fix(http2): move WINDOW_UPDATE handling to remoteSettings event

Author: KoenRijpstra

packages/grpc-js/src/transport.ts

@@ -723,28 +723,29 @@ export class Http2SubchannelConnector implements SubchannelConnector {
         }
       });
 
-      // Send WINDOW_UPDATE now to avoid 65 KB start-window stall.
+      // Prepare window size configuration for remoteSettings handler
       const defaultWin = http2.getDefaultSettings().initialWindowSize ?? 65535; // 65 535 B
       const connWin = options[
         'grpc-node.flow_control_window'
       ] as number | undefined;
-  
-      if (connWin && connWin > defaultWin) {
-        try {
-          // Node ≥ 14.18
-          (session as any).setLocalWindowSize(connWin);
-        } catch {
-          // Older Node: bump by the delta
-          const delta = connWin - (session.state.localWindowSize ?? defaultWin);
-          if (delta > 0) (session as any).incrementWindowSize(delta);
-        }
-      }
 
       this.session = session;
       let errorMessage = 'Failed to connect';
       let reportedError = false;
       session.unref();
       session.once('remoteSettings', () => {
+        // Send WINDOW_UPDATE now to avoid 65 KB start-window stall.
+        if (connWin && connWin > defaultWin) {
+          try {
+            // Node ≥ 14.18
+            (session as any).setLocalWindowSize(connWin);
+          } catch {
+            // Older Node: bump by the delta
+            const delta = connWin - (session.state.localWindowSize ?? defaultWin);
+            if (delta > 0) (session as any).incrementWindowSize(delta);
+          }
+        }
+        
         session.removeAllListeners();
         secureConnectResult.socket.removeListener('close', closeHandler);
         secureConnectResult.socket.removeListener('error', errorHandler);