perf(sftp): enable TCP_NODELAY on SFTP SSH sockets

electron/bridges/sftpBridge.cleanup.test.cjs

@@ -120,6 +120,12 @@ test("openSftp clears its authentication timer when SSH becomes ready", () => {
   );
 });
 
+test("openSftp disables Nagle on direct and jump-hop SSH sockets", () => {
+  const source = readFileSync(require.resolve("./sftpBridge/openConnection.cjs"), "utf8");
+  assert.match(source, /sshClient\.once\('ready', \(\) => \{\s*clearAuthReadyTimer\(\);\s*cleanup\(\);[\s\S]{0,200}enableSshNoDelay\(sshClient\);/);
+  assert.match(source, /conn\.once\('ready', \(\) => \{[\s\S]{0,400}enableSshNoDelay\(conn\);/);
+});
+
 test("openSftp forwards target hostId to keyboard-interactive prompts", () => {
   const source = readFileSync(require.resolve("./sftpBridge/openConnection.cjs"), "utf8");
   assert.match(

electron/bridges/sftpBridge/openConnection.cjs

@@ -9,6 +9,7 @@ const {
   terminateSshExecStream,
 } = require("../boundedSshExec.cjs");
 const { openBoundedSftpChannel } = require("../boundedSftpOpen.cjs");
+const { enableSshNoDelay } = require("../tcpNoDelay.cjs");
 const { openBoundedForwardOutCallback } = require("../boundedSshChannelOpen.cjs");
 const { remoteSoftwareRequiresSingleChannel } = require("../../../domain/singleChannelSshBanner.shared.cjs");
 
@@ -420,6 +421,10 @@ function createOpenConnectionApi(ctx) {
               if (settled) return;
               settled = true;
               clearAuthReadyTimer();
+              // SFTP RPCs are small request/response packets; with Nagle on, a
+              // second request behind an unacked one waits for the peer's
+              // delayed ACK (~40 ms per round trip on Linux, up to 200 ms on Windows).
+              enableSshNoDelay(conn);
               console.log(`[SFTP Chain] Hop ${i + 1}/${jumpHosts.length}: ${hopLabel} connected`);
               sendSftpProgress(sender, connId, hopLabel, 'connected');
               resolve();
@@ -1452,6 +1457,8 @@ function createOpenConnectionApi(ctx) {
           sshClient.once('ready', () => {
             clearAuthReadyTimer();
             cleanup();
+            // See jump-hop note above: SFTP is RPC-bound, so disable Nagle.
+            enableSshNoDelay(sshClient);
             if (remoteSoftwareRequiresSingleChannel(sshClient._remoteVer)) {
               peerSingleChannelSsh = true;
             }