff --git a/clients/web/src/test/core/mcp/serverList.test.ts b/clients/web/src/test/core/mcp/serverList.test.ts
index 824419b5..c6dc9436 100644
--- a/clients/web/src/test/core/mcp/serverList.test.ts
+++ b/clients/web/src/test/core/mcp/serverList.test.ts
@@ -925,6 +925,27 @@ describe("extractSecretsFromStored", () => {
     expect(stripped.oauth).toEqual({ enterpriseManaged: true });
   });
 
+  // The stripped entry now subtracts the secret instead of enumerating the
+  // fields to keep, so a field added to `oauth` later survives by construction.
+  // `onInsufficientScope` is the case the old allow-list had already lost.
+  it("preserves oauth.onInsufficientScope when lifting clientSecret to keychain", () => {
+    const stored: StoredMCPServer = {
+      type: "streamable-http",
+      url: "https://x.test",
+      oauth: {
+        clientId: "cid",
+        clientSecret: "shh",
+        onInsufficientScope: "throw",
+      },
+    };
+    const { stripped, secrets } = extractSecretsFromStored(stored);
+    expect(secrets).toEqual({ [SECRET_FIELD_OAUTH_CLIENT_SECRET]: "shh" });
+    expect(stripped.oauth).toEqual({
+      clientId: "cid",
+      onInsufficientScope: "throw",
+    });
+  });
+
   it("preserves oauth.authorizationParams when lifting clientSecret to keychain", () => {
     const stored: StoredMCPServer = {
       type: "streamable-http",
diff --git a/core/mcp/serverList.ts b/core/mcp/serverList.ts
index 0c3c759e..c6e5e507 100644
--- a/core/mcp/serverList.ts
+++ b/core/mcp/serverList.ts
@@ -642,23 +642,13 @@ export function extractSecretsFromStored(
 
   if (stored.oauth?.clientSecret) {
     secrets[SECRET_FIELD_OAUTH_CLIENT_SECRET] = stored.oauth.clientSecret;
-    const restOauth: {
-      clientId?: string;
-      scopes?: string;
-      authorizationParams?: Record<string, string>;
-      enterpriseManaged?: boolean;
-    } = {};
-    if (stored.oauth.clientId !== undefined)
-      restOauth.clientId = stored.oauth.clientId;
-    if (stored.oauth.scopes !== undefined)
-      restOauth.scopes = stored.oauth.scopes;
-    // Not a secret — the authorization parameters stay on the stripped entry so
-    // stripping the client secret doesn't silently discard them. (#2018)
-    if (stored.oauth.authorizationParams !== undefined)
-      restOauth.authorizationParams = stored.oauth.authorizationParams;
-    if (stored.oauth.enterpriseManaged === true) {
-      restOauth.enterpriseManaged = true;
-    }
+    // Keep every OAuth field except the one secret, rather than enumerating the
+    // non-secret ones. An allow-list here is a standing trap: it silently drops
+    // any field added to `oauth` afterwards, and it had already done so —
+    // `onInsufficientScope` was lost whenever a server carried both a client
+    // secret and a non-default SEP-2350 policy. Subtracting the secret instead
+    // means a future field is preserved by construction. (#2018)
+    const { clientSecret: _clientSecret, ...restOauth } = stored.oauth;
     if (Object.keys(restOauth).length > 0) {
       stripped.oauth = restOauth;
     } else {