[BUG] Performance is atrocious on Remote-SSH w/ high latency connections

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

In vscode with Remote - SSH on a vpn with a long latency, around 500ms, the vscode extension has an extreme amount of UI lag. it can take 30+ minutes for permission dialogs to show up or for the claude ui to become aware of edits that have already happened according to the file explorer or editor. From extension.js analysis the reason is quite obvious:

sendQueue = Promise.resolve();

send(r) {
    this.sendQueue = this.sendQueue.then(() => this.webview.postMessage({
        type: "from-extension",
        message: r
    }).then(() => {}))
}

This code is wrong. To be specific, webview.postMessage immediately sends the given message and returns a Promise that resolves to true or false depending on if the message was "successfully delivered". Leaving aside that "successful" delivery is poorly defined, this serializes the transmission of the next message until after a full RTT from the previous message (the minimum time to receive any kind of delivery confirmation from the frontend). When we are sending many messages per second containing streaming tokens, this transmission queue will get very far behind.

What Should Happen?

Just call webview.postMessage immediately and discard the returned promise, which isn't actually useful for anything. In other words: don't serialize UI updates in this way. I patched my installation to do this and it greatly increases update throughput.

Error Messages/Logs

Steps to Reproduce

Use Remote - SSH to connect to a server, use a vpn or something with a sizeable rtt, I would suggest at least 500ms. Log into claude code, and ask Claude Haiku to produce "a very long poem, about 100 lines should do it". Observe that the result takes an extremely long time to display, for longer than Haiku takes to write it.

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.17 (Claude Code for VS Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_